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Phylogenetic analysis of the genus Megalobatrachonema Yamaguti, 1941 (Ascaridida:Cosmocercoidea:Kathlaniidae)… Richardson, Jane P.M. 1988

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PHYLOGENETIC ANALYSIS OF THE GENUS MEGALOBATRACHONEMA YAMAGUTI, 1941 (ASCARIDIDA:COSMOCERCOIDEA:KATHLANIIDAE) WITH FIELD AND LABORATORY OBSERVATIONS OF M. WALDENI by JANE P.M. RICHARDSON B.Sc., U n i v e r s i t y o f V i c t o r i a , 1976 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENT FOR THE DEGREE OF MASTER OF SCIENCE m THE FACULTY OF GRADUATE STUDIES Z o o l o g y D e p a r t m e n t We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o t h e r e q u i r e d s t a n d a r d THE UNIVERSITY OF J u l y 0 J a n e P.M. BRITISH COLUMBIA 1988 R i c h a r d s o n , 1988 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department The University of British Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 DE-6G/81) ABSTRACT The genus Megalobatrachonema (Family Kathlaniidae; Order Ascaridida) was investigated using phylogenetic analysis. A single cladogram was produced with a consistency index of 92.6%. Six species were found v a l i d , two of which are new. D i v i s i o n of the genus into subgenera Megalobatrachonema and Chabaudqolvania was not supported by the phylogenetic hypothesis. Comparison of host and parasite phylogenies suggest that at least two instances of host switching have occurred. Biogeographical analysis of parasites and hosts indicated that vicariance, rather than d i s p e r s a l , best explains d i s t r i b u t i o n of f i v e of the s i x . F i e l d and laboratory observations on one of the more evolved species of the genus, M. waldeni, suggests that there i s probably a single generation a year, and that transmission to the d e f i n i t i v e host occurs i n spring and early summer. i i i TABLE OF CONTENTS PAGE # A b s t r a c t i i L i s t o f F i g u r e s i v L i s t o f Appendices v Acknowledgement v i INTRODUCTION 1 MATERIALS AND METHODS 3 DESCRIPTION OF SPECIES 7 FIELD AND LABORATORY OBSERVATIONS ON M. WALDENI R e s u l t s 28 D i s c u s s i o n 30 PHYLOGENETIC ANALYSIS AND GENERAL DISCUSSION C h a r a c t e r A n a l y s i s 35 The Cladogram 43 Comparison w i t h Host Phylogeny and Zoogeography 45 CONCLUSIONS 49 REFERENCES 90 APPENDICES 94 i v LIST OF FIGURES PAGE # 1. Megalobatrachonema nipponicum 50 2. M. elongatum 52 3. M. q i q a n t i c u m 54 4. M. moraveci 56 5 . M. moraveci ...... 58 6. M. t e r d e n t a t u m 60 7. M. w a l d e n i 6 2 8. M. w a l d e n i 64 9. Graph - Frequency d i s t r i b u t i o n A. g r a c i l e s i z e 66 10. Graph - Frequency d i s t r i b u t i o n o f M. w a l d e n i abundance 68 11. Graph - S c a t t e r P l o t o f Worms per Host vs Host S i z e ..70 12. Graph - P r e v a l e n c e o f M. w a l d e n i 72 13. Graph - Mean I n t e n s i t y o f M. w a l d e n i 74 14. Stages o f development o f M. w a l d e n i 76 15. S c a n n i n g E l e c t r o n M i c r o s c o p y 78 16. Caudal p a p i l l a e arrangement 80 17. T r a n s m i s s i o n E l e c t r o n M i c r o s c o p y 82 18. Cladogram o f Megalobatrachonema phylogeny 84 19. Cladogram o f h o s t phylogeny 86 20. Map - p a r a s i t e d i s t r i b u t i o n 88 V LIST OF APPENDICES PAGE # A. P r e v a l e n c e and i n t e n s i t y o f M. w a l d e n i 94 B. S e a s o n a l s a m p l i n g d a t a f o r M. w a l d e n i ( S u r r e y ) 95 C. Data M a t r i x f o r Megalobatrachonema 96 v i ACKNOWLEDGEMENTS I would l i k e t o thank Dr. M a r t i n Adamson f o r h i s s u p e r v i s i o n and e n t h u s i a s t i c s u p p o r t o f my r e s e a r c h . H i s e x p e r t i s e i n nematode morphology has been i n v a l u a b l e . A l s o , I would l i k e t o thank Dr. D a n i e l Brooks f o r h i s s u g g e s t i o n s and guidance i n p h y l o g e n e t i c a n a l y s i s . O t h e r s I would l i k e t o mention a r e M i c h a e l Weiss, f o r h i s i n s t r u c t i o n and a s s i s t a n c e i n e l e c t r o n m i c r o s c o p y . Dr. Ralph L i c h t e n f e l s , f o r the l o a n o f specimens from the U.S. H e l m i n t h o l o g i c a l C o l l e c t i o n , and Dr. Mary B e v e r l e y - B u r t o n and Dr. Roy Anderson f o r t h e i r a s s i s t a n c e and k i n d n e s s d u r i n g my v i s i t s t o the U n i v e r s i t y o f Guelph. F i n a l l y , I would l i k e o f f e r s p e c i a l thanks t o my husband M i c h a e l f o r a l l h i s f i e l d h e l p , p a t i e n c e , and encouragement over the p a s t s e v e r a l y e a r s . 1 INTRODUCTION Megalobatrachonema Yamaguti, 1941 i n c l u d e s s i x s p e c i e s o f nematode t h a t p a r a s i t i z e the i n t e s t i n e o f amphibians. T h i s genus i s c h a r a c t e r i z e d by s m a l l c e p h a l i c l i p s and a much reduced oesophageal isthmus and b u l b (Chabaud, 1978). T a x o n o m i c a l l y the group i s p r o b l e m a t i c . Megalobatrachonema, w i t h the type s p e c i e s M. nipponicum, was f i r s t proposed by Yamaguti (1941). Chabaud and G o l v a n (1957) d e s c r i b e d M_;_ campanae from the European Newt, T r i t u r u s  v u l g a r i s . F r e i t a s (1958) p l a c e d these s p e c i e s i n s e p a r a t e s u b f a m i l i e s : Megalotrachonematinae f o r Megalobatrachonema  nipponicum and Chabaudgolvaninae f o r C h a b a u d g o l v a n i a campanae (Chabaud and Golvan) F r e i t a s , 1958. H a r t w i c h (1960) synonymized C h a b a u d g o l v a n i a w i t h Megalobatrachonema but Baker (1980) r e i n s t a t e d the genera proposed by F r e i t a s a t the l e v e l o f subgenera based on the presence or absence o f c u t i c u l a r v a l v e s i n the oesophageal b u l b . There has a l s o been disagreement as to where the genus s h o u l d be p l a c e d a t the f a m i l y l e v e l . Yamaguti (1941) and Chabaud and G o l v a n (1957) p l a c e d i t i n the K a t h l a n i i d a e (Lane, 1914 subfam.) T r a v a s s o s , 1918 whereas F r e i t a s (1958) and S k r j a b i n et_ a l . (1976) p l a c e i t i n O x y a s c a r i d i d a e F r e i t a s , 1958. Baker (1980) s u p p o r t s placement i n the K a t h l a n i i d a e but f i n d s the genus b e a r s s t r o n g a f f i n i t i e s t o the Q u i m p e r i i d a e ( S e u r a t o i d e a ) . 2 T h i s s t u d y p r o v i d e s d e t a i l e d taxonomic i n f o r m a t i o n on the s i x s p e c i e s o f Megalobatrachonema i n c l u d i n g two new s p e c i e s . A p h y l o g e n e t i c a n a l y s i s o f the genus based on 21 m o r p h o l o g i c a l c h a r a c t e r s i s used to p r o v i d e hypotheses on h i s t o r i c a l , c o e v o l u t i o n a r y , and b i o g e o g r a p h i c r e l a t i o n s h i p s . The l i f e h i s t o r i e s o f z o o p a r a s i t i c nematodes have proved s t r o n g i n d i c a t o r s o f p h y l o g e n e t i c a f f i n i t y (Chabaud, 1955; I n g l i s , 1965; Adamson, 1986). Only one s p e c i e s i n the genus has been i n v e s t i g a t e d i n t h i s r e s p e c t , namely M. t e r d e n t a t u m (see Barus and G r o s c h a f t , 1962; P e t t e r and Chabaud, 1971) and t h e r e i s d i s a g r e e m e n t as t o whether the l i f e c y c l e i n monoxenous ( r e q u i r i n g o n l y one h o s t f o r i t s c o m p l e t i o n ) or heteroxenous ( r e q u i r i n g one or more i n t e r m e d i a t e h o s t s ) . T h e r e f o r e i n a d d i t i o n to the p h y l o g e n e t i c s t u d y , o b s e r v a t i o n s were made on one o f the l o c a l s p e c i e s i n the genus, M. w a l d e n i . 3 MATERIALS AND METHODS Specimen C o l l e c t i o n - Specimens o f p r e v i o u s l y d e s c r i b e d s p e c i e s were o b t a i n e d from the US N a t i o n a l Museum H e l m i n t h o l o g i c a l C o l l e c t i o n (Megalobatrachonema g i g a n t i c u m #9054, M_. elongatum #72190-72194, F a l c a u s t r a mascula #72195-72198), the P a r i s N a t i o n a l Museum (M. t e r d e n t a t u m Re. 620, and the C z e c h o s l o v a k i a n Academy o f S c i e n c e s (M. t e r d e n t a t u m ) . Megalobatrachonema moraveci n. sp. were c o l l e c t e d from T a r i c h a g r a n u l o s a on Vancouver I s l a n d i n May 1987. M. w a l d e n i n.sp. were found i n Ambystoma g r a c i l e c o l l e c t e d from f i v e s o u t h e r n B r i t i s h Columbia l o c a l i t i e s between March 1986 and September 1987. P a r a s i t e s were f i x e d i n hot a l c o h o l / g l y c e r i n e and p r e s e r v e d i n 70% a l c o h o l b e f o r e b e i n g c l e a r e d and examined i n l a c t o p h e n o l . Worms were drawn and measured w i t h the a i d o f a draw i n g tube. Ambystoma g r a c i l e was sampled monthly from March 1986 t o September 1987 i n r e t e n t i o n ponds o f the L i t t l e Cambell R i v e r i n S u r r e y , B r i t i s h Columbia. P r e v a l e n c e (% h o s t s i n f e c t e d ) , i n t e n s i t y (number o f worms per i n f e c t e d h o s t ) , and abundance (number worms per h o s t i n c l u d i n g u n i n f e c t e d h o s t s ) were c a l c u l a t e d (Appendix A ) . Samples were d i v i d e d i n t o b i m o n t h l y groups ( J a n u a r y / F e b r u a r y , M a r c h / A p r i l e t c . ; Appendix B) and a n a l y z e d w i t h the s t a t i s t i c a l package ISTAT. M a t e r i a l examined w i t h e l e c t r o n m i c r o s c o p y was p r e p a r e d as 4 f o l l o w s : specimens were f i x e d i n c o l d 2.5% G l u t e r a l d e h y d e i n 0.1M sodium c a c o d y l a t e b u f f e r (pH 7.3) f o r 2 hours on i c e and f o r 1 hour a t room tem p e r a t u r e . Specimens were p o s t - f i x e d i n 1% osmium t e t r o x i d e i n 0.1M sodium c a c o d y l a t e f o r 1 hour, r i n s e d i n b u f f e r and d i s t i l l e d w ater, en b l o c s t a i n e d i n 2% aqueous u r a n y l a c e t a t e , t h e n d e h y d r a t e d t h r o u g h a s e r i e s o f a l c o h o l s . Worms used f o r s c a n n i n g e l e c t r o n m i c r o s c o p y were s u b j e c t e d to c r i t i c a l p o i n t d r y i n g w i t h C02, s p u t t e r c o a t e d , and photographed w i t h a s c a n n i n g e l e c t r o n m i c r o s c o p e . Worms used f o r t r a n s m i s s i o n e l e c t r o n m i c r o s c o p y were p l a c e d i n p r o p y l e n e o x i d e f o l l o w e d by p r o p y l e n e o x i d e and p l a s t i c ( 3 : 1 , 1:1, 1:3, and 100%). Specimens were l e f t i n 100% p l a s t i c (Epon 812, DDSA, NMA) w i t h o u t a c c e l e r a t o r f o r 18 h o u r s , t h e n t r a n s f e r r e d t o f r e s h p l a s t i c w i t h 1% a c c e l e r a t o r (DMO-30) f o r 3 hours b e f o r e b e i n g p l a c e d i n molds and p o l y m e r i z e d a t 60° C f o r 2 days and c u t on an u l t r a m i c r o t o m e . S e m i - t h i n s e c t i o n s (l-2um) were s t a i n e d w i t h t o l u i d i n e b l u e and ob s e r v e d under l i g h t m i c r o s c o p y . S e r i a l s e c t i o n s (0.5 urn) were p i c k e d up on 100 mesh g r i d s , s t a i n e d a t room temperature w i t h 2% u r a n y l a c e t a t e f o r 15 minutes f o l l o w e d by l e a d c i t r a t e f o r 10 mi n u t e s , t h e n photographed w i t h a t r a n s m i s s i o n e l e c t r o n m i c r o s c o p e . To s t u d y development and t r a n s m i s s i o n , M. w a l d e n i from the st u d y sample were s a c r i f i c e d . Eggs, t e a s e d from the u t e r u s o f g r a v i d f e m a l e s , were t r a n s f e r r e d t o 35x10mm P e t r i d i s h e s o c o n t a i n i n g a u t o c l a v e d pond water and m a i n t a i n e d a t 20 C. 5 O b s e r v a t i o n s o f egg development were made over a two week, p e r i o d ; a t r e g u l a r i n t e r v a l s a sample o f eggs was p l a c e d i n a s m a l l drop o f water between s l i d e and v a s e l i n e - r i n g e d c o v e r s l i p and drawings were made w i t h the a i d o f a drawing tube. E x p e r i m e n t a l i n f e c t i o n was attempted u s i n g A. q r a c i l e l a r v a e c o l l e c t e d as eggs from the C u l t u s Lake a r e a and r a i s e d i n d i s t i l l e d water. A ni n e - m o n t h - o l d h o s t was c o n d i t i o n e d t o s w a l l o w i n g 4-5 mm chunks o f beef h e a r t o f f e r e d w i t h t w e e z e r s . I n f e c t i o n i n v o l v e d the f e e d i n g o f 60 nematode l a r v a e ( r a n g i n g from 4 to 14 d a y - o l d ) by i n s e r t i n g them i n h o l l o w e d o u t meat chunks; t h i s was done by f e e d i n g 15 nematode l a r v a e on 4 d i f f e r e n t o c c a s i o n s over a 10 day p e r i o d . A v a r i e t y o f i n v e r t e b r a t e s from the type l o c a l i t y were d i s s e c t e d t h r o u g h o u t the stu d y p e r i o d i n s e a r c h o f p o s s i b l e i n t e r m e d i a t e h o s t s . P h y l o g e n e t i c A n a l y s i s - C h a r a c t e r d a t a f o r s p e c i e s o f Megalobatrachonema were o b t a i n e d by e x a m i n a t i o n o f specimens and by r e f e r e n c e t o l i t e r a t u r e . P o l a r i z a t i o n o f c h a r a c t e r s was de t e r m i n e d by outgroup comparison. C h a r a c t e r s t a t e s were r e p r e s e n t e d by a "0" f o r the p l e s i o m o r p h i c ( p r i m i t i v e ) s t a t e , a n d a "1" or "2" f o r the apomorphic (more e v o l v e d ) . C h a r a c t e r s w i t h more t h a n two s t a t e s were t r e a t e d as unordered. That i s , no a p r i o r i t r a n s f o r m a t i o n s e r i e s i s assumed; unordered c h a r a c t e r s a re mapped onto a t r e e 6 which has i n i t i a l l y been r e s o l v e d u s i n g b i n a r y c h a r a c t e r s . A "9" was used f o r unknown c h a r a c t e r s t a t e s . Data were summarized i n a m a t r i x which was t h e n a n a l y z e d w i t h the computer program PAUP ( P h y l o g e n e t i c A n a l y s i s U s i n g Parsimony, by D a v i d S w o f f a r d , 1985). Key r e f e r e n c e s used i n the P h y l o g e n e t i c a n a l y s i s methodology were B r o o k s , 1981, Brooks e t a l , 1984, and W i l e y , 1981. Congruence between nematode and salamander h o s t phylogeny was used to t e s t an h y p o t h e s i s o f c o e v o l u t i o n . Methodology used i n t h i s a n a l y s i s i s from Brooks 1979, 1981, 1985, and Brooks and W i l e y , 1986. The h o s t phylogeny proposed by Duellman and Trueb (1986) was used. T h e i r cladogram was produced by a n a l y s i s o f 27 c h a r a c t e r s w i t h a WAGNER 78 program (by F a r r i s ) and has a c o n s i s t e n c y i n d e x o f 73%. The degree o f congruence between h o s t and p a r a s i t e cladograms i s used to i n d i c a t e the degree o f h i s t o r i c a l a s s o c i a t i o n ; i n c ongruence i s c o n s i d e r e d i n d i c a t i v e o f p a r a s i t e c o l o n i z a t i o n or h o s t s w i t c h i n g . A s t u d y o f the a s s o c i a t i o n between Megalobatrachonema s p e c i e s and t h e i r h o s t s was made u s i n g v i c a r i a n c e b iogeography i n which the p a r a s i t e phylogeny i s compared to a sequence o f g e o l o g i c a l e v e n t s a s s o c i a t e d w i t h c o n t i n e n t a l o r i g i n s . Lack o f congruence between a r e a and p a r a s i t e cladograms i n d i c a t e s p o s s i b l e d i s p e r s a l e v e n t s . 7 DESCRIPTION OF SPECIES (measurements i n micrometers (um) u n l e s s o t h e r w i s e s t a t e d ; the mean i s g i v e n i n p a r e n t h e s e s ) 1. Megalobatrachonema nipponicum Yamaguti, 1941 ( t y p e s p e c i e s ) ( F i g u r e 1) Host: M e g a l o b a t r a c h u s j a p o n i c u s ( t y p e h o s t ) D i s t r i b u t i o n : Syuzan near K y o t o , Japan (type l o c a l i t y ) S i t e : s m a l l i n t e s t i n e Specimens: Type and p a r a t y p e s i n Yamaguti H e l m i n t h o l o g i c a l C o l l e c t i o n . Specimens s e n t f o r but not r e c e i v e d . D e s c r i p t i o n ( A c c o r d i n g t o Yamaguti, 1941): G e n e r a l - Mouth s m a l l , l i p s i n d i s t i n c t . Oesophagus i n c l u d e s s h o r t pharynx, l o n g narrow corpus and v a l v e d b u l b . No a l a e p r e s e n t . C u t i c l e smooth. Male - P r e - a n a l muscles w e l l d e v e l o p e d , pseudosucker p r e s e n t . S p i c u l e s e q u a l and e l o n g a t e . Gubernaculum weakly d i f f e r e n t i a t e d . Ten p a i r s c a u d a l p a p i l l a e a r r a n g e d as f o l l o w s : 5 p r e - a n a l p a i r s and 4 or 5 p a i r s p o s t - a n a l (2 l a t e r a l l y p o s i t i o n e d ) ; no mention o f an u n p a i r e d p a p i l l a on l i p o f anus. Female - A m p h i d e l p h i c . V u l v a i n p o s t e r i o r h a l f o f body. No eggs found. 8 Measurements: Male - T o t a l l e n g t h 9.3-11.5 mm. Maximum w i d t h 310-450. T a i l 410-550 l o n g . Pseudosucker 1900-2300 from c l o a c a . Nerve r i n g 280-330 and c e r v i c a l p a p i l l a e 450-490 from c e p h a l i c end. Oesophagus 920-1150 i n c l u d i n g weakly d i f f e r e n t i a t e d p h a r y n g e a l p a r t 75-80 and oesophageal b u l b 100-135 wide. S p i c u l e s 650-1000 l o n g . Gubernaculum 110 l o n g . Female - T o t a l l e n g t h 12.13 mm. Maximum w i d t h 400-500. T a i l 920-1400 l o n g . Nerve r i n g 300-350, c e r v i c a l p a p i l l a e 450-540, and e x c r e t o r y pore 650-770 from c e p h a l i c end. Oesophagus 1000-1200 l o n g i n c l u d i n g p h a r y n g e a l a r e a 80 and b u l b 120-130. A n t e r i o r o v a r y e x t e n d i n g t o about nerve r i n g , p o s t e r i o r o v a r y to end o f t a i l . V a g i n a 250-400 l o n g , a n t e r i o r l y d i r e c t e d . V u l v a 4600-5300 from p o s t e r i o r end. Comments: The genus Megalobatrachonema and the type s p e c i e s M. nipponicum were f i r s t d e s c r i b e d by Yamaguti i n 1941 and p l a c e d i n the f a m i l y K a t h l a n i i d a e T r a v a s s o s , 1918. I t i s q u e s t i o n a b l e whether the a n t e r i o r o v a r y extends to the nerve r i n g and the p o s t e r i o r o v a r y extends t o the end o f the t a i l as d e s c r i b e d . The s p e c i e s i s d i s t i n g u i s h e d by i t s v a l v e d oesophagus and the presence o f a pseudosucker. 9 2. Megalobatrachonema elongatum ( B a i r d , 1858) Baker, 1986 ( F i g u r e 2) Synonyms: L e p t o d e r a e l o n g a t a B a i r d , 1858 S p i r o n o u r a e l o n g a t a ( B a i r d , 1858) Walton, 1932 F a l c a u s t r a e l o n g a t a ( B a i r d , 1858) F r e i t a s and L e n t , 1941 H o s t s : Ambystoma t i g r i n u m ( t y p e h o s t ) , A. l a c u s t r u s , Ambystoma sp. R h y a c o s i d e r o n a l t a m i r a n i , Emvs s e r r a t a D i s t r i b u t i o n : Mexico ( t y p e l o c a l i t y ) S i t e : s m a l l i n t e s t i n e Specimens examined: U.S. H e l m i n t h o l o g i c a l C o l l e c t i o n , from the f o l l o w i n g h o s t s and l o c a t i o n s : 72190 A. l a c u s t r i s - Lake Zumpango, Mexico 72191 Ambystoma sp. - Zapacu, Michoacan, Mexico 72192 A. t i g r i n u m - Lake A l c h i c h i c a , P u e b l a , Mexico 72193 A. t i g r i n u m - N o p a l t e p a c , Mexico 72194 R h y a c o s i d e r o n a l t a m i r a n i - La Marquesa, Mexico D e s c r i p t i o n : G e n e r a l - Three l i p s b e a r i n g two p a p i l l a e on each. P a p i l l a e r a i s e d on e l o n g a t e hypodermal p e d u n c l e s . S u b v e n t r a l l i p s w i t h m e d i a l amphids. Three o n c h i a p r e s e n t , each t h r e e - p r o n g e d . Oesophagus i n c l u d e s i n d i s t i n c t p h a r y n g e a l r e g i o n . D i v i s i o n s between c o r p u s , i s t h m u s , and b u l b not d i s t i n c t . B u l b e l o n g a t e 10 and w i t h o u t v a l v e s . E x c r e t o r y pore a t l e v e l o f p o s t e r i o r o f c o r p u s , s i n u s e l o n g a t e , l a t e r a l c a n a l s not ob s e r v e d . Male - T a i l e l o n g a t e , v e n t r a l l y c u r v e d . Pseudosucker p r e s e n t , c o n s i s t i n g o f 17-18 muscle p a i r s ; 31-39 o b l i q u e muscle p a i r s . E l e v e n p a i r s c a u d a l p a p i l l a e a r r a n g e d as f o l l o w s : 3 p r e - a n a l p a i r s , a s i n g l e p a p i l l a on a n a l l i p , 8 p o s t - a n a l p a i r s o f which 2 p a i r s a r e l a t e r a l l y p o s i t i o n e d . Gubernaculum i n d i s t i n c t when s p i c u l e s p r o t r u d i n g . S p i c u l e s b r o a d l y winged. Female - A m p h i d e l p h i c . A n t e r i o r l y d i r e c t e d v a g i n a . One ova r y o r i g i n a t i n g a n t e r i o r t o v u l v a , f l e x i n g p o s t e r i o r l y , f o r m i n g k n o t , e x t e n d i n g a n t e r i o r l y t o w i t h i n 8-12% body l e n g t h from oesophageal b u l b . Then f l e x i n g p o s t e r i o r l y and c o n t i n u i n g to p o s t e r i o r o f worm, f l e x i n g a n t e r i o r l y , e n t e r i n g o v i d u c t , f l e x i n g p o s t e r i o r l y t h e n a n t e r i o r l y as becomes u t e r u s , then r u n n i n g a n t e r i o r l y t o v a g i n a . Other o v a r y o r i g i n a t i n g i n p o s t e r i o r o f worm and e x t e n d i n g a n t e r i o r l y t o w i t h i n 5% body l e n g t h from o p p o s i t e o v a r y f l e x u r e . Then f l e x i n g and c o n t i n u i n g p o s t e r i o r l y e n t e r i n g o v i d u c t , f l e x i n g a n t e r i o r l y t h e n p o s t e r i o r l y as e n t e r s u t e r u s . U t e r u s f l e x i n g a n t e r i o r l y t h e n p o s t e r i o r l y and merging w i t h o p p o s i t e u t e r u s a t v a g i n a . Eggs i n u t e r u s t h i c k s h e l l e d and p a s t the f i r s t c l e a v a g e s t a g e o f development. Measurements: Male - based on 4 specimens - Length 17-31 (23) mm. Maximum w i d t h 256-500 (400). Oesophagus 1957-2960 (2417) i n c l u d i n g 11 p h a r y n g e a l p o r t i o n 119-130 (124). B u l b 215 l o n g by 150-225 (188) wide. Nerve r i n g 510-556 ( 5 3 3 ) , e x c r e t o r y pore 1537-2237 (1906), and d e i r i d s 1336 from a n t e r i o r end. R i g h t s p i c u l e 561-590 (577) l o n g by 57-75 (65) wide. L e f t s p i c u l e 540-650 (590) l o n g by 70-80 (75) wide. Gubernaculum 168-198 (181) l o n g by 23-50 (34) wide i n l a t e r a l view. T a i l 535-672 (628) l o n g . D i s t a n c e from anus to j u n c t i o n w i t h vas d e f e r e n s 1238-1765 (1485). D i s t a n c e from a n t e r i o r f l e x u r e o f t e s t i s t o oesophageal b u l b 1260-2840 (1984). Anus to pseudosucker 2010-3365 (2465). Female - based on 5 specimens - Length 27-35 (31)mm. Width a t l e v e l o f v u l v a 460=766 (578). Oesophagus 2112-3070 (2593) i n c l u d i n g p h a r y n g e a l p o r t i o n 110-156 (136). B u l b 232 l o n g by 190-230 (212) wide. Nerve r i n g 460-860 ( 6 4 0 ) , e x c r e t o r y pore 1422-2320 (1960), and d e i r i d s 1678 from a n t e r i o r end. Vagina 520-770 (591) l o n g . V u l v a 8153-9603 (9166) from p o s t e r i o r e x t r e m i t y . D i s t a n c e from oesophageal b u l b t o most a n t e r i o r o v a r i a n f l e x u r e 2420-3800 (2925). T o t a l egg number 101-168 (1 2 5 ) ; eggs 81-94 (87) l o n g by 70-72 (71) wide. Comments: M. elonqatum was o r i g i n a l l y d e s c r i b e d by B a i r d (1858) from the abdominal c a v i t y o f Ambystoma mexicanum i n Mexico. Walton (1932) r e d e s c r i b e d specimens from the i n t e s t i n e o f Emys  s e r r a t a i n Mexico and t r a n s f e r r e d the s p e c i e s to S p i r o n o u r a L e i d y , 1956. He r e f e r r e d to the type h o s t as A. t i g r i n u m which he c o n s i d e r e d synonymous w i t h A. mexicanum• C a b a l l e r o and H o l l i s (1938) r e d e s c r i b e d the s p e c i e s from specimens found i n 12 A. t i q r i n u m from Lake X o c h i m i l c o , Mexico, and F r e i t a s and Lent (1941) t r a n s f e r r e d the s p e c i e s t o the genus F a l c a u s t r a Lane, 1915 w i t h o u t r e d e s c r i p t i o n . F i n a l l y , Baker (1985) r e d e s c r i b e d the s p e c i e s as Megalobatrachonema (Chabaudgolvania) elongatum from v a r i o u s Mexican ambystomatids. S i n c e a l l subsequent d i s c o v e r i e s o f M. elongatum were from the i n t e s t i n e , B a i r d ' s o r i g i n a l abdominal l o c a l i t y i s i n doubt. M. elongatum i s d i s t i n g u i s h e d from o t h e r members o f the genus by i t s t h r e e - p r o n g e d o n c h i a and embyonated eggs i n the female. 13 3. Megalobatrachonema g i g a n t i c u m ( O l s e n , 1938) Baker, 1980 ( F i g u r e 3) Synonyms: A p l e c t a n a g i g a n t i c u m O l s e n , 1938 Oxysomatium g i g a n t i c u s ( O l s e n , 1938) S k r j a b i n and S c h i k h o b a l o v a , 1951. H o s t s : Rana p r e t i o s a ( t y p e h o s t ) , Bufo b o r e a s , Ambystoma  t i g r inum D i s t r i b u t i o n : Utah ( t y p e l o c a l i t y ) and Idaho, USA S i t e : stomach and i n t e s t i n e Specimen examined: ( t y p e ) USNM. Helm. C o l l . No. 9054 D e s c r i p t i o n : G e n e r a l - Three s m a l l l i p s w i t h two p a p i l l a e on the d o r s a l l i p and one p a p i l l a on each v e n t r a l l i p . P a p i l l a e s u p p o r t e d by r a i s e d hypodermal p e d u n c l e s . S l i g h t c h e i l o s t o m a l t h i c k e n i n g a t base o f l i p s . Onchia absent. P h a r y n g e a l r e g i o n d i s t i n c t and g l a n d u l a r i n appearance. The corpus and isthmus o f the oesophagus are not d i s t i n c t ; r e g i o n o f isthmus s w o l l e n . Oesophageal b u l b round and w i t h v a l v e s . E x c r e t o r y pore i n r e g i o n o f isthmus. S i n u s not d i s t i n c t ; l a t e r a l c a n a l s not obse r v e d . Male - S h o r t , v e n t r a l l y c u r v e d t a i l . S p i c u l e s s i m p l e , e l o n g a t e . O b l i q u e muscles i n 46 p a i r s ; pseudosucker 14 absent. E l e v e n p a i r s c a u d a l p a p i l l a e a r r a n g e d as f o l l o w s : 5 p a i r s p r e - a n a l , 6 p a i r s p o s t - a n a l o f which t h r e e p a i r s a re l a t e r a l l y p o s i t i o n e d . Gubernaculum w i t h h o l l o w e d , round appearance on broadened end. Female - A m p h i d e l p h i c , not p r o d e l p h i c as r e p o r t e d by O l s e n (1938). One ov a r y o r i g i n a t i n g i n a n t e r i o r o f worm, f l e x i n g p o s t e r i o r l y , t h e n a n t e r i o r l y t o w i t h i n 11% body l e n g t h from oesophageal b u l b . Then f l e x i n g p o s t e r i o r l y and c o n t i n u i n g p a s t r e g i o n o f v u l v a , e n t e r i n g o v i d u c t as f l e x e s a n t e r i o r l y , then e n t e r i n g u t e r u s , f l e x i n g p o s t e r i o r l y , t h e n a n t e r i o r l y and merging w i t h o p p o s i t e u t e r u s a t v a g i n a . Other o v a r y o r i g i n a t i n g near rectum and r u n n i n g a n t e r i o r l y t o w i t h i n 4% body l e n g t h from o p p o s i t e o v a r y f l e x u r e b e f o r e f l e x i n g and c o n t i n u i n g p o s t e r i o r l y , t h e n e n t e r i n g o v i d u c t , t h e n u t e r u s . U t e r u s f l e x i n g a n t e r i o r l y then p o s t e r i o r l y to merge w i t h v a g i n a . Eggs u n c l e a v e d and une v e n l y t h i c k e n e d on one s i d e . Measurements: Male - based on s i n g l e specimen - Length 11 mm. Maximum w i d t h 326. Oesophagus 1172 w i t h c o r pus 890 i n c l u d i n g p h a r y n g e a l p o r t i o n 86. Isthmus 148, b u l b 134 l o n g by 125 wide. Nerve r i n g 410, e x c r e t o r y pore 927 and d e i r i d s 852 from a n t e r i o r end. R i g h t s p i c u l e 675 l o n g by 26 wide. L e f t s p i c u l e 678 l o n g by 25 wide. Gubernaculum 58 l o n g by 17 wide i n l a t e r a l view. T a i l 268 l o n g . D i s t a n c e from anus t o j u n c t i o n w i t h vas d e f e r e n s 915. D i s t a n c e from a n t e r i o r f l e x u r e o f t e s t i s t o oesophageal b u l b 15 1958. No pseudosucker, 46 oblique muscle p a i r s . Female - based on s i n g l e specimen - Length 13.5 mm. Maximum width at l e v e l of vulva 418. Oesophagus 1406 with corpus 1061 i n c l u d i n g pharyngeal p o r t i o n 112. Isthmus 165, bulb 180 long by 175 wide. Nerve r i n g 435 from a n t e r i o r end. Excretory pore and d e i r i d s not v i s i b l e . Vagina 520 long. Vulva 6297 from p o s t e r i o r extremity. Distance from oesophageal bulb to most a n t e r i o r o v a r i a n f l e x u r e 1540. Total egg number 349, eggs 70 long by 51 wide. Comments: The species was f i r s t described from Rana p r e t i o s a as Aplectana qiqanticum by Olsen (1938). S k r j a b i n and Shikhobalova (1951; S k r j a b i n §_t a l , 1976) t r a n s f e r r e d the species to Megalobatrachonema and Baker (1980) redescribed the type specimen. The species i s a l s o known from Bufo boreas i n Utah (Frandsen and Grundman, 1960), A. tigrinum i n Utah (Parry and Grundman, 1965), and Rana p r e t i o s a and R. p r e t i o s a - R . s y l v a t i c a hybrids i n Idaho (Waitz, 1961). I t i s c h a r a c t e r i z e d by i t s swollen oesophageal isthmus and valved s p h e r i c a l oesophageal bulb. 16 4. Megalobatrachonema moraveci R i c h a r d s o n and Adamson, 1988 ( F i g u r e s 4 to 5) Host: T a r i c h a g r a n u l o s a ( t y p e ) S i t e : i n t e s t i n e L o c a l i t y : Brannen Lake, Nanaimo and unnamed l a k e , Cambell R i v e r (sometimes r e f e r r e d to as Quarry Lake, found a t 50' 1 5 ' l a t . by 125' 4 0 ' l o n g . ) , Vancouver I s l a n d , B r i t i s h Columbia. Specimens d e p o s i t e d : US N a t i o n a l Museum Helm. C o l l . h o l o t y p e #79940 and 7 p a r a t y p e s #79941 C z e c h o s l o v a k i a I n s t i t u t e o f P a r a s i t o l o g y 5 p a r a t y p e s #N-244 Etymology: T h i s new s p e c i e s was named i n honour o f F r a n t i s e k Moravec o f the C z e c h o s l o v a k Academy o f S c i e n c e s , who f i r s t s i g n a l l e d the presence o f a Megalobatrachonema s p e c i e s i n Tar i c h a found on Vancouver I s l a n d . D e s c r i p t i o n : G e n e r a l - O r a l o pening t r i a n g u l a r , s urrounded by t h r e e l i p s d i s t i n c t l y s e p a r a t e d from one a n o t h e r . C e p h a l i c sense organs l o c a t e d a t the end o f hypodermal p e d u n c l e s . D o r s a l l i p w i t h two p a p i l l a e ; s u b v e n t r a l l i p s each w i t h s i n g l e p a p i l l a and amphid. Inner p a p i l l a e not obse r v e d . C u t i c l e l i n i n g i n n e r s u r f a c e o f l i p s h e a v i l y s c l e r o t i z e d . A n t e r i o r o f oesophagus b e a r i n g t h r e e o n c h i a . Oesophagus l o n g and narrow, w i t h a n t e r i o r p h a r y n g e a l 17 p o r t i o n and f a i n t l y s e p a r a t e d c o r p u s , i s t h m u s , and b u l b . Very s l i g h t s w e l l i n g a t p o s t e r i o r o f c o r p u s . D e i r i d s a t l e v e l o f c orpus s w e l l i n g . Oesophageal b u l b l a c k i n g v a l v e s . E x c r e t o r y pore l o c a t e d a t l e v e l o f oesophageal b u l b , opening i n t o l a r g e s i n u s . Male - Caudal end c u r v e d v e n t r a l l y . P r e - a n a l m u s c u l a t u r e c o n s i s t i n g o f 52-69 muscle p a i r s . Pseudosucker absent. T a i l s h o r t . Twelve p a i r s c a u d a l p a p i l l a e a r r a n g e d as f o l l o w s : seven p a i r e d p r e - a n a l and median u n p a i r e d p a p i l l a e on a n t e r i o r a n a l l i p , f i v e p a i r s p o s t - a n a l ( f i r s t and t h i r d p a i r s l a t e r a l ) . H o l o t y p e and one p a r a t y p e . showing the above p a p i l l a e arrangement; two p a r a t y p e s showing v a r i a t i o n i n p a p i l l a e number. I n these c a s e s the f o u r t h p o s t - a n a l p a i r ( s u b v e n t r a l ) was absent i n one specimen and r e p r e s e n t e d by a s i n g l e p a p i l l a i n the o t h e r specimen. Phasmids between t h i r d ( l a t e r a l ) and f o u r t h p a i r s o f p a p i l l a e . S p i c u l e s e q u a l and b r o a d l y a l a t e . Gubernaculum w i t h rounded more d o r s a l end and c r o c h e t hook appearance on p o i n t e d v e n t r a l end. Female - V u l v a i n p o s t e r i o r t h i r d o f body. Vagi n a m u s c u l a r , a n t e r i o r l y d i r e c t e d . A m p h i d e l p h i c . Ovary a s s o c i a t e d w i t h p o s t e r i o r u t e r u s o r i g i n a t i n g i n a n t e r i o r o f worm, r u n n i n g p o s t e r i o r l y , f l e x i n g a n t e r i o r l y , t h e n f l e x i n g p o s t e r i o r l y 15-22% body l e n g t h b e h i n d oesophageal b u l b , and c o n t i n u i n g to l e v e l o f v u l v a b e f o r e f l e x i n g a n t e r i o r l y a t o v i d u c t . O v i d u c t emptying i n t o u t e r u s ; u t e r u s f l e x i n g a n t e r i o r l y to j o i n o p p o s i n g u t e r u s a t v a g i n a . Ovary a s s o c i a t e d w i t h a n t e r i o r 18 u t e r u s o r i g i n a t i n g near rectum, e x t e n d i n g a n t e r i o r l y t o w i t h i n 1-13% body l e n g t h from o p p o s i n g o v a r y f l e x u r e , f l e x i n g p o s t e r i o r l y , c o i l i n g back on i t s e l f once t h e n emptying i n t o o v i d u c t . O v i d u c t f l e x i n g a n t e r i o r l y a t j u n c t i o n w i t h u t e r u s ; u t e r u s f l e x i n g p o s t e r i o r l y and merging w i t h o p p o s i t e u t e r u s a t v a g i n a . Eggs undeveloped. Measurements: Male - (based on 4 specimens) - Length 21 - 31 (26) mm. Maximum w i d t h 619-715 (660). Oesophagus 2027-2742 (2529) i n c l u d i n g p h a r n g e a l p o r t i o n 130-200 (162). B u l b w i d t h 165-240 (215). Nerve r i n g 626-755 ( 7 0 9 ) , d e i r i d s 1612-1985 (1850), and e x c r e t o r y pore 1717-2491 (2226) from a n t e r i o r end. T a i l 329-380 (355) l o n g . A n t e r i o r f l e x u r e o f t e s t i s 6740-7754 (7277) p o s t e r i o r t o oesophageal b u l b . R i g h t s p i c u l e 600-646 (636) l o n g by 42-50 (45) wide, l e f t s p i c u l e 605-685 (649) l o n g by 43-50 (48) wide; gubernaculum 128-160 (143) l o n g by 27-32 (28) wide i n l a t e r a l view. Female - (based on 4 specimens) - Length 32 - 37 (34) mm. Width a t v u l v a 832-890 (869). Oesophagus 2340-2629 (2489) i n c l u d i n g p h a r y n g e a l p o r t i o n 165-172 (169). B u l b w i d t h 230-280 (261). Nerve r i n g 680-752 ( 7 2 7 ) , d e i r i d s 1690-1896 (1813), and e x c r e t o r y pore 1940-2507 (2245) from a n t e r i o r end. T a i l 676-820 (730) l o n g . V a g i n a 440-560 (521) l o n g . V u l v a 8861-10,100 (9292) from p o s t e r i o r end. D i s t a n c e from most a n t e r i o r f l e x u r e 19 o f o v a r y to oesophageal b u l b 4828-7018 (5702). T o t a l egg number 767-1325 (1050), eggs 69-82 (76) l o n g by 60-70 (67) wide. Comments: Moravec (1984) r e p o r t e d a Megalobatrachonema sp. from Swan Lake, Nanaimo, B.C. and r e f e r r e d h i s m a t e r i a l to M. t e r d e n t a t u m . E x a m i n a t i o n o f Moravec's specimen i n the p r e s e n t s t u d y showed, i n f a c t , t h a t i t was a new s p e c i e s and i t has been d e s c r i b e d as M. moraveci R i c h a r d s o n and Adamson, 1988. M. moraveci i s d i s t i n g u i s h e d from M. t e r d e n t a t u m by i t s s c l e r o t i z e d c h e i l o s t o m e , s l i g h t s w e l l i n g a t the base o f the c o r p u s , l a c k o f a pseudosucker, and i n h a v i n g two r a t h e r t h a n one p a i r o f l a t e r a l p o s t - a n a l p a p i l l a e and two more p r e - a n a l p a i r s . 20 5. Megalobatrachonema t e r d e n t a t u m ( L i n s t o w , 1890) H a r t w i c h , 1960 ( F i g u r e 6) Synonyms: Oxysoma t e r d e n t a t u m L i n s t o w , 1890 S p i n i c a u d a sp. o f Otcenasek, 1957 Megalobatrachonema campanae Chabaud and G o l v a n , 1957 C h a b a u d g o l v a n i a campanae (Chabaud and G o l v a n , 1957) F r e i t a s , 1958, H o s t s : T r i t u r u s c r i s t a t u s L a u r e n t i ( t y p e h o s t ) , T. v u l g a r i s , T. a l p e s t r i s D i s t r i b u t i o n : Germany ( t y p e l o c a l i t y ) , F r a n c e , C z e c h o s l o v a k i a S i t e : i n t e s t i n e Specimens examined: 4 male specimens from 620Q Museum n a t i o n a l d ' h i s t o i r e n a t u r e l l e , P a r i s . C z e c h o s l o v a k i a n Academy o f S c i e n c e s ( s e v e r a l male and female s p e c i m e n s ) . D e s c r i p t i o n : G e n e r a l - H i g h l y c o i l e d e l o n g a t e worms, t h r e e s m a l l l i p s w i t h two p a p i l l a e on each l i p . P a p i l l a e r a i s e d by b i f i d hypodermal p e d u n c l e s . M e d i a l amphids on s u b v e n t r a l l i p s . Three prominent o n c h i a . Oesophagus i n c l u d e s p o o r l y d i f f e r e n t i a t e d c o r p us w i t h p h a r y n g e a l p o r t i o n , i s t h m u s , and b u l b . Corpus extends 2/3 oesophageal l e n g t h . B u l b w i t h o u t v a l v e s . E x c r e t o r y pore a t l e v e l o f oesophageal b u l b . E x c r e t o r y s i n u s s a c c a t e ; no l a t e r a l 21 c a n a l s o b s e r v e d . Male - S h o r t v e n t r a l l y c u r v e d t a i l . W e l l d e v e l o p e d a n a l m u s c u l a t u r e . Pseudosucker formed by 22-28 muscle p a i r s . O b l i q u e m u s c u l a t u r e c o n s i s t i n g o f 45-53 muscle p a i r s . S p i c u l e s winged but s l e n d e r . Gubernaculum s i m p l e . P a p i l l a e a r r a n g e d as f o l l o w s : 6 p r e - a n a l p a i r s , a s i n g l e u n p a i r e d p a p i l l a on a n a l l i p , and 5 p o s t - a n a l p a i r s o f which the 4 t h p a i r i s l a t e r a l l y p o s i t i o n e d . Females - were not r e c e i v e d f o r e x a m i n a t i o n . D e s c r i p t i o n a c c o r d i n g to Chabaud and G o l v a n , 1957. A m p h i d e l p h i c . P o s t e r i o r o v a r y o r i g i n a t i n g i n c a u d a l r e g i o n , e x t e n d i n g a n t e r i o r l y to 6mm from c e p h a l i c end, t u r n i n g p o s t e r i o r l y and f o r m i n g the s e m i n a l v e s c i c l e about 2mm b e f o r e the v u l v a . A n t e r i o r o v a r y b e g i n n i n g 8mm from c e p h a l i c end, f o r m i n g a l o o p 5mm p o s t e r i o r l y , r e a c h i n g to 6mm from a n t e r i o r end, t u r n i n g p o s t e r i o r l y to the s e m i n a l v e s c i c l e s i t u a t e d 4mm b e h i n d the v u l v a . Eggs i n u t e r i t h i n s h e l l e d w i t h segmented p r o t o p l a s m a ; eggs .095 by .065 mm. Measurements - based on 4 males ( i n micrometers u n l e s s o t h e r w i s e s p e c i f i e d ) - T o t a l l e n g t h 11-21 (16)mm. Maximum w i d t h 480-630 (534). Oesophagus 1640-1984 (1808) i n c l u d i n g p h a r y n g e a l p o r t i o n 63-97 ( 7 7 ) . Nerve r i n g 460-570 ( 5 1 2 ) , e x c r e t o r y pore 1408-1914 (1658), and d e i r i d s 1135-1280 (1208) form a n t e r i o r end. R i g h t s p i c u l e s 530-675 (631) l o n g , l e f t s p i c u l e s 567-710 (621) l o n g , s p i c u l e w i d t h 41-51 ( 4 7 ) . Gubernaculum 68-100 (81) l o n g by 12-30 (21) wide i n l a t e r a l view. T a i l 390-450 (411). 22 D i s t a n c e from anus to psuedosucker 2171-3002 (2507). D i s t a n c e from anus t o j u n c t i o n w i t h vas d e f e r e n s 1224-1650 (1394). A n t e r i o r f l e x t u r e o f t e s t i s to p o s t e r i o r o f oesophageal b u l b 3342-4092 (3811). Comments: Megalobatrachonema t e r d e n t a t u m was f i r s t d e s c r i b e d by L i n s t o w (1890) from T r i t u r u s c r i s t a t u s i n Germany. Chabaud and G o l v a n (1957) d e s c r i b e d M. campanae from T. v u l g a r i s and T. a l p e s t r i s i n F r a n c e . H a r t w i c h (1960) r e d e s c r i b e d the type specimen o f M. t e r d e n t a t u m and synonymized the s p e c i e s w i t h C. campanae. However, a c c o r d i n g to H a r t w i c h ' s (1960) d e s c r i p t i o n , M. t e r d e n t a t u m d i f f e r s from M. campanae i n h a v i n g a more a n t e r i o r l y p o s i t i o n e d e x c r e t o r y pore and t e n ( r a t h e r t h a n e l e v e n ) c a u d a l p a p i l l a e p a i r s . E x a m i n a t i o n o f m a t e r i a l from France and C z e c h o s l o v a k i a i n the p r e s e n t s t u d y showed the e x c r e t o r y pore to be more a n t e r i o r i n s m a l l e r (presumably l e s s mature) specimens. Males from both l o c a l i t i e s had 11 p a i r s o f p a p i l l a e . The p a i r c l o s e s t to the anus i s d i f f i c u l t t o d i s c e r n and may have been o v e r l o o k e d by Harwich (1960). H i s synonymy i s a c c e p t e d h e r e i n . M a t e r i a l from T. v u l g a r i s i n C z e c h o s l o v a k i a t h a t Otcenasek (1957) d e s c r i b e d as S p i n i c a u d a sp. i s p r o b a b l y r e f e r r a b l e to M. t e r d e n t a t u m . M. t e r d e n t a t u m a r e d i s t i n g u i s h e d from o t h e r members o f the genus by the presence o f a pseudosucker, e l o n g a t e oesophageal isthmus and u n v a l v e d b u l b , and s l i g h t l y e l e v a t e d l i p s . 23 6. Megalobatrachonema w a l d e n i R i c h a r d s o n and Adamson, 1988 ( F i g u r e s 7 to 8) Host: Ambystoma g r a c i l e S i t e : Most worms were found i n the duodenum, however some were f u r t h e r p o s t e r i o r i n the i n t e s t i n e . L o c a l i t y : L i t t l e Cambell R i v e r , S u r r e y , B r i t i s h Columbia (type l o c a t i o n ) , G o l d i e Lake, Mt. Seymour, B.C., Whonnock Lake, B.C., M a r i o n Lake, UBC Research F o r e s t , B.C. Specimens d e p o s i t e d : US N a t i o n a l Museum Helm. C o l l . H o l o t y p e #79929 9 P a r a t y p e s and 4 specimens mounted f o r SEM #79930 Canadian N a t i o n a l Museum o f N a t u r a l S c i e n c e s . 8 P a r a t y p e s NMCP 1987-2315-2322. Museum n a t i o n a l d ' h i s t o i r e n a t u r e l l e , P a r i s . 8 P a r a t y p e s Ref. 190HC N539 Etymology: The new s p e c i e s i s named i n honour o f Mr. Frank C. Walden, f a t h e r o f the a u t h o r , i n r e c o g n i t i o n o f h i s c o n t i n u a l s u p p o r t and encouragement. D e s c r i p t i o n : G e n e r a l - S m a l l s l e n d e r worms w i t h prominent c e r v i c a l a l a e . C e r v i c a l a l a e b e g i n n i n g j u s t p o s t e r i o r t o l i p s r e a c h i n g maximum w i d t h about h a l f w a y t o nerve r i n g , g r a d u a l l y n a r r o w i n g a n t e r i o r to d e i r i d s and c o n t i n u i n g p o s t e r i o r l y to a n a l r e g i o n as low l a t e r a l a l a e . O r a l opening t r i a n g u l a r , surrounded by t h r e e 24 l i p s . Two s m a l l p a p i l l a e p r e s e n t on i n n e r edge o f each l i p . D o r s a l l i p b e a r i n g two d i s t i n c t o u t e r p a p i l l a e ; s u b v e n t r a l l i p s each w i t h s i n g l e o u t e r p a p i l l a , and median s m a l l e r p a p i l l a near amphid. A n t e r i o r end o f oesophagus m o d i f i e d to form one d o r s a l and two s u b v e n t r a l o n c h i a . Oesophagus l o n g , narrow and c l a v a t e . Corpus w i t h a n t e r i o r p h a r y n g e a l p o r t i o n ; j u n c t i o n between t h i s and r e s t o f c o r pus i n d i s t i n c t , r e c o g n i z e d by more g l a n d u l a r c y t o p l a s m . Prominent s w e l l i n g p r e s e n t a t p o s t e r i o r end o f c o r p u s . Isthmus d i s t i n c t l y n arrower t h a n r e s t o f oesophagus. B u l b e l o n g a t e , l a c k i n g v a l v e s . E x c r e t o r y pore l o c a t e d a t l e v e l o f a n t e r i o r end o f i s t h m u s , opening i n t o s i n u s v i a t e r m i n a l d u c t surrounded by s a c - l i k e v e s c i c l e . Two s u b - v e n t r a l g l a n d c e l l s o r i g i n a t i n g j u s t p o s t e r i o r to nerve r i n g , merging w i t h e x c r e t o r y system i n r e g i o n o f s i n u s and becoming i n d i s t i n c t 100 to 200 m icrometers p o s t e r i o r to oesophageal b u l b . L a t e r a l e x c r e t o r y c a n a l s not o b s e r v e d . Male -Caudal end c u r v e d v e n t r a l l y i n l a t e r a l view. C u t i c l e t h i c k e n e d p o s t e r i o r to phasmids i n v e n t r a l view. P r e - a n a l o b l i q u e m u s c u l a t u r e c o n s i s t i n g o f 25 t o 34 p a i r s , f a i n t l y demarcated from one a n o t h e r . Pseudosucker absent. Nine p a i r e d and one u n p a i r e d c a u d a l p a p i l l a e p r e s e n t , d i s t r i b u t e d as f o l l o w s : f i v e p a i r s p r e - a n a l s u b v e n t r a l ; prominent s i n g l e p a p i l l a on a n t e r i o r l i p o f anus; f o u r p a i r s p o s t - a n a l ( o f which 3rd l a s t p a i r l a t e r a l l y p o s i t i o n e d ) Phasmids between 3rd ( l a t e r a l ) and 4th p a i r p o s t - a n a l 25 p a p i l l a e . S p i c u l e s e q u a l , a l a t e , r o b u s t . Gubernaculum s m a l l , t a p e r e d towards i t s v e n t r a l e x t r e m i t y . T e s t i s o r i g i n a t i n g i n p o s t e r i o r r e g i o n o f worm, e x t e n d i n g a n t e r i o r l y t o w i t h i n 20-33% o f body l e n g t h from a n t e r i o r end, f l e x i n g p o s t e r i o r l y and c o n t i n u i n g v e n t r a l l y t o s e m i n a l v e s c i c l e . Female - V u l v a l o c a t e d i n p o s t e r i o r t h i r d o f body. Vag i n a muscular and a n t e r i o r l y d i r e c t e d . A m p h i d e l p h i c . One ov a r y b e g i n n i n g on v e n t r a l s i d e i n a n t e r i o r h a l f o f worm, c o n t i n u i n g a n t e r i o r l y t o w i t h i n 7-14% body l e n g t h from oesophageal b u l b , f l e x i n g and e x t e n d i n g t o p o s t e r i o r o f worm, f l e x i n g f i r s t a n t e r i o r l y , then p o s t e r i o r l y a t o v i d u c t ; o v i d u c t f l e x i n g a n t e r i o r l y , l e a d i n g t o a n t e r i o r l y d i r e c t e d u t e r u s . Other o v a r y o r i g i n a t i n g near rectum, e x t e n d i n g a n t e r i o r l y t o w i t h i n 8-13% body l e n g t h from o p p o s i t e o v a r y f l e x t u r e , f l e x i n g p o s t e r i o r l y and c o n t i n u i n g to o v i d u c t ; o v i d u c t f l e x i n g a n t e r i o r l y l e a d i n g t o u t e r u s . U t e r u s f l e x i n g p o s t e r i o r l y t o merge w i t h p o s t e r i o r u t e r u s a t v a g i n a . Eggs n e a r e s t v a g i n a t h i c k , s h e l l e d and a t s i n g l e - c e l l e d s t a g e . Measurements: Male (based on 5 specimens) - Length 10-17 (15) mm. Maximum w i d t h 192-347 (271). Oesophagus 1508-2050 (1783) w i t h c o r pus 1150-1502 (1352), i n c l u d i n g p h a r y n g e a l p o r t i o n 90-110 (103). Isthmus 150-288 ( 2 2 5 ) , b u l b 170-260 (207) l o n g by 110-146 (128) 26 wide. Nerve r i n g 428-582 (527) and e x c r e t o r y pore 1177-1626 (1451) from a n t e r i o r end. Maximum w i d t h c e r v i c a l a l a e 39-49 (4 1 ) . D e i r i d s 949-1369 (1204) from base o f l i p s . T a i l 233-320 (282) l o n g . A n t e r i o r f l e x u r e o f t e s t i s 1549-2060 (1745) p o s t e r i o r to oesophageal b u l b . J u n c t i o n w i t h vas d e f e r e n s 619-1221 (1007) from anus. R i g h t s p i c u l e 325-460 (404) l o n g by 23-30 (26) wide, l e f t s p i c u l e 310-430 (403) l o n g by 20-34 (25) wide; gubernaculum 70-95 (86) l o n g by 13-18 (15) wide i n l a t e r a l view. Female (based on 5 specimens) - Length 13-21 (17) mm. Width a t v u l v a 309-398 (351). Oesophagus 1596-2462 (2042) w i t h c o r pus 1162-1896 (1568), i n c l u d i n g p h a r y n g e a l p o r t i o n 112-131 (120). Isthmus 172-288 ( 2 2 9 ) , b u l b 192-321 (245) l o n g by 140-172 (155) wide. Nerve r i n g 481-681 (582) and e x c r e t o r y pore 1096-1946 (1606) from a n t e r i o r end. Maximum w i d t h o f c e r v i c a l a l a e 22-60 (4 4 ) . D e i r i d 870-1576 (1355) from base o f l i p s . T a i l 692-970 (792) l o n g . V a g i n a 238-438 (329) l o n g . V u l v a 4220-6616 (5379) from p o s t e r i o r e x t r e m i t y . D i s t a n c e from oesophageal b u l b to most a n t e r i o r o v a r i a n f l e x u r e 1135-2042 (1706). T o t a l egg number 200-667 ( 4 7 0 ) , eggs 63-85 (71) l o n g by 43-58 (49) wide. 27 Key to the s p e c i e s o f Megalobatrachonema l a . Oesophageal b u l b w i t h v a l v e s 2 b. Oesophageal b u l b w i t h o u t v a l v e s 3 2a. Oesophageal b u l b s p h e r i c a l , isthmus s w o l l e n , pseudosucker absent . . . . M. . g i g a n t i c u m b. Oesophageal b u l b l e s s s p h e r i c a l , isthmus e l o n g a t e , pseudosucker p r e s e n t . M. . nipponicum 3a. Pseudosucker p r e s e n t 4 b. Pseudosucker absent 5 4a. P o s t e r i o r c o r p us s l i g h t l y s w o l l e n , s p i c u l e s b r o a d l y winged, o n c h i a t h r e e - p r o n g e d M. elonqatum b. Onchia s i m p l e , corpus not s w o l l e n M. t e r d e n t a t u m 5a. D i s t i n c t p o s t e r i o r corpus s w e l l i n g , l a r g e c a u d a l a l a e p r e s e n t , l i p s r educed M. • w a l d e n i b. Corpus s w e l l i n g b a r e l y v i s i b l e , no c a u d a l a l a e , l i p s e l e v a t e d , c h e i l o s t o m a l t h i c k e n i n g v i s i b l e M..moraveci 28 FIELD AND LABORATORY OBSERVATIONS ON M. WALDENI P r e v a l e n c e and I n t e n s i t y Ambystoma g r a c i l e were sampled from f o u r l o c a t i o n s i n the lower m a i n l a n d o f B r i t i s h Columbia. O v e r a l l p r e v a l e n c e ( p r o p o r t i o n o f h o s t s i n f e c t e d ) ranged from 66 to 100% o f the a q u a t i c s t a g e s ( l a r v a e and n e o t e n i c s ) , w i t h mean i n t e n s i t i e s (number o f worms per i n f e c t e d h o s t ) from 1 to 14.5 (Appendix A). Transformed h o s t s were not i n f e c t e d . 63% (104 o f 164) o f l a r v a l h o s t s examined from the type l o c a l i t y i n S u r r e y were i n f e c t e d , and 100% (3 o f 3) n e o t e n i c h o s t s were i n f e c t e d . Mean i n t e n s i t y o f i n f e c t i o n was 3 worms per l a r v a l h o s t and 10 worms per n e o t e n i c h o s t . None o f the 4 t r a n s f o r m e d a d u l t s examined was i n f e c t e d . 66% (2 o f 3) l a r v a l h o s t s from G o l d i e Lake, Mt. Seymour were i n f e c t e d . Mean i n t e n s i t y was 14.5 worms per h o s t . The s i n g l e n e o t e n i c h o s t examined was i n f e c t e d w i t h a s i n g l e worm. A s i n g l e n e o t e n i c h o s t examined from Whonnock Lake c o n t a i n e d one worm.100% (9 o f 9) l a r v a l h o s t s from M a r i o n Lake were i n f e c t e d w i t h 11.3 worms per h o s t . A f r e q u e n c y d i s t r i b u t i o n o f h o s t l e n g t h i s shown i n F i g u r e 9. Mean h o s t s i z e i s 5.91 cm (N=139, SD=2.94). F i g u r e 10 g i v e s the fr e q u e n c y d i s t r i b u t i o n o f worm abundance (number o f worms per h o s t ) . The o v e r a l l mean i s 2.1 worms per h o s t (N=165, SD=2.87). 36% (59 o f 165) o f the h o s t s were u n i n f e c t e d . 54% (57 o f 106) o f i n f e c t e d h o s t s had one or 29 two worms. 16% (17 o f 106) harboured s i x or more worms. F i g u r e 11 shows a s c a t t e r p l o t o f the number o f worms per i n f e c t e d h o s t a g a i n s t h o s t s i z e (mean i n t e n s i t y = 3.27, N=106, SD=3.00). R e g r e s s i o n a n a l y s i s shows the number o f worms to be p o s i t i v e l y , but weakly c o r r e l a t e d (r2=0.1895) w i t h h o s t s i z e w i t h o n l y 19% o f the v a r i a b i l i t y i n worm number e x p l a i n e d by v a r i a t i o n i n h o s t s i z e . A s t u d y o f s e a s o n a l v a r i a b i l i t y a t the type l o c a l i t y i n S u r r e y , B.C. showed M. w a l d e n i to be p r e s e n t t h r o u g h o u t the y e a r . P r e v a l e n c e was l o w e s t i n May/June samples o f both y e a r s . ( F i g u r e 12). E s t i m a t e s o f worm burden ( i n t e n s i t y and abundance) show p a r a l l e l t r e n d s ( l o w e s t i n May/June, h i g h e s t i n M a r c h / A p r i l and l a t e summer and f a l l s a m p l e s ) . A l t h o u g h a n a l y s i s o f v a r i a n c e suggested mean v a l u e s d i f f e r e d between b i m o n t h l y samples ( F i g u r e 13), subsequent Tukey M u l t i p l e Comparison t e s t s f a i l e d to r e v e a l s i g n i f i c a n t d i f f e r e n c e s ( Z a r , 1982). G r a v i d females worms were o b s e r v e d from May to August. Immature worms were p r e s e n t i n g r e a t e s t numbers i n summer. The f o l l o w i n g i n v e r t e b r a t e s from the type l o c a l i t y were d i s s e c t e d to i n v e s t i g a t e the p o s s i b i l i t y o f an i n d i r e c t l i f e c y c l e : 77 Lymnaeidae and 17 P l a n o r b i d a e gastropods, 33 P i s i d i i d a e b i v a l v e s , 56 Gammaridae Crustacea, 6 G l o s s i p h o n i d a e a n n e l i d s , and 46 L i m n e p h i l i d a e , 9 C o r i x i d a e , 3 B a c t i d a e , 4 C h i r o n i m i d a e , 4 B e l o s t o m a t i d a e , 2 N o t o n e c t i d a e , 6 G i r i n i d a e , 2 P e r l i d a e , 23 Ephemeridae, 8 L i b e l l u l i d a e i n s e c t s . No M. w a l d e n i 30 were found. Development o f M. w a l d e n i i n ovo (measurements i n yum): Eggs o f g r a v i d M. w a l d e n i females were o v a l w i t h a t h i c k h y a l i n e s h e l l , and measured 63-85 (71) l o n g by 43-58 (49) wide (based on a sample o f 20 eg g s ) . Ova i n the u t e r u s were unsegmented ( F i g u r e 14 A) but de v e l o p e d r e a d i l y when i n c u b a t e d i n s t e r i l e pond water a t room temperature ( 1 9 O - 2 0 O C ) (B, C). A f t e r 3 days o f i n c u b a t i o n , l a r v a e were p r e s e n t (D) and a f t e r 4 days (E) l a r v a e were moving. Some eggs had hatched by day 5 (F) and h a t c h e d f i r s t s t a g e l a r v a e measured 260 l o n g by 20 wide. M o u l t i n g o c c u r r e d a p p r o x i m a t e l y 5 minutes a f t e r l a r v a e emerged (G) and second s t a g e l a r v a e measured 280 l o n g by 16 wide (H). They had round a n t e r i o r and p o i n t e d p o s t e r i o r ends, and the t i p of the t a i l was t h i c k e n e d . The oesophageal o u t l i n e was v i s i b l e . L a rvae d i d not d e v e l o p f u r t h e r a f t e r day 8. Dead l a r v a e were n o t i c e d on day 9 and by day 14 a l l l a r v a e were dead. L a r v a l A. g r a c i l e f e d second stage l a r v a e o f M. w a l d e n i was examined 18 days a f t e r i n f e c t i o n . No worms were found. DISCUSSION Most (63%) o f the A. g r a c i l e c o l l e c t e d i n t h i s s t u d y i n S u r r e y were i n f e c t e d w i t h Megalobatrachonema w a l d e n i . L a r v a l and n e o t e n i c s t a g e s o f the h o s t harboured the p a r a s i t e whereas t r a n s f o r m e d a d u l t s d i d not. A c c o r d i n g t o I n g l i s (1971) h o s t 31 s p e c i f i c i t y may have e c o l o g i c a l and p h y s i o l o g i c a l components. Absence o f M_;_ w a l d e n i from t r a n s f o r m e d a d u l t s i s l i k e l y because o f e c o l o g i c a l f a c t o r s (e.g. h a b i t a t , f e e d i n g p r e f e r e n c e s ) and not p h y s i o l o g i c a l s t a t e s i n c e d i f f e r e n c e s between n e o t e n i c and t r a n s f o r m e d a d u l t ambystomatids a r e l a r g e l y e c o l o g i c a l . I n f e c t i v e s t a g e s o f the p a r a s i t e a re presumably r e s t r i c t e d to a q u a t i c h a b i t a t s t o which t r a n s f o r m e d ambystomatids are exposed o n l y d u r i n g b r e e d i n g i n s p r i n g . A l t h o u g h M. w a l d e n i has o n l y been found i n A. q r a c i l e , i t i s not known whether i t i s r e s t r i c t e d t o t h i s h o s t . The s i n g l e a d u l t T a r i c h a g r a n u l o s a found i n the type l o c a l i t y o f M. w a l d e n i d i d not harbour t h i s p a r a s i t e but more d a t a a r e needed b e f o r e t h i s q u e s t i o n can be d e c i d e d . Other members o f the genus w i t h the e x c e p t i o n o f M. g i g a n t i c u m are h i g h l y h o s t s p e c i f i c . Megalobatrachonema w a l d e n i i s o v e r d i s p e r s e d i n i t s h o s t p o p u l a t i o n . Comparison o f the obser v e d f r e q u e n c y d i s t r i b u t i o n o f worm abundance t o a P o i s s o n d i s t r i b u t i o n based on the same mean ( F i g u r e 10) i n d i c a t e s t h a t t h e r e a re more h o s t s which a re u n i n f e c t e d ( 3 6 % ) , or i n f e c t e d w i t h 6 or more worms th a n would be e x p e c t e d i n a random d i s t r i b u t i o n . T h i s i s a r e l a t i v e l y common phenomenon i n p a r a s i t e s and may be caused by a v a r i e t y o f f a c t o r s . For example, h o s t s may d i f f e r i n t h e i r s u s c e p t i b i l i t y t o i n f e c t i o n because o f i m m u n o l o g i c a l o r b e h a v i o u r a l d i f f e r e n c e s . A l t e r n a t i v e l y , i n f e c t i v e s t a g e s o f the p a r a s i t e may themselves have a clumped d i s t r i b u t i o n , as commonly o c c u r s i n p a r a s i t e s w i t h i n t e r m e d i a t e h o s t s . 32 Ambystoma g r a c i l e are common i n r e t e n t i o n ponds o f the L i t t l e Cambell R i v e r i n S u r r e y , B r i t i s h Columbia. Transformed a d u l t s are t e r r e s t r i a l , l i v i n g a l o n g pond and r i v e r banks under m o i s t l e a f l i t t e r . They are d i f f i c u l t to s p o t and specimens c a p t u r e d i n the p r e s e n t s t u d y were found m i g r a t i n g a c r o s s roads to b r e e d i n g waters i n the e a r l y s p r i n g . Egg b a l l s , which are common i n l a t e March, take about one month to h a t c h and l a r v a e t a k e a p p r o x i m a t e l y one year to metamorphose ( a t 75-120 mm l e n g t h ) and two to t h r e e y e a r s to s e x u a l l y mature; n e o t e n i c l a r v a e are f a i r l y common (Green and C a m b e l l , 1984). Megalobatrachonema w a l d e n i were p r e s e n t t h r o u g h o u t the year i n the s t u d y a r e a but p r e v a l e n c e was l o w e s t i n May and June. At t h i s time o f year a c o h o r t o f y o u n g - o f - t h e - y e a r h o s t s have e n t e r e d the p o p u l a t i o n and t h e i r presence presumably a c c o u n t s f o r lower p r e v a l e n c e a t t h i s t i m e . Young-of-the-year Ambystoma become i n f e c t e d g r a d u a l l y d u r i n g the summer and a l l h o s t s over 8 cm i n l e n g t h were i n f e c t e d . There i s p r o b a b l y o n l y a s i n g l e g e n e r a t i o n o f M. w a l d e n i a y e a r . G r a v i d females were found o n l y i n s p r i n g and e a r l y summer, and immature worms were most p r e v a l e n t a t t h i s t ime. P r e v a l e n c e was h i g h e s t (over 90%) i n the f a l l , but female worms c o l l e c t e d a t t h i s time o f year were s u b g r a v i d . They presumably w i n t e r i n the h o s t and r e l e a s e eggs the f o l l o w i n g s p r i n g . Worms p r o b a b l y do not l i v e l o n g e r t h a n one year s i n c e n e o t e n i c h o s t s d i d not harbour g r a v i d female worms a f t e r the summer. Thus, h o s t s must become r e i n f e c t e d each s p r i n g . 33 Eggs o f M. w a l d e n i take 5-6 days to h a t c h . F i r s t - s t a g e l a r v a e d e v e l o p by the 6 t h day o f i n c u b a t i o n and the f i r s t moult o c c u r s s h o r t l y a f t e r h a t c h i n g . I n the l a b l a r v a e d i d not s u r v i v e p a s t 10 days. T h i s may be because they l a c k e d p r o p e r n u t r i e n t s , or f r e e - l i v i n g s t a g e s may be s h o r t - l i v e d , r e q u i r i n g an i n t e r m e d i a t e h o s t f o r f u r t h e r development. The o n l y o t h e r Megalobatrachonema s p e c i e s i n which p o s t e m b r y o n i c development has been s t u d i e d i s M^ . t e r d e n t a t u m . Barus and G r o s c h a f t (1962) noted t h a t l a r v a e moulted once i n  ovo s h o r t l y b e f o r e h a t c h i n g . I n agreement w i t h our o b s e r v a t i o n s on M_i_ w a l d e n i , f r e e - l i v i n g s t a g e s o f M_;_ t e r d e n t a t u m d i e d w i t h i n two weeks o f h a t c h i n g . However, the s e l a r v a e p e n e t r a t e d the mantle c a v i t y o f s n a i l s and remained a l i v e f o r s e v e r a l days. F u r t h e r m o r e , Barus and G r o s c h a f t (1962) r e c o v e r e d l a r v a e from the i n t e s t i n e o f Tr i t u r u s v u l g a r i s f e d l a r v a e hatched from eggs one to two days p r e v i o u s l y . Chabaud and P e t t e r (1971) s t u d y i n g the same worm were a b l e t o i n f e c t s n a i l s and o l i g o c h a e t e s w i t h l a r v a e hatched from the egg; they were u n s u c c e s s f u l i n t h e i r a t t e m p t s t o i n f e c t T r i t u r u s d i r e c t l y . Chabaud and P e t t e r (1971) i n t e r p r e t e d the l i f e c y c l e t o be heteroxenous w i t h an o b l i g a t e i n t e r m e d i a t e h o s t . They noted t h a t Barus and G r o s c h a f t (1962) d i d not s p e c i f y the sour c e o f t h e i r e x p e r i m e n t a l salamanders, and s u g g e s t e d t h a t they were n a t u r a l l y i n f e c t e d . Our s i n g l e attempt t o i n f e c t A_j_ q r a c i l e w i t h M_;_ w a l d e n i was u n s u c c e s s f u l and i s c o n s i s t e n t w i t h Chabaud and P e t t e r ' s (1971) h y p o t h e s i s t h a t the l i f e c y c l e i n the genus r e q u i r e s an i n t e r m e d i a t e h o s t . 34 No M. w a l d e n i was found i n i n v e r t e b r a t e s from the type l o c a l i t y , but p r e v a l e n c e o f the p a r a s i t e i n i n t e r m e d i a t e h o s t s may be low, and/or r e s t r i c t e d t o p a r t i c u l a r t i m e s o f y e a r . Data o f a more c i r c u m s t a n t i a l n a t u r e f u r t h e r s u p p o r t the s u g g e s t i o n t h a t the l i f e c y c l e o f Megalobatrachonema i n v o l v e s an i n t e r m e d i a t e h o s t . Thus, p a r a s i t i s m i n nematodes i s thought to be t e r r e s t r i a l i n o r i g i n ( I n g l i s , 1965; Anderson, 1984) w i t h the e a r l i e s t l i f e c y c l e s b e i n g monoxenous (Chabaud, 1955). P a r a s i t e s o f s t r i c t l y a q u a t i c h o s t s a re w i t h few e x c e p t i o n s heteroxenous ( I n g l i s , 1965; Anderson, 1984; Adamson, 1986). What i s known o f the l i f e h i s t o r y o f Megalobatrachonema agrees c l o s e l y w i t h l i f e h i s t o r i e s d e s c r i b e d i n the Q u i m p e r i i d a e : i . e . l a r v a e moult a t or around the time o f h a t c h i n g and f r e e - l i v i n g s t a g e s a r e s h o r t - l i v e (see Moravec, 1974). An i n t e r m e d i a t e h o s t i s p r e s e n t i n q u i m p e r i i d s . 35 PHYLOGENETIC ANALYSIS AND GENERAL DISCUSSION C h a r a c t e r A n a l y s i s 1. L i p f u s i o n Members o f Megalobatrachonema have t h r e e l i p s , one d o r s a l and two s u b v e n t r a l . Two c h a r a c t e r s t a t e s a re r e c o g n i z e d . I n M. w a l d e n i and M. moraveci the l i p s are d i s t i n c t l y s e p a r a t e d from one a n o t h e r . I n o t h e r members o f the genus and i n F a l c a u s t r a  mascula they a re f u s e d ( F i g u r e 15). The c h a r a c t e r s t a t e c o u l d not be det e r m i n e d f o r M. q i g a n t i c u m or M. nipponicum. P o l a r i z a t i o n o f t h i s c h a r a c t e r was based on f u n c t i o n a l outgroup compar i s o n . 0 = l i p s f u s e d 1 = l i p s s e p a r a t e 2. L i p e l e v a t i o n I n M. m o r a v e c i , M. t e r d e n t a t u m , and M. elongatum the c i r c u m o r a l t i s s u e forms an e l e v a t e d r i n g t h rough which nervous t i s s u e a s s o c i a t e d w i t h c e p h a l i c sense organs pas s e s . T h i s e l e v a t i o n i s not seen i n o t h e r members o f Megalobatrachonema ( F i g u r e s 1-8). 0 = c i r c u m o r a l t i s s u e u n e l e v a t e d 1 = c i r c u m o r a l t i s s u e e l e v a t e d 36 3. Onchia Onchia are t e e t h a r i s i n g from the oesopharhabdion and tend t o be reduced i n members o f Megalobatrachonema. The o n c h i a o f M. elonqatum are t h r e e - p r o n g e d ( F i g u r e 2) and t h i s i s i n t e r p r e t e d as an autapomorphy. 0 = o n c h i a s i m p l e 1 = o n c h i a t h r e e - p r o n g e d 4. C h e i l o s t o m a l t h i c k e n i n g C u t i c l e l i n i n g the i n s i d e s u r f a c e o f l i p s o f Megalobatrachonema moraveci i s h i g h l y s c l e r o t i z e d ( F i g u r e 4 ) . T h i s t h i c k e n i n g i s not homologous w i t h the c h e i l o s t o m a l r i n g d e s c r i b e d by I n g l i s (1966). 0 = c h e i l o s t o m a l t h i c k e n i n g p r e s e n t 1 = c h e i l o s t o m a l t h i c k e n i n g absent 5. C h e i l o s t o m a l r i n g A r i n g o f dense c u t i c l e a t the l e v e l o f the j u n c t i o n o f the oesophagus and c h e i l o s t o m e i s p r e s e n t i n members o f the K a t h l a n i i d a e , F a l c a u s t r a , and M. nipponicum and M. g i g a n t i c u m . 0 = c h e i l o s t o m a l r i n g p r e s e n t 1 = c h e i l o s t o m a l r i n g absent 6. Pharynx Members o f the K a t h l a n i i d a e and Cosmocercidae have a d i s t i n c t muscular p h a r y n g e a l r e g i o n . T h i s a r e a i s p o o r l y 37 demarcated from the r e s t o f the corpus i n members o f Megalobatrachonema e x c e p t f o r M. g i g a n t i c u m and M. nipponicum ( F i g u r e s 1-8). 0 = p h a r y n g e a l a r e a s e p a r a t e d from corpus and muscular 1 = p h a r y n g e a l a r e a shows l i t t l e d i s t i n c t i o n from r e s t o f corpus 7. Corpus I n M. w a l d e n i the p o s t e r i o r end o f the corpus i s e n l a r g e d ( F i g u r e 7 ) . T h i s i s seen to a l e s s e r e x t e n t i n M. moraveci ( F i g u r e 5) and M. elongatum ( F i g u r e 2 ) . Members o f the outgroups do not e x h i b i t t h i s s w e l l i n g and i t i s c o n s i d e r e d apomorphic. 0 = c o r p u s s w e l l i n g a b s e nt 1 = corpus s w e l l i n g p r e s e n t 8. Isthmus The isthmus s e p a r a t e s the corpus from the oesophaeal b u l b . I t i s s w o l l e n i n F a l c a u s t r a and most members o f the K a t h l a n i i d a e , but i s narrow and e l o n g a t e i n s p e c i e s o f Megalobatrachonema, e x c e p t M. g i g a n t i c u m ( F i g u r e s 1-8). 0 = isthmus s w o l l e n 1 = isthmus e l o n g a t e 9. Oesophageal b u l b shape The oesophageal b u l b i s round i n most K a t h l a n i i d a e , 38 Cosmocercidae, and i n M. g i g a n t i c u m and M. nipponicum. I n o t h e r s p e c i e s o f Megalobatrachonema the b u l b i s e l o n g a t e ( F i g u r e s 1-8) . 0 = b u l b s p h e r i c a l 1 = b u l b e l o n g a t e 10. Oesophageal b u l b v a l v e s I n M. nipponicum and M. g i g a n t i c u m t h e r e are c u t i c u l a r v a l v e s i n the oesophageal b u l b ; i n o t h e r Megalobatrachonema s p e c i e s these are absent. V a l v e s are p r e s e n t i n Cosmocercidae, F a l c a u s t r a , and o t h e r K a t h l a n i d s , and t h e i r presence i s c o n s i d e r e d p l e s i o m o r p h i c . 0 = oesophageal b u l b w i t h v a l v e s 1 = oesophageal b u l b w i t h o u t v a l v e s 11. Oesophageal b u l b s t r u c t u r e The oesophageal b u l b i s muscular i n K a t h l a n i d s and i n C o s m o c e r c i d s , but i s more g l a n d u l a r i n Megalobatrachonema. 0 = muscular b u l b 1 = g l a n d u l a r b u l b 39 12. C e r v i c a l a l a e Large c u t i c u l a r a l a e were found i n the c e r v i c a l r e g i o n i n M. w a l d e n i . ( F i g u r e 9 ) . These are absent from o t h e r K a t h l a n i d s and C o s m o c e r c i d s , and are t r e a t e d as an autapomorphy. 0 = c e r v i c a l a l a e absent 1 = c e r v i c a l a l a e p r e s e n t 13. L a t e r a l a l a e Low l a t e r a l a l a e are p r e s e n t i n M. w a l d e n i and M. m oraveci but are absent i n o t h e r s p e c i e s o f Megalobatrachonema• P o l a r i z a t i o n o f t h i s c h a r a c t e r was based on f u n c t i o n a l outgroup comparison. 0 = l a t e r a l a l a e a b s ent 1 = l a t e r a l a l a e p r e s e n t 14. S p i c u l e shape The s p i c u l e s o f M. g i g a n t i c u m and M. nipponicum are s l e n d e r whereas those o f M. elongatum are broad ( F i g u r e s 1-8). S p i c u l e w i d t h i s e x p r e s s e d as a p e r c e n t a g e o f s p i c u l e l e n g t h . T h i s c h a r a c t e r i s t r e a t e d as an unordered t r a n s f o r m a t i o n s e r i e s . 0 = 6-9% 1 = <5% 2 = >10% 40 15. Gubernaculum, d o r s a l end The gubernaculum i s an a c c e s s o r y c o p u l a t o r y s t r u c t u r e which a i d s i n g u i d i n g the s p i c u l e s . P r i m i t i v e l y the gubernaculum i s s i m p l e w i t h s t r o n g c h i t i n i z a t i o n . M. g i g a n t i c u m d i f f e r s w i t h a rounded d o r s a l end ( F i g u r e 3) and t h i s i s i n t e r p r e t e d as an autapomorphy. 0 = gubernaculum w i t h s i m p l e d o r s a l end 1 = gubernaculum w i t h rounded d o r s a l end 16. Gubernaculum, v e n t r a l end M. moraveci d i f f e r s from o t h e r members o f because o f the c h a r a c t e r i s t i c hook shape on the end o f the gubernaculum ( F i g u r e 5 ) . 0 = gubernaculum w i t h s i m p l e v e n t r a l end 1 = gubernaculum w i t h hooked v e n t r a l end 17. Pseudosucker A l t h o u g h the presence o f one or more p s e u d o s u c k e r ( s ) i s common i n members o f the K a t h l a n i i d a e , they a re absent i n most Cosmocercidae, and may be p r e s e n t or absent i n F a l c a u s t r a . Of the Megalobatrachonema s t u d i e d , M. nipponicum, M. t e r d e n t a t u m , and M. elongatum have pseudosuckers ( F i g u r e s 1-8). T h i s i s p o l a r i z e d by the f u n c t i o n a l outgroup method. 0 = pseudosucker absent 1 = pseudosucker p r e s e n t the genus p o i n t e d v e n t r a l 41 18. Eggs Eggs i n u t e r o a re undeveloped i n a l l members o f Megalobatrachonema e x c e p t M. elongatum ( F i g u r e s 1-8) 0 = eggs undeveloped 1 = eggs segmented 19. Caudal p a p i l l a Caudal p a p i l l a e a r e s e n s o r y s t r u c t u r e s i n the male which presumably a i d i n c o p u l a t i o n . P r i m i t i v e l y t h e r e a re 10 p a i r s (2 l a t e r a l and 8 s u b v e n t r a l ) and 1 u n p a i r e d p a p i l l a on the l i p o f the anus. T h i s s t a t e i s found i n M. nipponicum, many F a l c a u s t r a s p e c i e s , o t h e r c o s m o c e r c o i d s , and even many f r e e - l i v i n g nematodes (Chabaud and P e t t e r , 1961). E l e v e n p a p i l l a e p a i r s a r e found i n M. g i g a n t i c u m , i n which an e x t r a l a t e r a l p a i r d e v e l o p s , and i n M. elongatum and M. t e r d e n t a t u m , i n which an e x t r a s u b v e n t r a l p a i r d e v e l o p s . Twelve p a i r s are found i n M. moraveci w i t h the f u r t h e r a d d i t i o n o f an e x t r a s u b v e n t r a l p a i r . Loss o f a l a t e r a l p a i r from the p l e s i o m o r p h i c s t a t e r e s u l t s i n the n i n e p a i r s found i n M. w a l d e n i ( F i g u r e 16). T h i s c h a r a c t e r i s t r e a t e d as an unordered t r a n s f o r m a t i o n s e r i e s . 0 = 10 p a p i l l a e p a i r s 1 = 11 p a p i l l a e p a i r s , e x t r a l a t e r a l p a i r 2 = 11 p a p i l l a e p a i r s , e x t r a s u b v e n t r a l p a i r 3 = 12 p a p i l l a e p a i r s , a d d i t i o n o f e x t r a s u b v e n t r a l p a i r 4 = 9 p a p i l l a e p a i r s , l o s s o f l a t e r a l p a i r 42 20. Caudal p a p i l l a e m i g r a t i o n Three p a i r s o f s u b v e n t r a l p a p i l l a e are l o c a t e d j u s t a n t e r i o r t o , or a t the l e v e l o f the anus i n Megalobatrachonema• I n M. elongatum these t h r e e p a i r s have m i g r a t e d p o s t e r i o r to the anus and are t r e a t e d as an autapomorphy ( F i g u r e 16). 0 = t h r e e s u b v e n t r a l p a p i l l a e p a i r s a t , or a n t e r i o r to anus 1 = t h r e e s u b v e n t r a l p a p i l l a e p a i r s p o s t e r i o r to anus 21. E x c r e t o r y g l a n d c e l l s Megalobatrachonema have a t u b u l a r "H1 type e x c r e t o r y system (see Lee 1970) c h a r a c t e r i z e d by l a t e r a l c a n a l s , a s i n u s , and t e r m i n a l d u c t t h a t opens v e n t r a l l y through an e x c r e t o r y pore and two l a r g e , e l o n g a t e s u b v e n t r a l g l a n d c e l l s ( F i g u r e 16). I n o t h e r nematodes i n which such an e x c r e t o r y system have been d e s c r i b e d , the g l a n d c e l l e x t e n d p o s t e r i o r l y from the l e v e l o f the e x c r e t o r y pore. I n Megalobatrachonema s p e c i e s examined h e r e i n ( w i t h the e x c e p t i o n o f M. g i g a n t i c u m ) the g l a n d c e l l s e x t e n d a n t e r i o r l y to near the l e v e l o f the nerve r i n g . F i g u r e 17 shows the g l a n d c e l l s o f M. w a l d e n i w h i l e F i g u r e 7 i n d i c a t e s t h e i r e x t e n t . 0 = s u b v e n t r a l g l a n d c e l l s not e x t e n d i n g to l e v e l o f nerve r i n g 1 = s u b v e n t r a l g l a n d c e l l s e x t e n d i n g to l e v e l o f nerve r i n g 43 The Cladogram P h y l o g e n e t i c a n a l y s i s o f Megalobatrachonema was based on 21 m o r p h o l o g i c a l c h a r a c t e r s (25 apomorphic c h a r a c t e r s t a t e s ) which are summarized i n a d a t a m a t r i x (Appendix C ) . P o l a r i z a t i o n o f c h a r a c t e r s was d e t e r m i n e d by outgoup comparison w i t h a composite F a l c a u s t r a outgroup. T h i s outgroup was chosen based on an h y p o t h e s i s by Baker (1980) i n which F a l c a u s t r a i s c o n s i d e r e d the a n c e s t r a l group to Megalobatrachonema. Disagreement c o n c e r n i n g the taxonomic placement o f the genus makes the c h o i c e o f outgroup p r o b l e m a t i c but cladograms c o n s t r u c t e d u s i n g o t h e r o u t g roups (e.g. composite c o s m o c e r c i d , o x y a s c a r i d i d or even s p i r u r i d o u t g r o u p s ) have the same t o p o l o g y a l t h o u g h the c o n s i s t e n c y index may be lower. A s i n g l e cladogram was produced ( F i g u r e 18) w i t h a c o n s i s t e n c y index o f 92.6%. Homoplasy i n the cladogram i n v o l v e s two r e v e r s a l s : e l e v a t e d l i p s ( c h a r a c t e r 2) a r i s e s i n the s i s t e r group o f M. nipponicum and d i s a p p e a r s w i t h M. w a l d e n i ; the pseudosucker ( c h a r a c t e r 17) a r i s e s i n the s i s t e r group o f M. q i q i a n t i c u m and d i s a p p e a r s a t the branch l e a d i n g t o M. w a l d e n i and M. m o r a v e c i . D i a g n o s i s o f Megalobatrachonema by Yamaguti (1941) was based on presence o f a t a p e r e d body, smooth c u t i c l e , s m a l l mouth w i t h i n d i s t i n c t l i p s , s h o r t p h a r y n g e a l a r e a , l o n g narrow corpus w i t h a s i m p l e b u l b , and l a c k o f l a t e r a l a l a e . Chabaud (1978) based h i s d i a g n o s i s on the presence o f s m a l l c e p h a l i c 44 l i p s and a reduced oesophageal isthmus and b u l b . C h a r a c t e r s used i n t h e s e d i a g n o s e s are vague and the p r e s e n t p h y l o g e n e t i c a n a l y s i s i n d i c a t e s t h a t monophyly o f Megalobatrachonema i s i n d i c a t e d by two synapomorphies - the g l a n d u l a r oesophageal b u l b and the prominent a n t e r i o r e x t e n s i o n to the e x c r e t o r y g l a n d c e l l s . F r e i t a s (1958) proposed Chabaudgolvania w i t h t o accomodate s p e c i e s f o r m e r l y a s s i g n e d to Megalobatrachonema i n which c u t i c u l a r v a l v e s were l a c k i n g i n the oesophagus. Chabaud (1978) t r e a t e d the genus as a synonym o f Megalobatrachonema but Baker (1986) d i v i d e d the genera between subgenera M. (Megalobatrachonema) and M. (Chabaudgolvania) based on presence or absence o f oesophageal v a l v e s . The phylogeny proposed h e r e i n does not s u p p o r t t h i s d i v i s i o n because t h e r e are no unique synapomorphies d e f i n i n g M. nipponicum and M. g i g a n t i c u m as a m o n o p h y l e t i c group. 45 Comparison w i t h Host Phylogeny and Zoogeography The h y p o t h e s i z e d phylogeny f o r Megalobatrachonema ( F i g u r e 18) was compared to a c u r r e n t h o s t phylogeny e s t a b l i s h e d by Duellman and Trueb ( F i g u r e 19 A ) . S u b s t i t u t i n g h o s t t a x a onto the p a r a s i t e cladogram shows two i n s t a n c e s o f incongruence ( F i g u r e 19 B) - M. g i g a n t i c u m , which o c c u r s i n Anura and Ambystomatidae, and M. m o r a v e c i , which o c c u r s i n the Salamandridae. Megalobatrachonema spp. are e s s e n t i a l l y p a r a s i t e s o f Caudata and the occurence o f M^ g i g a n t i c u m i n Anura i s e x c e p t i o n a l . I t i s u n l i k e l y t h a t t h i s r e p r e s e n t s a case o f a c c i d e n t a l p a r a s i t i s m (e.g. from f r o g s i n g e s t i n g i n f e c t e d salamanders) s i n c e the p a r a s i t e has been r e c o r d e d s e v e r a l times from anuran h o s t s ( O l s e n , 1938; P a r r y and Grundman, 1965; W a i t z , 1961) and from ambystomatids o n l y once ( P a r r y and Grundman, 1965). The presence o f the p a r a s i t e i n ambystomatids may be the r e s u l t o f h o s t t r a n s f e r from anuran h o s t s . Megalobatrachonema moraveci o c c u r s i n the s a l a m a n d r i d . T a r i c h a g r a n u l o s a but i s most c l o s e l y r e l a t e d to M_;_ w a l d e n i from ambystomatids. The most p a r s i m o n i o u s e x p l a n a t i o n f o r t h i s i s t h a t M^ moraveci a r o s e through a h o s t t r a n s f e r from ambystomatids. Megalobatrachonema moraveci and M.waldeni are the most d e r i v e d members o f the genus and t h e i r ranges i n B r i t i s h Columbia o v e r l a p . I t i s unknown i f mainland T a r i c h a are i n f e c t e d w i t h M. w a l d e n i (and i f Vancouver I s l a n d Ambystoma are 46 i n f e c t e d w i t h M. m o r a v e c i ) . Biogeography o f the Caudata i s c l o s e l y a s s o c i a t e d w i t h the break-up o f Pangaea. The a n c e s t r a l salamander s t o c k was a s s o c i a t e d w i t h L a u r a s i a . A c c o r d i n g to Duellman and Trueb (1986) t h i s a n c e s t r a l s t o c k may have d i v i d e d i n i t i a l l y d u r i n g the s p l i t t i n g o f L a u r a s i a as the N o r t h A t l a n t i c ocean formed -an A s i a n s t o c k g i v i n g r i s e to the K a r a u r o i d e a ( e x t i n c t ) and the Euramericana s t o c k g i v i n g r i s e t o p r e s e n t - d a y f a m i l i e s . Three o f these f a m i l i e s are o f i n t e r e s t i n t h i s s t u d y - the C r y p t o b r a n c h i d a e , the Salamandridae, and the Ambystomatidae. The C r y p t o b r a n c h i d a e o c c u r i n s o u t h e a s t e r n N o r t h America, s o u t h e a s t e r n C h i n a and Japan, but are thought to have been r e s t r i c t e d t o N o r t h America a t one t i m e . I n t r o d u c t i o n to A s i a p r o b a b l y o c c u r r e d i n the e a r l y C r e t a c e o u s as the Kolyma B l o c k (a p l a t e t h a t r i f t e d from N o r t h America and d r i f t e d westward) c o l l i d e d w i t h e a s t e r n A s i a (Duellman and Trueb, 1986). The C r y p t o b r a n c h i d a e o f today t h e r e f o r e r e p r e s e n t an a n c i e n t r e l i c group. The o l d e s t f o s s i l Salamandridae i n Europe ( T r i t u r i s ) date from the Eocene i n d i c a t i n g d i f f e r e n t i a t i o n o c c u r r e d d u r i n g the e a r l y C e n o z o i c . S a l a m a n d r i d f o s s i l s i n N o r t h America date back to the l a t e O l i g o c e n e i n d i c a t i n g they are more r e c e n t than t h e i r European r e l a t i v e s ; c o l o n i z a t i o n o f N o r t h America was l i k e l y v i a B e r i n g i a . The Ambystomatidae and P l e t h o d o n t i d a e are the most r e c e n t l y e v o l v e d f a m i l i e s . F o s s i l e v i d e n c e s u g g e s t s the 47 Ambystomatidae d a t e s back o n l y as f a r as the O l i g o c e n e . A c c o r d i n g t o Duellman and Trueb (1986) c e n t e r s o f d i f f e r e n t i a t i o n f o r the group are i n s o u t h e a s t e r n N o r t h America and a l o n g the s o u t h e r n edge o f the Mexican p l a t e a u . D i s p e r s a l i n t o B r i t i s h Columbia may have come from Mexico, f o l l o w i n g p l e i s t o c e n e g l a c i a l r e t r e a t . The s p o t t y d i s t r i b u t i o n o f Megalobatrachonema w i t h i n the Caudata c o u l d be due to a l a c k o f s a m p l i n g , d i s j u n c t d i s t r i b u t i o n s o f the h o s t s , or p h y s i o l o g i c a l or e c o l o g i c a l c o n s t r a i n t s p r e s e n t e d by the h o s t . The l a t t e r e x p l a n a t i o n i s most l i k e l y t r u e f o r the more t e r r e s t r i a l f a m i l i e s o f salamanders such as the P l e t h o d o n t i d a e , s i n c e the l i f e c y c l e o f Megalobatrachonema i s a q u a t i c . The p r e s e n t - d a y d i s t r i b u t i o n f o r Megalobatrachonema i s shown i n F i g u r e 21. An a r e a cladogram can be produced by s u b s t i t u t i n g the a r e a name f o r the p a r a s i t e t a x o n (see i n s e t A). There i s agreement between t h i s and the a r e a cladogram shown i n i n s e t B. Megalobatrachonema g i g a n t i c u m i s o m i t t e d s i n c e i t s presence i n Anurans and Ambystoma i s l i k e l y the r e s u l t o f a " c a p t u r e " from a more a n c i e n t h o s t group. S i n c e e v o l u t i o n o f the Caudata was r e s t r i c t e d t o L a u r a s i a , whereas anurans e v o l v e d a t an e a r l i e r time t h r o u g h o u t Pangaea ( l a t e T r i a s s i c / e a r l y J u r a s s i c ) , i t seems r e a s o n a b l e t h a t anuran p a r a s i t e s , such as M. g i g a n t i c u m , a re widespread and l e s s h o s t - s p e c i f i c . The congruence t h a t e x i s t s between the r e m a i n i n g h o s t s and p a r a s i t e s i n d i c a t e s t h e i r d i s t r i b u t i o n i s due to 48 c l o s e h i s t o r i c a l a s s o c i a t i o n r a t h e r than d i s p e r s a l e v e n t s . 49 CONCLUSION I n c o n c l u s i o n , Megalobatrachonema i s a m o n o p h y l e t i c genus based on the synapomorphies o f a g l a n d u l a r oesophageal b u l b and p resence of a l a r g e a n t e r i o r e x t e n s i o n o f the e x c r e t o r y g l a n d c e l l s . D i v i s i o n o f the genus i n t o subgenera i s s u p p r e s s e d s i n c e M. (Megalobatrachonema) i s p a r a p h y l e t i c . E v o l u t i o n o f the genus has i n v o l v e d a t l e a s t 2 i n s t a n c e s o f h o s t s w i t c h i n g a c c o r d i n g to comparison o f h o s t and p a r a s i t e p h y l o g e n i e s . Megalobatrachonema g i g a n t i c u m i s the most p r i m i t i v e member of the genus and shows the l e a s t h o s t - s p e c i f i c i t y ; i t s presence i n salamanders i s p r o b a b l y due to h o s t c a p t u r e i n an a q u a t i c environment. Megalobatrachonema  moraveci may r e p r e s e n t a r e c e n t l y - e v o l v e d s p e c i e s . B i o g e o g r a p h i c a l a n a l y s i s i n d i c a t e s d i s t r i b u t i o n o f s p e c i e s ( e x c e p t M. g i g a n t i c u m ) i s due to s p e c i a t i o n i r i s i t u r a t h e r than d i s p e r s a l . I n v e s t i g a t i o n o f the l i f e c y c l e o f M. w a l d e n i shows t h a t i n f e c t i o n o f h o s t s o c c u r s i n s p r i n g and summer. Eggs r e l e a s e d i n t o the environment h a t c h r e l e a s i n g l a r v a e which moult. I t i s not known i f an i n t e r m e d i a t e h o s t i s o b l i g a t o r y . Worms a p p a r e n t l y w i n t e r i n the d e f i n i t i v e h o s t and are l o s t a t metamorphos i s . 50 F i g u r e 1. Megalobatrachonema nipponicum Yamaguti, 1941 ( a f t e r Yamaguti, 1941). (A) A n t e r i o r e x t r e m i t y of female, l a t e r a l view. (B) P o s t e r i o r e x t r e m i t y of male, l a t e r a l view. (C) P o s t e r i o r e x t r e m i t y of female, l a t e r a l view. 52 F i g u r e 2. Megalobatrachonema elonqatum ( B a i r d , 1958) Baker, 1986. (A) C e p h a l i c e x t r e m i t y , v e n t r a l view. (B) S u b v e n t r a l view showing oesophagus. (C) Caudal end o f male, l a t e r a l view. (D) Egg. 53 54 F i g u r e 3. Megalobatrachonema g i g a n t i c u m ( O l s e n , 1938) Baker, 1980. (A) C e p h a l i c e x t r e m i t y , v e n t r a l view. (B) S u b v e n t r a l view showing oesophagus. (C) Caudal end o f male, l a t e r a l view. (D) E g g . 5 S 56 F i g u r e 4 . Megalobatrachonema moraveci n. sp. (A) Female r e p r o d u c t i v e t r a c t . (B) Egg. (C) C e p h a l i c e x t r e m i t y , a p i c a l view. (D) C e p h a l i c e x t r e m i t y , o p t i c a l s e c t i o n o f a p i c a l view. (E) C e p h a l i c e x t r e m i t y , v e n t r a l view. (F) C e p h a l i c e x t r e m i t y , l a t e r a l view. (G) Caudal end o f female, l a t e r a l view. (H) E x c r e t o r y system, l a t e r a l view. 5 7 58 F i g u r e 5. Megalobatrachonema moraveci n.sp. (A) Gubernaculum, l a t e r a l view. (B) S p i c u l e and gubernaculum, l a t e r a l view. (C) E n t i r e worm, male. (D) Caudal end o f male, v e n t r a l view. (E) V e n t r a l view showing p o s i t i o n o f nerve r i n g , d e i r i d s , n a r r o w i n g o f i s t h m u s , and e l o n g a t e oesophageal b u l b . (F) Caudal end o f male, l a t e r a l view. 60 F i g u r e 6. Megalobatrachonema t e r d e n t a t u m ( L i n s t o w , 1890) Harwic h , 1960. (A) V e n t r a l view showing oesophagus. (B) C e p h a l i c e x t r e m i t y , v e n t r a l view. (C) Caudal end o f male. 61 62 F i g u r e 7. Megalobatrachonema w a l d e n i n.sp. (A) V e n t r a l view showing c e r v i c a l a l a e , p o s i t i o n o f d e i r i d s , s u b v e n t r a l g l a n d c e l l s , and c l u b - s h a p e d oesophagus. (B) C e p h a l i c e x t r e m i t y , a p i c a l view. (C) C e p h a l i c e x t r e m i t y , l a t e r a l view. (D) E x c r e t o r y system, l a t e r a l view. 6 3 64 F i g u r e 8. Megalobatrachonema w a l d e n i n (A) Female r e p r o d u c t i v e t r a c t . (B) Caudal end o f female, l a t e r a l view (C) Egg. (D) E n t i r e worm, male. (E) Caudal end o f male, l a t e r a l view. (F) Caudal end o f male, v e n t r a l view. 6 5 66 F i g u r e 9. Graph showing f r e q u e n c y d i s t r i b u t i o n f o r s i z e o f h o s t A_. g r a c i l e h a r b o u r i n g M. w a l d e n i . Number of A. g r d c i l e o 1 ro O O o CP z CD O —* o" Z 9 68 F i g u r e 10. Graph showing f r e q u e n c y d i s t r i b u t i o n o f M. w a l d e n i abundance i n h o s t A. g r a c i l e . 60 50-Host frequency — observed D Poi : isson 40-30-20-10 • 3 4 5 6 7 8 9 10 Number of Worms per Host 12 13 14 15 16 17 18 19 70 F i g u r e 11. S c a t t e r p l o t o f number o f worms per h o s t v e r s u s h o s t s i z e (cm). Number of Worms o o o o I L 72 F i g u r e 12. Graph showing p r e v a l e n c e o f M.waldeni i n l a r v a l and n e o t e n i c A. q r a c i l e from S u r r e y , B.C. (sample s i z e i s i n d i c a t e d a t the top o f each b a r ) . 1.00 -12 0,9 0 0.80 0. 70 -0.60 _ 0.5 0 0.40 0. 30 0. 20 . 0.1 0 -15 4 7 37 16 I 4 Mar/Apr May/Jun JulAug 1986 Sep/Oct Nov/Oec Jarvfeb Mai/Apr May/Jun Jul/Aug Sep/Oct 1987 Month 74 F i g u r e 13. Graph showing mean i n t e n s i t y o f M. w a l d e n i i n l a r v a l and n e o t e n i c A. q r a c i l e from S u r r e y , B.C. ( c o n f i d e n c e l i m i t s i n d i c a t e d ) . Mean Intensity (worms per infected host) ro o W o o o cT> O O CD o to o o o c CD c CO CD TD O o 1 CD O a CD cr CD Q oo c : c CO CD •o \ O o 76 F i g u r e 14. Stages o f development f o r M. w a l d e n i . (A) Egg i n u t e r u s . (B) 24 hours a f t e r removal from u t e r u s . (C) Day 2. (D) Day 3. (E) Day 4. (F) Day 5. (G) Emerging l a r v a , day 5. (H) Day 6 l a r v a . 7 7 78 F i g u r e 15. Scanning E l e c t r o n M i c r o s c o p y . 1. Megalobatrachonema t e r d e n t a t u m - a p i c a l view (scale=40 urn). 2. M. elongatum - a p i c a l view (scale=40 urn). 3. M. moraveci - a p i c a l view (scale=40 urn). 4. F a l c a u s t r a mascula - a p i c a l view (scale=20 urn). 5. M. w a l d e n i - a p i c a l view (scale=20 urn). 6. M. w a l d e n i - v e n t r a l view showing c e r v i c a l a l a e (scale=100 urn). 7 9 80 F i g u r e 16. Schematic o f c a u d a l p a p i l l a e arrangement. (a) M. nipponicum. (b) M. elongatum. (c) M. g i g a n t i c u m . (d) M_. m o r a v e c i . (e) M. t e r d e n t a t u m ( f ) M. w a l d e n i . 8 I % @@© © © © ^ @ © © i) ^ 82 F i g u r e 17. T r a n s m i s s i o n E l e c t r o n M i c r o s c o p y (1) S e m i - t h i n c r o s s s e c t i o n o f M. w a l d e n i showing s u b v e n t r a l e x c r e t o r y g l a n d c e l l (G), oesophagus ( 0 ) , and e x c r e t o r y s i n u s (S) (scale=50 um). (2) S e r i a l s e c t i o n o f M. w a l d e n i showing s u b v e n t r a l e x c r e t o r y g l a n d c e l l (G) and oesophagus (0) (scale=10 um). 8 3 84 F i g u r e 18. Cladogram showing h y p o t h e t i c a l phylogeny f o r Megalobatrachonema s p e c i e s . 8 5 86 F i g u r e 19. (A) Cladogram o f c u r r e n t h o s t phylogeny a f t e r Duellman and Trueb, 1986. (B) Cladogram showing h o s t t a x a s u b s t i t u t e d on p a r a s i t e phylogeny. > Anurans 8 Ambystomatidae Cryptobranchidae Salamandridae Ambystomatidae Ambystomatidae Salamandridae Sirenidae Hynobiidae Cryptobranchidae Proteidae Dicamptodontidae a> Amphiumidae Salamandridae Ambystomatidae Plethodontidae 88 F i g u r e 20. Map showing p r e s e n t - d a y d i s t r i b u t i o n f o r Megalobatrachonema. I n s e t A - Area cladogram e s t a b l i s h e d by s u b s t i t u t i n g d i s t r i b u t i o n s onto p a r a s i t e phylogeny. I n s e t B - Cladogram o f d i s t r i b u t i o n a r e a s i n v o l v e d based on h i s t o r i c a l o r i g i n s . ^ w ro ° H I <Q ^ o 3-0 2 2. o ^ Q O C 1 I I 3 USA JAPAN EUROPE MEXICO CANADA CANADA JAPAN EUROPE MEXICO CANADA 6 9 90 REFERENCES Adamson, M.L. 1986. Modes o f t r a n s m i s s i o n and e v o l u t i o n o f l i f e h i s t o r i e s i n z o o p a r a s i t i c nematodes. Can. J . Z o o l . 64:1375-1384. Anderson, R.C. 1984. The o r i g i n s o f z o o p a r a s i t i c nematodes. Can. J . Z o o l . 62:317-328. B a i r d , W. 1858. D e s c r i p t i o n o f two new s p e c i e s o f E n t ozoa. P r o c . Z o o l . Soc. London 26:224-225. Baker, M.R. 1980. R e c l a s s i f i c a t i o n o f Oxysomatium i n q l i s i Anderson, 1964 and A p l e c t a n a g i g a n t i c a O l s e n , 1938 (Nematoda:Cosmocercoidea) from N o r t h American F r o g s . S y s t . P a r a s i t . 1(3/4):245-254. Baker, M.R. 1984. Nematode p a r a s i t i s m i n amphibians and r e p t i l e s . Can. J . Z o o l . 62:747-757 Baker, M.R. 1986a. R e d e s c r i p t i o n o f Megalobatrachonema (Chabaudgolvania) e l o n g a t a ( B a i r d , 1858) n.comb. (N e m a t o d a : K a t h l a n i i d a e ) p a r a s i t i c i n N o r t h American salamanders. Can. J . Z o o l . 64:1573-1575. Baker, M.R. 1986b. F a l c a u s t r a s p e c i e s ( N e m a t o d a : K a t h l a n i i d a e ) p a r a s i t i c i n t u r t l e s and f r o g s i n O n t a r i o . Can J . Z o o l . 64:228-237. B a r u s , V. and J . G r o s c h a f t . 1962. Megalobatrachonema t e r d e n t a t u m ( L i n s t o w , 1890) H a r w i c h , 1960 (Nematoda, S u b u l a s c a r i d i d a e ) i n C z e c h o s l o v a k i a , and i t s development. H e l m i n t h o l o g i a 4:67-76. B r o o k s , D.R. 1979. T e s t i n g the c o n t e x t and e x t e n t o f h o s t - p a r a s i t e c o e v o l u t i o n . S y s t . Z o o l . 28:299-307. B r o o k s , D.R. 1981. Hennig's p a r a s i t o l o g i c a l method: a proposed s o l u t i o n . S y s t . Z o o l . 30(3):229-249. 91 B r o o k s , D.R. 1985. P h y l o g e n e t i c s and the f u t u r e o f h e l m i n t h s y s t e m a t i c s . J . P a r a s i t o l . 71(6):719-727. B r o o k s , D.R., C a i r a , J.N., P i a t t , T.R., and M.R. P r i t c h a r d . 1984. P r i n c i p l e s and Methods o f P h y l o g e n e t i c s : a c l a d i s t i c s workbook. U n i v e r s i t y o f Kansas. B r o o k s , D.R. and E.O. W i l e y . 1986. T h e o r i e s and methods i n d i f f e r e n t approaches to p h y l o g e n e t i c s y s t e m a t i c s . C l a d i s t i c s 1 ( 1 ):1-11. Chabaud, A.G. 1978. CIH Keys t o the nematode p a r a s i t e s o f v e r t e b r a t e s . No.6 Keys to the s u p e r f a m i l i e s Cosmocercoidea, S e u r a t o i d e a , H e t e r a k o i d e a and S u b l u r o i d e a . Commonwealth A g r i c u l t u r a l Bureaux, Farnham R o y a l , B u c k i n g h a m s h i r e , England. Chabaud, A.G. and Y.J. Golvan. 1957. Megalobatrachonema campanae n. sp. (Nematoda: K a t h l a n i i n a e ) p a r a s i t e de t r i t o n s de l a r e g i o n p a r i s i e n n e . Ann. P a r a s i t o l . Hum. Comp. 32 : 243-263. Chabaud, A.G. and A.J. P e t t e r . 1961. Remarques sur l ' e v o l u t i o n des p a p i l l e s c l o a c a l e s chez l e s Nematodes phasmidiens p a r a s i t e s de V e r t e b r e s . P a r a s s i t o l o g i a 3:51-70. Cox, C B . and P.D. Moore. 1980. Biogeography - an e c o l o g i c a l and e v o l u t i o n a r y approach. B l a c k w e l l S c i e n t i f i c P u b l . , London. Duellman, W. and L. Trueb. 1986. The B i o l o g y o f Amphibians. McGraw H i l l , New York. F r a n d s e n , J.C. and A.W. Grundman 1960. the p a r a s i t e s o f some amphibians o f Utah. J . P a r a s i t o l . 46:678. F r e i t a s , J.F. T e i x e i r a de. 1958. Estudos sobre O x y a s c a r i d i d a e ( T r a v a s s o s , 1920) (Nematoda, S u b l u r o i d e a ) . Hems. I n s t . Oswaldo Cruz. 56:489-559. 92 Green, D.M. and R.W. Cambell. 1984. The Amphibians o f B r i t i s h Columbia B.C. Prov. Museum, V i c t o r i a . H a r t w i c h , G. 1960. Uber Megalobatrachonema t e r d e n t a t u m ( L i n s t o w , 1890) nov. comb, and d i e S t e l l u n g von Megalobatrachonema Yamaguti, 1941 im System der A s c a r i d i n a (Nematoda). Z. P a r a s i t e n k . 19:606-619. I n g l i s , W.G. 1966. The o r i g i n and f u n c t i o n o f the c h e i l o s t o m a l complex i n the nematode F a l c a u s t r a s t e w a r t i . P r o c . L i n n . Soc. Lond. 177(1):55-62. I n g l i s , W.G. 1971. S p e c i a t i o n i n p a r a s i t i c nematodes.Advances i n P a r a s i t o l o g y . Volume 9 Academic P r e s s , New York. Lee, D.L. 1970. The f i n e s t r u c t u r e o f the e x c r e t o r y system i n a d u l t N i p p o s t r o n g y l u s b r a s i l i e n s i s (Nematoda) and suggested f u n c t i o n f o r the ""excretory g l a n d s ' . T i s s u e and C e l l 2(2):225-231. Moravec, F. 1974. Some remarks on the development o f P a r a q u i m p e r i a t e n e r r i m a L i n s t o w , 1878 (Nematoda:Quimperiidae). S c r i p t a FAc. S c i . Nat. Ujep B r u n e n s i s , B i o l o g i a 5, 4:135-142. Moravec, F. 1984. Some h e l m i n t h p a r a s i t e s from amphibians o f Vancouver I s l a n d , B.C., w e s t e r n Canada. V e s t n . Cesk. S p o l . Z o o l . 48:107-114. N e l s o n , G. and N. P l a t n i c . 1981. S y s t e m a t i c s and Biogeography: C l a d i s t i c s and V i c a r i a n c e . Columbia Univ. P r e s s , N.Y. O l s e n , O.W. 1938. A p l e c t a n a g i g a n t i c a ( C o s m o c e r c i d a e ) , a new s p e c i e s o f nematode from Rana p r e t i o s a . Trans. Am. M i c r . Soc. 57:200-203. P a r r y , J.E. and A.W. Grundman 1965. S p e c i e s c o m p o s i t i o n and d i s t r i b u t i o n o f the p a r a s i t e s o f some common amphibians o f I r o n and Washington C o u n t i e s , Utah. P r o c . Utah Acad, o f S c i e n c e s , A r t s and L e t t e r s 42:271-279. 93 P e t t e r , A.J. and A.G. Chabaud 1971. C y c l e e v o l u t i f de Megalobatrachonema t e r d e n t a t u m ( L i n s t o w ) en F r a n c e . Ann. P a r a s i t o l . 46 (4):463-477. R i c h a r d s o n , J.P.M. and M.L. Adamson. I n P r e s s . Megalobatrachonema (Chabaudgolvania) w a l d e n i n.sp. ( N e m a t o d a : K a t h l a n i i d a e ) from the i n t e s t i n e o f the n o r t h w e s t e r n salamander, Ambystoma g r a c i l e ( B a i r d ) . Can. J . Z o o l . R i c h a r d s o n , J.P.M. and M.L. Adamson. 1988. A new K a t h l a n i i d a e (Cosmocercoidea;Nematoda), Megalobatrachonema (Chabaudgolvania) moraveci n.sp. from the i n t e s t i n e o f the r o u g h - s k i n n e d newt, T a r i c h a g r a n u l o s a S k i l t o n . P r o c . H e l m i n t h o l . Soc. Wash. 55(2):155-159. S k r j a b i n , K . I . , S h i k h o b a l o v a , N.P., and E.A. Lagodovskaya. 1976. E s s e n t i a l s o f Nematodology: Oxyurata o f Animals and Man P a r t Three, Volume X I I I . Academy o f S c i e n c e s o f the USSR, t r a n s l a t e d from R u s s i a n . W a i t z , J.A. 1961. P a r a s i t e s o f Idaho amphibians. J . P a r a s i t o l . 47:89. Watrous, L.E. and Q.D. Wheeler. 1981. The outgroup comparison method o f c h a r a c t e r a n a l y s i s . S y s t . Z o o l . 30:1-11. W i l e y , E.O. 1981. P h y l o g e n e t i c s : The Theory and P r a c t i c e o f P h y l o g e n e t i c S y s t e m a t i c s . W i l e y and Sons, N.Y. Yamaguti, S. 1941. S t u d i e s on the h e l m i n t h fauna o f Japan, p a r t 34. Amphibian nematodes I I . Jap. J . Z o o l . 9:397-408. Yamaguti, S. 1961. Systema Helminthum, V I I I Nematodes o f V e r t e b r a t e s . I n t e r s c i e n c e P u b l . New York. P t . I I 681-1261. Zar , J.H. 1984. B i o s t a t i s t i c a l A n a l y s i s . P r e n t i c e - H a l l , N e w J e r s e y . 94 APPENDIX A P r e v a l e n c e and i n t e n s i t y o f Megalobatrachonema  w a l d e n i i n Ambystoma g r a c i l e from v a r i o u s B.C. l o c a l i t i e s . LOCALITY N # INFECTED PREVALENCE INTENSITY S u r r e y ( l a r v a e ) 164 ( n e o t e n i c ) 3 ( t r a n s f o r m e d 4 104 3 0 63% 100% 3.0 10. 0 G o i d i e Lake ( l a r v a e ) ( n e o t e n i c ) 2 1 66% 100% 14. 5 1.0 Whonnock Lake ( n e o t e n i c ) 100% 1.0 M a r i o n Lake ( l a r v a e ) 100% 11. 3 95 APPENDIX B Megalobatrachonema w a l d e n i s e a s o n a l s a m p l i n g d a t a from l a r v a l and n e o t e n i c A_. g r a c i l e from S u r r e y , B.C. DATE N INFECTED PREVALENCE INTENSITY SD CL 1986 M a r c h / A p r i l 15 11 73% 2.8 1. 90 1.73 May/June 47 20 45% 2. 3 1. 38 1. 30 J u l y / A u g u s t 37 25 68% 2.3 1. 38 1. 30 Sept/October 12 11 92% 4.8 3. 95 1.73 Nov/December 0 0 — — — — 1987 J a n / F e b r u a r y 4 3 75% 7.4 4.62 3. 30 March/Apr i l 16 11 69% 4 . 3 3.23 1. 75 May/June 8 2 25% 3.5 3. 54 4.00 J u l y / A u g u s t 14 10 71% 4.0 5 . 60 1.81 Sept/October 14 13 93% 3.3 1. 75 1. 59 SD=standard d e v i a t i o n CL=confidence l i m i t s 96 APPENDIX C Data M a t r i x f o r Megalobatrachonema The p l e s i o m o r p h i c or p r i m i t i v e s t a t e i s r e p r e s e n t e d by 0. The d e r i v e d or apomorphic s t a t e s a re r e p r e s e n t e d by a 1 or 2, A 9 i s used f o r unknown c h a r a c t e r s t a t e s . Outgroup 000000000000010000000 F a l c a u s t r a 000000000000010000000 M. w a l d e n i 100011111111100000401 M. moraveci 110111111110100100301 M. elongatum 011011111110020011211 M. t e r d e n t a t u m 010011011110000010201 M. g i g a n t i c u m 900000000010011000101 M. nipponicum 900000010010010019001 

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