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The life cycle and incidence of black spot parasite in the lake shiner, Richardsonius balteatus, in British… Thom, Margaret Helen 1951

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THE LIFE CYCLE AND INCIDENCE OF BLACK SPOT PARASITE IN THE LAKE SHINER, RICHARDSONIUS BALTEATUS. IN BRITISH COLUMBIA  Margaret Helen Thorn  A T h e s i s Submitted i n P a r t i a l F u l f i l m e n t o f The Requirements  For The Degree o f  MASTER OF ARTS i n the Department of Zoology  We accept t h i s t h e s i s as conforming to the standard r e q u i r e d  from c a n d i d a t e s f o r the  degree o f MASTER OF ARTS  Members o f the Department o f  THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1951  THE  LIFE CYCLE AND  INCIDENCE OF BLACK SPOT PARASITE IN  THE  LAKE SHINER, RICHARDSONIUS BALTEATUS.IN BRITISH COLUMBIA.  Abstract  A d e s c r i p t i o n o f a new  s t r i g e i d metacercaria  Neascus group r e s p o n s i b l e f o r the productionof the l a k e s h i n e r , Richardsonius  of the  b l a c k spot i n  b a l t e a t u s i s g i v e n . The meta-  c e r c a r i a i s d i s t r i b u t e d over the body i n m e l a n i s t i c i n t e g u mentary c y s t s . A l l attempts to o b t a i n the a d u l t f l u k e s by i n f e c t e d f i s h to pigeons,  d u c k l i n g s , rats,and c a t s  Black spot i s e r r a t i c a l l y though widely  feeding failed.  distributed  throughout B r i t i s h Columbia. T h i r t y - s i x of the f o r t y - f o u r l a k e s examined showed the d i s e a s e to be present P t y c h o i e i l u s oregonensi, macrocheilus,  Cottus  Mylocheilus  i n the s h i n e r s .  c a u r i n u s , Catastomus  asper, S a l v e l i n u s f o n t i n a l i s , Salmo  p a i r d n e r i kamloops and Prosopium w i l l i a m s o n i are a l s o i n f e c t by b l a c k  spot.  ACKNOWLEDGEMENTS  I should l i k e to express my g r a t i t u d e to Dr. James R. Adams f o r suggesting the problem and f o r h i s h e l p f u l a s s i s t a n c e throughout the study and the p r e p a r a t i o n o f the  manuscript. T h i s o p p o r t u n i t y i s a l s o taken to express my appre-  ciation  to Dr. W. A. Clemens, Head o f the Department o f  Zoology, whose kindness and c o n s i d e r a t i o n made t h i s work p o s sible.  I wish to express my thanks to fellow.students  David Hum,  Casimer L i n d s e y and Tom Northcote f o r t h e i r  col-  l e c t i o n o f and s h i p p i n g o f f r e s h s h i n e r s to the campus, and t o Grant Robertson f o r h i s v a l u a b l e a d v i c e on photomicrography. I am indebted to Dr. Henry van der S c h a l l e o f the U n i v e r s i t y o f Michigan f o r the i d e n t i f i c a t i o n of the s n a i l s , to Mr. A r t Hlggg o f the Summerland Hatchery f o r t r a n s p o r t a t i o n and working  space i n the hatchery d u r i n g May 1950 and to  Wally C o t t l e f o r t e x t f i g u r e 2.  TABLE OF CONTENTS  Acknowledgements  1  Introduction  1  Survey o f L i t e r a t u r e  3  The M e t a c e r c a r t a  .*.  10  S t r u c t u r e of the c y s t  10  D e s c r i p t i o n of m e t a c e r c a r i a  12  Taxonomic p o s i t i o n of m e t a c e r c a r i a ... l b D i s t r i b u t i o n of b l a c k s p o t on the host.. 19 R e l a t i o n s h i p of b l a c k s p o t to age of fish  20  Experiments to determine L i f e Cycle  21  R e s u l t s o f experiments Discussion Geographic D i s t r i b u t i o n , B r i t i s h Columbia  22 •• 23 ... 27  Discussion  31  R e l a t i o n o f i n f e c t i o n t o age of h o s t . .  32  E f f e c t of p a r a s i t e on host  33  Economic c o n s i d e r a t i o n s  3&  Summary  3^  Literature Cited  39  1 THE  LIFE CYCLE AND  INCIDENCE OF BLACK SPOT PARASITE IN  THE  LAKE SHINER, RICHARDSONIUS BALTEATTJS. IN BRITISH COLUMBIA  INTRODUCTION Although "black spot d i s e a s e " had been n o t i c e d on the North American c o n t i n e n t more than t h i r t y - f i v e years  ago,  I t i s o n l y d u r i n g the l a s t f i f t e e n to twenty years t h a t much I n t e r e s t has been shown i n t h i s d i s f i g u r i n g trematode t i o n of f i s h .  infesta-  A l l the I n v e s t i g a t i o n s have been c a r r i e d out In  e a s t e r n Canada and e a s t e r n U n i t e d S t a t e s by such men  as  Cameron, L y s t e r , M i l l e r , Hunter, Lachance and K r u l l , who s t u d i e d the d i s e a s e In game f i s h .  ,  No i n v e s t i g a t i o n of the  d i s e a s e has been c a r r i e d out i n B r i t i s h Columbia, to the author'8 knowledge. Black spot occurs on the s k i n below the s c a l e s or In the muscles of s e v e r a l s p e c i e s of f i s h .  Elevated black  spots about the s i z e of a pinhead, are caused by the e n c y s t ment of c e r t a i n trematode l a r v a e , the a d u l t s of which occur In f i s h - e a t i n g b i r d s and mammals.  A f t e r the c e r c a r l a has  penetra-  ted the f i s h and s e c r e t e d i t s c y s t the i n j u r e d f i s h Is stimul a t e d to form a connective t i s s u e c y s t about which melanophores become concentrated, producing a b l a c k spot over the s i t e of Injury. Examination  In November 19^9  of a l a r g e c o l l e c t i o n  of  lake s h i n e r s or r e d - s i d e d bream ( R l c h a r d s o n i u s b a l t e a t u s ) ,  from the Columbia F r a s e r watershed r e v e a l e d the presence b l a c k spot.  of  Because of the l a r g e c o l l e c t i o n a v a i l a b l e f o r  Immediate study and the abundance of t h i s f i s h i n Columbia, the s h i n e r was  British  chosen as the b a s i s of the present  study. With the e x c e p t i o n of a small number of f i s h from E r i e lake on November 24, 1949 for  study u n t i l May  low water.  No  1950  no f r e s h m a t e r i a l was  when the f i s h began to move Into  first,  shal-  s h i n e r s have been o b t a i n e d d u r i n g the winter  months because of v a r i o u s d i f f i c u l t i e s The  available  i n making c o l l e c t i o n s .  present study has been made along two  an i n v e s t i g a t i o n of the occurrence  lines;  of b l a c k spot i n the  l a k e s h i n e r and other s p e c i e s of f i s h a s s o c i a t e d w i t h i t and second, a study of the l i f e  c y c l e of the trematode.  3  SURVEY OF LITERATURE A survey of the l i t e r a t u r e has two  shown that a t l e a s t  groups of trematodes, the heterophylds and  strlgelds,  r e s p o n s i b l e f o r the p r o d u c t i o n of "black spot" i n the of  e a s t e r n Canada and the U n i t e d S t a t e s .  life  are  fishes  Those s t r l g e l d s whose  c y c l e s have been worked out, u n l i k e the heterophylds,  a d i s t i n c t host s p e c i f i c i t y w i t h r e g a r d to t h e i r  show  definitive  host. Black spot i n f e c t i o n f i r s t  came i n t o prominence  d u r i n g the late; 1920's when LaRue, h i s c o l l e a g u e s and 1  students  began a thorough review of the Family S t r l g e l d a e (Holostomldae) In North America.  There are e a r l i e r r e p o r t s of the d i s e a s e on  t h i s c o n t i n e n t but I t was  not u n t i l the p o s s i b l e economic  portance of the d i s e a s e was g a t i o n s were c a r r i e d In 1S93  im-  r e c o g n i z e d t h a t thorough I n v e s t i -  out. L i n t o n r e p o r t e d the occurrence  of Neascus  c u t l o o l a (Van Nordmann) from Lepomls a u r l t u s , Eupomotls dus and Choenobryttus gulosus.  He  palll-  s t a t e s I t " e x i s t s i n cap-  s u l e s under s k i n e s p e c i a l l y under serous membrane...."  This  s t r i g e l d m e t a c e r c a r i a i s r e s p o n s i b l e f o r b l a c k spot In a number of European f i s h e s .  In h i s d e s c r i p t i o n L i n t o n f a l l s  mention a pigmented c y s t and h i s f i g u r e 2,  to  P l a t e XLII shows an  unpigmented c y s t attached to the serous membrane by a narrow pedicle.  Hughes  (I92g)  Is o f the o p i n i o n t h a t . t h i s  11915)  m e t a c e r e a r i a i s Neascus v a n c l e a v e l r a t h e r than Neascus c u t l c o l a . Cooper  r e p o r t e d Dlstomum sp.. l a r v a from  pig-  mented c y s t s i n the muscles of Perca f l a v e s c e n s and pigmented c y s t s of C e r c a r l a sp. from the s k i n of an u n i d e n t i f i e d , minnow. The worm from the perch l a not f i g u r e d hut that taken from  the  minnow i s shown i n f i g u r e 26 A and B o f P l a t e I I I of h i s paper. Prom these f i g u r e s i t would appear that C e r c a r l a sp.  is a  s t r l g e l d ; there being a d i s t i n c t f o r e and h i n d body and  an  extremely l a r g e " v e n t r a l sucker", p r o b a b l y the h o l d f a s t . true v e n t r a l sucker appears  to have been overlooked.  The  He  recorded t h a t " p r a c t i c a l l y a l l of the s m a l l s p e c i e s of f i s h e s t o g e t h e r w i t h the young and not a few a d u l t s of the l a r g e r s p e c i e s are more o r l e s s i n f e c t e d w i t h t h i s k i n d of c y s t , which statement  a p p l i e s p a r t i c u l a r l y to those f r e q u e n t i n g the  weedy bays and The  shores; first  i d e n t i f i c a t i o n o f an organism r e s p o n s i b l e  f o r the d i s e a s e i n North America was who  shallow  g i v e n by Hughes  d e s c r i b e d Neascus a m b l o p l l t e s from Ambloplltes  M l c r o p t e r u s dolomieu  and Eupomotls glbbosus  i n New  In the f o l l o w i n g s i x years f o u r more s t r i g e i d were i n c r i m i n a t e d .  (1927),  rupestrls, York S t a t e .  metacercariae  These were the m e t a c e r e a r i a of C e r c a r l a  1923, found by McCoy (1923) i n s u n f i s h ; Neascus wardl Hunter (1923) i n Lepomis c y a n e l l u s ; Neascus b u l b o g l o s s a Hughes (l92g) In Perca f l a v e s c e n s ; and Neascus r h l n l c h t h y s l ; hamata M i l l e r  Hunter  (1933)from  R h i n l c h t h y s atronasus and R h l n l c h t h y s c a t a -  ractae. Cameron  (1936) and  Lyster  (19^0)  r e p o r t e d the  5  d i s e a s e from Canada, the c a u s a l agent being two metacercarlae,  Apophallus  heterophyid  venustus and Apophallus  L y s t e r 1940=Apophallus b r e v l s Ransom 1920. a t t a c k s s e v e r a l f i s h , I c t a l u r u s punctatus  lmperator,  A. venustus and  Mlcropterua  dolomleu most f r e q u e n t l y , while A . b r e v l s a t t a c k s S a l v e l l n u s f o n t l n a l i s and  Salmo f a r l o .  In 19^0  Naascue c u t l c o l a Van Nordmann was  r e p o r t e d by L i n t o n from Huro f l o r d a n o , Mlcropterua S a l v e l l n u s f o n t l n a l i s and Perca f l a v e s c e n s .  again  dolomleu,  His figure  323>  P l a t e XXIV shows the worm enclosed i n a pigmented c y s t which he r e p o r t s as being found  "mostly on the f i n s but a l s o under  the s k i n and a few In the  flesh...."  The disease has been found to occur  sporadically  In f i s h e s of the southeastern p o r t i o n of Ontario and i n Quebec from "east o f L e v i s county  southeast and  States border, across Montreal  south a l o n g the U n i t e d  i s l a n d , along and I n c l u d i n g the  Ottawa r i v e r up to P o n t i a c county."  (Lachance,il9^7).  The -  i n f e s t a t i o n continues southward i n t o the United States where i t has been r e p o r t e d from New cut and  York, Michigan, Wisconsin,  Connecti-  Massachussetts. There have been no r e p o r t s of the d i s e a s e from  western Canada and the U n i t e d S t a t e s .  Although no account  been g i v e n of the disease i n Manitoba f i s h e s , McLeod r e p o r t s the presence  (19^0)  of C e r c a r i a b e s s l a e (Cort & Brooks, 1923),  the c e r c a r l a l stage of one U v u l l f e r ambloplltes  has  of the b l a c k spot organisms,  Dubois  1933.  Table I.  S p e c i f i c Name  D e f i n i t i v e Host  A p o p h a l l u s venus- Ardea h . h e r o d i a s tus Procyon l o t o r (Cameron, 193b) e x p er i m e n t a l  B l a c k s p o t In f i s h — l i f e  F i r s t Intermediate Host  Second I n t e r m e d i a t e Host  Gonlabasls  I c t a l u r u s punctatus Mlcropterus dolomleu  llveseens  Dogj  Apophallus b r e v l s , Ransom,1920 (Lyster, 19W  Crassiphiala b u l boglossa Van H l t s m a , l 9 2 5  G-avla immer  Amnlcola l l m o s a  Californian Gull (Larus c a l i f o r n i cus(?) Ceryle  1958.  Ceryle  Cameron, 1936,1937  Ransom,1920 Lyster,19^0, 1946; M i l l e r 1946.  alcyon  alcyon  Salvellnus fontlnalis Salmo f a r i o  References  1940,1941,  —  a  U v u l i f e r amblop l i t i s (Hughes, 1927) Dubois,  cycles  Helisoma  trlvolvls (Say) H.campanulaturn (Say)  Esox l u c i u s Perca flavescens Semotilus atromacul a t u s (Neascus b u l b o g l o s s a , Hughes) Ambloplites  VanHaltsma Hughes, 1928 •  r u p e s t - Hughes,l927 ris M l c r o p t e r u s dolomleu Cort & Brooks,1923 Hunter,1933.  Table 1, S p e c i f i c Name  D e f i n i t i v e Host  U v u l i f e r amblop l i t i s (Hughes, 1927) Dubois, 1932  Ceryle alcyon  B l a c k s p o t In f i s h — l i f e First  Intermediate Host  (C. b e s s i a e , Cort & Brooks)  cycles.  Cont'd  Second I n t e r m e d i a t e Host  References  Eupomotis glbbo$us  Hunter & Hunter,1930 1935. K r u l l , 1932, 193*1  (Neascus a m b l o p l i t e s Hughes) Lepomis c y a n e l l u s (Neascus wardi, Hunter) Rhinlchthys atronasus. R . c a t a r a c t a e (Neascus r h i n l c h thys!)  Posthodlplostomum c u t i c o l a (VanNordmann, 1832)  Ardea c i n e r e a Egretta garzetta Nycticorafe sp.  Huro f l o r l d a n a M i c r o p t e r u s dolmieu Salvelinus fontinalis Perca flavescens (Neascus c u t l c o l a (VanNordmann)) Planorbis t r i v o l v l s Say ( C e r c a r l a hamata, M i l l e r . 1923)  Hunter,1923 VanCleave & Mueller.193^ Hunter,1933  Linton, 19^0,  1392  Hughes,1923.  Helioperca i n c i s o r  Miller,1923  Apomotis _  McCoy, 1923 Todd, 1929.  cyanellus  Table 1.  S p e c i f i c Name •  Definitive  B l a c k s p o t In f i s h — l i f e c y c l e s .  Host  First  Intermediate Host  Hellsoma t r i v o l v i s (Cercarla flexicorpa Collins)  Cont'd.  Second  Intermediate Host  References  Apomotis c y a n e l l u s  Collins,1935  Helioperca macrochlra  Hobgood,1933  6 A l i s t o f organisms causing the d i s e a s e i n f r e s h water f i s h e s on t h i s c o n t i n e n t , t o g e t h e r w i t h p e r t i n e n t data r e g a r d i n g t h e i r l i f e c y c l e s i s given i n Table I . parentheses  In the columns g i v i n g f i r s t  Names i n  and second  intermediate  h o s t s r e f e r to the names g i v e n the c e r c a r i a l o r m e t a c e r c a r i a l stage before t h e i r r e l a t i o n s h i p to the a d u l t f l u k e was r e c o g nized.  References  c i t e d a r e of papers d e a l i n g w i t h l a r v a l or  a d u l t stages o f the worm as w e l l as d e s c r i p t i o n s o f complete l i f e cycles. The of  f o l l o w i n g d e s c r i p t i o n s of the l i f e  U v u l l f e r a m b l o p l l t e s and Apophallus  venustus w i l l  examples o f s t r i g e i d and h e t e r o p h i d l i f e The  histories serve as  cycles respectively.  a d u l t U v u l l f e r a m b l o p l l t e s i s found  i n the  s m a l l i n t e s t i n e of the b e l t e d k i n g f i s h e r , Ceryle a l c y o n .  In  the water, the eggs, which pass out i n the f e c e s o f the host, hatch l i b e r a t i n g m i r a c i d l a . t r a t e the s n a i l host in  These f r e e swimming l a r v a e pene-  (Hellsoma  t r l v o l v i s and H. campanulatum  the U n i t e d States and H. anceps i n Quebec),  w i t h i n the  d i g e s t i v e gland they g i v e r i s e to elongate, m o t i l e , unbranched s p o r o c y s t s which i n t u r n g i v e r i s e to c e r c a r i a e , the l a s t to  develop w i t h i n t h i s The  stage  host.  f o r k - t a i l e d c e r c a r i a e break through the s n a i l  t i s s u e to swim i n the water u n t i l contact I s made xvith the appropriate f i s h  ( s u n f i s h or b a s s ) , whereupon they a t t a c h them-  s e l v e s to the integument, c a s t o f f t h e i r t a i l s and burrow Into the f i s h .  Once they have reached  t h e i r f i n a l d e s t i n a t i o n , the  7 connective t i s s u e below the s c a l e s , the f i n s or the myomeres the l a r v a e begin to form h y l a l l n e c y s t s around  themselves.  A c c o r d i n g to Hunter and Hunter (1935) there i s l a i d down around t h i s t h i n - w a l l e d c y s t a t h i c k syndesmous c y s t of host However, K r u l l  origin.  (1932) b e l i e v e s that the l a r v a e begin to grow  w h i l e the f i s h forms the t h i c k connective t i s s u e c y s t .  Within  t h i s c y s t the worm develops and when growth i s completed, the Inner c l o s e l y i n v e s t i n g h y a l i n e  c y s t of p a r a s i t i c o r i g i n i s  produced, a f t e r which the host c y s t becomes pigmented. t a t i o n develops  three weeks a f t e r p e n e t r a t i o n of the  Development of other s t r l g e l d s may take longer and on the water temperature The  eercaria.  i s dependent  (McCoy, 192g and Todd, 1929).  l i f e c y c l e i s completed  eats an I n f e c t e d f i s h .  Pigmen-  when the k i n g f i s h e r  The raetacercariae are f r e e d from  their  surrounding c y s t s i n the b i r d ' s small I n t e s t i n e and i n twentyfour to t h i r t y days, a c c o r d i n g to Hunter (1933)> r e a c h m a t u r i t y . The a d u l t of Apophallus venustus. whose metacerc a r i a causes b l a c k s p o t i n c a t f i s h and bass, has been recovered from the small I n t e s t i n e o f the c a t , dog, racoon l o t o r ) and the great blue heron may  (Procyon  (Ardea h» h e r o d l a s ) .  Man,  too,  be I n f e c t e d ; one suspected case based on the recovery o f  ova from the f e c e s of a p a t i e n t In the Ste. Anne de B e l l e v u e M i l i t a r y H o s p i t a l being r e p o r t e d by Cameron i n 1937. As was the case i n IJ. a m b l o p l l t e s from the host w i t h the f e c e s .  the eggs pass  However, the m l r a c l d i a do nott  hatch u n t i l the eggs are eaten by the s n a i l host  Gonlobasls  llvescens. sequent to  No sporocyst stage has been d e s c r i b e d but a l l sub-  stages develop i n the l i v e r .  daughter  Mother r e d l a e give r i s e  r e d i a e which i n t u r n g i v e r i s e to c e r c a r i a e . The  c e r c a r l a o f A. venustus belongs  to the p ^ i r o -  lophocercus group and Is c h a r a c t e r i z e d by two pigmented eyespots and a l o n g t a i l  that has a continuous f i n running the  f u l l l e n g t h o f I t s d o r s a l and v e n t r a l s u r f a c e .  When a c e r -  c a r l a comes In contact with a f i s h ' s f i n i t holds a g a i n s t the s k i n by r a p i d movements o f i t s t a l l .  itself W i t h i n ten  minutes the c e r c a r l a has p e n e t r a t e d the host's s k i n l e a v i n g behind i t s t a i l .  The c e r c a r l a u s u a l l y enters a b l o o d v e s s e l  and, by a l t e r n a t e l y c o n t r a c t i n g and expanding I t s body, eventu a l l y reaches the deeper t i s s u e where i t encysts; the encysted worm being known as a metacerearia. Three to f o u r weeks are r e q u i r e d before the metac e r c a r l a e become i n f e c t i v e .  Seven to ten days a f t e r being  eaten by the d e f i n a t l v e host the f l u k e s become mature, though eggs may not be recovered from the f e c e s u n t i l twenty-four  days  a f t e r the i n f e c t i v e f e e d i n g . The  e f f e c t s o f the p a r a s i t e s on the host have been  n e g l e c t e d by most authors.  The few t h a t have been r e p o r t e d  probably r e p r e s e n t the r e s u l t s of extremely which o n l y occur s p o r a d i c a l l y i n nature.  (193*0, due  severe I n f e c t i o n s  McCoy, (I92g); K r u l l ,  and Hunter,(1937^, r e c o r d cases o f the deatfi of the host  to the p a r a s i t e and Hunter and Hunter,(1936, 193^\ r e c o r d  ) cases o f the l o s s of weight by the h o s t .  The o n l y r e a c t i o n o f  9 the  f i s h to the p a r a s i t e which has been s t u d i e d i n t e n s i v e l y i s  that o f c y s t formation, by Todd (1929), K r u l l (193*^ and Hunter and Hamilton (194]).  Hunter ( 1 9 ^ and Hunter and Hamilton 0.9^-1) pre**  sent an h y p o t h e s i s to e x p l a i n the appearance of melanophores In the host c y s t of some l a r v a l trematodes and t h e i r absence in  others.  Fig.  1.  Upper:- Cross s e c t i o n through s k i n showing the two p a r t s o f outer host c y s t . Lower:- Cross s e c t i o n through s k i n showing netac e r c a r i a , i t s inner c y s t and two p a r t s o f the outer host c - s t .  F i g . 2. Two 'encysted m e t a c e r c a r i a i n akin o f s h i n e r . P r o l i f e r a t i o n o f t i s s u e causes displacement o f scales.  S e c t i o n through f i n of s h i n e r . P r o l i f e r a t i o n o f t i s s u e causes displacement o f elements o f the f i n ravs.  10  THE STRUCTURE OF  THE The  cyst  The tive  CYST metacerearia  of p a r a s i t i c  mous c y s t  of host  outer layer tissue,  METACERCARIA  i s e n c l o s e d by an  origin  and  surrounding  origin  consisting  o f two  while  the  Innerr layer  c o n t a i n s no  The  connective  tissue  o f the  b e i n g l a r g e r and The  two  more p r o m i n e n t  p a r t s of the  dissection",  the  cyst  innermost  a t t a c h e d to the denser The and  b u t were n e v e r a s has  completely  i n the  be  found  in sufficient  been r e p o r t e d by  scales.  causes  The  Cameron  lying  o f the  r o u g h t e x t u r e . ( F i g . 2.) f i n rays.  the body, i s f o u n d  (Fig.l}  visible,  separated  by  remaining  On  on t h e  skin.  scales,  In very  i n the muscle  numbers t o b l a c k e n  the  heavy septa, flesh  (19^6) f o r b a s s .  profuse p r o l i f e r a t i o n  the d i s p l a c e m e n t  elements of the  closely  cells.  outer layer  d e r m i s and  U s u a l l y the p a r a s i t e l o d g e s two  connec-  inner area.  c y s t s may  found  loose  are c l e a r l y  i n the muscles beneath the  i n f e s t a t i o n s a few  layers.  outer pigmented p a r t .  p o r t i o n of the  cysts occur  only rarely  be  hyaline  syndes-  o f more  pigment  cells  i n the  cannot  i n the  i s made up  t i s s u e and  a thick  distinct  c o n t a i n s melanophores l y i n g  packed connective nuclei  this  elastic,  i n the d e r m i s between of connective  s c a l e s t h a t g i v e s the  the f i n s  ( F i g . 3.)  the  skin i t s  cyst d i s p l a c e s the  Pigmentation  c o n c e n t r a t e d i n the  tissue  here,  as  on  Immediate v i c i n i t y  of  11 the  cysts. There i s l i t t l e  where b l o o d v e s s e l s  c a p i l l a r y involvement i n the c y s t ,  have been found i n the c y s t they have been  l i m i t e d to the outer pigmented l a y e r . The f o l l o w i n g t a b l e g i v e s measurements of t e n c y s t s from a s h i n e r .  A l l measurements were made w i t h the a i d of an  o c u l a r micrometer from s e r i a l s e c t i o n s s t a i n e d w i t h H a r r i s ' haematoxylin u s i n g a l c o h o l i c eosin as a c o u n t e r s t a i n .  Table I I . Measurements i n microns o f t e n integumentary c y s t s of a s t r i g e i d m e t a c e r e a r i a from  Richardsonlus  baiteatus. Minimum T o t a l l e n g t h o f cyst Diameter o f pigment l a y e r Diameter o f denser p o r t i o n of c y s t Thickness of h y a l i n e S i z e of c y s t c a v i t y  cyst  Maximum  Average  357.0 26.0  500.0 59.0  4-23.0 4-0.0  19.0 0.7 291.0  1*6.0  33.0 1.1 3^2.0  Inside the connective  1.5  363.0  t i s s u e cyst and separated  from i t by a f l u i d i s the tough membranous cyst secreted by the parasite.  The f l u i d g e l s on p r e s e r v a t i o n  e a s i l y d i s c e r n e d d u r i n g manual d i s s e c t i o n .  i n f o r m a l i n and i s Twenty i n n e r  cysts  Fig. 4  Camera l u c i d a drawings o f inner  cysts-  12 measured without pressure a f t e r the d i g e s t i o n of the host c y s t by p e p s i n gave the f o l l o w i n g measurements. w i t h a l e n g t h of 289 u to 391 of 208 microns  l a r g e s t c y s t was  391  331  u, average  to 262 microns, average  222  microns l o n g by 2b2  s m a l l e s t 289 microns l o n g by 213  The  c y s t s are o v a l  u, w i t h a breadth  microns.  The  microns wide, the  microns wide.  F i g . 4- shows  the o u t l i n e s of some i n n e r c y s t s drawn with the a i d of a camera l u c i d a . Cysts c o n t a i n i n g moribund or dead metacercariae may  be d i s t i n g u i s h e d on s i g h t from those c o n t a i n i n g l i v i n g  worms by t h e i r d u l l grey contents i n c o n t r a s t to the  crystal-  l i n e cytoplasm and l a r g e r e f r a c t i l e granules seen i n v i a b l e cysts.  The  cytoplasm of moribund metacercariae l o s e s i t s  c l a r i t y , becoming grey and bubbly i n appearance.  Cysts i n  which the metacercariae have been dead f o r some time are  filled  by a homogeneous grey g e l .  DESCRIPTION OF METACERCARIA The metacerearia i s found l y i n g somewhat bent w i t h i n the cyst  surrounded by a g r a n u l a r f l u i d  ( P l a t e I, f i g .  1,2).  In l i v i n g specimens the c o n t r a c t i o n and expansion of the worms set these g r a n u l e s i n motion.  The a n t e r i o r end of the worm i s  u s u a l l y p o i n t e d w i t h the o r a l sucker a t the apex.  The body  then i n c r e a s e s i n width r e a c h i n g i t s g r e a t e s t dimension the middle of the forebody. and h o l d f a s t are v i s i b l e .  The o r a l sucker, v e n t r a l The remains  of cystogenous  near  sucker cells  E x p l a n a t i o n of ^ l a t e I  ^ i g . 1,° - e t a c e r c f i r i a i n i n n e r h y a l i n e M  cyst.  Fig.^  V e n t r a l view of l i v i n g worm f r e e d ^rom c y s t .  •^ig. 4  Camera l u c i d a drawing of f i e d worm showing i n t e r n a l s t r u c t u r e . V e n t r a l view.  Fig. 5  View o f worm showing l o n g i t u d i n a l s t r i a t i o n s of c u t i c l e -  , r  Abbreviations BC CC CE EB EC E? HB HF IC OS OV PH T. TJT ' VS  . ••••  ^ *  bursa c o p u l a t r i x cystogenous c e l l i n t e s t i n a l caecum • •• e x c r e t o r y bladder e x c r e t o r y canal e x c r e t o r y pore hindbody holdfast inner cyst o r a l sucker ovary :.. pharynx testis • uterus v e n t r a l sucker  13  can be seen, b e i n g p a r t i c u l a r l y c l e a r i n f i x e d and s t a i n e d specimens where they appear as l a r g e p i n k to orange h y a l i n e c e l l s arranged i n rows along the s i d e s o f the forebody fig.  ( P l a t e I,  3,  T h i s d e s c r i p t i o n i s based on two a d o l e s c a r i a f r e e d from t h e i r c y s t d u r i n g p e p s i n d i g e s t i o n . The broad forebody b e a r i n g the o r a l sucker, a c e t a bulum and " h o l d f a s t " organ i s separated from the narrower body by a c o n s t r i c t i o n ( P l a t e I , f i g . 3)  hind-  i n the l i v i n g worm.  A f t e r f i x a t i o n evidence of the c o n s t r i c t i o n was l o s t to a l a r g e degree  due to extreme c o n t r a c t i o n on the p a r t of the specimens  ( P l a t e I , f i g . 4-). Accurate body measurements on l i v i n g worms at any p a r t i c u l a r moment were impossible to o b t a i n because of the animals' constant a c t i v i t y .  General f i g u r e s as to the l e n g t h  and breadth o f the specimens w i l l be g i v e n .  The t o t a l l e n g t h  o f the worms ranged between 0 . 6 mm. and 1.1 mm. while the width o f the forebody a t the l e v e l of the h o l d f a s t v a r i e d b e t ween 0 . 2 5 nim. and 0 . 3 5 mnu  The hindbody  measured 0 . 2 - 0 . 4 -  mm.  l o n g by 0 . 1 mm. wide. The o r a l sucker, v e n t r a l sucker, " h o l d f a s t " and g e n i t a l prlmordium  can be i d e n t i f i e d , but the d i g e s t i v e and  e x c r e t o r y systems are obscured by r e f r a c t i l e d r o p l e t s which most o f the body. The striations  fill  No flame c e l l s were seen.  c u t i c l e of the f i x e d worms shows l o n g i t u d i n a l  (Plate I, f i g . 5 ) «  There i s no evidence o f s p i n e s .  14 The  o r a l and v e n t r a l suckers are w e l l developed.  The o v a l  " h o l d f a s t " organ I s found In the p o s t e r i o r t h i r d o f the f o r e body w i t h I t s l o n g a x i s l y i n g t r a n s v e r s e l y across  the body.  In n e i t h e r specimen i s i t seen to cover the v e n t r a l sucker. Remains o f cyatogenous c e l l s are to be found l y i n g between the I n t e s t i n a l c r u r a and l a t e r a l margins o f the body i n v a r y i n g numbers.  The p r i m o r d i a  of the r e p r o d u c t i v e  organs show e i t h e r AS  a s i n g l e o v a l shaped fundament o r as a lobed i n g the formation The  s t r u c t u r e suggest-  o f the f u t u r e organs ( P l a t e I , f i g . 4 ) .  o r a l sucker measures 0.03 mm. by 0.03  mm.  Dedlmal f o u r t e e n mm. p o s t e r i o r to the o r a l sucker Is the v e n t r a l sucker measuring 0,04 mm.  by 0.04 mm.  The l a r g e " h o l d f a s t "  l y i n g d i r e c t l y behind the v e n t r a l sucker Is 0.0b mm. 0.1 mm.  wide i n one specimen and 0.09 mm.  by 0.09 mm.  long by In the  other. The  d i g e s t i v e system c o n s i s t s of a subterminal  opening Into the muscular pharynx measuring 0.02 mm. 0.01 mm. wide. lacking.  mouth  long by  The prepharynx Is e i t h e r extremely short or  The I n t e s t i n a l c r u r a are g i v e n  o f f from a short  oesophagus and proceed p o s t e r i a d to the p o s t e r i o r margin o f the  "holdfast".  had  not formed. The  In one specimen the lumen of the I n t e s t i n e  reproductive  system which, as s t a t e d p r e v i o u s l y ,  may c o n s i s t of a s i n g l e u n d i f f e r e n t i a t e d o v a l fundament or show the b e g i n n i n g o f d i f f e r e n t i a t i o n i n t o the a d u l t organs, l i e s i n the hlndbody.  Both the worms show the beginning o f t h i s  15 d i f f e r e n t i a t i o n and rudiments o f the ovary,  t e s t e s and uterus  may be seen ( P l a t e I , f i g . 4-). The  ovary l i e s i n the a n t e r i o r p o r t i o n of the h i n d -  body d i r e c t l y behind  the " h o l d f a s t " organ.  and measures 0.02 mm. by 0 . 0 1 - 0 . 0 3 mm.  I t I s o v a l i n shape  The o v i d u c t and u t e r u s  are seen as a mass of denser t i s s u e coming from the r i g h t o f the ovary proceeding  a n t e r i o r l y and to the l e f t  ween the ovary and " h o l d f a s t " .  i n a loop b e t -  The ofltype may be r e p r e s e n t e d  by a small c l u s t e r of c e l l s a t the base of the o v i d u c t .  .There  i s no i n d i c a t i o n o f L a u r e r ' s c a n a l .  ,  The  male r e p r o d u c t i v e system c o n s i s t s o f two t e s t e s  l y i n g l a t e r a l to and s l i g h t l y p o s t e r i o r to the more v e n t r a l l y p l a c e d median ovary.  The t e s t e s measure 0.03.mm. by 0.02 mm.  No seminal v e s i c l e o r vasa e f f e r e n t i a are i n d i c a t e d . Bursa IS  c o p u l a t r l x ^ p r e sent. D e t a i l s o f the e x c r e t o r y system, obscured  during  l i f e by the granules f l o a t i n g i n the circumambient f l u i d and by the remains o f the cystogenous c e l l s , became c l e a r e r i n one o f the specimens a f t e r s t a i n i n g ( P l a t e I, f i g . 4-). The l a r g e median e x c r e t o r y bladder occupies approximately  a t h i r d of the  hlnd^body, l y i n g p o s t e r i o r and d o r s a l to the g e n i t a l p r i m o r d l a and opens to the e x t e r i o r through a d o r s a l l y p l a c e d e x c r e t o r y pore.  Two e x c r e t o r y c a n a l s , one on e i t h e r s i d e , are given o f f  from the bladder and proceed  anteriorly giving o f f lateral  branches to form a loose network of v e s s e l s .  These canals and  t h e i r branches c o u l d only be t r a c e d to the l e v e l o f the  16 " h o l d f a s t " where t h e i r course becomes obscured b y the  denser  s t r u c t u r e o f the forebody.  TAXONOMIC POSITION OF METACERCARIA S t r i g e i d metacercariae  have been d i v i d e d i n t o  five  groups, each having a more o r l e s s d e f i n i t e l o c a t i o n i n t h e i r host.  The three genera that concern us here are Dlplostomum, A  T e t r a c o t y l e and Neascus. The  genus Dlplostomulum i s u s u a l l y found f r e e w i t h -  i n the eyes o f f i s h e s . two p a r t s . present.  The body i s not c l e a r l y d i v i d e d i n t o  An o r a l sucker, pharynx and two l a t e r a l c o t y l a e a r e  A small v e n t r a l sucker Is found behind the midpoint  f o l l o w e d by a l a r g e " h o l d f a s t " organ which has a small t r a n s v e r s e " h o l d f a s t " gland a t I t s p o s t e r i o r margin.  The caudal  lobe c o n t a i n s the g e n i t a l p r i m o r d i a and the e x c r e t o r y bladder.. The  oesophagus i s o f v a r y i n g l e n g t h and the i n t e s t i n a l c r u r a  u s u a l l y extend  Into the caudal l o b e .  The  genus T e t r a c o t y l e i s c h a r a c t e r i z e d by having a  t h i c k round c y s t and i s found encysted t e r i e s , and p e r i c a r d i u m o f the host.  i n the muscles, mesenHughes (1923) says t h a t  the name T e t r a c o t y l e should be a p p l i e d to "only those metacercariae  having l a t e r a l c o t y l a e , a s l i g h t l y  strigeid  developed  hindbody and a reserve b l a d d e r c o n s i s t i n g o f an i r r e g u l a r ,  con-  tinuous coarse-meshed network o f spaces, not i n the form o f definite vessels". Neascus. the remaining  l a r v a l genus, i s d e s c r i b e d  17 by Hughes (1927) as follows:  "Strigeid metacercariae with  both fore-and hindbodies, well developed and set apart by a c o n s t r i c t i o n ; no l a t e r a l cups; forebody l e a f l i k e ;  holdfast  organ well developed; reserve bladder highly developed,  the  smaller branches of which usually anastomose; calcareous g r a nules mostly free i n the circumambient f l u i d ; encysted." Neasclds have a t h i n , ovate cyst and Is found i n the viscera mesenteries,  skin, and frequently i n the pericardium. The metacerearia, responsible for blackspot in the  shiner, believed to be a new speeies, Is a s t r i g e i d of the Neascus group found in melanotic, Integumentary cysts.  The  neascid larvae reported as causing blackspot i n North American fresh-water fishes are as follows:  Neascus bulboglosaa Hughes,  Neascus ambloplltes. Neascus rhlnlohthysl Hunter, Neascus c u t l cola van Nordmann, Neascus wardl Hunter, and the metacercariae of Cercarla hamata McCoy and Cercarla flexlcoroa Hobgood, The site of the cysts i n the host eliminates U v u l l fer ambloplltes (Dubois, 193*5) which i s found along the muscle septa.  The other metacercariae are a l l integumentary but d i f f e r  from the metacercariae found i n the shiners i n the following ways. Neascus c u t l c o l a ( l ) spherical cyst,  i s closely invested in a  (2) the forebody i s not l o n g i t u d i n a l l y s t r i a t e d  (3) acetabulum Is larger than o r a l sucker. The metacercariae of Cercarla flexlcorpa are charact e r i z e d by (1) absence of reproductive fundaments, (2) presence  lg of  gland c e l l s i n hlndbody, (3) o r a l sucker twice as large as  the acetabulum. Neaacua wardl d i f f e r a i n having i t a reproductive fundamenta i n the posterior portion of the fforebody rather than in  the hlndbody.  The ovary l a doraal to the acetabulum and the  teatea are widely separated, p a r a l l e l i n g one another poaterior to the holdfaat. Neascus rhlnlohthyal i a ( l ) r e a d i l y freed from i t 8 inner cy8t, (2) acetabulum weak and l i t t l e more than half the 8lze of the o r a l sucker. Neaacua bulboglossa i s characterized by (l) lack of acetabulum,  (2) aurface of forebody and holdfast covered quin-  c u n l c a l l y with minute 8pinea,  (3) oeaophagua very long b i f u r -  cating Juat in front of the h o l d f a 8 t , (4) large pharynx a l i g h t ly  amaller than o r a l sucker. Besidea the above morphological differencea  the  metacercaria i n queation alao d i f f e r a i n size but thia i a not believed to be of primary importance i n the i d e n t i f i c a t i o n of the parasite.  Wardle (1932) mentions that the lack of pronoun-  ced h08t a p e o i f i c i t y may r e 8 u l t i n the production of l a r v a l morphae of certain p a r a s i t e 8 which are s u f f i c i e n t l y unlike to appear as d i a t l n c t speciea.  Only with the completion of the  l i f e cycles of these neascids can the legitimacy of the species be f i n a l l y  established.  Table I I I .  D i s t r i b u t i o n of cysts on Taylor lake shiners.  (Ten at random.) August,  Body Area Head Trunk above l a t e r a l line Trunk below lateral line Base of t a i l f i n Tail  fin  Dorsal f i n Pelvic  fins  Pectoral Anal f i n  fins  57 1 223 t>3  -  22  -  12  1  8  4 22 11  -  - 19 12  5*  44  lg  3 2  3  3 10  3  2  -  1  -  1  4  1  3  —  —  —  —  —  1  2  3  -  -  2  2  2  2 1  -  4  -  1  15  -  4  -  -  -  -  1  2 1  1  -  2  1950-  Total for Per cent 10 f i s h of t o t a l 2 10  3  2  -  33 317  42.14  123  IS. 81  20  12.04  42  2.91 6.17  20  2.91  1  *3  1.17 6.17  2  20  2.91  Average 68.1 per f i s h  3  Table IV.  D i s t r i b u t i o n of Cysts on Snowshoe lake shiners.  (Ten at random.) September  Total Per eent for of t o t a l 10 cysts fish  Body Area  -  Head  1  Trunk above l a t e r a l line Trunk below l a t e r a l line Base of t a i l f i n  1  Tail  1  fin  Dorsal f i n Pelvic  fins  Pectoral Anal f i n  fins  -  7 10  1  - - -  -  1  1  27  -  2  2  —  3  68  3  2  11  2  97  b  -  1  2  2  -  15  9 13 - 4-  1  2  10  3  -  t  5  1  2  1  20  2  1  13  1  194-9.  1  12  1  -  9  2  1  b  5  1  -  6  31 50  4-0 12b  23.82  188  35.5^  -  -  15 25  8  41 18  -  41^  -  -  5  Average 52.9 per f i s h  7-5^  4-7 29  2.85 4.5*  7.73 3.^0 8.88  Table V.  D i s t r i b u t i o n of cysts on Puntchesakut lake shiners.  (Ten at random.) J u l y ,  Total for  Body Area  10  fish Head  -  1  -  Trunk above l a t e r a l line Trunk below l a t e r a l line Base of t a i l  -  -  1  Tail fin Dorsal f i n Pelvic  fins  Pectoral Anal f i n  fins  1 1  1  1 1 1  -  -  1  2  -  2  1 1 —  -  -  -  -  -  1  1  4  -  1  -  -  1  5 1 g  1 1 -  -  -  1 4 1 3  am  Average 2.5 per f i s h  l l  1949-  Per cent of t o t a l cysts  20.0 4.0 32.0 4.0 lb.0  4.0 12.0 4.0 4.0  19 DISTRIBUTION OF BLACKSPOT ON THE HOST To f a c i l i t a t e  the counting of cysts, the f i s h was  marked off into nine parts, the number of cysts i n each area being recorded.  The d i v i s i o n s were as follows: the head, the  trunk above the l a t e r a l l i n e ; the trunk below the l a t e r a l l i n e ; the caudal peduncle, the caudal f i n ; the dorsal f i n ; the p e l v i c f i n s ; and the anal f i n s . Table I I I , IV, and V show the d i s t r i b u t i o n of cysts on ten shiners from Taylor and Snowshoe lakes, both with a nigh incidence of i n f e c t i o n , and Puntchesakut lake, with low i n c i dence. There appears to be no preference for any p a r t i c u l a r s i t e on the f i s h , the cysts being scattered over a l l parts of the b o d y . ^ F i g .  However, i n l i g h t infections the body  proper i s infected more often than the f i n s .  Besides the skin  and f i n s of the f i s h the cysts have also been found i n the eye, mouth and g i l l s though these s i t e s are not infected very often, usually only i n heavily infested  shiners.  There are indications that infested f i s h i n lakes with a high percentage of infection have more cysts per f i s h than do f i s h from lakes of low incidence.  Taylor lake, with  go.5 per cent of the f i s h infected shows an average of  5&«1  cysts per f i s h ; Snowshoe lake, 64.5 per cent infected, has an average of  52.9 cysts  per f i s h while Puntchesakut lake,  per cent infected averages 2.5 cysts per f i s h .  17*65  Fig.  5. • Upper:- Shiner i n f e c t e d with b l a c k s^ot. U Lower:- n i n f e c t e d shiner  20  RELATIONSHIP OF BLACKSPOT TO AGE OF FISH During the p r e l i m i n a r y  survey o f the l a k e s i t was  n o t i c e d that f i s h o f about f o r t y m i l l i m e t e r s or l e s s were not I n f e c t e d as o f t e n or as h e a v i l y as were the l a r g e r f i s h .  The  r e s u l t s o f a thorough examination o f T a y l o r lake s h i n e r s gave the r e s u l t s seen In Table V I .  Table V I .  The average number o f c y s t s i n e i g h t l e n g t h o f s h i n e r s from T a y l o r l a k e .  Length C l a s s  Average Number o f Cysts p e r F i s h  0-20  S i z e of Sample  0,10 0.92 3.5 ' 6.4 10.7 39.9 20.1  mm. mm. mm. 4 1 - 5 0 mm. 51-60 mm. 61-70 mm. 7 1 - 8 0 mm. 8 1 - 9 0 mm. 21-30 31-40  46.5  The  28 40 73  38 41  40 21 2  t a b l e shows an I n c r e a s i n g number of c y s t s p e r  f i s h w i t h each Increase i n age except i n the 61-70 mm. The  classes  class.  average number of c y s t s p e r f i s h i n t h i s group was r a i s e d  by the presence o f two h e a v i l y i n f e c t e d f i s h , one having 204 c y s t s , the other  578.  I f the two h e a v i l y i n f e c t e d f i s h are  omitted the average f o r t h i s group i s 2 1 . 4 c y s t s p e r I n f e c t e d fish.  21  EXPERIMENTS TO DETERMINE LIFE CYCLE  INTRODUCTION The  experiments recorded  i n this section  describe  attempts to determine the complete development o f the s t r i g e i d m e t a c e r e a r i a causing b l a c k s p o t  i n shiners.  Two plans of  approach were u t i l i z e d . A.  Cercariae; S n a i l s from T a y l o r lake were c o l l e c t e d d u r i n g  May  and J u l y 1950 and p l a c e d i n p i n t Jars i n the l a b o r a tory.  S n a i l s were observed every three hours f-er the  f i r s t week f o r emerging c e r c a r i a e , then twice d a i l y . A l l c e r c a r i a e were s t u d i e d a l i v e with the a i d of i n t r a vitam s t a i n i n g w i t h n e u t r a l r e d . B. Adult word; In an attempt to o b t a i n the a d u l t  stage of the  f l u k e , i n f e c t e d s h i n e r s were f e d to experimental a n i mals, namely cats and pigeons.  P r i o r to feeding,  fecal  examinations to determine the presence of p a r a s i t e s were made.  Adult  c a t s were f e d e v i s e r a t e d  shiners,  while k i t t e n s were f e d chopped s h i n e r s , o r i f u n w i l l i n g to e a t , were f o r c e f e d . A l l the pigeons and the duck used were f o r c e f e d . The animals were g i v e n one  22 hundred  c y s t s on two c o n s e c u t i v e days.  The animals were s a c r i f i c e d a t v a r i o u s i n t e r v a l e f o l l o w i n g the l a s t f e e d i n g w i t h i n f e c t e d f i s h , a t l e a s t seven days e l a p s i n g from the date o f f e e d i n g to the -.1 date of s a c r i f i c e .  During t h i s p e r i o d f e c a l examina-  t i o n s were made to determine the presence o f eggs. The abdominal and t h o r a c i c c a v i t i e s of the s a c r i f i c e d animal were opened by a v e n t r a l I n c i s i o n , the v i s e r a removed and p l a c e d i n p h y s i o l o g i c a l  saline.  The d i g e s t i v e system was examined f i r s t — b e g i n n i n g w i t h the oesophagus.  The i n t e s t i n e was cut i n t h r e e - I n c h  l e n g t h s , washed, and washings examined under the b i n o c u l a r microscope. the sediment  The I n t e s t i n e was then scraped and  examined as b e f o r e .  F o l l o w i n g the exam-  i n a t i o n o f the d i g e s t i v e t r a c t , the l i v e r ,  and the r e s -  p i r a t o r y and u r o g e n i t a l systems were a l s o examined.  RESULTS OF EXPERIMENTS A. C e r c a r i a e : No s t r i g e i d c e r c a r i a e were found emerging  from  the s n a i l s while an examination o f the s n a i l e t i s s u e s f a i l e d to show any developmental stages o f a s t r i g e i d cycle.  Two echlnostomecercariae were found  from Hellsoma sp. 3ubcr.enatum (Carpenter) lake.  These bear resemblance  to C e r c a r l a  Cort (1914) and t o C e r c a r l a c i t a M i l l e r  emerging from T a y l o r  trlvolvls.  (1925).  Table V I I .  I n f e c t i o n t r i a l s with experimental animals  Host  P e r i o d of Infection  R e s u l t of f e c a l examlnatlon  R e s u l t o f postmortem examination  Rat  33 days  negative  negative  Cat  lM- days  negative  Cat  21 days  negative  Cat  14 days  negative  Pigeon  15 days  Kitten  10 days  Kitten  Positive for T r i clurus eggs  1 fluke-Psllostomum ondatrae  Remarks  Metacercariae few, approx.20 Fed two l o t s  of 100-200  c y s t s In e v l s e r a t e d shiners 2 days a p a r t . One hundred200 c y s t s In evlserated shiners. Fed e v l s e r a t e d E a s t e r n Brook trout containi n g 100 c y s t s . Fed s k i n containing cysts.  Negative  Fed 60 c y s t s by hand  12 days  Negative  Kitten  13 days  Negative  (evlserated (shiner, force ( f e d 60 c y s t s (on 2 consecu( t i v e days.  Cat  20 days  Pigeon  10 days  negative  negative  Fed approx. 150 c y s t s  Pigeon  13 days  negative  negative  Fed approx. 150 c y s t s .  7 days  negative  negative  100 c y s t s .  Duck  Lymnaea p a l u s t r l a M u l l e r c o l l e c t e d from Okanagan l a k e - were I n f e c t e d by an u n i d e n t i f i e d  xlphidiocercaria.  B. A d u l t worm: The r e s u l t s of the f e e d i n g experiments are summarized In Table V I I . No s u c c e s s f u l i n f e c t i o n s r e s u l t e d — a l l the a n i mals b e i n g f r e e o f trematodes was  i n f e c t e d with a s i n g l e  except one pigeon which  specimen.  DISCUSSION The  s h i n e r s used d u r i n g June to i n f e c t two c a t s as  w e l l as an E a s t e r n Brook t r o u t f e d to another c a t , were shipped dead from Summerland.  A sample o f c y s t s removed from these  f i s h f o r examination showed that the metacercariae were l i v i n g . However, as the f i s h had been dead f o r a t l e a s t  twenty-four  hours i t i s p o s s i b l e that there may have been some t o x i c  effect  upon the p a r a s i t e due to the decomposition o f the h o s t .  This  t o x i c e f f e c t , though not great enough to k i l l  the worm, may  have been g r e a t enough to a l t e r the p h y s i o l o g i c a l c o n d i t i o n t o such an extent that the worm was unable t o e s t a b l i s h i t s e l f i n the experimental host. The one worm r e c o v e r e d from the p r o v e n t r i c u l u s o f a pigeon used f o r the f e e d i n g experiments was not a s t r i g e i d . There was no evidence o f a p a t h o l o g i c a l c o n d i t i o n i n the p r o ventriculus.  A d e s c r i p t i o n o f the f l u k e  follows.  Expls• .nation o f p i e t e I I  C C  ....  . .cirrus intestiiJ  r  1 caecum.  CP  cirrus  FP  e x c r e t o r y pore  O.S  . o r a l sue. er. •  °V P  CT  sue  •  «  ovary . .ph- rynx  SG ....  s h e l l glc.nd  T  testis  UT "  nr  VS  .uterus vitelline follicles. vemtr^i sucker  Plate  II  24 Psllostomum ondatrae P l a t e I I Host: Pigeon Site:  (experimental)  Proventriculus The  l e n g t h by 0.81  f l u k e measures 2 . l b mm.  o v o i d body o f the mm.  In  i n width at the l e v e l of the acetabulum  i s f l a t t e n e d d o r s o - v e n t r a l l y at the a n t e r i o r end.  and  Cuticular  spines are d i s t r i b u t e d over the e n t i r e body In a l t e r n a t e t r a n s verse  rows, t h i n n i n g out  from the l e v e l of the p o s t e r i o r t e s t e s  to the p o s t e r i o r extremity In l e n g t h .  o f the body.  O r a l sucker i s subterminal,  o r a l aperature  slit-like.  0.77  mm.  c e n t e r of the o r a l  wide.  The  by 0.217  mm.  by 0 , 2 5 2 mm.  sucker and  Prepharynx s h o r t .  l o n g by 0 . 0 7 mm.  0.210  mm.;  The  Distance  that of the  acetabulum  muscular pharynx I s 0.14  oesophagus branches to form  I n t e s t i n a l caeca?.' are  the p o s t e r i o r margin of the body. minal.  mm.  the  The  e x c r e t o r y pore i s t e r -  system c o u l d not be  lowed, because of the d e n s i t y of the r e p r o d u c t i v e  The  the  simple, extending almost to  Other p a r t s of the e x c r e t o r y  l a r g e , t r a n s v e r s e l y elongated  and bet-  i n t e s t i n a l caeca'"' Just i n f r o n t o f the a n t e r i o r margin of c i r r u s sac.  u  V e n t r a l sucker s t r o n g l y muscular  almost c i r c u l a r measuring 0 . 2 7 3 mm. ween the  Spines average 18.9  fol-  system.  The  t e s t e s are tandem In p o s i t i o n .  a n t e r i o r t e s t e s measure 0 . 4 9 mm.  e r i o r t e s t e s 0 . 5 0 4 by O.308 mm.  The  by 0.287  mm.,  the  post-  c i r r u s pouch i s l a r g e  and  b l a d d e r - l i k e w i t h I t s p o s t e r i o r margin extending d o r s a l to  and  s l i g h t l y beyond the a n t e r i o r edge of the v e n t r a l sucker. l o n g s l e n d e r c i r r u s Is unarmed.  The  ovary (0.161 mm.  by  The  25  0.14-7 mm.) midline. ing  l i e s a n t e r i o r to the t e s t e s and to the l e f t o f the The v i t e l l a r i a  i s composed o f l a r g e f o l l i c l e s extend-  from the p o s t e r i o r margin o f the pharynx to the p o s t e r i o r  t i p o f the body.  The f o l l i c l e s meet medianly both i n the an-  t e r i o r p o r t i o n o f the body where they obscure the oesophagus and  i n the p o s t e r i o r p o r t i o n o f the body behind t h e t e s t e s .  The  uterus i s r e l a t i v e l y short and l i e s between the t e s t e s and  v e n t r a l sucker.  The uterus contains  approximately  thirty  yellowish-brown eggs which measure 0.08 mm. by 0 , 3 5 mm. gland],dorsal the  and a n t e r i o r to t e s t e s .  5  A  Kennedy ( 1 9 3 ) and Beaver (l939)« 2  its life  sucker.  measurements of t h i s f l u k e f i t the d e s c r i p t i o n s  of Psllostomum ondatrae, d e s c r i b e d  and  G e n i t a l pore' situated to  r i g h t o f the median l i n e a n t e r i o r to the v e n t r a l The  Shell  cycle.  by P r i c e (1931)» Law and Beaver d e s c r i b e s  the worm  The two a n t e r i o r i n t e s t i n a l d i v e r t l c u l a e  p i c t u r e d by Beaver were not seen, nor are they p i c t u r e d by P r i c e o r Law and Kennedy.  The d e n s i t y of the f o l l i c l e s  e a s i l y obscure these d i v e r t l c u l a e and as no s e r i a l were made o f the f l u k e i t i s impossible  to s t a t e  could  sections  definitely  whether o r not they are p r e s e n t . The in a thin-walled  metacercariae o f t h i s f l u k e are found encysted cyst along the l a t e r a l l i n e c a n a l , and nares  o f a number o f f i s h e s and amphibians, i n c l u d i n g b u l l h e a d s (Amelurus). perch (Perca f l a v e s c e n s ) , rupestrls).  rock bass  smallmouth b l a c k bass (Mlcropterus  pumpkin^seed (Eupomotls gibbosus),  the b l u e g l l l  (Ambloplltes dolomleu), (Lepomls  26  pallldus),  t a d p o l e s o f s e v e r a l species, and salamanders.  I t Is  probable that the pigeon became i n f e c t e d from c y s t s that were s i t u a t e d i n the l a t e r a l l i n e o f the s h i n e r s f e d to I t d u r i n g the  f e e d i n g experiments.  The s n a i l h o s t f o r t h i s  Hellsoma antrosum percarlnatum.  fluke Is  The Hellsoma sp. suborenatum  (Carpenter) found so common i n T a y l o r lake c o u l d v e r y l i k e l y harbour the c e r c a r i a e .  Table V I I I .  Incidence  of b l a c k s p o t  In R l c h a r d s o n l u s  balteatus  In B r i t i s h Columbia.  Locality  Size of Sample  Cardew l a k e  237 51 109 58  S. Champion lake  288  Allison  lake  B a p t l s t e lake Box lake  18  Chimney lake Cultus  362  lake  228  Douglas l a k e  E r i e pond  30 438 ^5  Erie  pothole  116  Erie  slough  Duck l a k e Erie  lake  Fleming lake Garnet V a l l e y  dam  Horseshoe lake Hyas lake Heffley  lake  Inonoaklln  river  Jewel lake Kalamalka lake  53 105 180 63 164 125 51 93 l4o  Per cent Infection  1.38 9.80 7.3* 0.00 3.^9 0.00 3.30 7.00 0.00 38.58 31.10 34.30 66.04  0.00 17.75 0.00 45.12 22.40 3.92 100.00 28.11  Table V I I I .  Incidence of blackspot i n Richardsonlus i n B r i t i s h Columbia. Cont ^  balteatus  1  Size of Sample  Locality  Per cent Infection  Kootenay r i v e r  155  0.00  Llard  193  51.31  229  10.50  Mara l a k e  33  0.00  McBains l a k e  94  54.25  Mitchell  39  0.00  Monte lake  34  3g.2g  N i c o l a lake  g6  0.00  Okanagan lake (Okanagan Landing) Paddy Ryan lake  log  6.43  52  59.60  Paul  lake  197  2.10  Pemberton lake  167  35.71  Plnantan  29g  4.38  lake  Madden lake  lake  lake  Puntchesakut lake  65  6.16  Rock lake  125  95.20  Rosebud lake  962  24.40  Shuswap lake  70  5.71  Skaha lake  124  7.26  Snowshoe lake  423  64.4g  50  96.00  339  80.47  63  52.37  159  64.15  Surveyor's lake T a y l o r lake West lake Beaverly Cluculz  creek  creek  27  GEOGRAPHIC DISTRIBUTION. BRITISH COLUMBIA  v Examinatlon  of some s i x thousand f i s h from f o r t y -  f o u r l o c a l i t i e s on the Columbla-Fraser  watershed p r o v i d e s the  i n f o r m a t i o n on the g e o g r a p h i c a l d i s t r i b u t i o n o f b l a c k spot. The  f i s h were caught and p r e s e r v e d i n f o r m a l i n d u r i n g the sum-  mers o f 1947;, 194S, sample from Garnet  19^?, and 1950, w i t h the exception of one V a l l e y Dam  of Zoology which was  b e l o n g i n g to the O n t a r i o Museum  taken on J u l y 6,  192S.  Blackspot Is e r r a t i c a l l y though widely throughout l a k e s and  B r i t i s h Columbia.  T h i r t y - s i x of the  distributed  forty-four  streams r e p r e s e n t e d i n the c o l l e c t i o n showed the  d i s e a s e to be present i n the  shiners.  These waters are  a l p h a b e t i c a l l y °along with the sample s i z e and percentage  listed of  I n f e c t e d f i s h i n Table V I I I . The  Incidence v a r i e s from almost  complete freedom  from the d i s e a s e In Skaha, A l l i s o n , Champion, Okanagan and  Paul  l a k e s to I n f e c t i o n s i n v o l v i n g f i f t y per cent or more of the f i s h as i n Jewel, Rock, T a y l o r and  Snowshoe l a k e s .  In Jewel  lake everyjone of the n i n e t y - t h r e e f i s h e s examined was F i g . 6 i s a map  of B r i t i s h Columbia showing the d i s t r i b u t i o n of  i n f e c t e d l a k e s and The  Infected.  the percentage  constancy  of f i s h w i t h the d i s e a s e .  of I n f e c t i o n has been n o t i c e d In  l a k e s where c o l l e c t i o n s are a v a i l a b l e f o r a number of y e a r s . However, more data are necessary before a d e f i n i t e  statement  F i g . 6.  D i s t r i b u t i o n and incidence of black spot i n the shiner, Ricbardsonius b a l t e a t u s .  28 may "be made.  It would be interesting to follow,  for a number  of years, the infestation i n a lake such as Paul lake where the shiners have recently been introduced to see i f there Is a gradual increase in the percentage of the f i s h infected.  The  table below gives the per cent infection of four lakes for which data are available for a number of years.  Table IX.  Per cent Infestation of shiners in four lakes for several years. 19.28  Garnet Valley Dam  1948  1949  18.3  17.2  Cultus lake  3.3  West lake  6l.l  Taylor lake  1950  81.4  80.1  2.1 58.3 80.8  Samples of shiners are available from May to August 1949 from Rosebud and Taylor lakes.  Rosebud shows an increase  in percentage of Infected f i s h from May t i l l August, a phenomenon not found among samples from Taylor lake.  The percentage  of f i s h infected and the size of the sample for the months of May, June and August for each lake follows.  29  Rosebud lake Percent  Fish Infected  S i z e of Sample  May  12.6  W-5  June  16.4  32g  August  4b.3  200  T a y l o r lake Percent  Fish Infected  S i z e of Sample  May  80.3  163  June  go.5  203  August  gl.7  159  Several f i s h e s o t h e r than the lake s h i n e r were found  to be i n f e c t e d with b l a c k s p o t ; squawfish,  oregonensis  (Richardson);  Ptychochellus  chub, M y l o c h e l l u s caurlnus, ( R i c h a r d -  son); c o a r s e - s c a l e d sucker,  Catastomus macrochellus  p r i c k l y s c u l p i n Cottus asp.er Richardson;  Gerard;  E a s t e r n brook t r o u t  S a l v e l l n u s f o n t i n a l i s ; Kamloops t r o u t , Salmo g a l r d n e r i l kamloops and the Rocky Mountain w h i t e f i s h , Pros opium wllllamson.l. (Gerard). as the  The  squawfish were found to be as h e a v i l y i n f e c t e d  s h i n e r s i n most l o c a l i t i e s ,  r e l a t i v e l y f r e e of the d i s e a s e . or may  a l l other s p e c i e s being  The d i s e a s e i n these f i s h  not be caused by the metacerearia  may  r e s p o n s i b l e f o r the  d i s e a s e i n the s h i n e r . E a s t e r n Brook t r o u t from Garnet V a l l e y Dam Mabel lake are h e a v i l y I n f e c t e d , while  and  the Kamloops t r o u t from  30 the same l a k e s are a p p a r e n t l y f r e e from the d i s e a s e . Fishermen from t h i s a r e a have made s e v e r a l complaints d i s e a s e i n the Eastern Brook t r o u t to Mr. Summerland Hatchery.  regarding  the  A r t Higgs of the  31  DISCUSSION The  sporadic d i s t r i b u t i o n of b l a c k s p o t i n the A  s h i n e r on the Columbia-Fraser  watershed i s a l s o n o t i c e a b l e In  e a s t e r n Canada and U n i t e d S t a t e s . to  T h i s cannot be  attributed  the d i s t r i b u t i o n o f the d e f i n i t i v e host, a f i s h - e a t i n g  (the  k i n g f i s h e r f o r both the s t r i g e i d s whose  bird  l i f e c y c l e have  been determined) f o r the b i r d w i l l be found wherever there Is a body of water c o n t a i n i n g enough f i s h to f u r n i s h I t with food. It  appears  presence  then that the s n a i l i s the f a c t o r upon which the  or absence of the d i s e a s e depends. Each of the s t r i g e i d s r e s p o n s i b l e f o r the d i s e a s e  i n North America '.whose, c e r c a r i a l stage i s known, has been found to u t i l i z e mediate h o s t .  some s p e c i e s of Hellsoma  The  as I t s f i r s t  lake i n which b l a c k spot occurs must p r o v i d e  the\|;ype of h a b i t a t necessary f o r the s u r v i v a l of these In  T a y l o r lake and  author, Hellsoma dant  s n a i l found.  inter-  Summit l a k e , the two  snails.  l a k e s examined by  of subcrenatum (Carpenter)  the  Is the most abun-  These s n a i l s were found on the waterplants  (sedge, b u l r u s h , and water l i l y ) and submerged l o g s near the edge of the l a k e , being most abundant where there Is a muddy bottom ( f i g .  7).  They were never found along the rocky  ches of s h o r e l i n e ( f i g .  3).  Shiners were both among the  stretreeds  and along the rocky areas. An attempt  was  made to c o r r e l a t e the d i s e a s e w i t h  Fig.7.  Fig. 8.  Snail habitat  at Taylor  lake.  Barren shoreline free of s n a i l s , Taylor l a k e .  32  the temperature and degree of hardness of the water i n l a k e s and  streams where the d i s e a s e was  known to occur, however, no  r e l a t i o n s h i p c o u l d be e s t a b l i s h e d . A l l other f a c t o r s being e q u a l ,  s n a i l s w i l l be more  abundant i n waters w i t h h i g h calcium and phosphorus tions.  An  i n c r e a s e i n the amount of calcium and  phosphorus i n  a s o f t water l a k e through the a d d i t i o n of chemical w i l l b r i n g about c o n d i t i o n s f a v o u r i n g the support  concentra-  fertilizers of a l a r g e r  s n a i l p o p u l a t i o n and hence a tendency f o r an Increase spot i n c i d e n c e .  Cases of t h i s nature  workers, among whom are Cross,  have been n o t i c e d by some  Cameron and Lachance.  (1933) found t h a t smallmouthed b l a c k bass and p e r c h s o f t water l a k e i n northern  Wisconsin  trematode c y s t s i n 1931  1932.  and  f i s h were found to be  s i m i l a r s i t u a t i o n was  However, In 1933» a f t e r  A  OF HOST  and  the  s i t e of  infec-  l e a d to p a r t i a l immunity to f u t u r e  the same p a r a s i t e , but  t h i s does not appear to be  the case i n s h i n e r s I n f e c t e d by b l a c k s p o t . paper i t was  cant  e f f e c t of p a r a s i t i s m on the host depends p r i -  I n i t i a l i n f e c t i o n may  a t t a c k s by  s i x per  two  i n f e s t e d with s t r i g e i d cysts,  m a r i l y on the number of p a r a s i t e s present tion.  i n a small  d e s c r i b e d by Lachance (1943) i n Quebec.  RELATION OF INFECTION TO AGE The  Cross  were e n t i r e l y f r e e from  summers of calcium and phosphorus f e r t i l i z a t i o n , of the  i n black  E a r l i e r i n the  p o i n t e d out that there appears to be a  signifi-  c a n t l y l a r g e r number of c y s t s i n o l d f i s h than i n young  fish.  33  A l s o f i s h i n t h e i r second year,  or o l d e r , show c y s t s i n v a r i o u s  s t a g e s — u n p i g m e n t e d , newly formed; f u l l y pigmentedaand In v a r i o u s  others  stages of d i s i n t e g r a t i o n i n d i c a t i n g s u p e r i m p o s e d  multiple infections.  Hunter (1928) working w i t h Lepomls  c y a n e l l u s n o t i c e d that the l a r g e r f i s h showed more c y s t s than d i d the due  s m a l l e r f i s h and  came to the c o n c l u s i o n  McCoy's experiments i n 1928  to m u l t i p l e exposures.  C e r c a r l a hamata to f u t u r e  that t h i s  showed that the f i s h d i d not a c q u i r e  was  with  resistance  attacks.  EFFECT OF PARASITE ON HOST From the i n f o r m a t i o n the p e n e t r a t i o n greatest  a v a i l a b l e In the  of the c e r c a r l a Into the  irritation.  The  author d i d not  literature  f i s h i s the p e r i o d f i n d any  of  strigeid  c e r c a r i a e d u r i n g examination of s n a i l s from T a y l o r l a k e , thus no experiments on the p e n e t r a t i o n c o u l d be  c a r r i e d out.  of c e r c a r i a e i n t o  McCoy ( 1 9 2 8 ) ,  Krull  (193*1-) and Hobgood  (1938) found t h a t experimental f i s h became h i g h l y d u r i n g a t t a c k s by c e r c a r i a e . t i o n and and  go  s t a t e s as f o l l o w s :  through the water by  a f t e r the by rubbing  irritable  K r u l l g i v e s the f u l l e s t "They are  stimulated  to  descrlpr activity  spurts i n a l l d i r e c t i o n s .  i n i t i a l a t t a c k they attempt to detach the against  shiners  the bottom and  cercariae  s i d e s of the aquarium."  a o t i v i t y i s r e p l a c e d by a f l e x i n g of the f i s h ' s body to s i d e or the other f o r s e v e r a l seconds. about f i f t e e n minutes and  "the  Soon  This one  A c t i v i t y ceases a f t e r  exhausted f i s h c o l l e c t  near  the s u r f a c e of the water, remaining m o t i o n l e s s f o r an hour or more except f o r profound r e s p i r a t o r y movements, before  resuming  t h e i r normal a c t i v i t y . " Such extreme exhaustion would make the f i s h prey f o r p r e d a t o r s .  easy  However, the extreme c o n c e n t r a t i o n s o f  c e r c a r i a e used i n the experiments  may  not occur i n nature  and  a t the same time the v i o l e n t a c t i v i t y of the f i s h caused by the p e n e t r a t i n g c e r c a r i a e would probably soon take them o u t s i d e the range of the l a r v a e . The wounds made by the c e r c a r i a e may p o r t of e n t r y f o r b a c t e r i a l have been observed.  provide a  and/or f u n g i but no such  infections  Some authors have r e p o r t e d the l o s s of a  few drops o f blood from the s k i n and the development of a s m a l l haemorrhaglc  few  areas i n the t i s s u e at the time of c e r c a r i a l  penetration. Small f i s h w i t h l a r g e numbers of c y s t s i n t h e i r muscle t i s s u e may  have t h e i r body permanently  f l e x e d or  stif-  fened to such an extent that t h e i r swimming speed i s decreased a c c o r d i n g to K r u l l  (1934).  T h i s l a t t e r e f f e c t was  n o t i c e d by  the w r i t e r while working a t T a y l o r l a k e and a g a i n i n the h a t c h e r i e s a t Summerland and  the U n i v e r s i t y of B r i t i s h  fish  Columbia,  being p a r t i c u l a r l y evident i n some of the l a r g e r s h i n e r s which were completely covered by b l a c k s p o t .  These f i s h , however, had  the c y s t s c o n f i n e d to the s k i n except f o r the o c c a s i o n a l one found i n the muscle.  T h e r e f o r e , u n l e s s the presence of the  c y s t s i n the s k i n reduces the e l a s t i c i t y of the s k i n to the  35 extent where movement i s hampered, i t i s more l i k e l y that r e t a r d a t i o n i n speed i s t h e " r e s u l t of lowered or upset b o l i c a c t i v i t i e s of the f i s h .  The  the ray elements, but  of l i t t l e  t h i s was  the  meta-  c y s t s i n the f i n s d i s p l a c e d Importance as  body Is used i n swimming, the f i n s merely a c t i n g as  the  stabili-  zers. R e t a r d a t i o n i n development of young f i s h has been r e p o r t e d by Hubbs (1927) and by K r u l l the problem was  (1934).  T h i s aspect  not i n v e s t i g a t e d but a heavy I n f e c t i o n of  p a r a s i t e d u r i n g a p e r i o d of r a p i d growth would e x e r t a p h y s i o l o g i c a l s t r a i n on the f i s h . i n f e s t e d by Schlstocephalus ded  I t was  of any  severe  n o t i c e d i n lakes  sp. t h a t i n f e c t e d f i s h were r e t a r -  In growth and body deformed, but here the s i z e of the  s i t e i s an Important f a c t o r , a f a c t o r which i s of l i t t l e  paracon-  sequence i n b l a c k s p o t except i n very heavy i n f e s t a t i o n s . The ly  sometimes a s i t e of I n f e c t i o n e s p e c i a l -  In the h e a v i l y i n f e c t e d f i s h ,  socket and No  eye was  the c y s t s being c o n f i n e d to  the c o n j u n c t i v a near the p e r i p h e r y of the  socket.  s i g n s of "pop-eye" were n o t i c e d as r e p o r t e d by K r u l l  C. b e s s l a e I n f e c t i o n s .  Blackspot  the  has been r e p o r t e d by  In Hsla  (1941) to have caused b l i n d n e s s i n the common cod G-adus ca.1l a r l s L.  but  t h i s i s without  doubt another i n s t a n c e of  exception r a t h e r than the r u l e .  The  the  presence of the metacer-  c a r i a e i n the s h i n e r s ' eyes would reduce the amount of l i g h t e n t e r i n g the eye and  cause some d i s t o r t i o n of the v i s u a l image  though they were never found i n s u f f i c i e n t numbers to cause  '  36 blindness,  ECONOMIC CONSIDERATIONS The  s h i n e r , R l c h a r d s o n i u s b a l t e a t u s , i s not of  d i r e c t economic value i n t h a t i t i s n o t a commercial or sport fish. mic  Blackspot d i s e a s e i n i t i s t h e r e f o r e not of d i r e c t econo-  significance.  However, the s h i n e r may serve as r e s e r v o i r  from which the i n f e s t a t i o n o f the d e f i n i t i v e host may be maint a i n e d at a h i g h l e v e l .  T h i s would mean an Increase i n the  number o f eggs r e a c h i n g the s n a i l r e s u l t i n g i n an Increase i n the number o f c e r c a r i a e a v a i l a b l e t o i n f e c t game and commercial fish. To date the o n l y complaints o f . b l a c k spot^ i n game f i s h have come from Garnet V a l l e y Dam and Mabel lake near Sumraerland where the E a s t e r n Brook t r o u t are h e a v i l y i n f e c t e d . Whether the m e t a c e r e a r i a i n t h i s f i s h for  i s the one r e s p o n s i b l e  the d i s e a s e i n s h i n e r s remains to be determined,  examined by the author show the same m o r p h o l o g i c a l t i c s as those i n the s h i n e r s . to be completed  but those characteris-  L i f e h i s t o r y s t u d i e s w i l l have  before a d e f i n i t e d e c i s i o n can be reached.  The  author, as s t a t e d e a r l i e r , has found the disease to be present i n the Kamloopss t r o u t and Rocky Mountain w h i t e f i s h , both o f which are Important  game or commercial  fish.  C o n t r o l of the d i s e a s e through the e r a d i c a t i o n o f s n a i l s may not be p r a c t i c a l because of expense.  Copper sulphate  37 I s the chemical  g e n e r a l l y used to d e s t r o y s n a i l s hut has the  disadvantage o f being h i g h l y t o x i c to f i s h and o f being r a p i d l y l o s t from s o l u t i o n by r u n - o f f and c o n v e c t i o n  currents.  A  mixture o f copper sulphate and copper carbonate In the r a t i o o f 2:1 by weight I s more e f f e c t i v e a c c o r d i n g to Cort  (1950)*  Cost  may be p r o h i b i t i v e i n l a r g e bodies o f water where.repeated a p p l i c a t i o n would be r e q u i r e d . As the r e d u c t i o n of p a r a s i t e p o p u l a t i o n s  i s attain-  ed by e f f e c t i v e l y I n t e r r u p t i n g the c h a i n of events necessary to complete the l i f e  c y c l e , the d e s t r u c t i o n o f s h i n e r s should  they  prove to be a r e s e r v o i r would a l s o h e l p c o n t r o l the d i s e a s e . I f the  s h i n e r s can be removed o r reduced In s u f f i c i e n t numbers  without  u p s e t t i n g the economy of the l a k e t o any great  extent,  c o n t r o l would r e s u l t from the r e d u c t i o n o f i n f e c t i v e metacercariae. C o n t r o l by k i l l i n g  the d e f i n i t i v e host  i s hardly  f e a s i b l e as i t w i l l l i k e l y prove to be e i t h e r a f i s h - e a t i n g b i r d o r mammal. ed but those migratory  P o s s i b l y numbers o f the mammal c o u l d be l i m i t -  o f b i r d s would be more d i f f i c u l t because of t h e i r  habits.  E f f e c t i v e c o n t r o l o f the d i s e a s e w i l l have t o  stem from the r e d u c t i o n o f the s n a i l p o p u l a t i o n , o r the s h i n e r p o p u l a t i o n , or both.  38  SUMMARY 1.  A d e s c r i p t i o n of the s t r i g e i d metacerearia r e s p o n s i b l e f o r  ^u^^^"  black spot i n Rlehardsonlus b a l t e a t u s i s g i v e n .  2. The host cyst c o n s i s t s of two l a y e r s , an outer area with melano phores i n the loose connective t i s s u e and an i n n e r more dense,, unpigmented connective t i s s u e l a y e r . 3 . Cysts are found i n the s k i n , f i n s , eye, mouth, and g i l l s . 4 Lakes with a high percentage  i n f e c t i o n show more c y s t s p e r  i n f e c t e d f i s h than do l a k e s with a low percentage  infection.  5 . Young f i s h have fewer c y s t s p e r f i s h than do o l d f i s h . g. Attempts to o b t a i n a d u l t s t r i g e i d s by f e e d i n g c y s t s to p i g eons, ducklings, cats, and r a t s f a i l e d . One worm, Psllostomum ondatrae was recovered from a pigeon. 7-r Black spot is. widely though e r r a t l c a l l y i f l i s t r i b u t e d i n B r i t i s h Columbia. T h i r t y three of f o r t y two lakes examined were i n f e c t e d . 8. P t y c h o l e i l u s oregonensi  J Mvlochellus caurlnas; f J a t a s t m i i R  . macrochellus; Cottus asper:. S a l v e l i n u s f o n t l n a l l s , Salmo g a l r d n e r l l kamloops."and Prosoplum w l l l i a m s o n l were a l s o i n f e c t e d by black spot.  39  LITERATURE CITED BEAVER, P a u l C. 1939.  The morphology and l i f e h i s t o r y o f Psllo.stomum ondatrae P r i c e , 1931* (Trematoda: Psllostomidae) J . P a r a s i t o i . 25:383-393. 14 f i g s . ..  CAMERON, Thomas, W. M. S t u d i e s oh the Heterophyid Trematode, 1936. Apophallus venustus (Ransom, 1920) i n Canada. I Morphology and Taxonomy. Can. Jour. Res., D. 14:59-69. CAMERON, Thomas W. N. S t u d i e s on the Heterophid Trematode, 1937. Aoophallus venustus (Ransom, 1920) i n Canada. I I L i f e H i s t o r y and Bionomics. Can. Jour, ges., D. 1 5 : 3 8 - 5 1 CAMERON, Thomas w, M. S t u d i e s on the Heterophyid Trematode, 1937. Apophallus venustus (Ransom, 1920) i n Canada. I l l F u r t h e r Hosts. Can. Jour. Res., D, 15:275 CAMERON, T. W. M, 1946.  COLLINS, W. W. 1935.  COOPER, A. R. 1915.  CORT, W. W, 1950.  CROSS, S. X. 1933.  DUBOIS, G. 193^.  B l a c k Spot and Yellow Grub I n F i s h . Rod and Gun Canada. Sept. and Oct. I s s u e . A d e s c r i p t i o n of C e r c a r l a J . P a r a s i t o i . 21:18-20.  f l e x l c o r p a n.  sp.  Trematodes from marine and f r e s h water f i s h e s . Trans. Roy. Soc. Can. £ ( 4 ) : l 8 l - 2 0 5 . T h r e e - p i . from minnow. S t u d i e s on Schistosome D e r m a t i t i s . XI Status of knowledge a f t e r more than twenty y e a r s . Am. J . Hygiene 52 ( 3 ) : 2 5 1 - 3 0 7 . Some host p a r a s i t e r e l a t i o n s h i p s of f i s h p a r a s i t e s o f the Trout lake r e g i o n o f Northern Wisconsin. Jour. P a r a s i t o i . 20:132-133. Monographie des S t r i g e l d a (Trematoda). Mem. Soc. N e u c h a t e l o i s e S c i . N a t . 6 : 1 - 5 3 5 352 f i g s .  40  H0BG00D, J . 0. 1938.  The m e t a c e r c a r i a of C e r c a r l a flexicorr>a Colling. Trans. Am. M i c r . Soc. f>7_: 1 5 8 - 1 6 4 . 3 f i g s .  HSIA, Sidney 0. T, Melanosis In the common cod, G-adus c a l l a r l s 1941. L., a s s o c i a t e d with Treraatoda i n f e c t i o n . Biol. Bull. 10(l):37-44. 2 figs. HUBBS, C. L. 1927.  HUGHES, R. C. 1927.  HUGHES, R. C. 1928.  HUGHES, R. C. 1928.  HUNTER, G. 1933.  The r e l a t e d e f f e c t s o f a p a r a s i t e on a f i s h : a r e t a r d a t i o n o f e a r l y growth, the r e t e n t i o n of l a r v a l c h a r a c t e r s and an Increase i n the number of s c a l e s . J . P a r a s l t o l . 14:75-84. 1 fig. S t u d i e s on the trematode f a m i l y S t r l g e l d a e (Holostomidae) No. 6. A new m e t a c e r c a r i a Neascus a m b l o p l l t l s . sp. nov., r e p r e s e n t i n g a new l a r v a l group. Trans. Am. M i c r . Soc. 46:248-267. S t u d i e s on the trematode f a m i l y S t r l g e l d a e (Holostomidae) No. VII, Tetracotyle plplent l s Faust. Trans. Am. M i c r . Soc. 4 7 ( l ) : 4 2 - 5 3 . S t u d i e s on the trematode f a m i l y S t r l g e l d a e (Holostomidae) No. 1 0 . Neascus b u l b o g l o s s a (Van Haitsma). Parasltol. 1£:52-57.  tf.III. The s t r i g e i d trematode, C r a s s l p h i ^ a l a a m b l o o l l t l a (Hughes, 1 9 2 7 ) . P a r a s l t o l . 2^:510-517.  HUNTER, G. W. I l l , P a r a s i t i s m o f f i s h e s i n the lower Hudson 1937. area. Suppl. 26th Ann. Report. N.Y. State Conserv. Dept. B i o l . Surv. No. XI, Lower Hudson Watershed, 1936:264-273. HUNTER, G. W. I I I . 1941.  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