UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

The effect of photoperiod on the goldfish (Carassius auratus) Hollands, Mary 1956

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-UBC_1956_A8 H6 E3.pdf [ 2.52MB ]
Metadata
JSON: 831-1.0106288.json
JSON-LD: 831-1.0106288-ld.json
RDF/XML (Pretty): 831-1.0106288-rdf.xml
RDF/JSON: 831-1.0106288-rdf.json
Turtle: 831-1.0106288-turtle.txt
N-Triples: 831-1.0106288-rdf-ntriples.txt
Original Record: 831-1.0106288-source.json
Full Text
831-1.0106288-fulltext.txt
Citation
831-1.0106288.ris

Full Text

THE EFFECT OF PHOTOPERIOD ON THE GOLDFISH (Carassius aur.atus') by Mary Hollands A thesis submitted i n p a r t i a l fulfilment of the requirements f o r the Degree of Master of Arts In the Department of Zoology We accept t h i s thesis as conforming to the standard required from candidates f o r the degree of Master of Arts Members of the Department of Zoology The University of B r i t i s h Columbia September 1956 In presenting t h i s thesis i n p a r t i a l f u l f i l m e n t of the requirements fo r an advanced degree at the University of B r i t i s h Columbia, I agree that the Library s h a l l make i t f r e e l y available f o r reference and study. I further agree that permission f o r extensive copying of t h i s thesis for scholarly purposes may be granted by the Head of my Department or by h i s representative. I t i s under-stood that copying or publication of t h i s t h e s i s f o r f i n a n c i a l gain s h a l l not be allowed without my written permission. Department of The University of B r i t i s h Columbia, Vancouver Canada, Date _s#f>*;l 4- /9G&. THE EFFECTS OF PHOTOPERIOD ON THE GOLDFISH (Carassius auratus) ABSTRACT Goldfish (Carassius auratus) of i d e n t i c a l thermal and dietary history were subjected to long-day (16 hour) and short-day (8 hour) l i g h t periods. Variation i n the a b i l i t y of these groups to withstand temperature extremes were compared during the f a l l and winter of 1955 and during the spring and summer of 1956. In the f a l l and winter group f i s h exposed to 8 hour d a i l y illumination were consistently more resistant to cold and l e s s resistant to heat while the reverse was true of the 16 hour group. In the spring and summer f i s h the differences were not as marked and were generally i n the opposite d i r e c t i o n . In general, the data showed that size as well as sex of the goldfish tested modified the observed resistance. At both seasons, f i s h exposed to shorter d a i l y illumination had higher tissue phospholipid and cholesterol than those exposed to longer illumination. Phospholipid and cholesterol were also compared i n the d i f f e r e n t sexes. ACKNOWLEDGEMENTS I wish to express my sincere appreciation to Dr. W.S. Hoar under whose supervision and guidance the present work was done. For t r a n s l a t i o n of pertinent French papers, I wish to thank D. Wilson and A. Werner. The assistance of fellow students, especially that given by K. Newman, E. Robertson and A. Houston have been greatly appreciated. My thanks also go to the National Research Council whose f i n a n c i a l assistance made t h i s project possible. i TABLE OF CONTENTS p a g e Acknowledgements Introduction 1 Material and Methods General 3 Thermal Resistance 4 Chemical Analysis 5 Results Eff e c t of Photoperiod on Thermal Resistance Winter Series 10 Summer Series 10 Influence of Size and Sex on Thermal Resistance Size 15 Sex 16 Biochemical Results of Photoperiod Moisture 21 Total L i p i d • 22 Changes i n Phospholipid and Cholesterol Progressive changes 22 Photoperiod effect 26 Sex effect 26 Review of Pertinent Literature on Photoperiodism 28 Discussion Photoperiod-Induced Changes i n Thermal Resistance Winter Series 32 Summer Series 32 Photoperiod-Induced Changes i n Tissue L i p i d 33 Summary 35 Appendix 36 Literature Cited 33 i i LIST OF TABLES Page Table I. Winter Heat Resistance 11 I I . Winter Cold Resistance 12 I I I . Summer Heat Resistance .. 13 IV. Summer Cold Resistance 14 V. Average Size 17 VI. Size E f f e c t on Thermal Resistance 18 VII. Sex Effe c t 19 VIII. Sex Effe c t 20 IX. Winter Total L i p i d 23 X. Summer Total L i p i d 24 XI. Summer Phospholipid and Cholesterol 25 XII. Winter Phospholipid and Cholesterol 27 LIST OP FIGURES Light E f f e c t on Winter Resistance Light E f f e c t on Summer Resistance Cholesterol / Phospholipid Ratio Short-Day / Long-Day Ratio Winter Illumination Ef f e c t on Phospholipid and Cholesterol Summer Illumination E f f e c t on Phospholipid and Cholesterol Sex Differences i n Phospholipid and Cholesterol INTRODUCTION Seasonal changes i n physiology are known to occur i n many f i s h . The metabolism of the carp (Cronheim, 1911) showed seasonal s h i f t s when compared under standard •". conditions. Seasonal variations i n the growth rate and thyroid gland a c t i v i t y have been demonstrated i n trout (Swift, 1955). In a series of f i s h , Schlicher (1926) showed a regular pattern of seasonal change i n the number of red and of white blood corpuscles. Brett (1946) noted seasonal v a r i a t i o n i n the thermal tolerance of f i s h and he attributed these differences to acclimatization of the f i s h to environmental temperature changes. The seasonal cycle i n temperature i s an obvious basis f o r such changes since the resistance of f i s h to extremes of heat or cold can be markedly altered by acclimatizing them to progressively higher or lower temperatures. In t h i s laboratory, goldfish maintained at a constant temperature and fed a standard diet showed seasonal changes i n thermal tolerance (Hoar, 1955). Other workers have also described temperature independent seasonal changes i n the physiology of fi s h e s . A r i s e i n the rate of oxygen consumption by the P a c i f i c k i l U f i s h occurred i n the spring independent of environmental temperature fluctuations (Wells, 1935). S i m i l a r l y , changes which are apparently independent of variations i n acclimation temperature take place i n the blood c e l l count of certain f i s h (Schaefer, 1924-25), and i n the growth rate (Brown, 1946) and i n the selected temperature (Sullivan and Fisher, 1953) of trout. Attempts to understand the physiological mechanism involved i n variable temperature resistance have, i n t h i s laboratory, centered around a study of tissue l i p i d s . The 2 a b i l i t y to withstand heat or cold has long been associated with the body l i p i d s (Heilbrunn, 1952). Cottle (1951) investigated changes i n the tissue l i p i d fractions of g o l d f i s h acclimated to different temperatures. She reported decreased phospholipid l e v e l s when the f i s h were cold acclimated; cholesterol values were reported r e l a t i v e l y constant at a l l temperatures. In addition, i t has been found that dietary l i p i d can markedly change the temperature resistance (Hoar and Cottle, 1952). Many seasonal changes i n physiology are known to be photoperiodieally controlled. The present study was planned to determine the possible role of photoperiodism i n the seasonal changes i n thermal resistance. Concomitant studies of tissue l i p i d s were carried out In the hope that the understanding of the role of the l i p i d s i n variable temperature resistance could be increased. 3 MATERIALS AND METHODS A. General Goldfish (Carasslus auratus) were procured from Goldfish Supply Company, S t o u f f v i l l e , Ontario i n l o t s of 200-600 f i s h per shipment. These f i s h had, presumably, been reared i n outdoor pools and had, thus, been subjected to regular seasonal cycles of climatic changes. Stock f i s h , i n the laboratory, were held i n large concrete tanks at about 18° - 1° C and were fed pablum. Photoperiod acclimation was carried out i n a separate darkened room where the aquaria were kept i n two separate wooden closets. Three glass aquaria (80 x 50 x 40 cm.) i n each cupboard, were excluded from a l l natural light"by s l i d i n g doors i n front of them. Experiments were carried out i n a winter (Oct.-Dec.) and summer series (May-July). In each series, two groups of f i s h were placed under dif f e r e n t photoperiod treatment. The f i r s t group received 8 hours illumination and 16 hours darkness while the second group received 16 hours illumination alternating with 8 hours darkness. The period of darkness was uninterrupted. A r t i f i c i a l l i g h t was supplied by fluorescent tubes, one placed above each aquarium. Lights were turned on and o f f by an automatic time switch (Inter-matic). Illumination was 58-66 foot candles at the water surface. The temperature of the water i n the aquaria of the winter series was 18° - 20° C i n a l l tanks. Each aquarium was provided with a Lo-lag immersion heater and Penwal - 0.5° C thermoregulator. The thermostats were set f o r 20° C. Since the summer temperature elevated the water above 21° C. a cooling system was introduced". This consisted of a long p l a s t i c tube (Diameter, 1 cm.) which was co i l e d through the 4 6 aquaria. Cold water from the tap was circulated through the hose. In t h i s way a constant temperature of 20° - 1° C. was maintained. The n u t r i t i o n a l requirements of the f i s h were met by 3 d a i l y feedings of pablum supplemented by a weekly feeding of shrimp meal. Approximately 0.15 gm. of pablum per f i s h per day was given. During the experimental series, as f i s h were removed, the amount of food per tank was adjusted. Each feeding took 15-20 minutes, only a small amount of the food being placed into each aquarium at a time. A l l feedings were made during the illumination period. The aquaria water was changed once a week. On these days, the f i s h were fed twice before changing the water. B. Thermal Resistance These experiments are based on 408 goldfi s h (136 winter, 272 summer). In test i n g thermal resistance, 34 f i s h from each group were randomly chosen, the caudal f i n of one group clipped and then the f i s h were placed i n 2 holding tanks at 20° i 2° C. u n t i l next morning when they were tested together i n the l e t h a l temperature baths. The f i s h were marked the previous day to avoid exciting and exhausting them just p r i o r to the c r i t i c a l thermal t e s t . The groups were alternatingly marked from test to t e s t j that i s , i n one test the 8 hour group had f i n c l i p s while the reverse occurred i n the next t e s t . i . Low Temperature Resistance Seventeen f i s h of each group were placed i n a thermostatically controlled r e f r i g e r a t o r tank. The i n i t i a l temperature varied from 2° - 4° C. and was slowly decreased to 1° C. (minimum 0.5° C ) . Checks to remove dead f i s h were made at frequent inter v a l s during the f i r s t few hours of the tes t , a f t e r which a check every hour suf f i c e d . Great d i f f i c u l t y i s encountered i n determining when a c h i l l e d f i s h has actually died (Sumner and Doudoroff, 1938) since many f i s h lay motionless, 5 i n a state of cold narcosis, on the bottom of the tank. To obtain an arbi t r a r y end point, a reproducible series of meehanieal stimuli were used. Pish showing no response to caudal f i n tapping while i n the cold tank were b r i e f l y removed to a cold wet glass plate and the caudal peduncle tapped 3 times with a glass rod. I f t h i s f a i l e d to e l i c i t a response, the f i s h was placed i n aerated water at a temperature of 16°-20° C. and examined 60 minutes l a t e r . Any f i s h not showing recovery a f t e r one hour were termed " t r u l y dead" while any f i s h f u l l y recovered were termed "recovery" (Irvine, 1954). The test was discontinued a f t e r 24-30 hours and the data (size and sex) on the survivors recorded. i i . High Temperature Resistance The remaining 17 f i s h from each group were placed i n a heated bath of i n i t i a l temperature 34.5° C - 36.5° 0. and the temperature was increased to 37.0° C. The f i s h were checked at 5-10 minute intervals by prodding the f i n s with a glass rod and unresponsive f i s h were removed to a beaker of fresh aerated water at 19° C - 1° C. After 20 minutes the "removals" were checked f o r "recovery". The test was discontinued a f t e r 7-9 hours. Smith (1950) found that length and weight of goldfish influence the c h i l l - m o r t a l i t y rate. Sex, also, i s a factor a f f e c t i n g the cold resistance (Irvine, 1954). Sub-sequently, pertinent data on each f i s h was recorded, including weight, length, sex of f i s h , the time and temperature at which each f i s h was removed from the l e t h a l bath and the reaction of f i s h to "warming up" or "cooling down". Goldfish used i n thermal resistance tests were never used f o r chemical assay. C. Ohemical Analysis The chemical analyses were conducted on 696 goldfish (390, short-day group; 306, long-day group). The photoperiod f i s h , a f t e r length, weight and sex had been recorded 6 were separated into male and female samples and analyzed immediately. The goldfish were put through a meat grinder and subsequently, macerated i n a Waring Blendor. Samples of tissue mash from each l o t were used to determine moisture content and t o t a l l i p i d value. I. Moisture Content The percentage moisture was determined by the Cenco Moisture Balance. Duplicate samples varied within 0.1 - 0.2$ and the average was calculated. Irvine (1954) compared average, t r i p l i c a t e moisture determinations using the Moisture Balance with results obtained by using the conventional oven drying method and found the values check within a maximum of 0.28$. Drying to a constant weight required 25-30 minutes when the rheostat was set at 80 u n i t s . i i . T otal L i p i d s Since ether extraction of tissue f a i l s to break some l i p i d s from t h e i r protein binding, hot alcohol-ether extract-ion was used to overcome t h i s d i f f i c u l t y (Bailey, 1952). Tissue samples (5-8 gms.) were exhaustively extracted with hot Bloor's reagent (3parts ethanol: Ipart anhydrous peroxide - free d i e t h y l ether) i n the presence of anhydrous sodium sulphate. The r a t i o of drying agent to tissue was approximately 1.5:1. The tissue was repeatedly extracted with Bloor's mixture by heating i n a water bath at 50° C. The solution was then f i l t e r e d through Whatman #42 f i l t e r paper, previously wetted with solvent. The solvent was removed by ins e r t i n g the flasks i n a 50° C. water bath and attaching a rubber hose vacuum manifold. Unfortunately during the summer the water pressure dropped to a very low l e v e l r e s u l t i n g i n an increased evacuation time with the water pump. The great disadvantage of prolonged drying i s the increased p o s s i b i l i t y of oxidation of the l i p i d material, especially the unsaturated f a t t y acids. Frequent checks fo r peroxides i n the ether were carried out. 7 The f l a s k s , a f t e r evacuation i n the water bath, were placed i n a vacuum oven set at 50 C ; the highest possible vacuum (25-30 lbs.) was maintained. A preliminary weighing was made of each f l a s k followed by repeated vacuumization and reweighing u n t i l constant weight (within 0.5 mgm.) was obtained. Bloor's reagent extracts materials which are not a l l ether-soluble. To determine quantitative values of ether-solubles the weighed Bloor's solubles were exhaustively extracted with ether, leaving an insoluble residue. The l a t t e r was weighed, giving by difference the weight of t o t a l ether-solubles i n the extracted tissue. This method f o r t o t a l l i p i d was subjected to tests evaluating i t s accuracy and percent recovery and was found to be satisfactory f o r following the changes i n tissue l i p i d of the f i s h . Since determination of t o t a l l i p i d i n t h i s manner involves extended drying, i t i s probable that l a b i l e f ractions may break down, despite the fact that drying i s carried out under vacuum. Consequently, t h i s method i s not suitable f o r the chemical analysis of i n d i v i d u a l l i p i d , f r a c t i o n s . L ipids f o r quantitative determination of the phospholipid content and the cholesterol content were extracted by Waring Blendor from the tissue mash mixed with drying agent, using anhydrous peroxide-free ether as solvent. It i s unfortunate that further investigations of t h i s extraction method were not carried out. True, t r i p l i c a t e analysis gave comparable r e s u l t s , but the quantity of anhydrous sodium sulphate used and the time of spinning i n the Blendor should have been standardized since both factors have been recently found to affect the amount of fat extracted. Moreover, i t seems l i k e l y that certain fractions may be released from the tissue more readily than others, dependent on the type and degree of bonding. Total l i p i d determinations were made on aliquots of these ether solutions as a basis f o r calculation of percentage 8 cholesterol and phospholipid i n the t o t a l l i p i d extract. i i i . Phospholipid The phospholipid technic i s a micro-gravimetric one devised i n t h i s laboratory by Irvine (1954). In t h i s the Bloor (1934) procedure i s modified by p r e c i p i t a t i n g the phospholipids with cold acetone i n the absence of magnesium chloride. The c h i l l e d mixture i s centrifuged; the prec i p i t a t e washed with cold acetone, recentrifuged and dried i n a vacuum oven (50° C. and 25 l b . vacuum). Care was taken during c e n t r i -fugation to prevent undue warming of the solut i o n . A r a t i o of 1:4 of the ether extract: acetone was used throughout these determinations. i v . Cholesterol Total cholesterol estimations were made by using the revised micro-method of Sperry and Webb (1950). This procedure involves p r e c i p i t a t i o n of the cholesterol as the digitonide followed by development and reading of the color. Two modifications of the technic were made. Under the conditions of the method, acetone-ethanol reagent was the required solvent so i t was necessary to evaporate an aliquot of ether extract to dryness i n a water bath (55° C. - 60 C.) and then add the desired solvent. The re s u l t i n g precipitate was removed by centrifuging the solution f o r 20-30 minutes at 2800 r.p.m. During the warm weather considerable evaporation of solvent occurred during t h i s step. Adjustment of the volume was made by addition of solvent. A l l samples were run i n duplicate. Two standards (0.1 mgm/l ml.) were done with each l o t of cholesterols; one at the beginning, and the other at the end of the time sequence. Colorimetric determinations were made with a Bausch and Lamb Colorimeter. This technic, involving more than 30 steps, i s tedious and time consuming but the precision afforded (error £ 0.05 mgm.) warrants i t s use i n preference to the routine Liebermann-Burchard method previously used i n t h i s laboratory. 10 RESULTS A. The Ef f e c t of Different Photoperiods on Thermal Resistance i . Winter -Series The precise differences i n l e t h a l times may be varied by changing the severity of the test as shown by the winter cold test data (Table I I ) . However, the results show that the short-day f i s h are consistently more resistant to cold and le s s resistant to heat than the long-day f i s h (Tables I and I I ) . This i s further apparent i n Figure 1;where the median removal time f o r 50$ of the sample f o r both photoperiod groups . are compared. These results are, thus, i n accord with the concept that seasonal variations i n the thermal resistance are photoperiodically controlled. i i . Summer Series In t h i s series an attempt was made to determine the effect of time on light-induced changes i n temperature resistance. The f i s h were tested a f t e r 10, 20, 40 and 80 days controlled illumination and the r e s u l t s presented in. Tables III and IV. In general, the differences i n thermal resistance between the two photoperiod groups were les s marked i n the summer series than those i n the winter series (Figure 2). For example, i n the cold tests (Table IV) no difference between the groups was evident i n several of the recorded m o r t a l i t i e s . The results (Tables III and IV) are not i n agreement with those found i n the e a r l i e r winter tests. During May and July, f i s h tested a f t e r 10, 20 and 40 days controlled illumination showed the short-day period f i s h more resistant to heat and less resistant to cold while the long-day f i s h were more resistant to cold and less resistant to heat. These TABLE I Comparison of heat resistance of goldfish maintained under short diurnal l i g h t period (8 hour) and long diurnal l i g h t period (16 hour) f o r 40 days and f o r 50 days. (winter series) Percent dead I n i t i a l exposure to removal-minutes Short-day Long-day Differences f i s h f i s h i n l e t h a l time I n i t i a l temperature of l e t h a l hath °C. Range of temperature of l e t h a l bath GC. 40 day group 25 50 75 31 39 48 41 49 65 10 10 17 34.5 34.5 - 36.8 50 day group 25 67 71 4 35.5 35.5 - 37.0 50 77 88 11 75 86 119 33 TABLE II Comparison of cold resistance of gold f i s h maintained under short diurnal l i g h t period (8 hour) and long diurnal l i g h t period (16 hour) f o r 40 days and f o r 50 days. (winter series) Percent dead I n i t i a l exposure to removal-minutes I n i t i a l Range of Short-day Long-day Differences temperature temperature f i s h f i s h i n l e t h a l time of l e t h a l bath of l e t h a l bath °C. °C. 40 day group 25 198 102 96 3 r0 3.0 - 1.1 50 330 168 162 .75 462 258 204 50 day group 25 372 342 30 4.0 4.0 - 0.2 50 446 418 28 75 492 461 31 To follow page 12 Figure 1. Histograms to show the heat and eold resistance of winter f i s h , as related to l i g h t treatment. Open bars, short-day f i s h So l id bars, long-day f i s h Figure 1 8 U 6 \-to a: O 4 h 2 H TABLE III The time effect of photoperiod acclimation on the heat resistance of goldfish. Negative sign indicates a reversal i n time duration -between the 2 groups. (summer series) Percent dead I n i t i a l exposure to removal-minutes I n i t i a l temperature of l e t h a l bath °C. Range of temperature of l e t h a l bath °C. Short-day f i s h Long-day f i s h Differences i n l e t h a l time 10. day' group 25 150 50 100 35.1 34.6 - 37.0 50 270 285 -15 75 365 660 -295 20 day group 25 65 40 25 36.4 36.1 - 37.1 50 100 90 10 75 270 125 145 40 day group 25 50 40 10 36.0 36.0 - 37.0 50 70 50 20 75 145 70 175 80 day group • 25 30 105 -75 36.2 35.8 - 37.0 50 120 120 0 75 660 305 355 TABLE IV The time effect of photoperiod acclimation on the cold resistance of goldfish. Negative sign indicates a reversal i n time duration between the 2 groups. (summer series) Percent dead I n i t i a l exposure to removal-minutes I n i t i a l I n i t i a l Short-day Long-day Differences temperature temperature f i s h f i s h i n l e t h a l time of l e t h a l bath C • of l e t h a l bath C • 10 day group 25 44 44 0 2.0 1.2 - 2.0 50 79 498 419 75 498 648 150 20 day group 25 65 65 • 0 2 1.0 - 2.0 50 65 220 155 75 250 250 0 40 day group 25 30 30 0 2 0.8 - 2.0 50 45 45 0 75 285 785 500 80 day group 25 650 265 -385 4 1.5 - 4.0 50 650 365 -305 75 1320 . 650 -607 To fol low page 14 Figure 2. Histograms to show the heat and cold resistance of summer f i s h , as related to l i g h t treatment. Open bars, short-day f i s h Solid bars, long-day f i s h Figure ; HEAT IO 8 ZD o 2 -C O L D IO 2 0 4 0 8 0 IO 2 0 4 0 D A Y S 15 findings are d i r e c t l y contrary to those f o r the November and December tests at 40 and 50 days. However, i n the f i n a l summer test (late J u l y ) , a f t e r 80 days controlled illumination, the short-day f i s h were perhaps somewhat les s resistant to heat and d e f i n i t e l y more resistant to cold than the long-day f i s h . The direct relationship between photoperiod duration and thermal resistance apparent i n the winter series i s not obvious here. It i s thus evident that the effect of controlled illumination must be d i f f e r e n t at the two seasons, or that other factors which modify the thermal resistance, such as sex and size differences, must have masked the photoperiod effect or the winter experiments presented spurious co r r e l a t i o n between l i g h t treatment and thermal resistance. Various possible reasons f o r these inconsistencies are examined i n the next section. Since thermal history and diet were the same these factors can be Immediately ruled out. Sex and size differences on the other hand, are known to aff e c t thermal resistance and might be responsible f o r the seasonal v a r i a t i o n i n r e s u l t s . B. Influence of Size and Sex on Thermal Resistance i . Size The average size (at the end of the experiments) of the winter f i s h was 14.12 gm. The 16 hour group mean weight was 14.61 gm. compared with 13.62 gm. mean weight f o r the 8 hour group. The average weight of the summer f i s h was 7.05 gm. The long-day group mean weight was 7.68 gm. compared with 6.42 gm. mean weight f o r the short-day group. Thus at both seasons the 16 hour f i s h were heavier than the 8 hour f i s h . The percentage difference was more marked i n the summer series because of the smaller size of the f i s h . The data presented i n Table V indicate f a i r l y comparable size between sexes i n both series. The relationship between size and survival time i s shown i n Table VI. These data have been compiled from a l l the experiments on thermal resistance (Tables III and IV) and involved some 400 g o l d f i s h . These data are i n agreement with the e a r l i e r findings (Keys, 1931; Smith, 1950) that larger f i s h are more resistant to cold than smaller f i s h . The pattern i s consistent whether considered on the basis of length or weight. The smallest f i s h are removed (dead or narcotized) during the f i r s t part of the test, the largest at the end of the test. Since the long-day f i s h are larger and larger f i s h are more resistant to temperature, the 16 hour f i s h may be expected to have a s l i g h t advantage, on the basis of s i z e , i n these thermal resistance tests. i i . Sex Female goldf i s h tend to die o f f f a s t e r than the male f i s h under i d e n t i c a l conditions of c h i l l i n g folbwing similar dietary and thermal treatment, (Irvine, 1954). Table VII shows that the goldfish studied here behaved i n a s i m i l a r manner. The actual sex r a t i o of g o l d f i s h used i n the winter series was 1:1.37 (51 males:70 females). In the summer series the o v e r a l l sex r a t i o of f i s h used i n the thermal tests was 1:1.04 (141 males:146 females). The o v e r a l l sex r a t i o s are so nearly equal that i t seems un l i k e l y that t h i s f a c t o r could pro-duce a bias i n r e s u l t s . This i s especially true of the summer group and consequently the unexpected results i n thermal resistance could not have been caused by unequal sex r a t i o unless the samples selected were unrepresentative. Inspection of the raw data showed that t h i s was not the case. Several additional points concerning the variable resistance of the sexes are evident i n Tables VII and VIII. The sex ra t i o s of f i s h removed at progressive stages during the thermal tests are compared i n Table VII. Here the observed ra t i o s have been adjusted to show differences i n resistance expected i n test samples containing an equal r a t i o of sexes. The method of adjustment was d i f f e r e n t to the method used by Hoar (1955). The experimental r a t i o s were adjusted to the expected r a t i o s on the basis of the number of f i s h remaining at 17 TABLE V Comparison of the average length and average weight of each sex at each season. Season Photoperiod (hours) Males Females Av. length Av. weight Av. length Av. weight Winter 8 16 Average 8.66 13.74 8.71 14.78 8.69 14.33 8.76 13.90 8.73 14.45 8.75 14.15 Summer 8 16 Average 6.67 6.63 7.09 7.79 6.87 7.30 6.47 6.93 6.69 6.19 7.36 6.78 18 TABLE VI Mean size of go l d f i s h (mixed sexes) removed early and l a t e i n thermal t e s t s . Season Photoperiod Early period Late period (hours) Av. length Av. weight Av. length Av. weight Winter 8 8.44 12.46 9.06 14.50 16 8.80 15.02 9.01 16.43 6.40 6.34 6.50 6.38 6.94 7.47 7.13 8.27 Summer 8 16 TABLE .VII Sex ratios of goldfi s h removed (dead or narcotized) early, intermediate and la t e i n cold and heat tests; further description i n text. Season Photoperiod Early period .Middle period Late period Actual r a t i o (hours) Males:Pemales Males:Pemales Males:Females Males:Females A. Cold Tests Winter 8 1:1.15 1:0.6. 1:1.1 1:1.31 16 1:1.69 1:1.42 1:1 1:1.07 Summer 8 1:1 1:1.03' "'• 1:0.82 1:2.10 16 1:1.28 1:0.80 , 1:1.25 1:1.23 B. Heat Tests Winter 8 1:0.87 1:3.0 1:1 1:0.89 16 1:1.30 1:5.2 1:1.17 1:1.13 Summer 8 1:0.97 1:0.80 1:0.69 1:1.13 16 1:1.06 1:0.80 1:0.89 1:0.94 TABLE VIII Sex rat i o s of goldfi s h removed (dead) early, intermediate and l a t e i n heat t e s t s j further description i n text. Season Photoperiod (hours) Early period Males:Females Middle period Late period Males:Females Males:Females Winter 8 16 1:1.06 1:0.64 1:1.79 1:2.67 1:0.25 1:1.1 Summer 8 1:0.43 1:0.91 1:0.91 16 1:0.49 1:0.40 1:1.69 ro o 21 progressive stages of the t e s t s . In both winter and summer, the long-day female f i s h were consistently less resistant to temperature extremes than the male f i s h of t h i s group, when compared on a removal basis (Table VII). However, when the heat test data are compared on the basis of t r u l y dead f i s h the sex difference i s reversed (Table VIII). Here the males show less resistance than the females during the early period of the t e s t s . These findings are i n agreement with those of Gibson(l954) f o r the guppy. It i s apparent that the 16 hour femalesbecome heat narcotized quickly and are, thus, removed early i n the t e s t . Further, the survivors ( f i s h a l i v e at the end of the test) of the heat tests had an o v e r a l l sex r a t i o of 1:1.58, males:females. Analysis of the data has shown that female f i s h do not d i f f e r s i g n i f i c a n t l y from the male f i s h i n average size (Table V) and, therefore, i t i s highly probable that the effect of sex i s d i s t i n c t from that of size. C. Biochemical Results of Photoperiod Experiments The chemical analyses included percentage moisture, t o t a l f a t s , cholesterol and phospholipids. The results reported here involved some 758 gold f i s h (winter series, 160 f i s h ; summer series, 598 f i s h ) . i . Moisture Moisture determinations were made primarily f o r the purpose of calcu l a t i n g the t o t a l l i p i d values per dry weight of tissue sample. The average difference i n moisture content between the short-day group and the long-day group was found to be 0.33% f o r the winter series and 1.83% f o r the summer series (Appendix, Tables I and I I ) . Further analysis of the summer data showed a 1.16% difference i n moisture content between the sexes (males showed higher percentages). Furthermore, the 16 hour treated f i s h showed more difference than the 8 hour group (1.58 and 0.75 percent respectively) when compared on a sex basis. 22 This difference i s probably due to sex maturation. The error i n the method was found to be 0.1 - 0.2$ so the differences appear s i g n i f i c a n t . i i . Total Lipids A f t e r 65 days illumination, during the winter, the t o t a l l i p i d values are higher i n f i s h experiencing the shorter d a i l y photoperiod (Table IX). The reverse occurr's a f t e r 109 days treatment. The male f i s h , on the average, showed s l i g h t l y l e s s fat than the female f i s h . This difference i s more pronounced \ (1.21$ average) i n the short-day group. In cert a i n instances, the difference between the duplicate tests of the same group were of s i m i l a r magnitude and consequently, no p a r t i c u l a r significance can be attached to these differences. The results of the summer t o t a l l i p i d determinations are present i n Table X. Here, the 8 hour treated fLsh show les s l i p i d than the 16 hour treated f i s h i n 7 out of 8 instances. Furthermore, i t i s apparent that the l i p i d values of the short-day group are consistently increasing as the photoperiod treatment continues. Progressive increases i n fat content of the long-day group i s not apparent u n t i l 80 day illumination time i s reached. Further analysis of the data i n Table X showed that i n almost a l l cases the size of the long-day: f i s h i s greater than the size of the short-day f i s h . Although the 16 hour group may have been i n i t i a l l y somewhat larger i t seems l i k e l y that these f i s h grew more and became f a t t e r during the period of l i g h t control. • i i i . Changes i n Phospholipid and Cholesterol Fractions a. Progressive Changes i n Tissue Lipids Phospholipids decreased progressively i n both male and female f i s h during 8 hour l i g h t exposure (Table XI). The 16 hour group show v a r i a t i o n but no orderly change i n phospho-l i p i d s . The cholesterol decline i n both groups with continued l i g h t control, with the exception of the 40 day group. This group as previously mentioned was procured at a di f f e r e n t time TABLE IX L i p i d content of winter goldf i s h subjected to different photoperiods f o r 65 days and 109 days. Experiments started October 18th, 1955. Females Males 16 hour 8 hour . 16 hour 8 hour 65 day group I II I II I II I II Number f i s h 19 16 12 21 10 ' 15 11 10 Mean wt.(gm.) 12.0 12.9 19.0 11.2 13.6 10.0 11.5 10.5 Total l i p i d 12.30 (#dry wt.) 13.51 15.18 15.78 12.95 13.18 13.69 14.86 Mixed Sexes 109 day group 16 hour 8 hour Mean wt. 8.26 9.-90 &m. °-/gm.cr^  1.25 1.40 Total l i p i d fo dry wt.) 16.58 14.96 ro TABLE X Progressive changes i n l i p i d content of summer goldfish produced by controlled illumination. The 40 day test was started May 25, 1956; the other three tests were started May;l,1956. Females 10 Day test 20 Day test 40 Day test 80 Day test 16 hour group -Number f i s h 17 11 19 15 24 12 27 28 Mean wt. (gm.) 7.54 5.77 8.72 6.47 8.03 8.29 7.56 6.98 Total l i p i d ($ dry wt.) 21.99 21.81 20.92 32.20 8 hour group Number f i s h 18 12 22 19 23 19 35 33 Mean wt. (gm.) 5.27 5.43 6.28 6.16 8.16 8.05 5.06 4.63 Total l i p i d (tfo dry wt.) 16.23 18.47 23.66 28.61 Males 16 hour group Number f i s h 23 8 15 21 19 13 20 13 Mean wt. (gm.) 7.18 7.84 7.98 6.59 8.39 8.21 7.53 5.95 Total l i p i d (fo dry wt.) 17.77 22.41 21.15 26.88 8 hour group Number f i s h 23 10 17 13 14 15 24 16 Mean wt. (gm.) 5.14 4.83 6.40 6.18 7.41 8.19 5.13 4.80 Total l i p i d ($ dry wt.) 13.13 19.61 17.39 24.69 TABLE XI-Progressive changes i n the phospholipid and cholesterol lev e l s of summer f i s h t issue. Values i n percent of t o t a l l i p i d . Pish maintained under different photoperiods. Sexes analyzed separately. Time of Treatment (days) Photoperiod (hours) Pemales Phospholipid Cholesterol Males Phospholipid Cholesterol 10 8 10.08 8.96 8.90 11.87 16 4.40 5.93 5.71 5.86 20 8 6.31 4.41 7.44 4.98 16 4.60 3.33 7.21 3.80 40 8 4.40 2.42 4.17 8.61 16 8.29 4.04 3.64 6.96 80 8 4.17 2.46 3.65 2.68 16 3.26 . 2.91 4.66 2.65 26 from our dealer and the f i s h were larger and probably more mature. The cholesterol:phospholipid r a t i o f e l l for.'the major part of the experiment (Figure 3). A s i m i l a r trend i s noted i n Figure 4, where the progressive change i n r a t i o of 8 hour:16 hour l i p i d values are presented. In the winter f i s h , irrespective of length of d a i l y photoperiod, tissue phospholipid increased and tissue cholesterol decreased between 65 and 109 days of treatment (Table XII). During t h i s time i n t e r v a l the cholesterol:phospho-l i p i d r a t i o of the long-day group f e l l from 1.68 to 0.48. A s i m i l a r trend i s noted i n the short-day group, here the r a t i o of cholesterol:phospholipid f e l l from 1.02 to 0.55 during t h i s period. b. Ef f e c t of Controlled Illumination on Tissue Lipids In the winter and i n the summer, f i s h subjected to short-day illumination generally show higher tissue phospholipid and tissue cholesterol than the long-day f i s h (Tables XI and XII). This tendency i s further emphasized i n Figures 5 and 6 showing the differences i n the 8 hour and 16 hour tissue phospholipid and cholesterol at the two seasons. c. Sex Differences i n Tissue Lipids During the winter, the male f i s h showed consistently higher tissue phospholipid and cholesterol than the female f i s h . In the summer experiments, a morecomplicated picture i s presented. Generally, the male f i s h show more tissue cholesterol than the females. Phospholipid values of the short-day female f i s h tend tp be higher than the male values while the opposite occurred i n the long-day f i s h . Here, the male tissue showed more phospholipid than the female tissue (exception, 40 day group). These chemical differences between sexes are presented i n Figure 7. / To follow page 26 Figure 3. Progressive changes i n cholesterol: phospholipid r a t i o produced by prolonged l i g h t treatment (summer s e r i e s ) . Sexes and photo-period considered separately. short-day female • short-day male long-day female long-day male Figure 3 I To follow page 26 Figure 4. Progressive changes i n the 8 hour: 16 hour tissue l i p i d r a t i o produced by continued photoperiod treatment (summer s e r i e s ) . phospholipid cholesterol Figure 4! To follow page 26 Figure 5. Histogram to show winter tissue phospholipid and cholesterol differences between short-day f i s h and long-day f i s h . Differences expressed i n percent. Open bars, phospholipid Solid bars, cholesterol Figure 5 To follow page 26 Figure 6. Histograms to show summer f i s h tissue phospholipid and cholesterol differences between the short-day f i s h and the long-day f i s h . Differences expressed as percent. Sexes considered separately. Open bars, phospholipid S o l i d bars, cholesterol 4 IO 2 0 4 0 8 H O U R 8 0 IO DAYS 2 0 4 0 8O 16 H O U R To follow page 26 Figure 7. Histogram to show phospholipid and cholesterol differences between male and female f i s h tissue (summer s e r i e s ) . Differences expressed i n percent. Photoperiod groups considered separately. Open bars, phospholipid Solid bars, cholesterol 20 4 0 FEMALES 8 0 1 IO DAYS 2 0 4 0 8O MALES TABLE XII Phospholipid and cholesterol l e v e l s i n winter go l d f i s h tissue. L i p i d fractions presented as percent of t o t a l l i p i d . Females Males Average sexes 16 hour 8 hour 16 hour 8 hour 16 hour 8 hour 65 day group Phospholipid 2.33 5.34 6.48 10.07 4.41 7.71 Cholesterol 7.11 7.30 7.66 8.38 7.39 7.84 109 day group Phospholipid Cholesterol Mixed Sexes 16 hour 8 hour 7.83 10.02 3.77 5.52 28 Review of Pertinent Literature on Photoperiodism There i s a li m i t e d number of reports regarding experimental work on the effects of temperature and l i g h t on the seasonal cycle of fi s h e s . In h i s investigation of the s t i c k l e -back Gasterosteus aculeatus, Craig-Bennett (1931) concluded that temperature was the important factor i n c o n t r o l l i n g the sexual cycle and that l i g h t was unimportant. Various l i g h t i n t e n s i t i e s were employed but maximum duration was only 90 minutes. It seems highly improbable that the method employed could produce positive r e s u l t s . This species has since been induced to breed at low temperatures during the winter months by means of l i g h t manipulation (Vanden Beckhoudt, 1947). Trout (Hoover and Hubbard, 1937) and minnows (Bullough, 1939) can be induced to mature sexually i n advance of t h e i r natural breeding season, by a r t i f i c i a l l y controlled l i g h t and temperature fluct u a t i o n . Recently, Harrington (1956) reported completion of the entire reproductive cycle of the Banded Sunfish at a simulated summer temperature (21.7°C.) by abruptly increasing the d a i l y photo-period to the annual maximum (15 hours). Elevated temperature alone was incapable of producing t h i s r e s u l t . However, l i g h t was found i n e f f e c t i v e i n yellow perch (Hoover c i t e d from Burger, 1939) and i n Pundulus (Mathews, 1939). Bullough (1941) reported that i n minnows kept i n t o t a l darkness or exposed to a very limited period of l i g h t each day, sexual maturation was delayed but not prevented. He concluded that i n these f i s h there i s an inherent reproductive rhythm, which i n normal circumstances i s rendered more precise i n i t s time of action by effects of seasonal v a r i a t i o n of the environment. Photoperiodism has been studied i n many animals; most studies were concerned with factors inducing gametogenesis. The factors involved i n inducing and maintaining non-breeding conditions are less well known. The basic test consists of 29 giving sexually quiescent animals a d a i l y period of a r t i f i c i a l l i g h t added to natural day lengths or by making an a r t i f i c i a l day s o l e l y by a r t i f i c i a l l i g h t . The fact that ordinary e l e c t r i c l i g h t s (3-30 foot candles) appear to be just as eff e c t i v e as spring sunshine which frequently measures some thousands of foot candles suggests that within l i m i t s t h i s factor i s unimportant. Nevertheless, there must be l i m i t s to i n t e n s i t y which are e f f e c t i v e and there seems reason to suppose these l i m i t s need not necessarily be the same f o r a l l species. Rowan (1938) states an i n t e n s i t y of a certain low l e v e l i s essential (minimum 0.7 foot candles) and that an increase behond t h i s point has no additive effect - a generalization borne out by more recent experimental work (Nicholas, Collenback and Murphy, 1944; Dobie, Carver and Roberts, 1946). Other workers report the rate of response i s dependent on the in t e n s i t y (Marshall, 1942; Bissonnette, 1931). Eirschbaum and co-workers (1939) found seasonal v a r i a t i o n i n the e f f e c t i v e -ness of response to di f f e r e n t i n t e n s i t i e s . These authors concluded there was either seasonal v a r i a t i o n i n the s e n s i t i v i t y of the p i t u i t a r y to l i g h t or seasonal v a r i a t i o n i n the s e n s i t i v i t y of the gonads to gonadotropic hormones. Generally, i n experiments where photoperiod has been a variable, 1he response has been independent of illuminance above a very low l e v e l . In investigating effectiveness of di f f e r e n t wave-lengths, i t would appear that with the possible exception of u l t r a - v i o l e t the use of a p a r t i c u l a r wavelength has no d e f i n i t e advantage over ordinary white l i g h t (Yeates, 1949). Investigators have induced sexual a c t i v i t y by use of a great variety of l i g h t treatments. A gradually increas-ing l i g h t period i s not essential i n i t s e l f but i s merely the means whereby the change over from short l i g h t : l o n g dark sequence to long light:short dark sequences i s effected in-nature (Hart,' 1951). Thus, i t i s the absolute daylength that i s important and not the change i n daylength. Among birds the optimum d a i l y period producing complete gametogehesis was 12% hours f o r the s t a r l i n g (Burger, 1940), 13-14 hours f o r the weaver finch (Rollo and Domm, 1943) and English sparrow (Bartholemew, 1949). Sex differences i n response to l i g h t have often been reported with birds (Riley and Witschi, 1938; Hart, 1951 and many others). Verhoeven and Van Oordt (1955) observed that long days of a r t i f i c i a l l i g h t act on the female b i t t e r l i n g i n such a way that i t i s made sensitive to high temperature - the same sequence as found i n nature. Temperature has the same influence on the male b i t t e r l i n g but l i g h t plays a minor or perhaps no r o l e . The limited observations on causation of photoperiod response of higher vertebrates indicate that the region of perception i s i n the neighborhood of the eye (Parker, et a l , 1952). Scharrer (1929), i n t h i s connection, reported blinded minnows are s t i l l capable of appreciating changes i n l i g h t i n t e nsity. Possibly l i g h t perception i s diff e r e n t i n cold blooded vertebrates than i n warm blooded forms. Doubtless the most important e f f e c t of increasing d a i l y photoperiod i n spring i s the acti v a t i o n of the anterior p i t u i t a r y (Parner, et a l , 1954). The most spectacular and best known function of t h i s a c t i v a t i o n i s the marked increase i n gonadotropic a c t i v i t y . The basic physiologic mechanisms are s t i l l not understood although progress has been made recently by studying the nature of the1' annual refractory period of the mechanism (Benoit, et a l , 1950) and by investigations using intermittent l i g h t (Parner, 1953; Kirkpatrick and Leopold, 1952; Jenner and Engels, 1952). The frequent f a i l u r e of the p i t u i t a r y gland to sustain f u l l a c t i v i t y of gonads for long periods i s a well recognized phenomena (Mi l l e r , 1949 and 1954} Bissonnette, 1936; Riley, 1936). In some species t h i s refractory period (period following development during which increased d a i l y photoperiods are i n e f f e c t i v e ) can be modified by photoperiod manipulation; long days effect a persistance of the refractory phase and short days favor i t s d i s s i p a t i o n (Burger, 1949). I f cycles are i n part inherent (dependent on recurrent refractoriness of the p i t u i t a r y ) i t i s evident l i g h t can control the cycle only within d e f i n i t e l i m i t s . Thomson (1951) suggests the p o s s i b i l i t y "that the annual cycle of the bird's l i f e i s linked only at one point with environmental sti m u l i ; that an i n t e r n a l rhythm has been established; and that a l l but one of the events i n the cycle occur as the r e s u l t of the mere eff l u x i o n of time, following refractory periods ". Seasonal v a r i a t i o n i n the c y t o l o g i c a l picture of the p i t u i t a r y of goldfish has been reported by Scruggs (1951). Light and temperature modify release of gonadotropins by the p i t u i t a r y and these secretions i n turn activate the gonads (direct mediation). The p o s s i b i l i t y remains, however, that environmental changes may be e f f e c t i v e i n a l t e r i n g the endocrine glands by modifying the general metabolism of the organism. 32 DISCUSSION Two major c r i t i c i s m s of the methodology used i n the present study exist. F i r s t , i n the summer series, the f i s h had received many weeks of increasing daylight before commence-ment of these experiments. The inconsistencies presented may be due, i n part, to varying degrees of maturation of the goldfish. The decreased effect of l i g h t on the sexual cycle, once maturation has started, has been stressed by many authors ( H i l l and Parkes, 1930; Zirschbaum and Ringoen, 1936; Benoit, 1956 and others). Second, i n these experiments the constant temperature may have interfered with the photoperiod effect since a l l f i s h were held at 20° C , during both seasons. Mathews (1939) has pointed out that the most obvious difference between laboratory f i s h and those i n nature i s the water temperature. Photoperiod changes have been shown to occur, i n some instances, only when combined with temperature change (Mathews, 1939; Medlen, 1951). Photoperiod-Induced Changes i n Thermal Tolerance Winter Series Here the short-day f i s h are consistently more resistant to cold and less resistant to heat than the long-day f i s h . These findings are b i o l o g i c a l l y sound, ind i c a t i n g a compensatory mechanism i n these poikilothermic animals, preparing them f o r sudden temperature changes "out-of-season". Such a mechanism would be a d e f i n i t e advantage to any animal subjected • to the changing temperatures with season as occur i n nature. Summer Series It i s impossible to explain the re s u l t s of the summer series on the same basis. Here, generally the short-day f i s h showed les s resistance to c o l d and more resistance to heat than the long-day group. In an attempt to explain these contradictory findings the following theory i s suggested i n a purely tentative manner. Photoperiodically controlled changes 33 i n temperature resistance may affect only the heat resistance. I f such i s the case and i f any "out-of-season" l i g h t change acts as a stimulus to the p i t u i t a r y , the increased heat resistance of the 16 hour f i s h i n the winter and of the 8 hour f i s h i n the summer might be explained i n t h i s manner. However, on the basis of the present understanding of t h i s problem, i t i s impossible to reach a f i n a l conclusion regarding the role of photoperiodism i n thermal resistance of goldfish. Much interesting research remains to be done before c l a r i f i c a t i o n of the s i t u a t i o n can be obtained. Photoperiod-Induced Changes i n Tissue Lipids The chemical findings were sim i l a r i n both series of experiments. The short-day f i s h showed higher tissue phospho-l i p i d and tissue cholesterol than the long-day f i s h . Some correlation between the metabolism of these l i p i d fractions has been reported i n the l i t e r a t u r e . Glover, Morton and Ranson (1952) have suggested that during f i s h development, cholesterol i s synthesized l a r g e l y , i f not wholly from the phospholipids. Clearly, too, the thyroid gland plays a large part i n determining the l e v e l s of the two l i p i d s (Kim and Ivy, 1952; Stamler, 1954). Milch, et a l (1953) working with low temperatures concluded cholesterol was important i n the repair of cold damage. In the present investigation, male f i s h showed higher cholesterol and demonstrated greater cold resistance. There i s , however, no clear c o r r e l a t i o n between the light-induced chemical changes and the light-induced temperature resistance changes. Thus, i n t h i s case, changing l i p i d s do not seem to be d i r e c t l y responsible f o r changing thermal resistance. It seems more l i k e l y that the l i p i d changes are associated with varying stimulation of the reproductive cycle through the p i t u i t a r y and are not related to the resistance e f f e c t . Sex differences i n l i p i d metabolism are well established. Kim and Ivy (1952) have found male-female d i f f e r e n t i a l 34 s u s c e p t i b i l i t y to b i l e s a l t s , held to be a r e f l e c t i o n of difference i n l i p i d metabolism between the sexes. Lovern (1934) showed a selective mobilization of depot fat took place i n male salmon during the spawning (starvation) period. Also, Deuel. (1952) found male rats used ten times as much of the essential f a t t y acid, l i n o l e i c , as do female r a t s . In the experiments reported here, sex differences i n the l e v e l s of l i p i d constituents of go l d f i s h tissue are apparent. Generally, male tissue had higher cholesterol values, irrespective of season or da i l y photoperiod, than female tissue. Sex differences i n phospholipid among summer f i s h exist , dependent on the d a i l y illumination period. Short-day female tissue phospholipid tend to be greater than the male tissue l e v e l s , while the reverse i s true of the long-day f i s h . Here, the male tissue showed higher phospholipid than the female ti s s u e . Since estrogen has been found to increase the l i p i d content i n chicken (Nollandov, 1953; Stamler, 1954) one might expect high tissue phospholipid i n mature female f i s h . This did not appear to be the case with the 16 hour summer female and no explanation i s offered here to explain these unexpected findings. In the winter series, however, an increased phospholipid i n the long-day female tissue did occur and these changes are probably associated with gonadal hormonal e f f e c t s . Since gonadal a c t i v i t y can be explained i n terms of p i t u i t a r y regulation (Schildmacher and Rautenber, 1952) t h i s appears to be a problem i n endocrine physiology. I t s elucidation depends on further biochemical studies of f i s h at known stages i n sexual maturity and on hyppphysectomized and gonadectomized animals. 35 SUMMARY Changes i n the resistance of gold f i s h to high and low temperature exposure were i n i t i a t e d by l i g h t treatment. The effects, however, of the d i f f e r e n t photoperiods varied with the season under investigation. A possible theory of the mechanism involved i n these light-induced changes i s presented. Other factors, such as size and sex were found to modify the thermal resistance of the f i s h . Male goldfish were more cold resistant than the corresponding female f i s h . However, the sex difference f o r t r u l y dead f i s h i s reversed during the heat t e s t s . Here the female f i s h showed greater resistance than the male f i s h , but the tendency to survive longer was masked by the greater tendency of the female f i s h to enter heat narcosis. In goldfish subjected to photoperiod manipulation, there was no correlation between the thermal resistance and the biochemical constituents of f i s h tissue. At both seasons, photoperiod-induced changes i n the tissue l i p i d s were s i m i l a r . The short-day f i s h , during the winter and summer series, generally showed higher tissue phospho-l i p i d and tissue cholesterol than the long-day f i s h . However, sex differences i n the l i p i d fractions of summer f i s h occurred when f i s h were maintained under controlled illumination. The results reported here, as well as related results of other investigators are discussed and a hypothesis put f o r t h attempting to explain the various phenomena assoc-iated with photoperiod treatment. To follow page 35 Appendix 36 TABLE I Average moisture content (percent) of summer goldfish tissue. Time of treatment Photoperiod Male tissue Female tissue (days) (hours) 10 8 78.3 76.6 16 76.8 74.3 20 8 76.8 76.2 16 75.7 74.4 40 8 75.6 75.7 16 75.9 75.6 80 8 73.9 73.1 16 74.7 72.5 * 37 TABLE II Average moisture content (percent) of winter go l d f i s h tissue. Time of treatment Photoperiod Male tissue Pemale tissue (days) (hours) 65 8 77.6 77.5 16 77.3 78.0 Mixed sexes 109 8 76.6 16 75.4 38 REFERENCES * Original a r t i c l e not consulted. Bailey, B.E. Marine o i l s with p a r t i c u l a r reference to those of Canada. 2nd Ed. Fish. Res. Bd. Can. B u l l . No. 89. 1952. Bartholomew, G.A. The effect of l i g h t i n t e n s i t y and daylength on reproduction i n the English Sparrow. B u l l . Mus. Comp. Zool. 101:433-476, 1949. Benoit, J . , Assenmacher, I., and Brard, E. Apparition et maintien.de cycles sexuels non saisonniers chez l e Canard domestique place'pendant plus de t r o i s ans a l'obscurite t o t a l e . J . Physiol. (Paris) 4J3:388-391, 1956. Benoit, J . , Mandel, P., Walter, F.X., and Assenmacher, I. Sensibilit6 t e s t i c u l a i r e aux hormones gonadotropes hypophysaires, chez l e canard domestique, au cours de l a p^riode de regression t e s t i c u l a i r e saisoniere. CR. Soc. B i o l . 144:1400-1405. 1950. Bissonnette, T.H. Studies on the sexual cycle i n birds. V. E f f e c t s of l i g h t on di f f e r e n t i n t e n s i t i e s on the t e s t i s a c t i v i t y of European S t a r l i n g (Sturnus v u l g a r i s ) . Physiol. Zool. 1:542-574, 1931. Sexual photoperiodicity. Quart. Rev. B i o l . I I : 371-386, 1936. Bloor, W. R., and Snider, R.H. Phospholipid content and a c t i v i t y i n muscle. J . Bio l . Chem. 107:459-470. 1934. Brett, J.R. Rate of gain of heat-tolerance i n goldfi s h (Carassius auratus). Pub. Ont. Fish . Res. Lab. No. 64-1-19. 1946. Brown, M.E. The growth of brown trout (Salmo trutta» Linn.) I I . The growth of 2-year old trout at a constant temperature"of 11.5 C J . Exptl. B i o l . 22:130-144, 1946. Bullough, W.S. A study of the reproductive cycle of the minnow i n r e l a t i o n to the environment. Proc. Zool. Soc. London. A, 109:79-102. 1939. The effect of reduction o f - l i g h t i n spring on the breeding season of the minnow (Phoxinus l a e v i s ) . Proc. Zool. Soc. London. A, 110:149-157. 1941. Burger, J.W. Some experiments on the relation of the external environment to the spermatogenetic cycle of Fundulus . heteroclitus (L.). B i o l . B u l l . 7J:96-103, 1939. 39 Some further experiments on the r e l a t i o n of the external environment to the spermatogenetic cycle of Fundulus heterolcitus. B u l l . Mt. Desert Is. B i o l . Lab. 21-22, 1940. Burger, J.W. A review of experimental investigations on -seasonal reproduction i n birds. Wilson B u l l . 61:211-230. 1949. Cottle, M.Z. Temperature tolerance of the goldfi s h (Carassius  auratus) i n r e l a t i o n to the degree of unsaturation of body l i p i d s , the cholesterol, phospholipid, f a t t y acid and water content of the tissues. Masters Thesis. University of B r i t i s h Columbia (unpub.), 1951. Craig-Bennett, A... The reproductive cycle of the three-spined stickleback, G-asterosteus aculeatus Linn. P h i l . Trans. Roy. S o c . B, 219:197-279. 1931. * Cronheim, W. Gesamtstoffwechsel der kaltblutigen Wirbeltiere, im besonderen der Pische. Z. Fisch. 15:519. 1911. Deuelj H.J. J r . The l i p i d s : t h e i r chemistry and biochemistry, v o l . 1, Chemistry. Interscience Publishers, New York, 1951. Dobie, J.B., Carver, J.S., and Roberts, J . Poultry l i g h t i n g f o r egg production. State College of Wash. Inst. Agric. S c i . , Agric. Exptl. Sta. B u l l . No. 471•1-27, 1946. Farner, D.S. The r e l a t i v e x>les of diurnal, periods of a c t i v i t y and dirunal photoperiods i n gonadal a c t i v a t i o n i n male. Zonotrichia leucophrys gambelii (Nuttall).. Experiaentia £: 219-221, 1955. . Farner, D.S., Mewaldt, L.R. and Zing, J.R. The diurnal a c t i v i t y patterns of caged migratory White-crowned Sparrows i n l a t e winter and spring. J . Comp. Physiol. Psych. 47:148-155. 1954. Gibson, M.B. Upper l e t h a l temperature relations of the guppy, Lebistes r e t i c u l a t u s . Can. J . Zool. 52:595-407. 1954. Glover, M., Morton, R.A., and Rosen, D.G. Astaxanthin, Cholesterol, and l i p i n s i n developing salmon eggs. Biochem. J . 50:425-429. 1952. Harrington, R.W. J r . An experiment on the eff e c t s of contrasting dai l y photoperiods on gametogenesis and reproduction i n the centrarchid f i s h , Enneacanthus obesus (Girard). J . Exptl. Zool. 131:203-223. 1956. Hart, D.S. Photoperiodicity i n thefemale f e r r e t ; J . Exptl. B i o l . 28:1-12, 1951. 40 Heilbrunn, L.V. An outline of general physiology. 3rd. Ed. revised. .. W.B. Saunders Company, Ph i l a . , 1952. H i l l , M., and Parkes, A.S. On the r e l a t i o n between the anterior p i t u i t a r y body and the gonads. I I . The induction of ovulation i n the anoestrous f e r r e t . Proc. Roy. Soc. London. B, 107:59-49. 1930. Hoar, W.S., and Cottle, M.K. Dietary f a t and thermal tolerance of g o l d f i s h . Can. J . Zool. 50:41-48. 1952. Hoar, W.S. Seasonal variations i n the resistance of g o l d f i s h to temperature. Trans. Roy. Soc. Canada. V.(III\ 4^:25-54, 1955. Hoar, W.S. Photoperiodism and thermal resistance of goldfish. Nature 178:564-565. 1956. Hoover, E.E., and Hubbard, H.E. Modification of the sexual cycle i n trout by control of l i g h t . Copeia (4)» 206-210, 1957. Irvine, D.G. The cold resistance of g o l d f i s h (Carassius auratus) fed certain l i p i d d i e t s . Masters Thesis. University of  B r i t i s h Columbia (unpub.), 1954. Jenner, C.E., and Engels, W.L. The significance of the dark period i n the photoperiodic response of the male juncos and White-throated Sparrows. B i o l . B u l l . 105:545-355. 1952. Keys, A. Personal communication to Dr. W.S. Hoar, Department of Zoology, University of B r i t i s h Columbia, 1931. Kim, K.S. and Ivy, A.C. Factors influencing cholesterol absorption. Amer. J . Physiol. 121:302-518, 1952. Kirkpatrick, CM., and Leopold, A.C. The role of darkness i n sexual a c t i v i t y of the q u a i l . Science 116:280-281. 1952. Kirschbaum, A., and Ringoen, A.R. Seasonal sexual a c t i v i t y and i t s experimental modification i n the male Sparrow Passer  domesticus Linnaeus. Anat. Rec. 64:455-474. 1956. Kirschbaum, A., P f e i f f e r , C.A., Van Heuverswyn, J . , and Gardner, W.U. Studies on gonad-hyphyseal relationships and c y c l i c osseous changes i n English Sparrow, Passer domesticus L. Anat. Rec. 15_:249-265, 1959. Lovern, J.A. CCLV Pat metabolism i n fishes. IV. Mobilization of depot fat i n the salmon. Biochem. J . 28:1955-1961, 1954. 41 Marshall, F.H.A. Exteroceptive factors i n sexual p e r i o d i c i t y . B i o l . Rev. 12:68-89, 1942. Mathews, S.A. The effects of l i g h t and temperature on the male sexual cycle i n Fundulus. B i o l . B u l l . 22:92-95, 1939. Medlen, A.B. Preliminary observations on the effects Of temperature and l i g h t upon reproduction i n Gambusia a f f i n i s . . Copeia (2) 148-152, 1951. Milch, L.J., Redmond, R.P., Calhoun, W.W., and the Cardiovascular Research Group. Plasma lipoprotein changes induced by acute l o c a l cold injury. Amer. J . Med. S c i . 22_5_:416-420, 1953. M i l l e r , A.H. P o t e n t i a l i t y f o r t e s t i c u l a r recrudescence during the annual refractory period of the Golden-crowned Sparrow. Science 109_:546, 1949. M i l l e r , A.H. Further evidence on the refractory period i n the reproductive cycle of the Golden-crowned Sparrow. Auk. 68: 381-383, 1954. Nicholas, J.E., Collenback, E.W., and Murphy, R.R. Light i n t e n s i t y as a factor i n the a r t i f i c i a l illumination of pu l l e t s . B u l l . Pa. Agric. Exptl. Sta. No. 462-1-24. 1944. Nollandov, A.V. Endocrine control of physiological function. Poultry S c i . ,22:88-103, 1953. Parker, M.W., Hendricks, S.B., and Borthwick, H.A. Photoperiodic response of plants and animals. Nature 169:242-243.. 1952. Riley, G.M. Light regulation of sexual a c t i v i t y i n the male Sparrow Passer domesticus. Proc. Soc. Exptl. B i o l . Med. 34: 331-332, 1936. Riley, G.M., and Witschi, E. Comparative effects of l i g h t stimulation and administration of gonadotropic hormones on female Sparrows. Endocrinology 25:618-624. 1938. Rollo, M., and Domm, L.V. Light requirements of the weaver finc h . 1. Light period and int e n s i t y . Auk 60:357-367, 1943. Rowan, W. Light and season reproduction i n animals. B i o l . Rev. 12:374-402, 1938. . Schaefer, A.A. The number ofblood corpuscles i n fishes i n re l a t i o n to starvation and seasonal cycles. J . Gen. Physiol. 2:341-545, 1924-25. * Scharrer, E. De Lichtempfindlichkeit blinder E l r i t z e n (Untersuchungen liber das Zwischenhirn der Pische). Z. ver g l . Phvsiol. J:l-28, 1928. 42 Schildmacher, H., and Rautenber, W. Uber die Wirkung k l e i n e r Mengen von Thyroxin auf daa K&rpergewicht bei Pihkenv6geln. B i o l . Zentralbl. Jl:397-405, 1952. *-Schlicker, _ J . Vergleichend physiologische Untersuchungen der Blutkorperchenzahlen bei Khochenfischen. Zool. Jb. (Abt. a l l g . Zool. Physiol.). i3_:122, 1926. Skruggs, W.M. The e p i t h e l i a l components and t h e i r seasonal changes i n the p i t u i t a r y gland of the carp (Cyprinus carpio. L.) and goldf i s h (Carassius auratus. L.). J . Morphol. 88:441-470. 1951. Smith, P.D. Mechanisms involved i n the injury and death of f i s h by c h i l l i n g temperatures. Masters Thesis. University of  B r i t i s h Columbia, (unpub.), 1950. Sperry, W.M., and Webb, M* A rev i s i o n of the Schoenheimer-Sperry method f o r cholesterol determination. J . B i o l . Chem. 187; 97-106, 1950. Stamler, J . Endocrine influences on l i p i d metabolism and atherosclerosis. Proc. Inst. Med. Chicago 20;17-18. 1954. Sullivan, CM., and Pisher, K.C. Seasonal fluctuations i n the selected temperature of speckled trout, Salvelinus f o n t i n a l i s ( M i t c h i l l ) . J . Pish. Res. Bd. Can. 10:187-195, 1953. Sumner, P.B., and Doudoroff, P. Some experiments on temperature acclimatization and respiratory metabolism i n fish e s . B i o l . B u l l . 2i:403-429, 1938. Swift, D.R. Seasonal variations i n the growth rate, thyroid gland a c t i v i t y and food reserves of brown trout (Salmo  t r u t t a Linn.). J . Exptl. B i o l . .22:751-764, 1955. Thomson, A.L. Reproduction, migration and moult: factors c o n t r o l l i n g the annual cycle i n birds. Proc. 10th Int. Ornithol. Congr.. Uppsala, 241-244, 1951. Vanden Eepkhoudt, J.P. Reseherches sur. I 1 influence de l a lumiere sur l e cycle sexuel de l'epinoche (Gasterosteus  aculeatus). Ann. Soc. Roy. Zool. Belg. 77:83-89r 1947. Verhoeveh, B., and Van Oordt, G.J. The influence of l i g h t and temperature on the sexual cycle of the b i t t e r l i n g , Rhodeus amarus. Proc. Acad. S c i . Amst. C, 58:628-654. 1955. 43 Wells, N.A. Variations in the respiratory metabolism of the Pacific k i l l i f i s h Fundulus parvipinnis due to size, season and continued constant temperature. Physiol. Zool. 8:318-336, 1935. Yeates, N.T.M. The breeding season of the sheep with particular reference to i t s modification by a r t i f i c i a l means using light. J. Agric. Sci. 29_:l-43, 1949. 

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.831.1-0106288/manifest

Comment

Related Items