Male three-spined sticklebacks without territories cannot reproduce; and in order to establish and maintain a territory, a male must behave aggressively toward other fish. Such social organization raises questions about determination of the size of the breeding population and the selective advantage of particular levels of aggressive behaviour. Experiments varying the amount and kind of social contact with other fish showed some of the effects of social organization. Grouped males build nests sooner, and hatch a smaller proportion of clutches of eggs than isolated males. Fry survive less well with grouped males. There are consistent differences between individual males in aggressiveness during the reproductive cycle. Changes in aggressive behaviour and territory size have similar U-shaped temporal patterns which are common to all males. Aggression is lowest and territory size smallest just before the clutch hatches when the male spends most time fanning. Males without clutches sometimes attack the nests of other males. Interference by these males is often responsible for hatching failure. Individuals that hatch clutches seem no more aggressive than those that do not. However, males hatching clutches have larger territories during the first part of the reproductive cycle. They spend more time at the nest, and tend to remain closer to it. / Science, Faculty of / Zoology, Department of / Graduate

Parental investment, defined as any parental activity that1 increases the survival of offspring at a cost to the parent, is a useful concept for examining the selective bases of parental behavior. To maximize its lifetime production of surviving offspring, a parent should adjust its level of risk in a parental investment depending on the value of its future "prospects" in relation to its present young. as present young increase in value, either by number or age, a parent should expend more risk in a parental investment so long as the effectiveness of its behavior does not diminish. This will often be the case for a parent that defends a nest containing eggs. The prediction of an increase in parental risk for more eggs or older eggs has been tested using two natural populations of threespine stickleback, Gasteros teus- acule^tus L. Male sticklebacks that were guarding nests were presented with a dummy predator, the prickly sculpin Cottus asper, and their responses were measured. Those males that remained within their nest area and attacked the dummy sculpin had a larger number of eggs or older eggs than those males that deserted their nests and never attacked the dummy. In the population that is sympatric with sculpins, males that initially attacked the sculpin's head had older eggs than those which avoided the head but attacked the tail area. The level of the male's responsiveness, and associated risk, was recorded in a series of quantitative measures. The time it took a male to return to its nest, as well as the time to attack the sculpin dummy, was shorter for males with a larger number of eggs or older eggs. The number of bites at the dummy in the first minute after the initial attack increased as the egg number and egg age increased. Changes in male risk were in the predicted direction and none of the responses could be associated with any single biological or environmental factor other than the number or age of the eggs. / Science, Faculty of / Zoology, Department of / Graduate

To date, models of sexual size dimorphism do not explain selection for small females, and they are also limited in their ability to explain intraspecific variation in sexual size dimorphism. I propose that small females, in species which produce multiple clutches in a breeding season, could have a selective advantage if the interval between clutches is shorter for small clutches of eggs. When the breeding season is long, small females may produce more eggs in total than large females by producing more clutches, and thus small size could be selected for. Two populations of threespine stickleback (Gasterosteus aculeatus) showing divergence in the sexual bias of size dimorphism were used to determine if large or small females had a seasonal fecundity advantage in these multiple spawning fish, and whether the two populations had diverged in life-history characteristics (age at first reproduction, number of clutches, length of breeding season). In addition, the mechanisms by which the differences in size were achieved was investigated. Size-frequency diagrams obtained from field samples indicated that the Lewis Slough population was an annual one, while fish at the Angus Campbell site apparently survived for more than one breeding season. The larger size of females at the Angus Campbell site resulted primarily from continued growth with age, while males stopped growing in about one years time. In an environment chamber female fish from Lewis Slough grew more slowly, as they approached maturity, than males and were therefore were smaller than males. Data from field collections, fry raised to maturity in an environment chamber, and females individually monitored in captivity over the course of a breeding season indicated that the populations have diverged in life-history characters. Females from the Angus Campbell ditch site produced fewer clutches and eggs over the breeding season (a measure of reproductive effort), delayed maturity and matured at a greater size, and had a longer life-span than Lewis Slough females. These observations are more in accordance with the predictions from bet-hedging theory than r & K selection theory. Data from individually monitored females held in a common environment indicated that clutch size and interclutch interval increased with increasing body size but small females still did not attain the seasonal fecundity advantage predicted by the model. However, these results suggest that small females are capable of achieving a greater seasonal fecundity relative to large females than would be predicted by the difference in average clutch size alone. Actual counts of the total numbers of eggs produced by individuals in a breeding season showed seasonal fecundity to be independent of body size. Female body size and fecundity are more weakly linked than previously realized and this confers an increased flexibilty for responding to diverse selective pressures. / Science, Faculty of / Zoology, Department of / Graduate

The present longitudinal study examines a natural population of threespine sticklebacks, Gasterosteus aculeatus form Little Mud Lake in British Colombia, Canada to determine if individual fish within a given population exhibited a preference for finding prey on the bottom of the lake, prey floating in the water column of the lake, or prey in other microhabitats of the lake. Foraging behaviors were recorded to determine the presence of individual specialization within the focal sympatric population. Comparing the proportion of strikes on various microhabitats for multiple individuals shows that individual specialization is present within the focal population of sticklebacks. Data shows that some fish prefer the feed on benthic prey while others prefer to feed on prey found on the surface of the water. Diet preferences were also compared to morphology to determine if individual fish traits had a relationship to preferred foraging location. Length of the longest gill raker and protrusion length results showed a relationship to limnetic-like and benthic-like feeding behaviors. / text

Proefschrift (Ph. D.)--Groningen, 1956. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (p. 203-213).

Proefschrift (Ph. D.)--Groningen, 1956. / Includes bibliographical references (p. 203-213). Also issued in print.

Excretion of radioiodide by Gasterosteus aculeatus has been shown to vary directly with increases in salinity and inversely with size of fish. Erroneous excretion values may be produced by an apparent laboratory diuresis which seems to vary with season and salinity. During the initial stages of sexual maturation in sea water temporary changes in excretion occur which result in an increased retention of radioiodide by the fish. These changes show a greater development at lower salinities. The demonstrated dependence of thyroid uptake upon available radioiodide make this parameter an unreliable estimate of thyroid activity. The conversion ratio, except for errors which occur under conditions where the rate of radioiodide excretion is not constant over the period of the measurements, seems to be a valid estimate of thyroid activity. Technical factors, such as the binding of inorganic radioiodide to precipitated protein, can also produce erroneous conversion ratio values. Differences in the protein binding of inorganic radioiodide suggest that changes in blood proteins occur during sexual maturation. Although a seasonal increase in thyroid activity occurs there is no correlation between this and the increase in radioiodide retention. There is therefore no reason to believe that the thyroid is responsible for the observed changes in retention of radioiodide. / Science, Faculty of / Zoology, Department of / Graduate

The role of prolactin in osmotic and ionic regulation of the marine threespine stickleback (Gasterosteus aculeatus L., form trachurus) in fresh water has been investigated in winter (or late autumn) and spring. Sticklebacks in late autumn or early winter, when transferred from sea water to fresh water, suffered a high mortality which could be reduced by prolactin treatment. The fish also displayed a greater fall in plasma osmolality and a smaller fall in urine osmolality than late-spring fish transferred to fresh water in the same way; this seasonal difference was apparently triggered by photoperiodic changes and could be eliminated by prolactin treatment of the late-autumn or early-winter fish. Similarly, a seasonal difference exists in the histological picture of the glomeruli of late-autumn and late-spring sticklebacks, and this difference could be eliminated by prolactin treatment of the former fish. The fall in plasma osmolality in late-autumn and winter fish after transfer to fresh water was paralleled by a rapid drop in plasma sodium and chloride, which could be corrected by a single injection of prolactin given 24 hr before the transfer. Plasma potassium, however, seemed unaffected by prolactin treatment. The evidence suggests that prolactin is essential for freshwater survival of sticklebacks and that prolactin undergoes seasonal changes in secretion associated with photoperiodic changes; the secretion is minimal in the autumn and winter when the fish live in sea water or brackish water, and maximal in the spring and summer when the fish migrate to (or are in) fresh water, to breed. Thus prolactin may be involved in the freshwater migration of sticklebacks. Next, the mechanism of action of prolactin was studied. Prolactin seems to exert its effects (in fresh water) on the three recognized organs of osmotic and ionic regulation in teleosts, viz. kidneys, gills and gut. In the kidneys, prolactin increased urine flow, apparently as a result of an increased GFR. Prolactin reduced the apparent increase in intracapsular space in the glomeruli of the late-autumn and winter sticklebacks, and, consequently, increased the percentage frequency of glomeruli with no evident intracapsular space. The data are interpreted to mean that prolactin rendered glomeruli more functional or more glomeruli fully functionaland, hence, increased GFR. Since the increase in urine flow and GFR was paralleled by a decrease in urine osmolality and urine concentrations of sodium and chloride, prolactin must also increase renal tubular reabsorption of sodium and chloride (A) and/or decrease water reabsorption (B); and since the total renal loss of sodium and chloride did not appear to be significantly increased despite an increase in GFR, A must occur with or without B. Prolactin, however, apparently increased the total renal loss of potassium and did not affect the tubular potassium reabsorption, although there was a suggestion that prolactin actually decreased tubular reabsorption of potassium. In the gills (or other regions around the head), prolactin reduced the net osmotic influx of water and the net loss of sodium, chloride and C¹⁴ (from injected C¹⁴ -inulin); the latter was probably because prolactin reduced the outflux. These changes were accompanied by the behaviour of the gill mucous cells, which were increased in density by prolactin treatment, suggesting a cause-or-effect relationship. In the gut, prolactin reduced water absorption and, at the same time, seemed to reduce the freshwater drinking rate. Thus, it appears that prolactin was able to reduce or prevent osmotic flooding of sticklebacks in fresh water by reducing extrarenal osmotic influx of water and increasing renal loss of water via an increase in GFR and urine flow, and also, possibly, by reducing drinking rate and water absorption by the gut; at the same time, prolactin reduced extrarenal loss of sodium and chloride but did not apparently affect renal loss of the ions, which was small compared to the extrarenal loss. By these mechanisms, prolactin maintained plasma osmolality and sodium and chloride levels after transfer of the fish to fresh water, and, consequently, was able to promote freshwater survival of the fish in the autumn and winter. / Science, Faculty of / Zoology, Department of / Graduate

Five populations of the threespine stickleback, Gasterosteous aculeatus,from the upper Cowichan River system (Vancouver Island, British Columbia) were surveyed to assess interpopulation levels of variability in trophic morphology. Phenotypic divergence is assumed to be a post-glacial event. Nine characters were scored; eight were related to feeding and the ninth character was lateral plate number. All populations surveyed were the low plate morph; however populations of Gasterosteus in lakes lacking piscivorous fish had significantly fewer lateral plates than populations in lakes with predatory fish species. Three trophic 'morphotypes' were identified, each associated with one of three lake environments. Populations inhabiting benthic dominated environments ('benthic morph') were found to possess reduced gill raker number and reduced gill raker length but increased upper jaw length relative to populations from lentic environments ('limnetic morph'). An intermediate morph may also exist and is characterized by a morphology suitable to either trophic regime. Analysis of stomach contents showed diet type (benthic or limnetic) to be significantly dependent on morph. The functional significance of differences in trophic morphology was investigated in three feeding experiments using a representative population from each morphotype. The longer jaw of the benthic and intermediate morphs allowed them to ingest a larger benthic prey than the limnetic. No behavioural component to benthic foraging success between populations was identified, although increased jaw length shortened the time spent manipulating prey. Both the intermediate and limnetic morphs were better foragers on an experimental limnetic prey than was the benthic. Head length, snout length, gill raker density and gill raker number were strongly correlated with limnetic foraging success. The quantitative genetics governing the eight trophic characters were investigated using the same three representative populations. Broad sense estimates of character heritabilities ranged from 0.132 to 0.677; all estimates were significant. Character genetic correlations were reasonably strong (0.3 ≤ |rG| ≤ 0.9), while character correlations arising through environment tended to be lower. Cluster analyses of the genetic correlation matrices defined two character suites, the first grouped measures of head shape, the second grouped measures of gill raker structure. The patterns of genetic correlations suggest the three populations are distinct races. Selection gradients for divergence between morphotype indicated that directional selection had operated hardest on head length, snout length, gill raker number, head depth and upper jaw length; hence selection has operated to modify characters related to food size. The benthic-limnetic and intermediate-limnetic morphs were separated by the greatest selection distance while the intermediate-benthic morphs were separated by the shortest selection distance. These results support the conclusion that directional selection, arising from trophic resource differences between lakes, has organized interpopulation variability for Gasterosteus within the upper Cowichan drainage. The racial distinction of each population coupled with the functional significance of some components of trophic morphology indicate that at least the benthic and limnetic morphs must be considered 'ecotypes'. / Science, Faculty of / Zoology, Department of / Graduate

Testis-specific protein (TSP) variability has been examined in the three-spined stickleback, Gasterosteus aculeatus and related species including Gasterosteus wheatlandi, Punqitius pungitius, and Aulorhynchus flavidus, in order to determine if such proteins can act as molecular markers for different species of Gasterosteiformes and for different populations of a single species. Cytochemistry of the sperm histones of Gasterosteus aculeatus revealed that these basic proteins can be classified as intermediate sperm histones according to Bloch's (1969 and 1976) categories. Electron microscopy indicates that the chromatin in the nucleus condenses in a granular pattern as the somatic histones of the spermatogonia are replaced by the sperm histones in the spermatid during spermiogenesis in this teleost. The testis specific proteins (TSP's) of G. aculeatus and related species were characterized by electrophoresis on polyacrylamide gels and by hydrolysis of the amidoblack stained bands from the gel and subsequent amino acid analysis. The compositional analysis revealed that all the TSP's of the fish in the order Gasterosteiformes were intermediate type containing histidine, lysine, and arginine amino acid residues. However, the TSP's of different species could be distinguished by their electrophoretic mobilities on polyacrylamide gels and by differences in the amino acid composition. Apparently TSP's can act as molecular markers to distinguish these particular teleosts. To establish the electrophoretic pattern for the TSP's of mature, breeding G. aculeatus, the developmental profile was investigated over the course of a season for a population of these fish in Jericho Pond, Vancouver, B.C. As the testis matures, somatic histones are replaced gradually by one or several rapidly moving TSP's. Some protein bands that are present in fish with immature testes are removed by the time the electrophoretic pattern typical for mature males occurs during the breeding season. This pattern shows only rapidly moving TSP's and very low levels of somatic histones. Experiments using alkaline phosphatase indicated that the electrophoretic profile of the multiplicity of TSP'.s of mature fish was not due to differences in charge because of phosphorylation of serine side chains in TSP bands. In addition to acting as molecular markers for different species, the TSP's showed an electrophoretic profile in anadromous G. aculeatus that differed from the profile in freshwater fish with respect to band morphology and also the number of bands seen on long gels. Here, too, the similarity of the freshwater and anadromous TSP profiles was reinforced by similar digestion patterns with cyanogen bromide, confirming the presence of methionine in these proteins. However, different populations of anadromous G. aculeatus either from British Columbia or from Quebec were indistinguishable by electrophoretic analysis. Moreover the electrophoretic and amino acid analysis could not distinguish between G. aculeatus from different freshwater populations. There was no discernable trend for the multiplicity of TSP's from such populations. However, in the fish from two freshwater lakes there was an indication that the benthic forms (bottom dwellers) might have reached sexual maturity later than the limnetic forms (top dwellers) as the limnetic animals lost their somatic histones before the benthics did. From these analyses, TSP's apparently can act as molecular markers between different species of Gasterosteiformes, and to a lesser extent between anadromous and freshwater forms of G. aculeatus. This agrees with the findings of Mann et. al. ( 1982) that the spermatid/sperm-specific proteins of the frog genus Xenopus can distinguish between different species of the genus and somewhat between different subspecies of Xenopus laevis. Both the Gasterosteiformes and anuran TSP's are of the intermediate type. In several instances, particular species of fish gave anomalous results. For example, an anadromous G. aculeatus showed the presence of a band typical for the TSP of G. wheatlandi on polyacrylamide gel electrophoresis. Perhaps this is due to hybridization between Gasterosteidae of different species. Finally, incubation of TSP preparations at 37 °C indicated the presence of endogenous protease at neutral pH. Such a protease was not active at acid pH and therefore did not interfere with the electrophoretic analysis. / Science, Faculty of / Zoology, Department of / Graduate