Threespine sticklebacks (Gasterosteus aculeatus) inhabit both marine and freshwater environments along the Pacific coast of North America, In this study, sticklebacks collected from 73 locations on Vancouver Island, the Sechelt Peninsula and the lower Fraser River Valley of British Columbia, and six sites in northwestern Washington State, were assayed by starch gel electrophoresis in order to examine relationships among and between marine (trachurus) and freshwater (leiurus) populations. Six enzymes, coded for by eight genetic loci, were examined. Of these, two aere monomorphic for the same allele in all populations, the remainder were polymorphic to varying degrees. Laboratory breeding studies employing both marine and freshwater fish as parents confirmed the genetic interpretation of observed variability in isozyme banding patterns. One of the monomorphic enzytaes, isocitrate dehydrogenase, exhibited a sexually dimorphic isozyme pattern. Levels of polymorphism and heterozygosity were slightly higher than average, bat within the range of those characterizing other vertebrate species. In general, genotypic ratios conformed to Hardy-Heinberg expectations, and allele frequencies within populations did not shift over short time periods. Gene frequencies did not vary among sticklebacks of different sizes nor among those caught by different methods from the same population. Gene frequencies at all polymorphic loci were significantly heterogeneous among stickleback populations. Average frequencies at two loci (Pgm and Mdh-3) differed significantly between marine and freshwater fish. In addition, average frequencies at two other loci (Mdh-1 and Ck) were different among sticklebacks inhabiting different types of freshwater environments. Among freshwater populations the Ck ⁸⁵ and Pgm ⁹⁰ alleles displayed clinal geographic variability in frequency, possibly as a result of the differential sampling of various freshwater habitat types in different regions. Allele frequencies at three loci (Pgm, Ck and Pgi-2) differed between marine sticklebacks collected from the Strait of Georgia and those from waters off the vest coast of Vancouver Island. Calculation of Nei’s genetic distance indicated that while marine populations are relatively homogeneous at electrophoretic loci, freshwater populations are highly heterogeneous. The average genetic distance between marine and freshwater populations was similar to that separating pairs of freshwater populations. The genetic distance between freshwater populations was greater between than within watersheds, but allele distributions at individual loci did not differ significantly between two watersheds levels of polymorphism and heterozygosity were relatively high in populations from the ocean, large lakes and low-lying streams, and low in those from small lakes and isolated streams. Both deterministic (natural selection) and stochastic (founder effects and genetic drift) mechanisms can be invoked to explain these patterns. Morphologically and ecologically distinct benthic and limnetic sticklebacks within single lakes, and freshwater and marine sticklebacks within a stream, constituted genetically discrete populations. There was a striking congruence in the patterns of morphological and electrophoretic variability among the populations comprising such 'species pairs'. The results of this study are compatible with the suggestion that freshwater populations of the study area are polyphyletic, and have arisen independently from marine sticklebacks which invaded the region since the last ice age, about 10,000 years ago. / Science, Faculty of / Zoology, Department of / Graduate

The three general body armour forms of Gasterosteus aculeatus (Linnaeus), high, intermediate and low plate count forms, are found in nonbreeding marine populations. In breeding season initially the population in the nontidal portion of Bonsall Creek consisted of the low and intermediate plate count forms. Later when the tidal zone was occupied by breeding sticklebacks all three body armour forms were present and from the limit of the tidal influence the low and intermediate forms became less frequent seaward. In Chase Creek there exists an anadromous breeding population but there was no adjoining freshwater population. In Chase Creek however there did exist a zone where all three body armour form were present. Therefore, the development of the pattern of plate variation in the creek's tidal zone does not appear to be dependent upon the presence of both freshwater and marine population tyrjes. In Bonsall Creek where both a freshwater and a marine population bred, low plate count individuals from the freshwater zone and high plate count individuals from the adjoining tidal zone were reciprocally transferred in wire baskets. Mortalities of transferred fish were shown to be significantly higher than those of the controls indicating a possible barrier to gene exchange between the two populations. However, the presence of the intermediate plate count form in the freshwater zone of Bonsall creek strongly implicates gene flow between these two groups of fishes. all three forms collected from the tidal zone of Chase Creek. Showed the same mortality rate when placed in freshwater. This suggests that the low and intermediate plate count fish breeding in the tidal portion of Chase Creek were of marine origin. Ten morphological characters were combined in a discriminant function and used to classify breeding individuals from Bonsall Creek. The discriminant function showed a gradual change in morphology of the fish distributed from marine to freshwater. It is concluded that while there was considerable differentiation between adjoining freshwater and anadromous breeding populations of Gasterosteus aculeatus, no evidence of a morphological discontinuity as would be expected of separate species. However, the presences of the hybrid form in the freshwater zone of Bonsall Creek strongly implicates gene flow between those freshwater and marine groups of fish. Eleven populations ranging geographically from the Alaska Peninsula to Chehalis Biver in Washington State were similarly subject to discriminant function analysis. These samples did not show clinal variation in their scores, though the scores of the populations were significantly different suggesting local adaptation and possible restriction of gene flow within the marine environment. / Science, Faculty of / Zoology, Department of / Graduate

The present study investigated aspects of the biology of the cestode, Proteocephalus filicollis from the three-spined stickleback Gasterosteus aculeatus from Airthrey Loch, Scotland. The population biology study demonstrated that the parasite has an annual cycle of recruitment, which occur mostly in late summer and early autumn. The cestode did not show preference for any sex of the host. Maturation of the cestode also showed a seasonal cycle with the majority of worms maturing in late spring and early summer, but this period may be extended in different generations. Proteocephalus filicollis was overdispersed throughout the year in all sizes of fish, moreover variance to mean ratio always exceeded unity. No severe pathology was observed due to attachment of the worm to the intestine of the fish. The worm population in different sections of the intestine varied according to season and maturity stage. The P. filicollis migrate from the rectum to the anterior intestine as they mature and it is suggested that growth and maturation of the worm is a major stimulus for this migration. Proteocephalus filicollis has a high fecundity as indicated by the higher number of eggs per mm of gravid portion of the strobila and high fertility. Infrapopulation size did not show any relationship with length of worm, percentage gravid portion, number of gravid segments or mean length of gravid segments. Numbers of eggs are correlated to length of the worm, but not to infrapopulation size. Numbers of eggs per mm of the gravid portion are not correlated to length of worm or infrapopulation size. Acanthocyclops robustus was used as an experimental intermediate host. 15-16°C was the optimum experimental temperature for growth and a fully developed larva was formed in 23-27 days at this temperature. No growth was observed at 4°C, growth was slow at 10°C, but rapid at 21-22°C. The eggs are infective for 25 days at 4°C, 10°C and 15-16°C, but for only 15 days at 21-22°C. Prevalence and mortality of copepods are significantly correlated to their exposure time to parasite eggs, but mean intensity of infection did not show any relationship to the exposure time to the eggs. Ultrastructural studies demonstrated that a mature egg is surrounded by at least four embryonic envelopes, the capsule, the outer envelope, the inner envelope, and the oncospheral membrane. All these envelopes originate differently and undergo definite changes during their development.

A population of three-spined stickleback, Gasterosteus aculeatus L., was sampled every two weeks for 14 months from Airthrey Loch on the campus of the University of Stirling. A total of 857 fish were collected and three species of parasites were studied. The monogenean Gyrodactylus gasterostei was found on the skin and fins and two myxosporean parasites, Sphaerospora elegans and Myxobilatus gasterostei, were present in the kidney. All parasite species were present throughout the year but abundance was correlated with the yearly life cycle of the host fish. Lower prevalence and intensity were observed in summer due to the large number of young fish in the samples. The comparative ultrastructure and development of the two myxosporeans was studied by light and transmission and scanning electron microscopy. Both myxosporeans followed the general pattern of myxosporean development but showed some novel features. Sphaerospora e/egans had two distinct developmental cycles. A proliferative cycle involving extrasporogonic stages occurred in the blood whereas spore production occurred in the kidney. Light microscopy of Giemsa stained blood smears suggested proliferation of extra-sporogonic stages by external budding or plasmotomy. Structural similarities between extra-sporogonic blood stages and sporogonic kidney stages are discussed. Although S. elegans mostly formed disporous plasmodia, monosporous plasmodia were also occasionally observed. Before the appearance of sporogonic cells within the early pseudoplasmodia, certain areas of pseudoplasmodial cytoplasm became electron lucent, eventually acquired cell organeUes and later appeared as sporogonic cells. Developing valvogenic cells contained protuberances at the posterolateral side of spores which disappeared in mature spores. Characteristic lipid bodies were seen in developing capsulogenic cells and developing uninucleated sporoplasmic cells contained abundant glycogen granules. The sporoplasmic cells were devoid of sporoplasmosomes. Plasmodia of M. gasterostei were mono, di or polysporous and showed features of both coelozoic and histozoic myxosporeans, including a unit surface membrane, simple pinocytosis aanand presence of a number of vegetative nuclei and generative cells, the latter which formed pansporoblasts before the initiation of sporogenesis. A membrane bound tubular structure and some electron dense fibrillar bundles are previously undiscovered cytoplasmic organelles of the plasmodia. Developing capsulogenic cells contained characteristic membrane bound vacuoles filled with electron dense (glycogen) material. Myxobilatus gasterostel attached to the epithelial cells by plasmodial surface projections and there were electron dense areas at the point of attachment. Sphaerospora elegans showed occasional hairlike processes projecting from the pseudoplasmodial surface to the microvillous brush border of the epithelial cells. There were no electron dense areas at the point of attachment to the epithelial cells of the kidney tubules. Early undifferentiated pre-sporogonic stages of both parasites were occasionally present intracellularly in the tubular epithelium suggesting this is a route of entry into the tubular lumen. Early stages of S. elegans were also seen in the capillary lumen of the glomerulus. Intracellular and intraluminal stages of S. elegans and M. gasterostel caused pathological changes in different ways. Histopathological changes associated with S. elegans included vacuolation and accumulation of electron dense material in the epithelium whereas M. gasterostei caused large vacuolation with necrosis of the epithelial layer. Both parasites caused destruction of glomerular tufts in heavy infections and an increased number of rodlet cells in the epithelial layer were common in both cases. The two myxosporean species were most abundant during the winter and spring. Extra-sporogonic stages of S. elegans were found only in January and June in the rete-mirabile of the eye, circulating blood and kidney. In infections with S. elegans sex of the host fish was apparently of no significance, whereas significantly lower infestations occurred in male sticklebacks infected with M. gasterostei compared with females. Host size was important in determining the prevalence and intensity of both myxosporean species. Older fish were less heavily infected, possibly due to an acquired immunity or pathogenic effects on the host. A high number of mixed infections indicated that there was no interspeciflc competition between the two parasites. There appeared to be a continuous recruitment of myxosporeans throughout the year. Studies on myxosporean spore shedding suggested that spore production and shedding was continuous throughout the year and was uninfluenced by temperature or season. Gyrodactylus gasterostel was generally more abundant in winter and spring than in summer and autumn, reflecting the greater numbers of small young of the year fish at these times. The age of the host fish was a significant factor influencing the prevalence and intensity of infestation with G. gasterostei. Sex of the host had no apparent influence on infestation. The parasite was highly overdispersed within the host population and its distribution was best fitted by the negative binomial.

x, 154 leaves : ill. ; 29 cm Typescript. (Another copy on microfilm is located in Archives) Thesis (Ph.D.)--University of Oregon Vita Bibliography: leaves 144-154

A population of threespine sticklebacks (Gasterosteus aculeatus) infected with the cestode parasite S. solidus was studied to determine the effects of the parasite on stickleback reproductive. success, mortality rates, and swimming ability. The S. solidus infection increased stickleback mortality rates in 'natural' mortality, and in stressed mortality (low oxygen, high temperature) experiments. Infections of S. solidus at intensities of 30% of the stickleback body weight or greater, clearly affect the sticklebacks ability to swim. How infections at this or lesser levels effect predation on parasitized sticklebacks was not established. The effects of S. solidus on stickleback reproductive success were found to be minimal in this study, chiefly because the stickleback breeding season is essentially complete before the S. solidus infection becomes severe. / Science, Faculty of / Zoology, Department of / Graduate

Two morphologically and ecologically distinct forms of threespine stickleback (Gasterosteus), a "limnetic" form and a "benthic" form, co-exist in Enos Lake on Vancouver Island. I used three experiments to compare the feeding performance of the two forms, to test the hypothesis that limnetics are adapted to planktivory and benthics are adapted to foraging on benthic substrates. The results support this conclusion. When tested for maximum prey size, benthics were able to consume larger prey (relative to their body size) than limnetics. Benthics were also more successful than limnetics in foraging on a benthic substrate. When allowed to forage on a detritus substrate for a fixed time interval, benthics of both sexes captured more prey than male limnetics, despite the fact that male limnetics directed as many feeding strikes at the substrate as did the benthics. Female limnetics did not forage on the substrate at all. In contrast, limnetics were more successful in feeding on plankton than benthics. When held in mesh enclosures suspended in the water column of Enos Lake, limnetics consumed more plankton than benthics. "Small" limnetics (26-35 mm standard length) consumed nearly four times more plankton than "large" limnetics (44-50 mm standard length). The small limnetics were all either mature females or immature males; the large limnetics were all mature males. These results, along with morphological, biochemical, ecological and behavioural data obtained in other studies, support the conclusion that the two forms of Gasterosteus in Enos Lake are distinct biological species. The results of this study also support another (unexpected) conclusion: mature male and female limnetics also differ in feeding behaviour. Female limnetics appear to be almost totally planktivorous; whereas, male limnetics are intermediate between female limnetics and benthics (both sexes) in feeding behaviour. / Science, Faculty of / Zoology, Department of / Graduate

Two small streams on Vancouver Island, British Columbia, were examined for patterns of morphological variation in Gasterosteus aculeatus. A progressive analysis beginning with Principle Components Analysis, followed by Nested and Partially Nested Multiple Analysis of Variance and then Duncan's Multiple Range Test was used for pattern determination. This new technique allows the researcher to sequentially isolate the pattern of variation at different levels of generality from species to individual organisms. The pattern of variation for G. aculeatus in Bonsall Creek and Nunns Creek can be summarized as follows: The largest amount of variation accounted for by the analysis is interpreted as individual variation. Populations also account for a large amount of variation and show consistent, fully nested patterns of variation at each of the analysed geographic and microgeographic levels. These populations are probably genealogical units. The so-called "leiurus" and "trachurus" forms on the Pacific coast of North America do not appear to be evolutionary entities, but to be historical artifacts that are best viewed as labels for the extremes of a continuum of variation. In areas where distinct populations meet, different clines are documented in the two stream systems. In Nunns Creek there is a smooth cline between populations, whereas in Bonsall Creek there is a step cline. / Science, Faculty of / Zoology, Department of / Graduate

<p>This study used amplified fragment length polymorphism (AFLP) to detect changes of genetic variation in threespine stickleback exposed to industrial pollution from pulp- and paper mills along the southern east coast of Sweden. A general loss of allelic diversity was associated with exposure (table 3, linear model, F1,4=7.2 [P=0.055]) and exposed populations also displayed a similar pattern of response (fig 5) despite geographic distance, indicating that evolution toward pollution resistant ecotypes of threespine stickleback is occurring in the Baltic Sea. The result suggests that pollution can be regarded as an agent of directional selection, causing a decrease of evolutionary potential of exposed species in the Baltic Sea.</p>

This study used amplified fragment length polymorphism (AFLP) to detect changes of genetic variation in threespine stickleback exposed to industrial pollution from pulp- and paper mills along the southern east coast of Sweden. A general loss of allelic diversity was associated with exposure (table 3, linear model, F1,4=7.2 [P=0.055]) and exposed populations also displayed a similar pattern of response (fig 5) despite geographic distance, indicating that evolution toward pollution resistant ecotypes of threespine stickleback is occurring in the Baltic Sea. The result suggests that pollution can be regarded as an agent of directional selection, causing a decrease of evolutionary potential of exposed species in the Baltic Sea.