Treatment of male sticklebacks with methallibure brings about a marked reduction in the level of prespawning aggressiveness. Gametogenesis in the testes of the testes of the treated fish is slowed down so that after 30-38 days of treatment most testes contain spermatozoa and spermatogonia while the testes of the controls are more mature and contain spermatocytes and spermatozoa or spermatozoa only. Forty-nine days of treatment result in testes with spermatogonia, spermatocytes and spermatozoa, control testes are completely mature and contain only spermatozoa. Methallibure causes no significant increase in thyroid epithelial cell height evidence that the I.C.I. compound is not having a direct goitrogenic effect such as is found when fish are immersed in a solution of thiourea. The adenohypophysis of methallibure treated fish contains less basophilic material than that of untreated controls. / Science, Faculty of / Zoology, Department of / Graduate

No description available.

x, 36 p. : ill. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / Natural biological variation exists at different geographic scales. We compared phenotype distribution across latitude, region and habitat type in threespine stickleback (Gasterosteus aculeatus) to determine local adaptation. To quantify variation in photoperiodic response, the day length cue was used to time sexual maturation and morphological characters across these various scales. Using lab-reared lines, we developed an index of sexual maturation and experimentally determined critical photoperiod for Alaskan and Oregon populations. Results showed that photoperiodic response existed in Alaskan but not Oregon populations. We also collected morphological data and made comparisons between wild Alaskan and Oregon populations and found similarities within habitat type across latitude but differences across region and habitat type. These data support the hypothesis that local adaptation results in variation across geography and habitat and, in stickleback, parallel evolution of morphological phenotypes within similar but geographically distant habitats. / Committee in Charge: William E. Bradshaw, Chair; William A. Cresko; Christina M. Holzapfel

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The relative importance of stochasticity and adaptation to biodiversity has long been of interest to evolutionary biologists. Multiple, closely related insular populations provide ideal natural experiments with which to determine die relative strength of these two factors. An example of one such system is the threespine stickleback, Gasterosteus aculeaius. Threespine stickleback have predator defenses comprised of heritable lateral bony plates and large spines. Morphologically invariant marine stickleback have colonized freshwater habitats across the northern hemisphere, resulting in multiple independently derived freshwater forms highly variable in predator defenses. The islands of Haida Gwaii (the Queen Charlotte Islands), British Columbia, contain populations of freshwater stickleback that exhibit defensive variability comparable to the entire species, and vary in defensive asymmetry. Previous studies showed that numbers of defensive lateral plates and plate symmetry are positively correlated with the presence of predatory trout on these islands, but the effect of avian predators, another predator of stickleback, on plate number evolution remains unexplored. The purpose of this thesis is to determine whether plate number reduction is a defensive adaptation to avian predation, and to study functional implications of asymmetry in structural defenses from 115 natural populations. Experiments showed that plate number reduction in threespine stickleback enhanced fast-start velocity; a possible advantage to fish being pursued by diving birds with similar swimming speeds. Avian injury frequencies increased in populations as plate numbers increased at low plate numbers, but did not increase in populations wife plate numbers greater than ten. Trout injury frequencies decreased as plate numbers increased among populations, probably due to methodological problems. There were no correlations between avian or trout induced injuries and plate number within populations. Experiments indicated that selective predation of lateral plate numbers in stickleback by captive Hooded Mergansers was weak but insignificant, resulting in a very slight reduction in plate numbers after predation. The degree of fluctuating asymmetry (FA) of defensive structures showed a geographical cline across the archipelago, being elevated in lowland stained ponds, and reduced in clear large lakes. FA of juveniles was not correlated with pH, conductivity, light transmittance, or lake size among populations. Asymmetric individuals did not have reduced survivorship, contrary to predictions from previous studies of FA. However, asymmetry of lateral plates was negatively correlated wife plate number, and asymmetry of plates that provide structural integrity to the defensive spines was greatly reduced relative to ‘non-structural’ plates, supporting fee hypothesis that biomechanically important traits have greater symmetry. Structural plate asymmetry decreased as water clarity, and the chances of capture by predators, increased, and when the degree of overlap between plates and spine supports increased. Plate asymmetry was weakly associated with susceptibility to parasitism, but only where overall plate numbers were low. This supports the hypothesis that FA/fitness correlations are trait and habitat specific, and that sensitivity of asymmetry to developmental instability can be reduced in biomechanically important traits. In conclusion, reduction in armour in stickleback may be adaptive, but there is only weak evidence of selection by avian predators on lateral plates in the wild. Whether armour reduction is a direct adaptation to avoid capture or a cost-minimization strategy is not clear, but repeatability of reduced armour in habitats with diving birds, and the hydrodynamic benefit it provides, suggest the former. The associations between asymmetry and function suggest that asymmetry should be included in comparisons of divergent populations, as it lends insight into the functional implications of morphological diversity. Lastly, because multiple independent Iineages have evolved similar phenotypes in similar habitats in stickleback, this research has reinforced the idea that local adaptation to unique habitats is the driving force of diversification. / Graduate

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Treatment of gonadectomized adult male and female sticklebacks as well as normal juvenile, with methyl testosterone, either by immersion in a hormone solution or by implanting hormone pellets, induces the kidney cells to develop into granular and mucous cells, accompanied by an increase in cell height. Increase in cell height, up to a limit, is a function of the length of hormone treatment. Prespawning aggressiveness and territoriality is induced in gonadectomized fish of both sexes by maintaining them under long photoperiod for four to five weeks. Short photoperiod has no effect. Administration of methyl testosterone to the already aggressive fish showed no definite effect on this behaviour. The combined effect of long photoperiod and methyl testosterone treatment induces the nest-building behaviour in gonadectomized males and females with a much higher percentage in the former than in the latter. The component elements of the nest-building movement in the treated gonadectomized male is similar qualitatively and quantitatively to that of the normal reproducing male. Treated gonadectomized females show deviations from the normal male in their nest-building movements. Sexual behaviour is the same in castrates treated with methyl testosterone as in the normal reproducing male, but completely absent in the similarly treated gonadectomized females. / Science, Faculty of / Zoology, Department of / Graduate

Male stickleback did not show a greater increase in displacement or parental fanning when injected with prolactin than they did when injected with saline solvent alone. Displacement fanning was higher in gonadectomized fish with pituitary activity suppressed by short photoperiod than in gonadectomized fish with an active pituitary under long photoperiods when both groups were treated with the same testosterone concentration. Injection of pituitary fractions into the short photoperiod fish reduced fanning to the levels found under long photoperiods. Normal males under long photoperiod showed significantly higher fanning than any of the gonadectomized groups indicating that methyl testosterone in concentrations used did not fully replace the effects of the normal gonad. Exposure of males to a wide range of testosterone concentrations indicated that a relatively high concentration of testosterone was required for normal fanning. Low levels of fanning occurred after gonadectomy of fish in breeding condition in both "displacement" fanning and parental fanning stages, indicating the gonad was not required for performance of the fanning pattern as such but was required for fanning to reach levels approaching these found in normal fish. No evidence was found that prolactin initiates or maintains the parental fanning cycle. Testosterone however was necessary for normal fanning levels. / Science, Faculty of / Zoology, Department of / Graduate

This study compared three methods used to measure aggression in the male three-spined stickleback. These methods have been used in different studies without the certainty that they measure the same behavioural phenomenon. A number of different measures of aggression must be highly correlated if aggression in the male stickleback is to be regarded as a unitary drive. The methods consisted of recording the behaviour of an experimental male when: (i) a tube containing another male (or a female in some tests) was visible for 5 min; (ii) another male was visible across a glass partition at all times; (iii) a fish-shaped wax model was visible for 2 min. Each method showed that in the 12 days after fertilization of an egg-mass, there was a U-shaped trend in frequency of biting, frequency of charging and the rate of biting per minute spent oriented towards the other fish or the model. In Method (i), total oriented time formed about 70 % of a test period and this measure was not correlated with frequency of biting, nor did it follow a U-shaped trend. In Methods (ii) and (iii), total oriented time formed less than 50 % of a test period, was correlated with frequency of biting, and did follow a U-shaped trend. In Methods (i) and (ii), the measures, frequency of biting and bites per min of oriented time were at a maximum in the first 15 min after fertilization. Method (iii) did not show this maximum in biting. All methods showed that frequency of biting, of charging, and bites per min of oriented time were higher for fish with nests than for fish which had yet to build nests. Gonadectomy of fish with nests reduced all measures to the levels found for intact fish that did not have nests. An experiment using only Method (i) showed that a male with a nest attacked another male more than a non-gravid female. A male without a nest attacked both a male and a non-gravid female equally. The use of more than one measure for a behaviour pattern improved both the comparisons between methods and the analysis of changes in behaviour of the male. Examples of this are given for biting and parental fanning. Results from Method (iii) were not always consistent with those from Methods (i) and (ii). Method (iii) was exceptional in the number of charges the experimental males made with both dorsal and ventral spines erect. A wider range of behaviour patterns were recorded more regularly in Method (ii) than in Method (i). But these two methods consistently showed the same trends in frequency of biting, charging and bites per min of oriented time. In spite of the similarities in the results from the three methods there was not sufficient evidence to conclude that aggression in the male stickleback is a unitary drive and that all potential measures of aggression will be equivalent. / Science, Faculty of / Zoology, Department of / Graduate

No description available.