Recently, it has been discovered that serotonin (5-HT) receptors exist as subtypes in the mammalian brain. At least two major subtypes that differ in their distribution, and affinity for serotonergic drugs, have now been described. These receptors have been labeled 5-HT₁, and 5-HT₂ receptors. The purpose of this thesis is to determine what roles the 5-HT₁, and 5-HT₂ receptors might play in the modulation of sexual behaviour in the female rat. The administration of the 5-HT₂ receptor antagonist pirenperone inhibited sexual receptivity in adult, ovariectomized Sprague Dawley rats that had been primed either chronically with estradiol benzoate (EB), or acutely with EB plus varying doses of progesterone (P). An inhibition occurred at peripherally administered doses of 50, 100 and 150, but not 25 µg/kg of pirenperone. Pirenperone also inhibited receptivity when administered intraventricularly at a dose of 15 µg/kg, however this dose of pirenperone was ineffective when administered peripherally. Increasing the dose of P did not attenuate the inhibitory effect of pirenperone. The 5-HT₂ antagonists ketanserin (2.5 mg/kg) and spiperone (250 µg/kg) also inhibited receptivity in females that had been primed with EB plus P. The inhibitory effect of pirenperone was attenuated by the 5-HT₂ agonist quipazine , however the 5-HT precursor 5-hydroxytryptophan (5-HTP) (20 mg/kg), and the 5-HT₁, agonists 5-methoxy-N,N-dimethytryptamine (5MeODMT) (200 µg/kg) and tryptamine (2 mg/kg) did not attenuate the effect of pirenperone. Quipazine, 5-HTP, and 5MeODMT did not effect receptivity in females that had been primed with EB plus P, however tryptamine inhibited receptivity. Whereas the nonselective 5-HT antagonist methysergide (3 mg/kg) failed to have an effect on receptivity in females that had been primed with EB, methysergide coadministered with quipazine facilitated receptivity. Pirenperone also inhibited proceptivity in females that had been primed with EB plus P. Although quipazine did not attenuate the inhibitory effect of pirenperone upon proceptivity, quipazine alone facilitated proceptivity in females that had been primed either with EB, or with EB and P. Methysergide did not effect proceptivity, and 5-HTP, 5MeODMT, and tryptamine were also ineffective with regards to proceptivity. The results of the present series of experiments are not entirely consistent with Meyerson's widely held theory of serotonergic inhibition , rather they suggest a dual role for 5-HT in female sexual behaviour. Therefore, a new theory regarding the role of 5-HT in sexual behaviour is proposed. Specifically, it is proposed that inhibitory effects of 5-HT are mediated by activity at 5-HT₁, receptors, whereas facilitatory effects are mediated by activity at 5-HT₂ receptors. / Arts, Faculty of / Psychology, Department of / Graduate

I consider the relationship between natal dispersal, the acquisition of breeding resources and the proximate maintenance of the mating system in a population of song sparrows (Melospiza melodia) resident on Mandarte Island, B.C.. The general hypothesis tested was that intrasexual competition for the resources that limit reproduction in each sex is the main factor affecting patterns of natal dispersal, territory turnover and mating system organization. This study reveals differences in the competitive ability of individuals and the consequences of these for natal dispersal, territory acquisition and the ability to monopolize mates. In this population, natal dispersal, territoriality and the mating system are related through the common mechanism of intrasexual competition for breeding resources. This competition affected reproduction within each sex, and in the opposite sex, raising potential conflicts of interest between mated males and females. I identify correlates of competitive ability, and consider how individuals of each sex maximize the number of young they raised. All suitable habitat was defended even at low density, resulting in high levels of competition for space. Song sparrows contested for territories year-round. Most settlers were yearlings, but several males were older and had previously owned a territory. Most floaters settled by evicting owners from all or part of their territories, in contrast to the assumption of most models of dispersal that floaters gain territories only after an owner's death. Relative age and dominance within cohorts affected recruitment and territorial status in the year following hatch in each sex. Differences in age also affected territorial and mating behaviour, particularly in males. Although competitive ability varied with age, differences in competitive ability between males persisted through life. Approximately 9% of male breeding attempts occurred after a male territory owner had evicted a neighbour and thereby gained access to an additional female. Polygynous males raised more young than monogamous males. Females vigorously defended their territories against female intruders, presumably to prevent polygyny by their mates. Females in polygynous groups often lost the aid of their mate, and raised fewer young, because polygynous males did not aid two females simultaneously. Adding supplemental food altered female time budgets, increased their ability to prevent settlement by female floaters, and increased their reproductive success. This suggests that females are constrained in the amount of time they can spend in territory defence by time spent foraging. The maintenance of monogamy was affected by differences in the abilities of individual males and females to defend their territories against intruders of the same sex. Dispersal distances were similar among sexes, in contrast to the usual pattern of female-biased dispersal in birds. Given the intense territorial behaviour of males and females, this study supports the hypothesis that biases in dispersal arise when territory establishment is substantially more difficult in one sex than the other. Dispersal on Mandarte was unrelated to inbreeding, common parentage, or reproductive success. However, emigrants from Mandarte were socially subordinate birds that must have outbred if they settled successfully. Female emigrants from local populations in the vicinity of Mandarte may settle more often than males. Dispersal occurred as young birds established ranges in the period following independence, from which they challenged or replaced owners. Adding food during the breeding period reduced dispersal in males and females in late summer and the following spring. Competitive ability probably affects dispersal from the natal population, the likelihood of settlement, and the time of settlement for those birds that remain in the natal population. / Science, Faculty of / Zoology, Department of / Graduate

The present series of studies was undertaken to determine the effects of peripherally and centrally administered alpha-melanocyte stimulating hormone (MSH) on lordosis and to investigate some of the mechanisms underlying these effects. The results of Experiments 1-5 (Section I) indicated that, when confounding factors were minimized, peripherally administered MSH facilitated receptivity. Centrally administered MSH was found to produce both a long and a short term inhibitory effect. Experiment 6 (Section II) tested the hypothesis that the facilitatory action of peripherally administered MSH was due to an MSH-induced release of progesterone or some other facilitatory adrenal steroid. Results indicated that, while adrenalectomy per se did not inhibit lordosis, it blocked the facilitatory action of MSH, supporting the hypothesis. In Experiments 7-9 (Section III), the role of estrogen and progesterone in the inhibitory actions of MSH was examined. The results of these studies suggested that both estrogen and progesterone are necessary for the short term inhibitory action of MSH. However, the long term inhibitory action of MSH appears to be due, in part, to an MSH-induced decrease in the availability of cytoplasmic progestin receptors. In Experiments 10-15 (Section IV), the role of serotonin in the production of the inhibitory actions of MSH was examined. Parachlorophenyl-alanine (PCPA), a serotonin depletor, was found to prevent the long term inhbitory action of MSH. In addition, the inhibitory effects of PCPA or pirenperone, a serotonin type II receptor antagonist, did not summate with the inhibitory action of MSH. This suggested that serotonin type II receptors were involved in the production of the inhibitory actions of MSH. In Experiment 12, quipazine, a serotonin type II agonist, was found to attenuate fully the short term Inhibitory action of MSH. However, quipazine did not fully attenuate the long term inhibitory action of MSH, suggesting that the short and long term inhibitory actions of MSH are mediated through different mechanisms. This possibility was supported by the results of Experiment 13, which indicated that 20 ng MSH produced a long term, but not a short term, inhibitory effect. The results of Experiment 14 indicated that subthreshold doses of pirenperone and of MSH, when administered together, would inhibit receptivity. Experiment 15 indicated that this inhibition could be attenuated by quipazine. Thus, the following conclusions can be drawn: 1) the facilitatory action of peripherally administered MSH is probably mediated by an MSH-induced release of progesterone from the adrenals, 2) the short term inhibitory action of MSH is mediated, to a large extent, by an MSH-induced decrease in serotonin type II activity, and 3) the long term inhibitory action of MSH is mediated, in part, by an MSH/serotonin-induced decrease in the availability of progestin receptors. In addition, it was hypothesized that: 1) progesterone acts in the MRF to increase serotonin type II activity. Thus, MSH-induced decreases in serotonin type II activity and in progestin receptors probably occur at this location, and 2) estrogen acts in the AH-POA to decrease serotonin type I activity. Therefore, any actions of MSH on serotonin type I activity or on estrogen receptors is likely to occur in this region. Finally, it was suggested that MSH plays a role in the induction and maintenance of pseudopregnancy, thereby providing MSH with a functional role in the regulation of receptive states. / Arts, Faculty of / Psychology, Department of / Graduate

The genetic relationship of anadromous (sockeye salmon) and non-anadromous (kokanee) Oncorhynchus nerka was examined in conjunction with the breeding behaviour of the two forms to determine: (1) if there is evidence of genetic divergence between the forms where they spawn sympatrically; (2) if such divergence is associated with significant premating isolation between the forms and; (3) if premating isolation results directly from the size difference between the forms (sockeye are much larger than kokanee at maturity). Both sexes exhibit spawning territoriality; females establish and defend particular nest sites until death or displacement, males defend access to specific females from other males until the female has spawned out, they are displaced, or leave to compete for additional mates. Size and prior access to resources (mates and/or specific areas) are significant factors in intrasexual aggression in both sexes, with size the major factor in males and prior access the major factor in females. Females accompanied by males larger than themselves lose weight at a faster rate than those accompanied by males smaller than themselves. Weight loss is related to egg loss, indicating females spawn at a faster rate when accompanied by large males. Male mate preference depends on the size of the male. Males of various sizes prefer females of their own size or larger over females smaller than themselves. In contrast, all sizes of males tested demonstrated no preference between females of their own size and those larger. Large males, which have the widest range of potential mates (because of male intrasexual competition and female choice), are the most selective and small males, which have the narrowest range of potential mates, are the least selective. There were significant differences in allele frequencies between sympatrically spawning sockeye and kokanee. However, there were no consistent differences between sockeye and kokanee at any of five polymorphic loci examined. The extent of genetic differentiation between sympatric forms appears to be less than that between neighbouring populations of the same form, judging from an examination of allele frequencies and/or allele compositions. There was extensive assortative mating by form between sockeye and kokanee, which was not totally accounted for by the large size difference. In the two systems examined, males preferred to mate with females of their own form. In sockeye, such preferences are expected because of the size difference between forms. In kokanee, such preferences are not expected based on size alone, suggesting the evolution of premating isolating mechanisms. The degree of premating isolation was positively correlated with the extent of genetic divergence between sympatric forms. The results of this study are related to existing models of sympatric speciation to hypothesize that sockeye and kokanee have diverged in sympatry. The probable differences in selection between the marine and freshwater environments coupled with the assortative mating resulting from their size difference may have caused subsequent genetic divergence. This divergence appears to have been followed by the evolution of premating isolation. / Science, Faculty of / Zoology, Department of / Graduate

This study examines the reproductive and population biology of a long-lived (80-y life span) fish, Sebastes alutus (Gilbert). The objectives of the study were (i) to establish whether groups of adult S. alutus delineated by exploitation histories could be objectively identified as separate sub-populations; (ii) to identify the effects of density-independent mortality caused by exploitation, and relate them to predictions of life history theory (iii) to examine the long-term implications of this mortality pressure on the dynamics of the species; and (iv) to determine the contribution of these results to the development of management programs for this species. A lernaepodid copepod gill parasite (Neobrachiella robusta (Wilson 1912)) was used for the first time as a biological tag to delineate separate sub-populations (stocks) of a commercial fish. Intensity of infection and mean characteristics of the parasite population per fish achieved complete separation between stocks indistinguishable with morphological features. Discriminant analysis showed the parasite also functioned moderately well (34-76% correct classification) as a stock discriminator of individual fish. Use of auxilliary information on the stock identity of hosts improved the classification power of the discriminant function. The density-independent mortality of the commercial fishery on S. alutus has severely truncated the age spectrum of some stocks. Some compensatory growth changes for fish in the stocks under the strongest selection are evident. Examination of the variance structure of female length at age suggests an inverse relation of mortality and growth rate giving rise to smaller, older fish. Smaller, older fish can be accounted for using the same growth function as for the larger fish seen at younger ages, and these similar growth forms can give an aggregate appearance of quadratic growth. Growth changes do not yield significant differences in size at maturity, although age at maturity changes, implying developmental or environmental constraints on maturation. Fecundity estimation methodology was evaluated and the volumetric method previously used for this species found to be inferior to a gravimetric method. Significant differences in fecundity as a function of body variables were found among exploitation groups. Significant differences in oocyte characteristics among stocks were found, with size and age shown to have separable effects. Lightly exploited stocks had significantly higher oocyte quality (as expressed in oocyte weight), effected through differences in the oocyte diameter-oocyte weight relationship. Histological examination details the developmental sequence of oocytes and establishes the maturation period of oocytes and fish. Northern stocks were shown to have significantly larger oocytes. Follicular atresia is suggested as an alternative energy source to the embryo death which has been presented as the source for matrotrophy in this genus. Complete atresia of a ripe oocyte complement was identified in this genus for the first time. No evidence of reproductive senescence was found. The hypothesis of increasing reproductive effort with age, including the independence of age and size effects, was confirmed. No evidence of reproductive cost could be found. The hypothesis of increased reproductive effort earlier in life as a mechanism to offset increased adult mortality was supported. However, the potential of this increase, achieved by growth rate increases, is much less than is needed to compensate for the reduction in lifetime reproductive effort caused by high fishing mortality. The effects of changing mortality rates on several reproductive value indices was examined with deterministic and stochastic simulation models. Cohort reproductive value is the most sensitive of the indices examined and may be the most robust to measurement error. Reproductive value is a more sensitive index of population state than other indices in use and may play a role in determination and evaluation of optimal harvest policies. However, an experimental approach to its use will be required. / Science, Faculty of / Zoology, Department of / Graduate