Two methods of collection were employed in the investigation of the density, distribution, and movements of invertebrates inhabiting the Chara zone of lakes: (1) Chara samples were obtained at regular depth intervals over the Chara shoals with the aid of Scuba gear, partitioning the Chara stand into two approximately equal vertical halves - top half and bottom half; (2) a long-handled dipnet was used to sample the surface of the Chara stand and the waters above the stand. Sampling with the dipnet on a 24-hour basis provided data on the diel movements of organisms in the Chara zone. The density of the invertebrate populations was lowest in June due to the reduction of stocks over the winter months by predation and other causes of death. The high numbers in September were attributed to the results of early summer reproduction. Fluctuations in density over the summer months were traced to the changing interplay between hatching and emergence of various invertebrate groups. Eradication of fish from one of the lakes resulted in an increase in numbers of the major fish-food organisms, indicating predation by fish as an important factor controlling density of invertebrate stocks. The distribution of invertebrate organisms over the Chara shoal from shore to the limit of the vegetation offshore and vertically within the Chara bed itself was remarkably homogeneous. Minor differences in distribution of several invertebrate groups were demonstrated by statistical means. Daily vertical and horizontal movements of many of the organisms were shown to produce large density fluctuations on the Chara surface. / Science, Faculty of / Zoology, Department of / Graduate

A continuous-time model, describing the interaction between a "'facultative"' predator and a prey is used to study the consequences of exploitation of either the predator, the prey or both. The model assumes a logistic growth pattern in absence of the interaction. The change in steady-state levels of the associates due to different combinations of fishing intensities are described mathematically and diagrammatically. The effect of density of predation, on the equilibrium populations associated with the yield of either, or both, the predator and the prey are studied. Yield curves were constructed for both the predator and the prey under different fishing intensities of the other associate. The model is given in a discrete-time form, of which the stochastic version is derived to show the effect of intrinsic variability. The stochastic version was simulated on the computor through the use of random normal deviates. Fair agreement between the calculated values of the variances of the steady states, and those empirically found through simulation is listed. This simple structural model reveals that in such an association, fishing the prey population alone gives a lower maximum sustained yield than can be maintained, if the predator is also fished. It is hoped that such a model, which is a preliminary but a necessary step, will lead to a more comprehensive model applicable to natural fish populations. / Science, Faculty of / Zoology, Department of / Graduate

A comparative study was made of the social communication patterns of Pelecanus erythrorhynchos, P.onocrotalus, P.crispus, P.occidentalis, Morus bassanus, Sula sula, Anhinga anhinga, Phalacrocorax carbo, Ph.auritus, Ph.olivaceust Ph.aristotelis, Ph.urile, Ph.pelagicus, Ph.penicillatus, and Fregata magnificens. It was found that the signal patterns are combinations of a limited number of discrete postures, movements, and sounds, and that they are mainly derivatives from four main sources, locomotion, fighting, nest-building, and begging. The take-off was found to consist of three phases, look, crouch, and leap. From the look and crouch phases the Suloidea have evolved their pre-take off displays, while from the recovery after landing they have evolved their post-landing displays. The pre-take off and post-landing displays are combined into a hop display in this super-family. The sky-pointing, a male-advertising display of Sula, is a derivative of the pre-take off display of Morus and is the origin of the wing-waving as a male-advertising display in Anhinga and Phalacrocorax. The throw-back which is the second part of the male-advertising display of Phalacrocorax arlstotelis is a derivative of the wing-waving display of the other cormorants. Threat displays have evolved into recognition displays in the bill-raising of the Pelecanidae, the head-throwing of Sula sula, the gaping of the Phalacrocoracidae, and into the first part of a male-advertising display, the darting, of Phalacrocorax aristotelis. Nest-indicating displays have evolved from the reaching for nest-material into the reach-bowing of Pelecanus erythrorhynchos, and from nest-worrying movements into the wave-bowing of P.erythrorhynchos, the wing-bowing of Moras, the front-bowing of Sula sula, the quiver-bowing of S.leucogaster and S.dactylatra, the snap-bowing of Anhinga anhinga, the front-bowing of Ph.aristotelis and the gape-bowing of Ph.melanoleucus. The food-begging displays of the chicks have evolved into the pre-landing displays of the Pelecaniformes which in some species also serve as recognition and male-advertising displays on the nest site and in the Sulidae, Anhingidae, Phalacrocoracidae, and Fregatidae accompany the transfer of nest-material between members of a pair at the nest site. The food-begging derived displays also include the aerial displays of Pelecanus erythrorhynchos, the head-wagging of the Sulidae, the kink-throating of the Anhingidae and Phalacrocoracidae, the rattling of the Fregatidae, and the aerial displays of the Phaethontidae. From a comparison of the taxonomic distribution of the form, function and derivation of the social communication patterns in the Pelecaniformes, it was concluded that they reflect the phylogenetic implications of the current systematic classifications of the order. / Science, Faculty of / Zoology, Department of / Graduate

The primary purpose of this investigation has been to attempt to assess the relative value of beef, pork, and whale liver after each has been processed into a meal by a similar method. The secondary purpose has been to establish the relative value of whale liver when processed into a meal by several different methods. All liver preparations have been found to be relatively low in thiamine when this vitamin is assessed by bioassay using the Wistar strain rat as an experimental animal. In almost all cases, further supplementation with cod liver oil has produced a beneficial effect with respect to the growth rate and feed consumption of rats. Many of the difficulties associated with bioassay have come to light in the course of this investigation. These difficulties have been examined in detail and some suggestions have been made as to how the detrimental effect of these difficulties may be minimized. An attempt has been made in this thesis to analyze all the pertinant data statistically. It was pointed out that when group differences in feed consumption and weight gain are large there is not too much difficulty in the interpretation of the experiment. However, when group differences are small and the group consuming the most feed makes the largest weight gain, caoution must be used if one states the differences between groups are due to the ration only. Under this set of circumstances, if the data are subjected to an analysis of covariance no difference may be noted between groups even though when either feed consumption or weight gain are analyzed separately the difference between groups are significant. In this case one must rely heavily on common sense before asserting any conclusions. / Land and Food Systems, Faculty of / Graduate

The role of brain dopamine (DA) systems in the control of anticipatory and consummatory aspects of the sexual behavior of male rats was examined in the present experiments. Experiment I explored the statistical relationship among anticipatory and consummatory measures of male sexual behavior using multiple correlations and factor analysis. Level changing, a measure of anticipatory behavioral excitement, was not related statistically to any of the consummatory measures of copulation, whereas several consummatory measures were correlated. The factor analysis revealed the existence of five factors: copulatory rate, initiation, hit rate, mount count, and anticipation; given tentative names based on the measures that loaded most heavily onto each factor. These results established that anticipatory and consummatory measures of male sexual behavior are unrelated statistically. Experiment II examined the dose-response effects of several DA receptor antagonists on anticipatory and consummatory measures of male sexual behavior. Systemic administration of the typical neuroleptics haloperidol and pimozide, and the Dl-selective antagonist SCH 23390, significantly reduced the number of level changes, increased the intromission latencies, and decreased the number of intromissions and the total number of ejaculations. The atypical neuroleptic clozapine and the D2-selective antagonist sulpiride reduced the number of level changes and significantly increased the intromission latencies, but did not affect the number of intromissions or ejaculations. In almost every case, the doses required to reduce level changing were lower than those required to increase the intromission latencies, indicating that the measure of anticipatory sexual behavior was more sensitive to disruption by DA antagonists than were consummatory measures of sexual behavior. The antiemetic agent metoclopramide decreased the number of intromissions but did not affect other anticipatory or consummatory measures of sexual behavior significantly. High doses of haloperidol, pimozide, or clozapine delayed or abolished level changing and the initiation of copulation. These results indicated that anticipatory and consummatory measures of male sexual behavior are affected differentially by DA antagonists. Experiment III provided the first evidence that haloperidol affects anticipatory and consummatory measures of male sexual behavior selectively in different brain DA terminals. Bilateral infusions of haloperidol to the nucleus accumbens reduced level changing without affecting the initiation of copulation or other consummatory measures. Bilateral infusions of haloperidol to the striatum increased the total number of ejaculations but did not affect other consummatory or anticipatory measures. Unilateral infusions of haloperidol to the medial preoptic area (MPOA) produced nearly all of the effects of systemic administration, including reduced number of level changes, increased intromission latencies, and decreased number of intromissions and ejaculations. These results indicated that DA in the nucleus accumbens and striatum are involved in the display of anticipatory sexual behavior and copulatory rate, respectively, whereas DA in the MPOA is involved in anticipatory sexual behavior, the initiation of copulation, and copulatory rate. In Experiment IV, in vivo voltammetry revealed a differential pattern of DA efflux in the nucleus accumbens and striatum, and catecholamine efflux in the MPOA, during anticipatory and consummatory phases of sexual behavior in male rats. Increased DA efflux in the nucleus accumbens and increased catecholamine efflux in the MPOA were associated with the presentation of a receptive female behind a screen and with the initiation of copulation. Efflux in both regions decreased following ejaculation but increased prior to each reinitiation of copulation. DA efflux in the striatum increased nonspecifically during copulation. Use of in vivo microdialysis confirmed the general pattern of DA efflux in the nucleus accumbens and striatum observed with voltammetry. These results were interpreted as supporting a role of DA terminals in the nucleus accumbens and MPOA, but not the striatum, in the display of anticipatory sexual behavior and in the initiation of copulation. In particular, the increased release of DA in the MPOA was viewed as sensitizing hypothalamic mechanisms involved in the control of penile erection whereas the increased release of DA in the nucleus accumbens was viewed as sensitizing motor programs necessary for the execution of anticipatory sexual responses and the initiation of mounting. / Arts, Faculty of / Psychology, Department of / Graduate

This thesis investigates the role of male vocalizations in two aspects of Pacific Tree Frog breeding behavior: Spacing out of males on breeding areas and selection of mates by females. Spacing out: An analysis of nearest neighbor distances of calling frogs showed that males space out more than if distributed randomly on the available calling sites. An addition experiment provided corroborative evidence that males tend not to call too close together; of equal numbers of frogs added to an empty (control) enclosure and an enclosure occupied by calling frogs, more subsequently called in the control. The species' "mating" call (D call), as well as attracting females, functions in spacing out; in an addition experiment, fewer frogs called in an enclosure occupied only by loudspeakers playing back D calls than in the control. Another vocalization (S call) seems to function only in spacing out. If two calling frogs come close together (less than ca. 50 cm), both usually begin making the S call. One frog may then move away; if not, physical combat may follow. I hypothesized that the S call is a stronger warning to nearby males than the D call. A playback experiment partially supported this hypothesis. I consider possible functions of spacing out, and suggest that males which maintain spacing may attract more females than they would otherwise, perhaps because females can more easily locate them. Mate selection: I attempted to test two hypotheses: First, females select large males on the basis of their low-pitched vocalizations (there is an inverse correlation between call pitch and body length). A comparison of body lengths and call pitches of males found in amplexus with a sample of males from the calling population did not support this hypothesis. Second, females choose males which initiate bouts of calling (chorus leaders). Both systematic field observations and a laboratory experiment support this hypothesis. Chorus leaders also end choruses, call at a faster rate during choruses, call more during periods not defined as choruses, and call louder than other frogs. In nature, females may also use these differences as cues in mate selection. The advantages of being a chorus leader should select for frogs calling all of the time, yet frogs show frequent lulls in calling. A playback experiment showed that frogs are less responsive (measured by latency to call) to stimulus calls shortly after having stopped calling than later in the lull period. I hypothesized that fatigue is responsible for this short-term waning of calling tendency. A respirometry experiment suggested (but quite inconclusively) that the fatigue hypothesis is feasible. / Science, Faculty of / Zoology, Department of / Graduate

The mechanisms of osmotic and ionic regulation in marine mammals are of interest because of the apparent lack of "fresh" water in their environment. Previous investigation on the harbor seal, (Phoca vitulina, L.), generally indicated that the seal can obtain all the water it requires from its food. However, some dispute still exists as to whether the seal may ingest sea water along with its food and conserve water by concentrating ions and excreting them with a net water gain. The effects of a 16-hour period with no fluids and also of intubation with varying amounts of distilled water and varying amounts and concentrations of sea water were determined. The concentrations of sodium, chloride and potassium ions as well as the osmotic pressures of plasma and urine were measured for the periods before and after intubation. The results of this study are discussed with respect to published data and proposed mechanisms of osmotic and ionic regulation by the kidney. The findings indicate, as suggested by others, that the seal does not gain any substantial amount of water from sea water ingestion. / Science, Faculty of / Zoology, Department of / Graduate

Gross and histological analyses of reproductive tracts from multiparous, nulliparous, and non-pregnant females of Pribilof Islands (eastern Pacific) origin have been used to determine the histology and physiology of the estrus cycle, the age of sexual maturity, and certain causes of prenatal mortality. The ovaries alternate in function, one ovary ovulating in one breeding season, the opposite ovary ovulating in the next. An undetermined factor suppresses follicular development in the ovary containing a corpus luteum of pregnancy; suppression maintains for 6 months after parturition. Graafian follicular development is greatest in July, with an average 15 follicles in the ovary destined to ovulate. About 4 of these will enlarge abruptly prior to ovulation; one will reach ovulation size (10 mm or greater in diameter) and rupture; the rest will become atretic. Mating occurs 3-5 days after parturition in mid-July. If fertilization is accomplished, the resulting blastocyst remains free in the uterus until early or mid-November, when it implants in the mucosa. The newly formed corpus luteum is actively secretory for a month after ovulation. During this time, follicular development is suppressed in both1 ovaries, and the uterine mucosa is progesteronic. From the end of August, the corpus luteum is regressive; the luteal cells are vacuolated, and secretion is minimal. This is reflected in a recrudescence of follicular activity in the ovary containing the corpus luteum, and regression of the associated uterine mucosa. Immediately prior to implantation the corpus luteum resumes secretion, and the mucosa is prepared for implantation. Placentation is established during December. Luteal degeneration begins in January and is progressive until parturition, when the corpus luteum appears to be non-secretory. Luteal degeneration has no affect on the pregnant uterine horn; it is assumed that the placenta secretes sufficient hormone to replace the luteal hormones. Prenatal mortalities take 3 forms: "missed” pregnancies, abortions, and resorptions. On the basis of histological examinations, "missed" pregnancies are ultimately due to failure of implantation. Three conditions are responsible: failure of fertilization, failure of implantation, or malfunction of the reproductive tract which precludes pregnancy. Abortion results in the expulsion of a conceptus from the uterus before term; resorption is a gradual process of dissolution of the conceptus within the uterus. On the basis of histological evidence, three causative agents of abortion and resorption are evident: degeneration of the corpus luteum after implantation, malfunction of the uterine mucosa, and intra-uterine mortality of the conceptus. Annovulatory cycles, dominated by Follicle Stimulating Hormone, occur among females 1 to 3 years of age. A cycle increasingly dominated by Luteinizing Hormone and culminating in ovulation occurs among the majority of 4-year-old females. The follicular cycle resulting in the first ovulation is later than subsequent cycles; the peak of first ovulations occurs around August 25th. On the basis of gross examinations, 60% of females ovulate for the first time at 4 years of age. Since the pregnancy rates of 5-year-old females are consistently about 50%, probably a number of 4-year-olds do not mate, either because ovulation occurs after the breeding season, or because breeding males are not available. Gross and histological analyses of reproductive tracts from nulliparous females of Robben and Commander Islands (western Pacific) origin have been used to compare the reproductive potential of two breeding populations of fur seals,; Pregnancy rates among females 4 years of age of Robben and Commander Islands origin are approximately 50%; those of 4-year old-females of Pribilof Islands origin are approximately 5%. The disparity in the age of reproductive maturity between females of the two populations is based on a physiological delay of one year in the maturation of the endocrine system controlling reproduction among females of Pribilof Islands origin. / Science, Faculty of / Zoology, Department of / Graduate

The structural and functional organization of the pinniped eye, as represented by the harbour seal, Phoca vitulina, is much more complex than previously realized. The retina of the harbour seal is similar to that of the harp seal, in that it shows little zonation of the inner nuclear layer, possesses large horizontal cells, and has similar nuclear densities within the different retinal layers throughout the retina. The outer nuclear layer is the thickest of all the retinal layers. Photoreceptor cells of types B and C were observed with a ratio of roughly 1:23 respectively. This ratio and photoreceptor density along with a well-developed and extensive tapetum, indicates a highly light-sensitive retina. The existence of retinal folding in marine mammals is also questioned and discussed. Refractive observations obtained through retinoscopy show that the harbour seal eye is very myopic and astigmatic in air, and hypermetropic with no discernable astigmatism in water. The axis of least corneal curvature is horizontal; current theories predict that the stenopeic pupil would thus correct for astigmatism in air. The functional significance of the astigmatism, which is in the order of 7 to 13 diopters, has not been adequately determined to date, however. These observations are in agreement with those recently reported for the harp seal. Behavioural studies have also confirmed the high sensitivity of the harbour seal eye to light, as suggested by the histological observations. Two captive harbour seals were trained to select a two-bar pattern over a one-bar pattern in both air and water, discriminating for the presence of a gap. Their abilities to carry out this task were measured as the gap in the two-bar pattern was gradually reduced in size. The light intensity of the white parts of the stimulus cards was 284-369 candela/m² . Under these conditions, the harbor seal can detect a gap as small as 1 mm at a distance of 1.7 m in both air and water. These studies fail to provide values of the visual acuity of the harbour seal in the strict sense, however, owing to the physics of the pattern utilized. Rather, they indicate a measure of the absolute sensitivity of the eye to light. / 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