Thesis (M.S.)--University of Wisconsin--Madison, 1981. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 66-70).

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves 87-111). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves 87-111). Also available on the Internet.

Thesis (doctoral)--Ludwig Maximilians-Universität zu München, 1979.

Thesis (M.S.)--University of Wyoming, 2009. / Title from PDF title page (viewed on July 22, 2010). Includes bibliographical references (p. 74-91).

No description available.

Doctorat en sciences médicales / info:eu-repo/semantics/nonPublished

In cooperatively breeding societies, where individuals (termed ‘helpers’) provide care to young which are not their own, group members can vary substantially in their contributions to cooperative activities. Individuals are expected to exhibit higher levels of cooperative investment if the benefit of performing that behaviour greatly outweighs the cost of performing that behaviour. This may be achieved by directing investment towards kin (thereby maximising indirect fitness benefits) and/or attaining large direct fitness benefits. In this thesis, I explore whether direct fitness benefits shape patterns of helping behaviour in the cooperatively breeding white-browed sparrow weaver (Plocepasser mahali). White-browed sparrow weavers live in year round territorial groups with high reproductive skew, comprising a dominant pair and subordinates of both sexes. Although all group members contribute to a wide range of highly conspicuous cooperative activities, there is large inter-individual variation in investment. In chapter 2, I use simulated territorial intrusions to show that sexually-selected direct benefits shape the expression of sentinel behaviour. In chapter 4, I provide evidence that the direct benefits associated with either the pay-to-stay or social prestige hypotheses are unlikely to modulate patterns of provisioning in male white-browed sparrow weavers. Evidence of marked individual differences in contributions to offspring care in cooperative societies is also generating increased interest in the proximate causes of such variation. In chapter 5, I use within-individual measurements to demonstrate that variation in provisioning effort is not directly regulated by variation in circulating levels of prolactin (a pituitary hormone). The evidence does suggest, however, that provisioning behaviour may be induced by exceeding a threshold hormone level. Individual contributions to parental behaviours (as opposed to alloparental) may be shaped by constraints associated with life-history traits. In chapter 3, I show that parents in white-browed sparrow weaver societies perform different provisioning rates yet employ similar food allocation tactics, and that these patterns are expected in tropical living bird species. Combined, these findings provide insights into the selection pressures that may shape individual contributions to cooperative activities.

The possible role of prolactin in the freshwater osmoregulation of laboratory reared juvenile chum (Oncorhynchus keta) and sockeye (0. nerka) salmon was investigated. Pituitary cytology indicated that prolactin cells of both species develop gradually during freshwater residence and downstream migration. During this time the prolactin cells increase slightly in size; the number of prolactin cell follicles also increases. Simultaneously, the intensity of cytoplasmic staining with erythrosin increases. Alternate day injections of 5 or 15 μg/g body wt prolactin (ovine) did not affect survival of chum fry in deionized water. Thirty micrograms per gram slightly increased survival while 60 μg/g decreased survival in deionized water. Prolactin injections prolonged, to a small extent, the survival of sockeye smolts in deionized water. Sockeye fry suffered only slight mortality after transfer from fresh water to deionized water. A prolactin dose of 5 μg/g did not alter this survival; however, doses of 15 μg/g or higher resulted in 40 to 70% mortality after 10 days in deionized water. Alternate day injections of 10 μg/g prolactin had no effect on plasma sodium concentrations of chum fry, sockeye fry, or sockeye smolts after transfer from sea water to either fresh water or deionized water. It is concluded, from histological and physiological evidence, that prolactin does not play an obvious role in the freshwater osmoregulation of juvenile chum and sockeye salmon. The possible role of prolactin in the spawning migration of adults is discussed. / Science, Faculty of / Zoology, Department of / Graduate

Thesis: M.S., Massachusetts Institute of Technology, Department of Nutrition and Food Science, 1975 / Vita. / Includes bibliographical references. / M.S. / M.S. Massachusetts Institute of Technology, Department of Nutrition and Food Science