No description available.

No description available.

No description available.

Thesis (M.Sc.)--University of the Witwatersrand, Faculty of Science, 1950.

Oviparous reproduction in Carditamera floridana was studied in St. Andrew's Sound, near Mexico Beach, Florida, between May 1992 and February 1994. The oviparous mode of development of Carditamera floridana is unique in the number of juveniles produced, the extent of parental care involved, the subtropical range of the species, and the lack of a distinct vitellogenic mechanism. / Typescript. / "1995." / "Submitted to the Department of Biological Science in partial fulfillment of the requirements for the degree of Master of Science." / Advisor: William H. Heard, Professor Directing Thesis. / Includes bibliographical references.

No description available.

Populations of Chlamydomonas were maintained in a benign laboratory environment as obligatory sexual or asexual populations for five years. Sexual reproduction is expected to facilitate the elimination of mildly deleterious mutations and thereby increase the mean fitness of a sexual population relative to an asexual population (Kondrashov 1988). Fitness in competition and in pure culture was measured. In neither of the fitness assays, both in solid and liquid cultures of Chlamydomonas, was a fitness advantage of sexual reproduction seen, even though the results varied depending on the definition of fitness. I hypothesized that the effect of mutation clearance could be masked by different forces acting on the selection strain (such as an antagonistic relationship between sexual and vegetative fitness).

The distributional range of the Tete veld rat, Aethomys ineptus, extends from the Limpopo Province in the north through to the south of KwaZulu Natal. The Tete veld rat is a seasonal breeder, with the breeding period confmed to the wet summer months of the year in the Gauteng Province of South Africa. The seasonality of reproduction in the Tete veld rat is confirmed by reproductive tract morphometrics, ovarian histology, plasma progesterone, and oestradiol-17β in females, and testicular histology and plasma testosterone concentrations in males. The presence of some spermatogenic activity and spermatozoa in the epididymides, as well as some follicular activity and raised circulating progesterone, and oestradiol-17β concentrations in some females during winter intimates that the Tete veld rat is possibly an opportunistic breeder. Reproduction during winter is presumably restricted by food availability and adverse winter conditions. The Namaqua rock mouse, Aethomys Namaquensis, on the other hand is widely distributed in the southern African subregion. Reproductive tract morphometrics, ovarian histology, plasma progesterone and oestradiol-17β in females, and testicular histology, seminiferous tubule diameters and plasma testosterone concentrations in males confirm that the Namaqua rock mouse is a strictly seasonal breeder. The breeding period starts in October and extends to the end of February. The absence of Graafian follicles, corpora lutea, corpora albicans, corpus hemorrhagicum, lower plasma progesterone and oestradiol concentrations in females, and small seminiferous tubule diameters, and lower testosterone concentrations during winter months suggest that reproduction is completely inhibited during this period of the year. Photoperiodic responsiveness was determined in both the Tete veld rat and the Namaqua rock mouse by exposing the animals to long day (LD) and short day (SD) lengths. Testicular mass expressed against body mass, testicular volume, and seminiferous tubule diameters were significantly larger and plasma testosterone concentrations were significantly higher in males subjected to a long day photoperiod than in males exposed to a short day. These fmdings suggest that both species are photoperiodically responsive and that photoperiod could potentially play a role in reproduction in both the Tete veld rat and the Namaqua rock mouse. In conclusion, the results in this study suggest that the Tete veld rat is a seasonal breeder with the breeding period confined to the rainy summer months in South Africa. The breeding season starts in October and extends to April. Reproduction in the Tete veld rat appears to involve photoperiod. The Namaqua rock mouse is a strictly seasonal breeder with a breeding period occurring between October and the end of February. Breeding during the winter months is completely inhibited. The Namaqua rock mouse may also utilize photoperiod to initiate reproductive events. / Dissertation (MSc)--University of Pretoria, 2006. / Zoology and Entomology / Unrestricted

The reproductive biology of Tadarida aegyptiaca was studied using specimens collected in the Cape Province of South Africa. The morphology of the reproductive tract of the species was generally similar to that of other molossids, however, the absence of Cowpers glands was unusual. Spermatogenesis began in February and spermatozoa were released to the cauda epididymis during August and September. Follicular development started in March and culminated with the appearance of Graafian follicles in July. Ovulation probably occurred in August and specimens were pregnant by September. Gestation length was estimated to be four to five months and a single young was born in December. The data suggest that T. aegyptiaca is monotocous and monoestrous.

Patterns and causes of variation in the reproductive success of Song Sparrows (Melospiza melodia) are investigated in this thesis. The two general patterns looked for were: inter-annual variation in reproductive success, and repeatability of reproductive success of individual parents. The specific problems addressed were: (1) whether intra-seasonal variation in reproductive success was the result of differences in the quality of parents or their territories; (2) whether nutritional condition of nestlings affected their subsequent survival; (3) whether variation in morphology of adult sparrows was influenced by the conditions under which birds grew up; and (4) given the patterns discovered in the first three sections, how trade-offs between present and future reproduction constrain the effort expended by adult sparrows in reproduction. Data used in this thesis came from a long-term (1975-present) descriptive study of the population of Song Sparrows living on Mandarte Island, B.C., Canada. Data on survival, reproductive success, and nestling and adult morphology were all available. The approach taken in the thesis was to search for systematic variation in the data, and from these patterns to make inferences about cause and effect. The following conclusions are made: (1) the intra-seasonal decline in clutch size, observed in populations of many species of birds, was the result of poor birds or birds on poor quality territories both nesting later and laying smaller clutches; (2) nestlings in better nutritional condition had a higher probability of survival while under the care of their parents, than nestlings in poor nutritional condition; (3) the probability of survival of offspring after they left their parents' care was lower for young born later in the year, but this pattern is not caused by variation among parents or their territories (contrary to the cause of seasonal decline in clutch size); (4) morphology of birds as adults was affected by the environment that birds grew up in, with nutritional condition and population density while a nestling both affecting adult morphology; (5) the effort that parents expend on reproduction is constrained by ability to vary reproductive effort with date of nesting and parental age. / Science, Faculty of / Zoology, Department of / Graduate