by Chung Sze-bun. / Thesis (M.Ph.)--Chinese University of Hong Kong, 1987. / Bibliography: leaves 211-242.

Thesis (Ph. D.)--University of Queensland, 2001. / Includes bibliographical references.

Thesis (Ph.D.)--Murdoch University, 2007. / Thesis submitted to the Division of Science and Engineering. Includes bibliographical references (p. 231-254)

Thesis (PhD--Marine Science)--University of Auckland, 2009. / " A thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Marine Science." Includes bibliographical references (leaves 161-173).

Thesis (Ph.D.)--Boston University / The potential usefulness of the membranous cheek pouch of the hamster as an investigative tool in experimental embryology has been explored* After preliminary studies involving the transplantation of ova, morulas, and various embryonal tissues, the anterior limb buds of embryos in the eighth to eleventh day of development were chosen for intensive study.

Thesis (Ph.D.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / Recent experimental work has indicated that the thymus in late fetal and early neonatal life plays a major role in the development of mechanisms of immunity. To date, however, no study of the ultrastructure of the prenatal thymus has been reported in the literature, and histochemical and cytochemical studies of this early period are fragmentary. Therefore, in an effort to extend present knowledge of thymic differentiation and function during its early development, the thymus in the golden hamster (Mesocricetus auratus) was studied by selected histochemical methods and by electron microscopy from 9 1/2 days post coitum through 24 hours post partum. Histochemical techniques for the light microscopy included the periodic acid-Schiff technique with salivary digestion control for glycogen, the methyl green-pyronin technique as an indicator for protein synthesis, the sudan black B technique for determination of total unbound lipid, the Nile blue and oil r ed 0 techniques for deter mination of neutral lipid, and the Elftman t echnique for determination of phospholipid. Material was prepared for electron microscopy by fixation for one hour in l% osmium tetroxide (Millonig, 1963), dehydration in graded acetones followed by propylene oxide, and embedding in Maraglas epoxy resin (Freeman and Spurlock, 1962). Grids prepared from these specimens were stained either with 1% phosphotungstic acid in 95% alcohol, or with lead citrate (Reynolds, 1963). They were scanned with either an R.C.A. EMU 2-B electron microscope or a Siemens Elmiskop I. [TRUNCATED] / 2031-01-01

Thesis (Ph.D.)--Boston University / The golden hamster, Mesocricetus auratus, is unique in that it frequently accepts not only homografts but even heterografts of normal and malignant tissues. One of the many theories a tterpting an explanation of this phenomenon, namely that lymphatic tissues that drain the sites of imphntation do not respond in a t;rpicol fashion, motivated this study. Thus, the weight changes ,and the c;'tolof'ical variations of the superficial cervical nodes in response to homologous and heterologous normal and malignant tissue transplants in the cheek pouch of the hamster were studied. The major objectives were: (1) to determine if there be any "defect" in the hamster's lymphatic tissue response to the various transplants; (2) to investigate the effects of the grafts on the large lymphoid cells of the cortex and on the plasma cells of the medulla; and ( 3) to investigate the feasibility of employing the histological picture of a regional node draining the site of a tumor heterotransplant as a base line for anti-tumor studies during the cortisone conditioning. [TRUNCATED]

This study focused on obtaining sound quantitative data on the reproductive biology, length and age compositions and growth of the snapper Pagrus auratus in the waters off Carnarvon at ca 25oS and Perth at ca 32oS on the west coast of Australia and at ca 34oS on the south coast of Western Australia. Sampling thus encompassed both sub-tropical and temperate waters and the geographical range within which this species is abundant in Western Australia. The resultant data were used to explore the ways in which the biological characteristics of P. auratus differ with latitude and thus water temperature. An intensive sampling regime for eggs and spawning individuals of P. auratus was conducted in Cockburn Sound, a large marine embayment in the Perth region at ca 32oS. The resultant data were used to elucidate where and when spawning occurs in this large marine embayment and to determine more precisely the factors that influence the timing of spawning. The implications of the results presented in this thesis for the management of P. auratus, a species that has been subjected to very heavy fishing pressure in recent years, are discussed. The time and duration of spawning of P. auratus in the subtropical waters of Carnarvon differed markedly from those recorded for this sparid in the temperate and cooler waters of the Perth and the south coast regions. Spawning at Carnarvon occurred predominantly in the five months between late autumn (May) and mid spring (September), whereas it took place mainly in the three months between mid spring (October) and early summer (December) in the Perth region. Spawning of P. auratus on the south coast occurred predominantly in October and November in 2003 and 2004 and scarcely at all in 2005. Gonadal recrudescence was thus initiated when water temperatures were close to their maximum but declining in Carnarvon, and close to their minima and rising in the Perth and south coast regions, respectively. The prevalence of fully mature and spawning females in all three regions was greatest in those months when water temperatures lay between 19 and 21oC. Collation of the data in this thesis and those provided in the literature for other populations showed that the spawning period was related to latitude, occurring far earlier in sub-tropical than temperate waters. The females and males attained maturity at a far smaller total length (L50) in the Carnarvon region, i.e. 378 and 353 mm, respectively, than in the Perth region, 585 and 566 mm, respectively, and also the south coast region, i.e. 600 and 586 mm. The trends exhibited by the age at maturity parallel those for length, with the A50s for the two sexes increasing from ca 4 years in Carnarvon to ca 5.6 years in the Perth region and nearly 7 years in the south coast region. The L50 and A50 at maturity thus both increased with increasing latitude. Marginal increment analysis demonstrated that, irrespective of the number of opaque zones in the otoliths of P. auratus, a single such opaque zone is laid down each year in these otoliths. Furthermore, the trends exhibited by the monthly marginal increments showed that the opaque zone is laid down predominantly in winter in the subtropical waters of Carnarvon, as opposed to mainly in spring in the temperate waters of the Perth and south coast regions. Thus, the timing of formation of the opaque zone in the otoliths of P. auratus along the Western Australian coast is not related to the trends exhibited by water temperature, but, in both the Carnvarvon and Perth regions, was coincident with the timing of spawning. The maximum total lengths recorded for females and males in the Carnarvon region, i.e. 864 and 840 mm, respectively, were considerably less than the corresponding values of 1051 and 1056 mm in the Perth region, and 1083 and 1099 mm in the south coast region. Growth in the Perth and south coast regions was greater than in Carnarvon, as is reflected in, for example, the respective lengths of 820, 720 and 610 mm for females at 10 years of age, as determined from the von Bertalanffy growth equations. The length and age compositions in the Carnarvon and south coast regions were essentially unimodal, whereas those in the Perth region were bimodal. However, the “mode” in the length-frequency distribution for the south coast region was located well to the right of that in the Carnarvon region, reflecting relatively lower contributions by individuals of the age cohorts of 3 to 6 years. The marked bimodality in the length-frequency distribution for P. auratus in the Perth region was due to the presence of a group of mainly smaller individuals caught outside Cockburn Sound and another of mainly larger individuals that were caught in Cockburn Sound and which formed part of a spawning aggregation in that embayment. The proportion of fish > 10 years old in the Carnarvon region declined markedly between 2003 and the following two years, presumably reflecting the effect of heavy fishing pressure. This contributed to the decision by fisheries managers to reduced the TAC in those waters after 2003. Age-frequency data demonstrated that annual recruitment success in Cockburn Sound varied greatly, with the 1991, 1992 and 1996 year classes being particularly strong, and recognizing that the relative numbers of the first two year classes did decline progressively between 2002 and 2004. Annual recruitment was particularly variable in the south coast region, with the catches of the 1996 year class dominating the samples. The relative number of early stage P. auratus eggs in ichthyoplankton samples collected from Cockburn sound on each of four new moons during the spawning seasons of four consecutive years peaked in November in three of those years, i.e. 2001, 2003 and 2004, and in November/December in the remaining year, i.e. 2002. This showed that spawning in this embayment peaked during these months, at which times the mean sea surface temperatures ranged only from 19 to 20oC. The prevalence of spawning fraction females in sequential samples demonstrated that spawning peaks at the new and, to a lesser extent, full moons. This helps account for the strong positive correlation between spawning fraction and tidal regime, with spawning being greatest when the tidal range is greatest. Spawning times, back-calculated from the ages of the eggs collected during ichthyoplankton surveys in Cockburn Sound on each of 16 new moons within the spawning periods of four successive years, demonstrated that, in this embayment, P. auratus spawns at night and within the first three hours of the onset of the ebb tide. The distribution of egg concentrations on the 16 new moons showed that, each year, spawning occurred firstly in the north-eastern area of Cockburn Sound and then in the middle and finally north-western areas of this embayment. In the Perth region, the marine embayments of Cockburn and Warnbro Sound act as nursery areas for P. auratus during the first two years of life. The majority of 2 to 5 year old fish and a large proportion of the 6 year old fish occupy the marine waters outside the embayments. The remaining 6 year old and almost all of the older fish begin to move in September into particularly Cockburn Sound, where they form relatively large spawning aggregations between October and December, before undergoing a massive emigration from this embayment in December/January. The limited returns from fish that were tagged in Cockburn Sound and were subsequently caught outside this embayment indicate that, following spawning, P. auratus does not tend to move in a particular direction. Pagrus auratus stocks are heavily exploited in offshore, oceanic waters and in embayments, such as Cockburn Sound, where they are particularly susceptible to capture because of the tendency of this species to form spawning aggregations in these same easily accessible locations each year. The data obtained during this thesis show that the L50 at maturity of females and males in temperate waters, i.e. nearly 600 mm, is far greater than the current minimum legal length (MLL) of 410 mm TL. There is thus a need to increase the MLL and/or reduce fishing pressure on immature individuals in open waters. However, the effectiveness of an increase in the MLL may be limited because there is evidence that P. auratus suffers from fishing-induced barotrauma. Closures of specific areas during the spawning season of P. auratus, such as those that have been applied in Cockburn Sound and Shark Bay, are potentially a very effective method for reducing the effects of heavy fishing on spawning individuals.

The causes and consequences of variation in aposematic signals during immature stages are not clearly understood. This thesis explores the effects of early environment on the expression of aposematic signals in the green and black poison frog (Dendrobates auratus), and the consequences of variation in such components in the wild. It also explores how aposematic expression relates to levels of chemical defences in immature froglets. Embryos and larvae of poison frogs in the genus Dendrobates are known to be darkly pigmented. This thesis reports for the first time polymorphism in egg pigmentation in D. auratus and ontogenetic colour change through development reverting to a normally pigmented phenotype; however whether this pigmentation results from constraints or has adaptive consequences remains unclear. Evidence on how immature individuals allocate resources to growth and warning signalling is scarce. Experimental results in this thesis show that food supply during early environment affected body size and signal luminance in post-metamorphic froglets. Therefore the relative importance of these traits in relation to predation risk was further tested, using artificial prey in a field experiment. The results indicated that rates of attack by birds correlated negatively with body size, and on the contrary survival of artificial prey was independent of signal luminance. I therefore tested the hypothesis that in the wild larger, relatively well-nourished juvenile frogs are chemically better defended. I found that in fact larger juveniles are at a selective advantage conferred by their greater foraging efficiency and their superior levels of chemical defences. Overall, these results shows plasticity in aposematic traits in relation to early environmental nutrition in D. auratus; and suggests that acquiring large body size and similar integument colour as to adults are key determinants for survival during the early stages of their terrestrial life.

Thesis (PhD)--University of South Australia, 2003.