This dissertation deals with a study of certain aspects of the physiology of digestion of Petromyzon marinus with emphasis on the localization of certain enzymes. It was found that the physiology of digestion adjusted to the drastic change in feeding habits at metamorphosis. / Thesis / Doctor of Philosophy (PhD)

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Currently published data on the role of the lymphatic system in amphibians are inadequate and contradictory. Estimates of the rate of formation of lymph and the role of the lymph hearts in returning this fluid to the circulation are not based on actual volume determinations but rather estimates derived from changes in hematocrit using published values of plasma and blood volume. The lymph hearts are known to be vital to the maintenance of normal fluid compartment physiology and to increase their rate of activity during episodes of hypovolemic stress. Yet, significant redistribution of body fluids following hemorrage appears to occur in animals without lymph hearts. In this study, plasma and blood volumes were determined by the dye dilution technique using injected Evan's blue dye to label the plasma. Eight intact and 6 animals with their lymph hearts destroyed were hemorrhaged to 78% and 75% of their initial blood volumes, respectively. Changes in blood volume were measured following the hemorrhage by analysis of Evan's blue washout and hemodilution.

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To date, the majority of studies into sex determination and sexual development have focused on the mammalian system due to the mouse model being an excellent tool for developmental biology as well as obvious implications to human health and development. However, the focus on the mammalian system has caused a large fraction of other vertebrate groups to be overlooked. The last decade has seen an array of studies into various non-mammalian organisms like fishes, birds, reptiles, and amphibians. These studies have unveiled a remarkably conserved molecular background utilized for sexual differentiation amongst all vertebrates, ranging from the alligator which employs temperature dependent sex determination to the mouse, which employs genotypic sex determination In this project, I implemented molecular methods traditionally used to study model organisms, to investigate an amphibian species, the cane toad (Bufo marinus). The cane toad was chosen due to its invasive status in Australia, as well as being a representative of one of the most successful and specious families of vertebrates, Bufonidae. Since, its introduction, this species has rapidly spread across the continent, adversely effecting native species throughout its introduced range. Recent studies have identified the disruption of the sex-determination pathway as a realistic goal in an otherwise, seemingly futile, effort to curtail their expansion. We decided to approach the study of cane toad sex determination and development on three levels, in order to have a broader understanding of the similarities between toads and other groups, and additionally, to better assess the feasibility of utilizing molecular means to control cane toads in non-native habitats. Firstly, I used a candidate gene approach to clone and characterize five genes which were previously known to be involved in both mammalian as well as amphibian sex determination: Sox9, Dmrt1, p450arom, Sf1, and Dax1. I chose Sox9 and Dmrt1 due to their known involvement in the male-specific pathway of mammals. Dmrt1 was also known to be male specific in other groups, including amphibians. Conversely, I also decided to investigate p450arom and Dax1, due to their affiliation with the female pathway, while Sf1 has a role in both sexes. All of these genes were expressed in the gonads of both sexes of cane toads. However, Sox9 exhibited strong transcriptional up-regulation in testes at the time of sexual differentiation, similar to mammals. Thus, using the candidate gene approach, I was successful in identifying a sex-specific marker which could be utilized in the manipulation of the sex determination pathway (e.g. female to male sex reversal). VIIThe second approach involved the study of sex determination on a cytogenetic level. Traditionally, Bufonids have been assumed to utilize a ZZ/ZW (male homogametic/female heterogametic) sex chromosome system, yet only one recent study has been successful in the identification of sex chromosomes in a toad species. Moreover, the authors identified the sex chromosomes in only one population (of 18 studied), highlighting the scarcity of discernible sex chromosomes in toads. When we began to investigate the karyotype of cane toads, we were able to identify a female-specific length polymorphism in the nucleolus organizer region (NOR) of chromosome 7, making this chromosome pair a strong candidates for the Z and W sex chromosomes. In order to verify our hypothesis, we also performed chromomycin A3 staining to reveal a differential signal between the chromosome pair, indicative of heterochromatin accumulation on the brighter NOR. This study lent strong support to the observed difference between the chromosomes, yet we required further investigation in order to identify the W and the Z chromosomes, specifically. By utilizing comparative genomic hybridization (CGH), I was able to identify a female specific region on the chromosome with the larger NOR, identifying it as the W chromosome. This study was successful in identifying the sex chromosomes in the cane toad. Moreover, it allows us to make a more accurate prediction of the possible sex determination method utilized: either a dosage dependent male determination system, or a female-specific gene in a female determination system. The third approach focused on the Bidder’s organ and its role in sexual development of cane toads. The Bidder’s organ is a gonadal structure comprised of ovary-like tissue, found in both males and females, with no known function. Since our study was focused on female to male sex-reversal of cane toads, we decided to investigate the potential of the Bidder’s organ to interrupt this process. By utilizing the candidate genes, which I had previously cloned, I was able to identify the Bidder’s organ as having an entirely distinct transcriptional pattern in comparison to the gonads of either sex. Additionally, the Bidder’s organ showed significantly higher levels of p450arom expression than the gonads, identifying it as a possible key player in the production of aromatase enzyme for oestrogen production. Moreover, gene expression patterns in the Bidder’s organ strongly correlated with the significant developmental time points in the sexual development of the toads, implying a possible function in the development process of toads. In conclusion, I have performed the first study of the molecular, cytogenetic and anatomical aspects of sexual development in a toad. I was able to verify that cane toads utilize a ZZ/ZW chromosome system and furthermore, likely utilize the mammalian male-linked gene, Sox9, in male development. I was also able to show that the Bidder’s organ is transcriptionally active at key time points, likely indicative of a functional role during development.

Thesis (Ph. D.) -- University of Tennessee, Knoxville, 2005. / Title from title page screen (viewed on Sept. 6, 2005). Thesis advisor: Arthur C. Echternacht. Thesis advisior: Christine R. B. Boake. Document formatted into pages (xvi, 151 p. : ill. (some col.)). Vita. Includes bibliographical references.

Infection levels of eastern oysters by the unicellular pathogen Perkinsus marinus have been associated with anthropogenic influences in laboratory studies. However, these relationships have been difficult to investigate in the field because anthropogenic inputs are often associated with natural influences such as freshwater inflow, which can also affect infection levels. We addressed P. marinus-land use associations using field-collected data from Murrells Inlet, South Carolina, USA, a developed, coastal estuary with relatively minor freshwater inputs. Ten oysters from each of 30 reefs were sampled quarterly in each of 2 years. Distances to nearest urbanized land class and to nearest stormwater outfall were measured via both tidal creeks and an elaboration of Euclidean distance. As the forms of any associations between oyster infection and distance to urbanization were unknown a priori, we used data from the first and second years of the study as exploratory and confirmatory datasets, respectively. With one exception, quarterly land use associations identified using the exploratory dataset were not confirmed using the confirmatory dataset. The exception was an association between the prevalence of moderate to high infection levels in winter and decreasing distance to nearest urban land use. Given that the study design appeared adequate to detect effects inferred from the exploratory dataset, these results suggest that effects of land use gradients were largely insubstantial or were ephemeral with duration less than 3 months.

The relative contribution of arteriovenous oxygen (A-V O2) difference to thermally-induced and activity-induced changes in metabolic rate (VO2) were delineated in the toad, B. marinus. In conjunction, the influence of rest and activity, temperature, and removal of the pericardia! sac on separation efficiency (Es) in the anuran ventricle was determined by direct measurement of arterial and venous percent oxygen saturation (% saturation), using a microsampling technique.

The large population of breeding Herring Gulls and Great Black-backed Gulls on South Monomoy Island, Cape Cod, Massachusetts has been thought to negatively affect the breeding success of the threatened Piping Plover. Following the Piping Plover Recovery Plan s call for gull colonies to be removed from Piping Plover breeding sites, in 1996, the USFWS conducted gull removal on part of South Monomoy Island. We determined relative gull abundance on South Monomoy Island from 1998-2000 by counting gulls within 100-m radius plots located on the shoreline. We quantified Piping Plover behavior and habitat use by conducting instantaneous and 5-minute behavioral observations. We quantified characteristics of Piping Plover nesting habitat by measuring characteristics along random transects. We measured gull abundance, beach width, and prey abundance, and then used logistic regression to determine what habitat characteristics influenced Piping Plover nesting area selection. We monitored Piping Plover reproductive success and population fluctuations on South Monomoy Island. Gull abundance in the gull-removal area was lower than gull abundance in the reference area throughout the Piping Plover breeding season. The difference in gull abundance between the areas did not affect Piping Plover behavior, nest success, chick survival, or productivity. We found that gull removal did not result in an increased Piping Plover population on the island. In both management areas, prenesting plovers preferred to forage in moist substrate habitats. Wide backshore and open vegetation habitats characterized nesting areas. Broods spent most of their time foraging and preferred moist substrate habitats when available. Plovers were not prevented from occupying more suitable habitat by large gulls. Fewer large gulls were observed near prenesting plovers, plover nests, and plover broods than near random plots. Fewer large gulls were observed in plover nesting areas than in unused areas when the nesting areas were defined by all area within 100-m or 500-m of a plover nest. We argue that this apparent spatial separation between Piping Plovers and large gulls is due to different habitat preferences among the species. We found that gull removal on South Monomoy Island did not result in increased Piping Plover reproductive success, and large gulls did not affect breeding Piping Plovers on South Monomoy Island from 1998-2000. / Master of Science

Zhou Liran. / "June 2003." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (p. 182-216). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.