Thesis (M.S.)--Georgia Southern University, 2008. / "A thesis submitted to the Graduate Faculty of Georgia Southern University in partial fulfillment of the requirements for the degree Master of Science." Directed by Christopher P. Cutler. ETD. INDEX WORDS: Aquaporin, Aquaglyceroporin, Osmoregulation, Water Homeostasis, Elasmobranch, Biological Transport, Molecular Sequence, Sequence Homology, Kidney, Rectal Gland Includes bibliographical references (p. 116-120) and appendices.

No description available.

Thesis (Ph.D.) -- University of Rhode Island, 2008. / Typescript. Includes bibliographical references (leaves 170-184).

This study examines the spatial and temporal distribution and life history of the "offshore" component of the Northeastern Pacific spiny dogfish (Squalus acanthias) population. Distribution was examined in relation to latitude, depth, the Columbia River plume and large-scale climate changes. Fishery and survey data indicate that the Northeastern Pacific spiny dogfish population has a broad range along the Washington and Oregon coasts, with the highest abundance occurring off the northern Washington and central Oregon coasts. Catches, however, were patchy throughout the 37-year period of available survey data. In terms of depth, the greatest abundances of spiny dogfish were captured in shallow waters (55-184 m). An examination of the influence of the Columbia River plume using a generalized additive model (GAM) indicated that the fish were influenced significantly by the salinity, chlorophyll and surface temperature patterns associated with the plume, preferring the oceanic zone to the plume zone. In contrast, there was no indication that the catch-per-unit-effort of spiny dogfish was influenced by the Pacific Decadal Oscillation (PDO) or the El-Niño (ENSO) over 24-year period of the National Marine Fisheries (NMFS) triennial shelf groundfish survey (1977-2001). The multi-cohort age structure of the population, due to the spiny dogfish's late age at maturity and long lifespan, as well as the low fecundity make it difficult to detect the loss of a single cohort or two when examining abundance trends. Moreover, effects on abundance may be time-lagged, especially if, as is likely, the youngest cohort(s) is the most vulnerable life stage. Their absence would not become evident until they were large enough to have been captured by the survey gear. Sensitive abundance data and/or age-structured data would be needed to identify a pattern. I quantified the age, maturation and fecundity of the spiny dogfish and use these data to develop an age-structured matrix model to examine the sensitivity of the population's growth rate to changes in mortality (i.e. fishing). Female spiny dogfish in this population have an average age at 50% maturity of 28 years and males 20 years. Average length at 50% maturity was 85.0 cm for females and 71.5 cm for males. Female fecundity was extremely low, averaging eight pups per clutch biennially and ranging from four to 14. The number of pups increased with length, but not age. Using these data, a deterministic, female-based model was developed. Asymptotic population growth rate (λ) was determined to be very low, 1.01, and comparable to population growth rates calculated for "coastal" populations. When fishing mortality was incorporated into the model, the fishery was only sustainable when exploitation was low and strict size limits enforced. When fecundity was doubled, the population growth rate increased from 1% to 3% per year. This 33% increase in population growth was equivalent to the effect of a decrease in the age at first maturity of three years. Given that responses to changes in population demographics through shifts in fecundity or spawning frequency are likely constrained, responses would then seem likely to involve changes in age at maturity. These life history traits translate into a low potential population growth and as a consequence high susceptibility to overfishing. My findings indicate that the Northeastern Pacific spiny dogfish are relatively slow growing, late to mature, and have low fecundity and a patchy distribution, with large catches occurring off the northern Washington and central Oregon coasts in shallow waters (55-184 m). These life history traits and distributional patterns are useful in the development of population models to predict responses to environmental fluctuations or increased mortality and thus the management of the population. It is evident from my findings that periodic monitoring is necessary to track possible catch declines off the northern Washington and central Oregon coasts and prevent collapse of the population should it be targeted by a fishery and overfishing occur. / Graduation date: 2005

Thesis (M.Sc.)--Acadia University, 1998. / Includes bibliographical references (leaves 40-50). Also available on the Internet via the World Wide Web.

Thesis (M.Sc.)--Acadia University, 1998. / Includes bibliographical references (leaves 40-50). Also available on the Internet via the World Wide Web.

<p>The melanocortin (MC) receptors are G-protein coupled receptors thatparticipate in several important physiological functions such as the regulation of the energy balance. This thesis focuses on the evolutionary aspect of the MC receptors and their pharmacology.</p><p>One MC4 receptor and two MC5 receptor subtypes were found in a teleost fish, zebrafish. This indicates that the MC receptor subtypes arose very early in vertebrate evolution. Important pharmacological and functional properties, as well as gene structure and syntenic relationships have been highly conserved over a period of more than 400 million years implying that these receptors participate in vital physiological functions. Moreover, we found a MC4 receptor from a shark, spiny dogfish that represents the most distant MC receptor gene cloned to date. We also characterized the pharmacology of a MC4 receptor in goldfish. The conserved central expression pattern and physiological role in regulation of food intake of the MC4 receptor suggests that neuronal pathways of the melanocortin system may be important for regulation of energy homeostasis in most vertebrates. We determined the chromosomal position of the chicken MC receptors genes and found conserved synteny of the MC2, MC5, and MC4 receptor genes. These results suggest that there exist a clustering of these genes that is ancient. Analysis of conserved synteny with mammalian genomes and paralogon segments prompted us to predict an ancestral gene organization that may explain how this family has been formed through both local duplication and tetraploidization processes.</p><p>There are several common point mutations in the human MC1 receptor that are over represented in North European red-heads, and in individuals with pale skin. We pharmacologically characterised four naturally occurring human MC1 receptor variants providing molecular explanation to the respective phenotype.</p><p>The MC receptor subtypes have highly diverse physiological functions despite having relative high similarities in their primary structure. Our studies on the structural and functional properties of the MC receptor subtypes have provided insight into the molecular mechanism of how the specification of these receptors may have occurred.</p>

The melanocortin (MC) receptors are G-protein coupled receptors thatparticipate in several important physiological functions such as the regulation of the energy balance. This thesis focuses on the evolutionary aspect of the MC receptors and their pharmacology. One MC4 receptor and two MC5 receptor subtypes were found in a teleost fish, zebrafish. This indicates that the MC receptor subtypes arose very early in vertebrate evolution. Important pharmacological and functional properties, as well as gene structure and syntenic relationships have been highly conserved over a period of more than 400 million years implying that these receptors participate in vital physiological functions. Moreover, we found a MC4 receptor from a shark, spiny dogfish that represents the most distant MC receptor gene cloned to date. We also characterized the pharmacology of a MC4 receptor in goldfish. The conserved central expression pattern and physiological role in regulation of food intake of the MC4 receptor suggests that neuronal pathways of the melanocortin system may be important for regulation of energy homeostasis in most vertebrates. We determined the chromosomal position of the chicken MC receptors genes and found conserved synteny of the MC2, MC5, and MC4 receptor genes. These results suggest that there exist a clustering of these genes that is ancient. Analysis of conserved synteny with mammalian genomes and paralogon segments prompted us to predict an ancestral gene organization that may explain how this family has been formed through both local duplication and tetraploidization processes. There are several common point mutations in the human MC1 receptor that are over represented in North European red-heads, and in individuals with pale skin. We pharmacologically characterised four naturally occurring human MC1 receptor variants providing molecular explanation to the respective phenotype. The MC receptor subtypes have highly diverse physiological functions despite having relative high similarities in their primary structure. Our studies on the structural and functional properties of the MC receptor subtypes have provided insight into the molecular mechanism of how the specification of these receptors may have occurred.