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

The survival of Elasmobranch fishes (sharks, skates and rays) depends critically on their ability to sense odor cues. The outstanding question of detection thresholds to food odors in the shark is investigated in this study. The tracking behavior of Mustelus canis (the smooth dogfish) was analyzed using a binary choice flume designed specifically for testing odor preferences of aquatic animals. To determine threshold, odor was serially diluted until no tracking responses were observed. Sharks spent significantly more time in the odor side of the flume, regardless of their individual side bias, until the "squid juice" was diluted several orders of magnitude. For the whole flume the two greatest dilutions (10-4-10-5 at the odor source) did not cause significant choice and for the upstream flume half, all but the greatest dilution (10-5 at the odor source) caused significant odor side preference. To interpret these results fully we need to consider the structure of odor plumes and the function of the sharks' olfactory responses. Nonetheless, assuming that M. canis represent sharks in general, these findings demonstrate that their extraordinary sensitivity to food attractants may indicate aspects still unknown about life history of elasmobranch fishes including the ranges that benthic elasmobranchs are capable of traveling to feed.

Understanding and predicting the way in which species interactions may change under the uncertain climatic future is imperative if the management of important resources is to be successful. Consumer – resource interactions underlie population dynamics and distribution, yet there is little known about how these interactions will respond to increasing temperature. Temperature increase can facilitate the movement and settlement of alien species into new ranges. Introduced species can often be ecologically damaging and unpredictable due to novel predator-prey interactions. Comparative functional response analysis has been used to gain insight into resource dependent behaviour and population dynamics. This study is an assessment of the way in which predicted temperature changes can affect resource consumption in three predators. The red lionfish Pterois volitans (Linnaeus, 1758) is a successful and hugely damaging invader in the Western Atlantic and sources point to an ongoing Mediterranean invasion. Through a series of laboratory experiments I assessed how temperature, habitat complexity, and light wavelength affect the functional response of lionfish towards a crustacean prey. I establish that lionfish have a persistent Type II functional response and that lower temperature decreased the magnitude of the functional response, suggesting that movement into the comparatively colder waters of the Mediterranean and British Isles could reduce the per capita response. Further, I found that red light reduced the maximum feeding rate of lionfish, compared to blue and white light, by dampening the attack rate. I assessed how temperature increase affects the proportional consumption of an amphipod prey by an intertidal predator, the bleniid, Lipophrys pholis (Linnaeus, 1758). Functional response analysis revealed that the shanny has a hump shaped relationship with increasing temperature wherein maximum feeding rate decreased at the highest temperature. Two prey supply models, where prey density was allowed to deplete, and where prey were replaced after consumption were compared and found to have differential results due to model choice. I used gut content data to assess the abundance, prey selection, degree of dietary overlap, in a commercial predator, cod (Gadhus morhua; Linnaeus, 1758) and a non-commercial predator, dogfish (Sycliorhinus canicula; Linnaeus, 1758) with regards to substrate type. While there were no significant conclusions to be made about habitat use, I found significantly larger populations of S. canicula and higher consumption of commercial invertebrates by S. canicula. I vi used this field data to inform further experiments, having highlighted S. canicula as a potential threat to commercial fisheries. A two-by-two experimental design was used to understand how differential acclimation of predator (S. canicula) and amphipod prey species (Echinogammarus marinus; Leach, 1815) affects the functional response of the predator. Increasing temperature concomitantly increased the magnitude functional response of S. canicula, however raised temperature caused a shift in functional response type, from Type II to Type III, conferring low prey density protection. Handling time was shorter when both predator and prey were acclimated to the raised temperature and as a result there was a significant interaction effect where maximum feeding rate was significantly higher when both predator and prey were acclimated. This increase in predation impact by S. canicula has the potential to affect valuable fisheries stocks due to the increasing populations of Scyliorhinus canicula and the additive effects of acclimation to raised temperature. Having highlighted the differential ways in which temperature can affect the per capita response of consumers I postulate a new metric wherein “Relative Impact Potential” of a consumer can be predicted under a set of environmental variables. This metric takes into account the per capita response, numerical response, and the potential change in predator and prey populations under the proposed conditions. I suggest the use of this metric as a rapid way of assessing and predicting potential threats to sustainability of fisheries under predicted climatic change. Overall, this thesis identifies species and scenarios wherein sustainability of important fisheries could be threatened. While this work focuses mainly on thermal responses, it demonstrates: (i) the utility of functional response analysis in assessing relative change in ecological impact under climate change scenarios; (ii) the species specificity of thermal responses and provides empiricle evidence of a hump shaped thermal response; (iii) the importance of considering both predator and prey when assessing ecological change, with reference to acclimation and population dynamics; and (iv) a metric with which to assess potential threats and ecological impact in a way that is standardized and easily accessible by managers and stakeholders alike.

<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.