Thesis (Ph. D.)--University of Canterbury, 2008. / Typescript (photocopy). Includes bibliographical references (leaves 201-229). Also available via the World Wide Web.

Antarctic fish from the Perciform suborder Notothenioidei inhabit arguably the most thermally stable ocean environment on earth. In order to populate the subzero environment Antarctic fish have evolved numerous adaptations. However, specialisation to -1.9°C has incurred a trade off, thermal flexibility is lost likely due to modifications to the cold and as a result Notothenioidei are extremely stenothermic. Climate change mediated warming is predicted to increase the ocean temperature surrounding the Antarctic continent by 2°C within the next century. This increase is projected to affect individuals, populations and the community structures of those inhabiting the area and therefore the physiological study of the acclimation ability and thermal limitations of Antarctic fish is an area scientific interest. The present study is a series of discrete experiments relating to one species, Trematomus bernacchii, a circumpolar benthic Notothenioidei found in nearly all inshore waters surrounding the Antarctic coastline. These studies included investigation of the response of this species to both chronic and acute temperature exposure prior to and following a feeding event, a reduction in environmental oxygen and an exhaustive exercise event, as well as examination of T. bernacchii ability to recovery from these challenges. T. bernacchii demonstrated variable success when acclimated to +3°C. Failure appeared to be determined by the recovery period following capture and aquarium housing, 7 days housing following capture resulted in 100% mortality, conversly 3 months resulted in 100% survival. Following successful acclimation T. bernacchii showed physiological adjustment as acclimated resting metabolic rate mirrored that of T. bernacchii tested at environmental temperature, 20.63 ± 1.3 compared to 22.38 ± 1.02 mg. O₂. kg⁻¹. h⁻¹. The previously undefined specific dynamic action response (SDA), in T. bernacchii was characteristic of polar species. At environmental temperatures SDA scope was small 14.52 ± 3.52 mg O₂. kg⁻¹. h⁻¹, and lengthy ,72 hours; SDA duration was reduced to 9 hours in acclimated fish. Resting metabolic rate was elevated following acute exposure to +3°C, 34.27 ± 2.35 mg O₂. kg⁻¹. h⁻¹, masking the SDA response and associated parameters. T. bernacchii were relatively sensitive to hypoxia, Pcrit over four acute temperature exposures, ranged between 69 and 102mmHg, higher than the average range for teleosts (40 – 60 mmHg). Above -1°C Pcrit increased, rising with acute temperature exposure. Ventilation rate was temperature dependent and completely absent at +4 and +6°C. A bradycardia (beginning at 60 and 70mmHg) was observed at all temperature exposures, this response was consistent as all heart rates reduced by 25%. Recovery from both hypoxia and acute temperature exposure was rapid. Following an exhaustive exercise event aerobic Scope of T. bernacchii was constrained over an acute temperature increase, reducing from 38.58 ± 5.64 to 24.41 ± 4.92 mg.O₂. kg⁻¹.h⁻¹ over a 7°C temperature increase, respiratory scope too was reduced such that at +4 and +6°C scope was absent. Heart rate of T. bernacchii was highly constrained at -1°C, increasing by 2.54 ± 0.9 bpm following exercise. Acute temperature increase resulted in an increase in cardiac scope, maximum 6.29 ± 1.2 bpm at +2°C, due likely to a thermally mediated loss of cholinergic tonus following exhaustive exercise. Recovery of all parameters was temperature dependent and rapid upon return to -1°C. The present study is the first to quantify and assess the effect of acute and chronic temperature exposure on the SDA response of T. bernacchii. Furthermore, it supplements the current literature on acclimation ability, acute temperature exposure, aerobic scope and hypoxia tolerance for this species. This work will be of use in future investigations of the effects of rapid climate change on Antarctic notothenioid fish and the interconnected ecosystem.

Muitos países possuem estações de pesquisa instaladas na Antártica. Hidrocarbonetos de petróleo e os esgotos lançados no mar pelas estações são as fontes potenciais de poluição na Antártica. Peixes da espécie Trematomus newnesi foram utilizados para investigar o potencial genotóxico e os efeitos sobre a morfologia de fígado e brânquias da água diante dos tanques de combustível e da saída de esgoto da Estação Antártica Brasileira ?Comandante Ferraz?, em experimentos in situ e no laboratório. No Ensaio de Mn e ANE, observou-se que a freqüência de R foi, em geral, menor nos controles do que nos grupos expostos, tanto nos bioensaios como nos experimentos in situ, porém não houve diferenças estatisticamente significativas em nenhum dos experimentos. As lesões branquiais mais observadas, nos grupos expostos, foram hipertrofia do epitélio e telangiectasia lamelar. No fígado, as lesões predominantes foram a vacuolização lipídica e a presença de macrófagos, principalmente nos peixes dos experimentos in situ. Não foram verificadas diferenças significativas nos índices de lesões histopatológicas entre os grupos expostos e os controles em nenhum dos experimentos. Contudo, os resultados obtidos sugerem que dos dois locais analisados nas proximidades da Estação Brasileira, a saída de esgoto apresenta maior potencial de risco para T. newnesi. / Many countries have installed research stations in Antarctica. Petroleum hydrocarbons and the sewage disposed into the sea by the stations are potential sources of pollution in Antarctica. Trematomus newnesi specimens were used to assess genotoxic potential and histopathology of the liver and gills of the water surrounding the Brazilian Antarctic Station ?Comandante Ferraz?. Fish were exposed to seawater at the sewage outfall and in front of the fuel tanks, in both in situ and laboratory assays. The Mn and ENA assay showed that the frequency of R was, in general, lower in the control groups than in the exposed ones in both in situ and laboratory assays, however there were no statistically significative differences in any of the experiments. The most frequent branchial lesions observed in the exposed groups were epithelium hipertrophy and lamelar telangiectasis. In the liver, predominant microscopic findings included lipid vacuolization and macrophages, specially in fish from the in situ experiments. Exposed groups did not show significative differences in the histopathological indexes from those of the controls in any of the experiments. Nevertheless, our results suggest that of the places studied the sewage outlet may present a greater potential of risk to T. newnesi nearby the Brazilian Station.

Muitos países possuem estações de pesquisa instaladas na Antártica. Hidrocarbonetos de petróleo e os esgotos lançados no mar pelas estações são as fontes potenciais de poluição na Antártica. Peixes da espécie Trematomus newnesi foram utilizados para investigar o potencial genotóxico e os efeitos sobre a morfologia de fígado e brânquias da água diante dos tanques de combustível e da saída de esgoto da Estação Antártica Brasileira ?Comandante Ferraz?, em experimentos in situ e no laboratório. No Ensaio de Mn e ANE, observou-se que a freqüência de R foi, em geral, menor nos controles do que nos grupos expostos, tanto nos bioensaios como nos experimentos in situ, porém não houve diferenças estatisticamente significativas em nenhum dos experimentos. As lesões branquiais mais observadas, nos grupos expostos, foram hipertrofia do epitélio e telangiectasia lamelar. No fígado, as lesões predominantes foram a vacuolização lipídica e a presença de macrófagos, principalmente nos peixes dos experimentos in situ. Não foram verificadas diferenças significativas nos índices de lesões histopatológicas entre os grupos expostos e os controles em nenhum dos experimentos. Contudo, os resultados obtidos sugerem que dos dois locais analisados nas proximidades da Estação Brasileira, a saída de esgoto apresenta maior potencial de risco para T. newnesi. / Many countries have installed research stations in Antarctica. Petroleum hydrocarbons and the sewage disposed into the sea by the stations are potential sources of pollution in Antarctica. Trematomus newnesi specimens were used to assess genotoxic potential and histopathology of the liver and gills of the water surrounding the Brazilian Antarctic Station ?Comandante Ferraz?. Fish were exposed to seawater at the sewage outfall and in front of the fuel tanks, in both in situ and laboratory assays. The Mn and ENA assay showed that the frequency of R was, in general, lower in the control groups than in the exposed ones in both in situ and laboratory assays, however there were no statistically significative differences in any of the experiments. The most frequent branchial lesions observed in the exposed groups were epithelium hipertrophy and lamelar telangiectasis. In the liver, predominant microscopic findings included lipid vacuolization and macrophages, specially in fish from the in situ experiments. Exposed groups did not show significative differences in the histopathological indexes from those of the controls in any of the experiments. Nevertheless, our results suggest that of the places studied the sewage outlet may present a greater potential of risk to T. newnesi nearby the Brazilian Station.

Antarctic fish from the suborder Notothenioidei inhabit what is perhaps the most thermally stable ocean environment on Earth. Evolutionary theory suggests that by specialising for this environment, Antarctic fish have traded-off their ability to respond to variations in temperature, and like their environment, have become extremely stenothermal. However, previous research has revealed that the Antarctic notothenioid fish Pagothenia borchgrevinki is not as thermally limited as evolutionary theory might predict, and is capable of acclimation to 4 ℃ during a one month period. The purpose of the current research was to investigate the physiological mechanisms that underpin this remarkable acclimatory ability. P. borchgrevinki were acclimated for one month to 4 ℃ and changes in oxygen consumption, prolonged swimming ability, cardiovascular function, enzyme activity and haematology were measured. Significant changes in resting oxygen consumption rate and prolonged swimming ability occurred during the acclimation period, and these changes were mediated by adjustments of enzyme activity and specific aspects of the haematology. By monitoring resting oxygen consumption and prolonged swimming ability over a much longer, six month, acclimation period it was confirmed that the adjustments evident during one month at 4 ℃ were sustainable in the long-term, and were not short-term compensatory mechanisms. Interestingly, fish infected with x-cell gill disease did not possess the same ability to acclimate as was demonstrated by healthy P. borchgrevinki. P. borchgrevinki are unusual among the notothenioids, possessing an active, pelagic lifestyle which differs from the sedentary, benthic lifestyle of most other species within the suborder. Therefore, it was hypothesised that the acclimatory ability demonstrated by this species may also be unusual among the notothenioids. To test this hypothesis, the acclimation ability of three sedentary, benthic notothenioids (Trematomus bernacchii, T. hansoni and T. pennellii) was investigated. Results confirmed the hypothesis, with all three species demonstrating very poor survival at 4 ℃ and absolutely no capacity for acclimation. Such results present a disturbing scenario for the future of Antarctic notothenioid fish in Earth?s rapidly warming climate, and highlights the need for continued research combined with immediate action to combat the warming which currently threatens Antarctic marine biodiversity.

Antarctic fish from the suborder Notothenioidei inhabit what is perhaps the most thermally stable ocean environment on Earth. Evolutionary theory suggests that by specialising for this environment, Antarctic fish have traded-off their ability to respond to variations in temperature, and like their environment, have become extremely stenothermal. However, previous research has revealed that the Antarctic notothenioid fish Pagothenia borchgrevinki is not as thermally limited as evolutionary theory might predict, and is capable of acclimation to 4 ℃ during a one month period. The purpose of the current research was to investigate the physiological mechanisms that underpin this remarkable acclimatory ability. P. borchgrevinki were acclimated for one month to 4 ℃ and changes in oxygen consumption, prolonged swimming ability, cardiovascular function, enzyme activity and haematology were measured. Significant changes in resting oxygen consumption rate and prolonged swimming ability occurred during the acclimation period, and these changes were mediated by adjustments of enzyme activity and specific aspects of the haematology. By monitoring resting oxygen consumption and prolonged swimming ability over a much longer, six month, acclimation period it was confirmed that the adjustments evident during one month at 4 ℃ were sustainable in the long-term, and were not short-term compensatory mechanisms. Interestingly, fish infected with x-cell gill disease did not possess the same ability to acclimate as was demonstrated by healthy P. borchgrevinki. P. borchgrevinki are unusual among the notothenioids, possessing an active, pelagic lifestyle which differs from the sedentary, benthic lifestyle of most other species within the suborder. Therefore, it was hypothesised that the acclimatory ability demonstrated by this species may also be unusual among the notothenioids. To test this hypothesis, the acclimation ability of three sedentary, benthic notothenioids (Trematomus bernacchii, T. hansoni and T. pennellii) was investigated. Results confirmed the hypothesis, with all three species demonstrating very poor survival at 4 ℃ and absolutely no capacity for acclimation. Such results present a disturbing scenario for the future of Antarctic notothenioid fish in Earth?s rapidly warming climate, and highlights the need for continued research combined with immediate action to combat the warming which currently threatens Antarctic marine biodiversity.