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Early development and metabolic physiology of the temperate lesser spotted shark (Scyliorhinus canicula) under high CO2 levels
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Embora os tubarões proliferam em múltiplos habitats e evoluíram de modo a poder ocupar diversos nichos ecológicos, estes peixes têm uma capacidade adaptativa limitada associada às suas estratégias reprodutivas (e.g. maturação sexual tardia, baixa fecundidade) e de vida (e.g. longevidade elevada). Neste contexto, é de extrema importância analisar os possíveis impactos da acidificação (pCO2 ~1000 μatm) na ontogenia inicial (desenvolvimento e fisiologia) do tubarão temperado pata roxa (Scyliorhinus canicula). Mais especificamente, nesta dissertação avaliou-se os efeitos da acidificação no: i) tempo de desenvolvimento (i.e. duração da embriogénese) e primeira alimentação, ii) índice de condição Fulton (dos recém-nascidos), iii) sobrevivência, iv) taxa metabólica basal (RMR), v) taxa metabólica máxima, (MMR) e vi) taxa metabólica normal (AS). A duração do desenvolvimento embrionário variou entre 118 a 125 dias. Após a eclosão, a média de número de dias para o começo da alimentação (i.e. primeira refeição) variou entre 4 a 6 dias. Em ambos os resultados não houve uma diferença significativa entre tratamentos (i.e. normocapnia e hipercapnia; p>0.05). A sobrevivência juvenil (150 dias depois de eclodirem) também não variou significativamente com os níveis de CO2 mais elevados (p>0.05). Quanto às taxas metabólicas e performance aeróbica, também não houve diferenças significativas nos RMR, MMR e AS (p-value >0.005). Em suma, estes resultados sugerem que esta espécie bentónica é resiliente a condições de hipercapnia, o que poderá estar relacionado com o facto destes organismos estarem recorrentemente expostos a grandes variações abióticas na costa ocidental portuguesa (e.g. variações térmicas e de pH associados à sazonalidade do sistema de afloramento). Assim sendo, esta espécie de tubarão temperado não parece vir a ser afetada pelas condições de acidificação dos oceanos projetadas para o final deste século.
Although sharks thrive in many different kinds of habitats and evolved to fill many ecological niches across a wide range of habitats, these animals are characterized by the limited capability to adapt rapidly to future climate change. Thus, the objective of the present dissertation was to analyze the potential impact of seawater acidification (OA, high CO2 levels ~1000 μatm) on the early development and physiology of the temperate shark Scyliorhinus canicula. More specifically, we evaluated OA effects on: i) development time and first feed, ii) Fulton condition of the newborns, iii) survival, iv) routine metabolic rate (RMR), v) maximum metabolic rate (MMR), and vi) aerobic scope (AS). The duration of embrygenesis ranged from 118 to 125 days, and after hatching, the mean number of days to start feeding (i.e. first feeding) varied between 4 and 6 days. In both endpoints there were no significant differences among treatments (i.e. normocapnia and hypercapnia; p >0.05). Juvenile survival (after 150 days post-hatching) also did no change significantly under high CO2 levels (p >0.05). Regarding energy expenditure rates and aerobic window, there were no significant differences in RMR, MMR, and AS among treatments (p-value > 0.005). In the overall, we argue that these findings are associated to the fact that S. canicula is a benthic, cosmopolitan and temperate shark usually exposed to great variations of abiotic factors, like those experienced in the highly-dynamic western Portuguese coast (with seasonal upwelling events). Although the present dissertation only investigated acclimation processes, it is plausible to assume that this shark species will not be greatly affected by future acidification conditions.
Although sharks thrive in many different kinds of habitats and evolved to fill many ecological niches across a wide range of habitats, these animals are characterized by the limited capability to adapt rapidly to future climate change. Thus, the objective of the present dissertation was to analyze the potential impact of seawater acidification (OA, high CO2 levels ~1000 μatm) on the early development and physiology of the temperate shark Scyliorhinus canicula. More specifically, we evaluated OA effects on: i) development time and first feed, ii) Fulton condition of the newborns, iii) survival, iv) routine metabolic rate (RMR), v) maximum metabolic rate (MMR), and vi) aerobic scope (AS). The duration of embrygenesis ranged from 118 to 125 days, and after hatching, the mean number of days to start feeding (i.e. first feeding) varied between 4 and 6 days. In both endpoints there were no significant differences among treatments (i.e. normocapnia and hypercapnia; p >0.05). Juvenile survival (after 150 days post-hatching) also did no change significantly under high CO2 levels (p >0.05). Regarding energy expenditure rates and aerobic window, there were no significant differences in RMR, MMR, and AS among treatments (p-value > 0.005). In the overall, we argue that these findings are associated to the fact that S. canicula is a benthic, cosmopolitan and temperate shark usually exposed to great variations of abiotic factors, like those experienced in the highly-dynamic western Portuguese coast (with seasonal upwelling events). Although the present dissertation only investigated acclimation processes, it is plausible to assume that this shark species will not be greatly affected by future acidification conditions.
Descrição
Tese de mestrado, Ecologia Marinha, Universidade de Lisboa, Faculdade de Ciências, 2019
Palavras-chave
Oceanos Acidificação Metabolismo Tubarão Plasticidade pH Teses de mestrado - 2019