Differential effects of water loss and temperature increase in the physiology of fiddler crabs from distinct habitats
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Data
2017-08-23
Autores
Souza, Silas Candido Principe [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
A temperatura é uma das principais restrições ambientais à distribuição dos organismos, afetando a fisiologia e sobrevivência. Organismos que habitam a zona do entremarés estão constantemente expostos à variação da temperatura e, com as mudanças climáticas, esses organismos devem enfrentar condições diferentes, que incluem temperaturas mais elevadas, levando a maiores taxas de perda de água por evaporação e, consequentemente, redução do desempenho ou mortalidade. Neste estudo, testamos os efeitos da dessecação em duas espécies de caranguejos violinistas (Leptuca thayeri e Minuca rapax) que ocupam habitats distintos em relação à cobertura da vegetação e posição no entremarés e, portanto, podem responder de forma diferente ao estresse por dessecação e ao aumento da temperatura. Leptuca thayeri, que é restrita à zona intermediária do entremarés, é mais sensível à dessecação do que M. rapax, uma espécie generalista, com maiores taxas de dessecação e mortalidade quando expostas à dessecação por 120 minutos. Além disso, em comparação com M. rapax, L. thayeri possui uma carapaça mais permeável. Também avaliamos se o aumento de temperatura pode causar alterações fisiológicas na espécie mais restrita L. thayeri, tendo acesso a alimento e à água. Uma elevação de temperatura de 10 ° C e 20 ° C durante 72 h não causou mortalidade em L. thayeri nem mudanças na concentração de glicose e proteína na hemolinfa. No entanto, as temperaturas mais altas aumentaram os níveis de lactato desidrogenase, e houve alterações na osmolalidade da hemolinfa e grau de hidratação muscular na temperatura intermediária, sugerindo que a essa temperatura essa espécie tenha melhores capacidades osmoreguladoras. Nossos resultados mostram que espécies de diferentes habitats respondem de forma diferente à dessecação devido a adaptações morfológicas, e espécies de zonas de maré baixa e áreas sombreadas podem enfrentar os efeitos nocivos das mudanças climáticas de forma mais aguda.
Temperature is one of the main environmental constraints to organism distribution, affecting both physiology and survival. Organisms that inhabit the intertidal zone are constantly exposed to temperature variation and, with climate change, those organisms should face different conditions which include higher temperatures, leading to higher rates of water loss through evaporation and then fitness reduction or mortality. In this study we tested the effects of desiccation in two fiddler crabs species (Leptuca thayeri and Minuca rapax) that occupy distinct habitats in regard to vegetation cover and position on the intertidal zone and thus may respond differently to desiccation stress and increased temperature. Leptuca thayeri, which is restricted to the mid-tide zone, was more sensitive to desiccation than M. rapax, a generalist species, having higher desiccation and mortality rates when exposed to desiccation for 120 minutes. Also, compared to M. rapax, L. thayeri has a more permeable carapace. We also assessed if a temperature increase could cause physiological changes in the restricted species L. thayeri, while having access to both food and water. A temperature elevation of 10 °C and 20 °C for 72 h caused no mortality in L. thayeri nor changes in hemolymph glucose and protein concentration. However, higher temperatures increased hemolymph lactate dehydrogenase levels, and there were changes in hemolymph osmolality and muscle hydration in the intermediate temperature, suggesting that at this temperature this species has better osmoregulatory capacities. Our results show that species from different habitats respond differently to desiccation due to morphological adaptations, and species from lower tidal zones and shaded areas may face the harmful effects of climate change more acutely.
Temperature is one of the main environmental constraints to organism distribution, affecting both physiology and survival. Organisms that inhabit the intertidal zone are constantly exposed to temperature variation and, with climate change, those organisms should face different conditions which include higher temperatures, leading to higher rates of water loss through evaporation and then fitness reduction or mortality. In this study we tested the effects of desiccation in two fiddler crabs species (Leptuca thayeri and Minuca rapax) that occupy distinct habitats in regard to vegetation cover and position on the intertidal zone and thus may respond differently to desiccation stress and increased temperature. Leptuca thayeri, which is restricted to the mid-tide zone, was more sensitive to desiccation than M. rapax, a generalist species, having higher desiccation and mortality rates when exposed to desiccation for 120 minutes. Also, compared to M. rapax, L. thayeri has a more permeable carapace. We also assessed if a temperature increase could cause physiological changes in the restricted species L. thayeri, while having access to both food and water. A temperature elevation of 10 °C and 20 °C for 72 h caused no mortality in L. thayeri nor changes in hemolymph glucose and protein concentration. However, higher temperatures increased hemolymph lactate dehydrogenase levels, and there were changes in hemolymph osmolality and muscle hydration in the intermediate temperature, suggesting that at this temperature this species has better osmoregulatory capacities. Our results show that species from different habitats respond differently to desiccation due to morphological adaptations, and species from lower tidal zones and shaded areas may face the harmful effects of climate change more acutely.
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Palavras-chave
Fisiologia térmica, Dessecação, Leptuca thayeri, Minuca rapax, Thermal ecology, Thermal physiology, Desiccation, Ecologia térmica