Limites de tolerância térmica e respostas fisiológicas de Phalloceros caudimaculatus (Hensel, 1868) aclimatados à diferentes temperaturas
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Data
2022-03-23
Autores
Souza, Luiz Fernando Barbi de
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Universidade Estadual Paulista (Unesp)
Resumo
A temperatura é um dos fatores abióticos que mais têm influência na fisiologia de organismos ectotérmicos aquáticos. A determinação da temperatura crítica máxima (CTMáx) e a avaliação do metabolismo são ferramentas importantes na compreensão dos limites fisiológicos dos peixes e de suas respostas frente ao estresse térmico. Em nosso estudo avaliamos os limites de Tolerância Térmica Crítica Máxima (CTMáx) e respostas do metabolismo (consumo de oxigênio, excreção de nitrogênio, fluxo iônico líquido de cloreto e sódio) em indivíduos da espécie Phalloceros caudimaculatus. Os animais, com peso médio de 0,670 ± 0,119 g, ficaram durante 7 dias nas temperaturas de aclimatação (20-25-30°C). Avaliamos a CTMáx na salinidade 6‰ (38,567±0,207, 39,833±0,111 e 41,756±0,194) e a CTMáx na salinidade 11‰ (39,138±0,172, 39,983±0,06 e 41,057±0,121), em cada um dos regimes térmicos selecionados, respectivamente. Houve variação significativa entre as temperaturas de aclimatação no CTMáx (P<0,05). Não houve um aumento nas taxas de consumo de oxigénio em função do aumento nas temperaturas de aclimatação (20-25-30°C), e as taxas médias foram de (263,497±43,338, 217,892±61,594, 287,803±28,248), respectivamente. O valor do coeficiente de temperatura (Q10) calculado entre as temperaturas de 20-30oC foi (Q10) = 1,24. Na excreção de amônia foi observada diferenças estatísticas entre 25-30°C e 20-30 °C (P<0,05). Não foi observada diferenças estatísticas significativas na excreção de amônia entre 20-25°C (P = 0,259). O fluxo líquido de cloreto (JClnet) não apresentou diferenças significativas entre as diferenças temperaturas de aclimatação (P = 0,261). Por outro lado, o fluxo líquido de sódio (JNanet), foi significativamente aumento em 25°C (-48,607±10,05), em comparação com os demais regimes térmicos testados. No entanto, não foram observadas diferenças estatísticas significativas no fluxo líquido de sódio entre as temperaturas de 20-30°C (P = 0,261). Nossos resultados indicam que o aumento da temperatura de aclimatação resulta no aumento do limite máximo de tolerância térmica (como indicado pela CTMáx) e redução da capacidade de aclimatação térmica de Phalloceros caudimaculatus, promovendo pequenos distúrbios na excreção de produtos nitrogenados e balanço de Na+ nos animais.
Temperature is one of the abiotic factors that most influence the physiology of aquatic ectothermic organisms. The determination of the maximum critical temperature (CTMax) and the assessment of routine metabolism are important tools to understanding the physiological limits of fish and their responses to heat stress. In our study, we evaluated the limits of Maximun Critical Thermal Tolerance (CTMax) and metabolic responses (oxygen consumption, nitrogen excretion and net ion fluxes of chloride and sodium) in individuals of the species Phalloceros caudimaculatus., weighing. The animals weighting in average 0.670 ± 0.119 g were kept for 7 days in three thermal regimes (20-25-30°C). We evaluated the CTMax at salinity 6‰ (38.567±0.207, 39.833±0.111 and 41.756±0.194) and the CTMax at salinity 11‰ (39.138±0.172, 39.983±0.06 and 41.057±0.121), at each thermal regime selected, respectively. There was a significant variation in CTMax between the three temperatures acclimation (P<0.05). No statistically significant differences were observed in routine oxygen consumption with the increment in temperature. The value of the temperature coefficient (Q10) calculated between 20-30oC was (Q10) = 1.24. Regarding to the ammonia excretion, there is statistical differences between temperature acclimation of 25-30°C and 20-30°C (P<0.05). No statistically significant differences were observed in ammonia excretion between 20-25°C (P = 0.259). The net chloride flux (J Clnet) was not statistically different between the acclimation temperatures tested (P = 0.261). On the other hand, sodium net fluxes sodium (J Nanet) was significantly increased at 25°C (-48.607±10.05) compared to 20 and 30oC. However, no differences were seen in J Nanet between the acclimation temperatures of 20-30°C (P = 0.261). The results indicate that increases in temperature acclimation promote the increase of maximun thermal limits (as seen as by CTMax) and reduce the thermal acclimation capacity of Phalloceros caudimaculatus, also resulting in smaller disturbances in both the excretion of nitrogenous waste products and Na+ balance in animals.
Temperature is one of the abiotic factors that most influence the physiology of aquatic ectothermic organisms. The determination of the maximum critical temperature (CTMax) and the assessment of routine metabolism are important tools to understanding the physiological limits of fish and their responses to heat stress. In our study, we evaluated the limits of Maximun Critical Thermal Tolerance (CTMax) and metabolic responses (oxygen consumption, nitrogen excretion and net ion fluxes of chloride and sodium) in individuals of the species Phalloceros caudimaculatus., weighing. The animals weighting in average 0.670 ± 0.119 g were kept for 7 days in three thermal regimes (20-25-30°C). We evaluated the CTMax at salinity 6‰ (38.567±0.207, 39.833±0.111 and 41.756±0.194) and the CTMax at salinity 11‰ (39.138±0.172, 39.983±0.06 and 41.057±0.121), at each thermal regime selected, respectively. There was a significant variation in CTMax between the three temperatures acclimation (P<0.05). No statistically significant differences were observed in routine oxygen consumption with the increment in temperature. The value of the temperature coefficient (Q10) calculated between 20-30oC was (Q10) = 1.24. Regarding to the ammonia excretion, there is statistical differences between temperature acclimation of 25-30°C and 20-30°C (P<0.05). No statistically significant differences were observed in ammonia excretion between 20-25°C (P = 0.259). The net chloride flux (J Clnet) was not statistically different between the acclimation temperatures tested (P = 0.261). On the other hand, sodium net fluxes sodium (J Nanet) was significantly increased at 25°C (-48.607±10.05) compared to 20 and 30oC. However, no differences were seen in J Nanet between the acclimation temperatures of 20-30°C (P = 0.261). The results indicate that increases in temperature acclimation promote the increase of maximun thermal limits (as seen as by CTMax) and reduce the thermal acclimation capacity of Phalloceros caudimaculatus, also resulting in smaller disturbances in both the excretion of nitrogenous waste products and Na+ balance in animals.
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Palavras-chave
Temperatura, Tolerância, Aclimatação, Salinidade, Estresse, Peixes, Fisiologia