This study evaluated the effects of an acute change in water pH (from pH 7.5 to 4.0, 5.0, 6.0, 7.5, 8.0 or 9.0) on several biochemical parameters in juveniles of the silver catfish, Rhamdia quelen. ...Ammonia levels decreased in the liver and increased in the muscle with increasing water pH. In the kidney, lower ammonia levels were observed at neutral pH. An increase in water pH decreased the glucose, glycogen and lactate levels in the liver and kidney (except for glycogen levels in the kidney and lactate levels in the liver, which presented lower levels at neutral pH). In muscle, the glucose and glycogen levels decreased with increasing water pH, whereas lactate levels tended to be lower at neutral pH. Gill and kidney Na+/K+-ATPase activities tended to increase in alkaline water, and the highest value was observed in fish exposed to pH 9.0. The optimal levels of the analyzed biochemical parameters occurred at neutral pH. In conclusion, exposure to acidic and alkaline pH changes the metabolic parameters of silver catfish as well as gill Na+/K+-ATPase activity.
•We report the effects of an acute water pH change to silver catfish.•Gill and kidney Na+/K+-ATPase activities tended to increase in alkaline water.•In acidic and alkaline water, glucose, glycogen and anaerobic route provide energy.
Ion fluxes in silver catfish (Rhamdia quelen) juveniles exposed to different dissolved oxygen levels Rosso, Felipe Link de(Universidade Federal de Santa Maria Departamento de Fisiologia e Farmacologia); Bolner, Keidi C. S.(Universidade Federal de Santa Maria Departamento de Fisiologia e Farmacologia); Baldisserotto, Bernardo(Universidade Federal de Santa Maria Departamento de Fisiologia e Farmacologia)
Neotropical Ichthyology,
12/2006, Volume:
4, Issue:
4
Journal Article
Open access
Low dissolved oxygen levels in the water (hypoxia) can be provoked by oxygen consumption by fish and other organisms, organic matter decomposition, phytoplankton blooms, and temperature increase. The ...objective of the present study was to investigate Na+, Cl-, K+, and ammonia fluxes in silver catfish (Rhamdia quelen) exposed to different dissolved oxygen levels. Juveniles (9 ± 1g) maintained at 6.0 mg.L-1 dissolved oxygen were transferred to four 40 L aquaria with different dissolved oxygen levels (in mg.L-1): 6.0, 4.5, 3.5, and 2.5. In another series of experiments, juveniles were acclimated at 6.0 or 2.5 mg.L-1 dissolved oxygen levels, and then placed in two 40 L aquaria with 6.0 mg.L-1 dissolved oxygen. For both series of experiments, 1, 24, 48 or 120 h after transference juveniles were placed in individual chambers of 200 mL (with the same dissolved oxygen levels of their respective aquaria) for 3 h. Water samples were collected for analysis of Na+, Cl-, K+, and ammonia levels. The obtained results allow concluding that exposure to 2.5 mg.L-1 dissolved oxygen levels promotes loss of ions and lower ammonia excretion in silver catfish juveniles, but these losses are rapidly stabilized for Na+ and Cl-. Exposure to less hypoxic levels also changes ion fluxes and ammonia excretion, but there is no clear relationship between both parameters in this species. Therefore, silver catfish osmoregulation seems to be affected when this species is transferred from normoxic to hypoxic waters and vice-versa.
Baixos níveis de oxigênio dissolvido na água (hipóxia) podem ser causados pelo consumo de oxygênio por peixes e outros organismos, decomposição de matéria orgânica, "blooms" de fitoplâncton e aumento de temperatura. O objetivo do presente estudo foi analisar os fluxos de Na+, Cl-, K+ e amônia em jundiás (Rhamdia quelen) expostos a diferentes níveis de oxigênio dissolvido. Juvenis (9 ± 1g) mantidos em 6,0 mg.L-1 oxigênio dissolvido foram transferidos para quatro aquários de 40 L com diferentes níveis de oxigênio dissolvido (em mg.L-1): 6,0; 4,5; 3,5 e 2,5. Em outra série de experimentos, juvenis foram aclimatados a 6,0 ou 2,5 mg.L-1 oxigênio dissolvido e então colocados em dois aquários de 40 L com 6,0 mg.L-1 oxigênio dissolvido. Para ambas séries de experimentos, 1, 24, 48 ou 120 h depois da transferência os juvenis foram colocados em câmaras individuais de 200 mL (com os mesmos níveis de oxigênio dissolvido dos seus respectivos aquários) por 3 h. Amostras de água foram coletadas para análise dos níveis de Na+, Cl-, K+ e amônia. Os resultados obtidos permitem concluir que a exposição a 2,5 mg.L-1 oxigênio dissolvido promove uma perda de íons nos juvenis de jundiá, mas estas perdas são estabilizadas rapidamente no caso de Na+ e Cl-. A exposição a níveis não tão hipóxicos também altera os fluxos iônicos, mas não há nenhuma relação clara entre ambos parâmetros. Portanto, a osmorregulação do jundiá parece ser afetada quando exemplares são transferidos de águas normóxicas to hipóxicas e vice-versa.
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