Calcium fluxes in Hoplosternum littorale (tamoatá) exposed to different types of Amazonian waters

Abstract

Fishes that live in the Amazonian environment may be exposed to several kinds of waters: ''black waters'', containing high dissolved organic carbon and acidic pH, ''white waters'', with ten fold higher Ca 2+ concentrations than black waters and neutral pH, and ''clear waters'', with two fold higher Ca 2+ concentrations than black waters and also neutral pH. Therefore, the aim of the present study was to analyze Ca 2+ fluxes in the facultative air-breather Hoplosternum littorale (tamoatá) exposed to different Amazonian waters. Fishes were acclimated in well water (similar to clear water) and later placed in individual chambers for Ca 2+ fluxes measurements. After 4 h, water from the chambers was replaced by a different type of water. Transfer of tamoatás to ion-poor black or acidic black water resulted in net Ca 2+ loss only in the first 2 h of experiment. However, transfer from black or acidic black water to white water led to only net Ca 2+ influxes. The results obtained allowed us to conclude that transfer of tamoatás to ion-poor waters (black and acidic black water) led to transient net Ca 2+ loss, while the amount of Ca 2+ in the ion-rich white water seems adequate to prevent Ca 2+ loss after transfer. Therefore, transfer of tamoatás between these Amazonian waters does not seem to result in serious Ca 2+ disturbance.Os peixes que vivem na Amazônia são expostos a vários tipos de água: águas pretas, contendo grande quantidade de carbono orgânico dissolvido, águas brancas, com concentração de Ca 2+ dez vezes maior que as águas pretas e pH neutro, e águas claras, com concentração de Ca 2+ duas vezes maior que as águas pretas e pH também neutro. Dessa forma, o objetivo deste trabalho foi analisar o fluxo de Ca 2+ no peixe de respiração aérea facultativa Hoplosternum littorale (tamoatá) exposto a diferentes tipos de águas amazônicas. Os peixes foram aclimatados em água de poço artesiano (semelhante à água clara) e depois colocados individualmente em câmaras para medir o fluxo de Ca 2+ . Após 4 h, a água das câmaras foi trocada por um tipo diferente de água. A transferência do tamoatá das águas pobres em íons água preta e preta ácida ou da água branca, rica em íons, para as águas preta e preta ácida, pobres em íons, resulta em uma perda de Ca 2+ apenas nas duas primeiras horas de experimento. Entretanto, a transferência da água preta e preta ácida, para a água branca resulta em um influxo de Ca 2+ . Os resultados obtidos nos permitem concluir que a transferência do tamoatá para as águas preta e preta ácida, pobres em íons, leva a uma temporária perda de Ca 2+ , e a quantidade de Ca 2+ na água branca, rica em íons, é adequada para prevenir sua perda após a transferência. Sendo assim, a transferência do tamoatá entre as águas estudadas não resulta em sérios distúrbios no Ca 2+ .

Growth and biochemical variables in Amazon catfish ( Pseudoplatystoma reticulatum ♀ x Leiarius marmoratus ♂) under different water pH

“…Fish inhabit different aquatic environments, and changes in water quality parameters may compromise their development and welfare. For example, in Amazon basin there are acid or alkaline water environments and fish can migrate from one river to another mainly in the flood season (Baldisserotto et al 2009). These changes can trigger stress and, consequently, reduce growth and impair physiological homeostasis (Barcellos et al 2011).…”

Expression of Ion Transporters and Na+/K+-ATPase and H+-ATPase Activities in the Gills and Kidney of Silver Catfish (Rhamdia quelen) Exposed to Different pHs

“…In fish exposed to low pH, acid loading through the gills is a source of acid-based disturbance, with increased H + and NH 4 + excretion in the urine to compensate for this problem [18]. In addition, it increases the ion loss [19,20], which decreases plasma ion levels and the pH [18,21]. Very acidic pH levels impair branchial protein junctions, which increases paracellular ion loss [22,23].…”

“…The silver catfish inhabits different FW environments from Central and South America [30] and has economic and ecological importance [20]. This species can survive acute changes in the 4.0 to 9.0 pH range for 96 h without significant mortality [31], but plasma and urinary Na + and Cl − levels were altered after 24 h exposure to different water pH [18].…”