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Título: Ion and acid-base balance in three species of Amazonia fish during gradual acidification of extremely soft water
Autor(es): Rod W Wilson
Christopher Michael Wood
Richard J Gonzalez
Marjorie Lynn Patrick
Harold Bergman
Anne Narahara
Adalberto Luis Val
Assunto: Peixes
Regulação iônica
ISSN: 1522-2152
Revista: Physiological and Biochemical Zoology
Volume: 72
Resumo: Sensitivity to acid water was assessed in three species of Amazonian fish that encounter naturally acidic blackwaters to differing degrees in the wild: tambaqui (Colossoma macropomum),matrincha (Brycon erythropterum), and tamoata ́(Hoplosternum littorale), in decreasing order of occurrence in blackwater. Fish were exposed to a graded reduction in water pH, from pH 6 to 5 to 4 to 3.5, followed by return to pH 6. Fish were exposed to each new pH for 24 h. During these exposures, net transfers of ions (Na1,K1,Cl2, and Ca21) and acid-base equivalents to and from the external water were used as physiological indicators of acid tolerance. Exposure to pH 5 had a minimal effect on net ion fluxes. Significant net losses of all ions (except Ca21)were recorded in all three species during the first few hours of exposure to pH 4. However, ion balance was usually restored within 18 h at pH 4. Exposure to pH 3.5 caused even greaterion losses in all three species and proved to be acutely lethal to tamoata ́ . Matrincha sustained irreversible physiological damage at pH 3.5, as ion fluxes did not recover following return to pH 6 and there was some mortality. Tambaqui suffered the least ionoregulatory disturbances at pH 3.5 and was the only species to make a full recovery on return to pH 6. In all species, there was a tendency for ammonia excretion to increase at low water pH, but even at pH 3.5, there was no significant net uptake of acid from the water. Overall, there was a strong relationship between the magnitude of ionic disturbances and the lethality of exposure to low pH. The relative insensitivity of the ionoregulatory system of tambaqui to low pH indicates that this is a feature of fish native to blackwater systems rather than one that is common to all Amazon fish.
ISSN: 1522-2152
Aparece nas coleções:Coordenação de Biodiversidade (CBIO)

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