Net ion fluxes in the facultative air-breather <Emphasis Type="Italic">Hoplosternum littorale</Emphasis> (tamoata) and the obligate air-breather <Emphasis Type="Italic">Arapaima gigas</Emphasis> (pirarucu) exposed to different Amazonian waters |
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Authors: | Bernardo Baldisserotto Carlos E Copatti Levy C Gomes Edsandra C Chagas Richard P Brinn Rodrigo Roubach |
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Institution: | Departamento de Fisiologia e Farmacologia, Universidade Federal de Santa Maria, Santa Maria, RS, Brazil. bernardo@smail.ufsm.br |
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Abstract: | Fishes that live in the Amazon environment may be exposed to several kinds of water: black water (BW), acidic black water
(pH 3.5) (ABW) and white water (WW), among others. The aim of the present study was to analyze net ion fluxes in the facultative
air-breather Hoplosternum littorale (tamoata) and the obligate air-breather Arapaima gigas (pirarucu) exposed to different types of water. Fishes were acclimated in well water and later placed in individual chambers
containing one type of water for ion flux measurements. After 4 h, the water in the chambers was replaced by a different type
of water. The transfer of both species to ABW (independent of previous water exposure) increased net ion loss. Tamoatas transferred
from ABW to BW or WW presented a net ion influx, but pirarucus showed only small changes on net ion efflux. These results
allow us to conclude that tamoatas and pirarucus present differences in terms of ion regulation but that the general aspects
of the ion flux are similar: (1) exposure to ABW led to net ion loss; (2) transfer from BW to WW or vice-versa induced only
minor changes on net ion fluxes. These observations demonstrate that any osmoregulatory difficulties encountered by either
species during changes between these latter two waters can be easily overcome. |
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Keywords: | Acidic water Amazon Negro River Osmoregulation Solim?es River |
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