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

Bernardo Baldisserotto,Rodrigo Roubach,Levy Carvalho Gomes,Carlos Eduardo Copatti,Edsandra Campos Chagas,Richard Philip Brinn

doi:10.1590/s1679-62252009005000002

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 Ca2+ concentrations than black waters and neutral pH, and "clear waters", with two fold higher Ca2+ concentrations than black waters and also neutral pH. Therefore, the aim of the present study was to analyze Ca2+ 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 Ca2+ 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 Ca2+ loss only in the first 2 h of experiment. However, transfer from black or acidic black water to white water led to only net Ca2+ 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 Ca2+ loss, while the amount of Ca2+ in the ion-rich white water seems adequate to prevent Ca2+ loss after transfer. Therefore, transfer of tamoatás between these Amazonian waters does not seem to result in serious Ca2+ disturbance.

Highlights

Tributaries in the Amazon basin exhibit a range of different chemical characteristics
Tamoatás transferred from the tanks of ionpoor well water to flux chambers containing ion-poor acidic black water showed significantly greater Ca2+ loss than those transferred to the other waters during the first two hours of exposure
Fish transferred from ion-poor black water and those maintained in well water presented low net Ca2+ efflux, while those transferred to white water showed net Ca2+ influx

Summary

Introduction

Tributaries in the Amazon basin exhibit a range of different chemical characteristics. They were classified into three major types on the basis of their appearance as ‘‘white waters’’, ‘‘clear waters’’ and ‘‘black waters’’ (Gibbs, 1972). The white water (brownish in reality) of the Solimões River has a high amount of suspended sediments (Tardy et al, 2005), neutral pH and is comparatively rich in ions (Aucour et al, 2003). The Negro River is called “black water river”, with much lower ion concentrations (5-20 fold lower than white water), pH of 5.0-6.0 and greater amounts of dissolved organic matter (Aucour et al, 2003; Mortatti & Probst, 2003). Clear water is found in few rivers like the Tapajós River and has two fold higher Ca2+ concentrations than black waters and neutral pH (Konhauser et al, 1994)

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Conclusion