Changes in gill ultrastructure and haemolymph chloride concentrations in the crayfish, Astacus astacus, exposed to de-acidified aluminium-rich water

Abstract

Individuals of the crayfish, Astacus astacus, exposed to aluminium-rich, de-acidified water in a crayfish farm (acid-reactive aluminium fraction 180 μg All −1, labile aluminium fraction 20 μg All −1, pH 6.7) showed symptoms such as bulging of the integument between the carapace and the abdomen, and browning of the gills, generally followed by death in the pre-molt or molting stages. Exposed individuals had a significant decrease (≈35%) in haemolymph chloride concentrations compared to unexposed control individuals. Examination of the gills by transmission electron microscopy (TEM) revealed severe morphological changes in gill epithelia and underlying tissue. By X-ray microanalysis a pronounced accumulation of aluminium was detected on the gill surface of exposed specimens. This aluminium probably interferred with the normal ion-exchange mechanisms and led to crayfish death.