The effect of eyestalk ablation on haemolymph osmotic and ionic concentrations during acute salinity exposure in the freshwater shrimpMacrobrachium olfersii(Wiegmann) (Crustacea, Decapoda)

摘要

The effect of bilateral eyestalk ablation on haemolymph osmotic and Na+, Cl−, K+, Mg2+and Ca2+concentrations was investigated in the freshwater shrimpMacrobrachium olfersiiduring acute exposure (1, 3, 6, 12 and 24 h) to sea-water of 21 S. Analysis of variance treatment indicated that haemolymph osmotic and Na+, Cl−, K+, Mg2+and Ca+concentrations were affected by exposure time (p≤ 0.01). However, only Na+ was affected by eyestalk ablation (p<0.01), destalked shrimps exhibiting haemolymph Na+concentrations approximately 15 to 30 lower than control shrimps. These results are interpreted to indicate that less Na+enters the haemolymph of eyestalkless shrimps on exposure to seawater of 21 S, presumably resulting from the absence of an eyestalk-located neurofactor. A factor causing the influx of Na+into the haemolymph is thus proposed to be present in the eyestalk ganglionic system of intactMacrobrachium olfersiiin freshwater. Reduction in secretion of the factor may act to reduce Na+entry in high salt environ