Haemolymph phosphatase activity levels in two fresh-water gastropods exposed to copper

Abstract

Molluscan haemolymph can be considered as a tissue capable of monitoring environmental pollution, and quantitative changes in haemolymph constituents can be taken as reliable indicators for diagnostic purposes. It has been suggested that quantitative determination of the levels of activity of lysosomal enzymes can be employed as an indicator of stress by environmental pollution. In the present study, the activity levels of acid and alkaline phosphatases in the haemolymph of copper-exposed snails were estimated to ascertain the effect of copper on the release pattern of these enzymes, and also to examine its diagnostic value. Acid phosphatase is a lysosomal marker enzyme, and alkaline phosphatase is considered both a lysosomal and a plasma membrane enzyme. Fifty specimens each of Lymnaea acuminata (Lamarck) f. rufescens (Gray) of the size group 18 ± 1 mm, and Indoplanorbis exustus (Deshayes) of the size group 11 ± 1 mm were exposed to each of three sublethal concentrations of copper, i.e., 0.010, 0.015 and 0.020 ppm. The sublethal concentrations were fixed after 96-h LC 50 studies. An equal number of specimens maintained in clean waters served as the controls. The activity of both the enzymes was measured at 2, 6, 12, 24 and 48 h post-exposure. Based on the results obtained it was concluded that (i) copper ions can cause hypersynthesis of lysosomal enzymes, (ii) hypersynthesis of acid and alkaline phosphatases need not take place simultaneously, (iii) copper ions, to a certain extent, can inhibit the activity of both the enzymes, and (iv) activity levels of phosphatases to a great extent are stress indicators.