Salinity tolerance of Darwinula stevensoni (Crustacea, Ostracoda)

Relatively few laboratory tests of the effect of salinity on ostracod speci es exist. Here we report the results of acute and chronic bioassay tests to study the effects of six different salinities (deionised water, 22, 120, 9 22, 9600 muS.cm(-1), and marine water) on survival and reproductive paramet ers (number of eggs and hatching). The test was carried out on individuals of Darwinulla stevensoni from different localities characterised by differe nt salinity (from 111 muS.cm(-1) at Monate, Italy, to 3440 muS.cm(-1) at Ho llandersgatkreek, Belgium). Individuals belonging to three life cycle stage s were used (pre-adult, adult, ovigerous). Surprisingly low mortality was o bserved in all treatments and for all life stages, independently of populat ion of provenance. Only in marine water was mortality noticeable although r eproductive parameters were hardly affected. Given the high genetic homogen eity of the species, our re suits seem to support the hypothesis of high ph enotypic plasticity for salinity tolerance in D. stevensoni.