Salinity tolerance ofDarwinula stevensoni(Crustacea, Ostracoda)

Abstract

Relatively few laboratory tests of the effect of salinity on ostracod species exist. Here we report the results of acute and chronic bioassay tests to study the effects of six different salinities (deionised water, 22, 120, 922, 9600 μS-cm -1 , and marine water) on survival and reproductive parameters (number of eggs and hatching). The test was carried out on individuals of Darwinula stevensoni from different localities characterised by different salinity (from 111 μS-cm -1 at Monate, Italy, to 3440 μS-cm -1 at Hollandersgatkreek, Belgium). Individuals belonging to three life cycle stages were used (pre-adult, adult, ovigerous). Surprisingly low mortality was observed in all treatments and for all life stages, independently of population of provenance. Only in marine water was mortality noticeable although reproductive parameters were hardly affected. Given the high genetic homogeneity of the species, our results seem to support the hypothesis of high phenotypic plasticity for salinity tolerance in D. stevensoni.

Low genetic variability in the ancient asexual ostracodDarwinula stevensoni

“…In D. stevensoni the experimental testing of salinity and oxygen deprivation tolerance did not reveal differences among different genotypes and suggested a general purpose genotype for the species (Gandolfi et al, 2001c;Rossi et al, 2002;Van Doninck etal, 2002). An association has been found only between the most common genotypes found in a habitat and starvation resistance (Rossi et al, 2002).…”

Spatial segregation of Darwinula stevensoni (Crustacea: Ostracoda) genotypes in lentic and lotic habitats of Northern Italy

“…We have described a very high tolerance of both homozygous and heterozygous genotypes from lacustrine and riverine habitats to conductivity variation and to long-term hypoxia (Gandolfi et al 2001c;Rossi et al 2002). Females from lotic habitats have a smaller clutch size and lower hatching percentage than females from lentic habitats (Gandolfi et al 2001b).…”

Interpreting the Tyrrhenocythere (Ostracoda) signal from Palaeolake Kopais, central Greece

“…The number of ostracod shells present within a sample is often a re ection of salinity, such that in hypersaline waters (salinity >60% ) ostracod assemblages may be monospeci c (De Deckker & Forester 1988). Salinity in Palaeolake Kopais can be inferred from two of the taxa identi ed to species level: (1) C. angulata meridionalis, which has a preference for oligosaline waters but will tolerate up to 14% (De Deckker in Anadón et al 1986); and (2) D. stevensoni, which preferentially inhabits waters with µ1% salinity but can tolerate up to 15% (Gandol et al 2001).…”