Mysid crustaceans as standard models for the screening and testing of endocrine-disrupting chemicals.
Two species of mysid shrimp, the sub-tropicalMysidopsis bahia and the northern temperateMysidopsis bigelowi, were exposed simultaneously to cadmium (as CdCl2) in a continuous-flow bioassay system to determine the effect on survival and reproductive success. Temperature and salinity were maintained at 21 ± 1°C and 30‰,respectively. The 96-h LC50 was 110 µg ℓ−1 for both species. The 23-day life cycle LC50 forM. bahia was 19.5 µg ℓ−1 and forM. bigelowi the 27-day LC-50 was 14.8 µg ℓ−1. At 10 µg ℓ−1 a series of morphological aberrations were observed in both species at the onset of sexual maturity. Carapace malformations apparently prevented molting after the release of the initial brood and resulted in death of brooding females. As a result, although the initial reproductive rate at this concentration was successful, successive broods could not be produced. For both species in this study the no observed effect concentration was 5.1 µg ℓ−1; the effect concentration was 10.0 µg ℓ−1. Mechanisms were postulated in this study to explain the effect of cadmium on the molting process and on calcification and enzymatic reactions of osmosis.