The effect of salinity on cadmium toxicity in the estuarine mysid Mysidopsis bahia: roles of osmoregulation and calcium

Abstract

Calcium exerted a sparing effect on Cd 2+ toxicity in the bay mysid, Mysidopsis bahia, although the effect was not as pronounced as effects that were due to Cd 2+-salinity interactions. Molt rate, expressed as number of exuviae recovered per mysid day, was significantly increased by Cd 2+-salinity interaction. Partial correlations of the number of dead mysids with the number of molt casts recovered, when adjusted for the independent effect of salinity on molt rate, were significant for most periods, suggesting that the observed increase in apparent molt rate may actually reflect enhanced sensitivity of post-molt animals to Cd 2+. A slight, but statistically insignificant change in serum osmolality was observed after 24 h exposure to 3·62 μg/liter Cd 2+ at the low test salinity of 12‰ in the first osmoregulation experiment. No effects on hemolymph osmoregulation were observed in the second experiment following exposure up to 48 h to similar Cd 2+ levels at 12–30‰ salinity.