Survival and chloride ion regulation of the porcelain crab Petrolisthes armatus exposed to mercury.

Acute toxicity bioassays conducted at various salinities demonstrated that mercury (as mercuric chloride) at low concentrations was lethal to Petrolisthes armatus. Ninety-six hour LC50 values varied from 50 to 64 parts per billion (ppb) of mercury, depending on test salinities. Lower salinities decreased the time to death of mercury-exposed crabs. Differences in survival after 96 hr due to salinity were not statistically significant. Blood chloride concentrations were regulated hyperchloride to the medium at low salinities and hypochloride to the medium at high salinities by acclimated crabs. The salinity isochloride to blood was 22 parts per thousand S. Transfer of crabs from 15 parts per thousand S to salinities ranging from 7 to 35 parts per thousand S resulted in new steady-state chloride levels within 12 hr. Exposure to 50 ppb mercury did not alter chloride ion regulation of either acclimated crabs or crabs adjusting to new salinities.