EFFECTS OF MERCURY EXPOSURE ON IONIC REGULATION IN THE CRAYFISH ORCONECTES-PROPINQUUS

Hemolymph sodium, potassium and calcium concentrations were determined in crayfish (Orconectes propinquus) exposed to (HgCl2)-Hg-203 mixed w ith food to a concentration of 1 mug Hg g-1. Dummy-fed animals were ex posed to Hg-dosed food wrapped in dialysis tubing to control for mercu ry reaching the animals via leaching from food to water. Hemolymph ana lyses were made following 14-day Hg exposures and again after a furthe r 21-day 'depuration' period during which all animals we're fed Hg-fre e food After 14 days, the mercury reached a concentration of 0.175 mug g-1 in the hepatopancreas and approximately half this level in the gi lls of Hg-fed animals. No depuration occurred from the hepatopancreas although the gills lost approximately two-thirds of their labelled mer cury during the depuration period Hemolymph sodium concentrations in H g-exposed crayfish, both fed and dummy-fed, after 14 days were signifi cantly lower than in Hg-free controls and remained low following the 2 1-day depuration period Hemolymph calcium concentrations were lower in Hg-fed animals than in dummy-fed and control animals after 14 days al though calcium levels rose in all treatments after 35 days. This may h ave been due to the incidence of pre-molt animals in all experimental groups, although the relationship between this and mercury exposure wa s not established unequivocally. Hemolymph potassium levels showed no differences between treatments.