Drinking and osmoregulation in the mangrove crab Ucides cordatus following exposure to benzene.

In benzene-exposed Ucides cordatus acclimated for 96 h to 9 and 34 per thousand SW, haemolymph, urine and gastric juice are isosmotic with each other, but differ significantly in osmolality from external media. In both salinities, under benzene action, urine K+ excretion and calcium absorption are increased significantly, whereas Na+ absorption and Mg2+ excretion show U/B ratios similar to control values. In 9 per thousand SW, some ionic exchanges via benzene-exposed gills are possibly hastened. Benzene exposure decreases significantly branchial chamber water osmolality, [Na+] and [K+], whereas [Ca2+] and [Mg2+] are unaffected. However, faster medium exchange presumably occurs in 34 per thousand SW, both crab groups show branchial chamber water osmotic and ionic concentrations similar to surrounding medium. Benzene exposure unaffected gastric juice composition. In both media, [Ca2+] and [Mg2] accumulate several times higher than surrounding media, and [Na+] and [K+] are significantly hypo-ionic to haemolymph. Na+ and K+ G/H ratios are lower in crabs acclimated to 34 per thousand SW than in crabs acclimated to 9 per thousand SW. Drinking rates are enhanced by benzene exposure and are higher at 34 per thousand SW than in seawater isosmotic with the haemolymph (26 per thousand SW). Benzene exposure affects significantly osmoregulatory capability, slowing haemolymph dilution after transfer to clean 9 per thousand SW. Lower haemolymph dilution rate accounts for higher osmolality, but 48 h after transfer there is no recovery like in control crabs. Haemolymph transfusion experiments suggest an interaction among effects of benzene and hormonal factors, possibly on water influx.