Effect of Mercury on Survival, Metabolism and Behaviour of Larval Uca Pugilator (Brachyura)

A battery of tests was used to determine the effects of three dilute mercuric chloride solutions on larval stages (Zoea I, III, V) of the fiddler crab Uca pugilator (Bosc). The influence of both acute and chronic exposures on viability, oxygen consumption, and swimming activity was measured. No stage V and only a few stage I or III larvae were able to survive a concentration of 9 * 10-7 M HgCl2 (0.18 ppm Hg) longer than 24 hr; an exposure as short as 6 hr resulted in reduced metabolism and swimming rate of all stages. Although concentrations of 9 * 10-9 M HgCl2 (0.0018 ppm) and 9 10-11 M HgCl2 (0.000018 ppm) were sublethal, 24-hr exposures did affect metabolism and swimming. Some larvae reared in the more dilute mercury solutions developed to the megalopa stage, but survival was reduced in relation to the mercury concentration. The data from all tests suggest that toxicity of mercury increases with larval age.