EFFECTS OF EMBRYONIC EXPOSURE TO METHYLMERCURY ON LARVAL PREY CAPTUREABILITY IN THE MUMMICHOG, FUNDULUS-HETEROCLITUS

Embryos of the mummichog (Fundulus heteroclitus) were exposed to 2, 5, or 10 mu g/L methylmercury (meHg) throughout development; these are c oncentrations below those which cause teratological effects in this sp ecies. After hatching, larvae were maintained in clean seawater and te sted for prey-capture ability, using Artemia salina nauplii. Larvae th at had been exposed to 10 mu g/L methylmercury (and in two out of thre e trials, 5 mu g/L) initially exhibited slower prey-capture ability th an did the other groups. This is an indication of a subtle functional impairment due to the toxicant (''behavioral teratology''). However, t he effect was transitory, and by about 1 week after hatching the prey capture of these larvae equalled that of the controls and the other tr eated groups. Growth of these larvae was also comparable to that of co ntrols. The exposure may have caused retardation of neurological devel opment, which was subsequently compensated for, and therefore no long- lasting effects were produced. In the field, however, embryos exposed to toxicants would probably continue to be exposed as larvae, and migh t not have the opportunity to recover from the deleterious effects, bu t rather might have them augmented.