Swimming behavior and predator avoidance in three populations of Fundulus heteroclitus larvae after embryonic and/or larval exposure to methylmercury

Abstract

We determined effects of embryonic and/or larval exposure to methylmercury (MeHg) on swimming behavior and predator avoidance ability in larval mummichogs ( Fundulus heteroclitus) from a site polluted with heavy metals and organic materials (Piles Creek (PC), NJ) and two reference sites (Tuckerton (TK), NJ and East Hampton (EH), NY). Mummichog eggs and sperm were stripped from ripe females and males captured from the field, and their embryos and larvae were raised in clean sea water or MeHg solution. After hatching, larval spontaneous activity, swimming performance and predator avoidance were tested periodically. Embryonic and/or larval exposure sometimes caused hyperactivity in PC or EH larvae, hypoactivity in TK larvae, and depression of swimming performance in all the three populations. Embryonic and/or larval exposure also increased vulnerability to predation by yearling mummichogs, but the effects of embryonic exposure were transitory. Among the three populations, TK was the least vulnerable to predation by blue crabs (i.e. most resistant to MeHg), which may have been associated with their lower swimming activity induced by MeHg, making them less conspicuous to the predator. The higher prey susceptibility in PC or EH larvae was correlated with their MeHg-induced hyperactivity.