Development and behavior of megalopae of the non-native crab Hemigrapsus sanguineus in response to chemical cues from coastal fishes

Abstract

Understanding the invasibility of marine species with complex life cycles requires examination of the ecology of both larval and adult stages. The goal of our study was to determine whether several species of coastal fish native to the western North Atlantic Ocean can consume megalopae of the nonindigenous Asian shore crab Hemigrapsus sanguineus and, if so, whether megalopae can respond to chemicals from potential fish predators by either molting faster to a benthic crab stage or exhibiting avoidance behaviors. Laboratory predation experiments showed that all fish species tested (cunner, Tautogolabrus adspersus; tautog, Tautoga onitis; grubby, Myoxocephalus aeneus; scup, Stenotomus chrysops; and mummichog, Fundulus heteroclitus) consumed H. sanguineus megalopae. When megalopae were reared in seawater in which fish or adult crabs had been housed, fish chemical cues had no effect on molting rate whereas chemicals from adult conspecific crabs accelerated molting. Behavioral responses of H. sanguineus megalopae to chemicals from fish and crabs were tested in still and flowing water. In still water, megalopae moved away from chemicals from T. adspersus and M. aeneus. In flowing water, chemicals from T. onitis caused a behavioral reaction that led to enhanced movement away from the source of the cue. All 3 species are related to fishes present in the native range of H. sanguineus. In contrast, chemicals from adult crabs and F. heteroclitus had no effect on behavior of megalopae. Behavioral responses of H. sanguineus megalopae to chemical cues from coastal fish species might function as antipredator strategies that enhance survival of this nonindigenous species.