Effects of chemical cues on metamorphosis of the Asian shore crab Hemigrapsussanguineus, an invasive species on the Atlantic Coast of North America

Abstract

The Asian shore crab Hemigrapsus sanguineus (Family Grapsidae) has been recently introduced to the east coast of North America. We present the results of an investigation of the response of postlarvae (megalopae) of H. sanguineus to putative water-soluble cues associated with newly colonized habitat in the Middle Atlantic region of the USA. Specifically, we tested the response of megalopae to exudates from adult H. sanguineus and to exudates from co-occurring native crabs Panopeus herbstii and Dyspanopeus sayi (Family Xanthidae). In addition, we tested the response of P. herbstii and D. sayi megalopae to exudates from adult H. sanguineus and to conspecific exudates. In a separate set of experiments, we also investigated the response of H. sanguineus megalopae to cues associated with substrata found in potential settlement sites. In all experiments, response was measured as the time to metamorphosis of megalopae exposed to the various exudates, as compared to megalopae maintained in filtered offshore seawater. Megalopae of the two native species responded to cues produced by conspecific adults. In addition, P. herbstii megalopae responded to cues produced by adult H. sanguineus. In contrast, H. sanguineus responded only to cues produced by conspecific adults and to cues associated with biofilm-covered substratum from natural rocky intertidal habitat. Thus, it appears that once established, adult H. sanguineus produce cues that promote gregarious settlement, but that initial invasion is not facilitated by response to cues produced by native xanthid crabs. Rather, this initial invasion may be facilitated by cues associated with more general characteristics of rocky intertidal environment.