Metamorphosis of the estuarine crab Rhithropanopeus harrisii: effect of water type and adult odor

Larvae of many estuarine crabs are transported to coastal/offshore areas where they develop and subsequently return to the estuary as postlarvae (megalopae), which settle and metamorphose. For these species, it is important for megalopae to be able to differentiate between offshore and estuarine areas as sites for metamorphosis. In contrast, larvae of the crab Rhithropanopeus harrisii (Gould) are retained in estuaries near the adult habitat throughout development. Although previous studies have demonstrated that the rate of metamorphosis of the megalopal stages of several estuarine crabs is accelerated when exposed to estuarine cues, it was hypothesized that metamorphosis of R, harrisii postlarvae is not affected by exposure to offshore and estuarine waters but is accelerated by exposure to adult odor cues. Metamorphosis of R. harrisii megalopae was accelerated upon exposure to estuarine water and delayed in offshore water at salinities ranging from 5 to 25 PSU. Time to metamorphosis in both water types increased as the salinity decreased. Adult odor also accelerated metamorphosis. Thus, the test hypothesis was only partially supported, and the results indicate that differentiation between offshore and estuarine areas for metamorphosis is common among estuarine crabs regardless of their patterns of larval development.