MOLTING OF MEGALOPAE FROM THE BLUE-CRAB CALLINECTES-SAPIDUS - EFFECTSOF OFFSHORE AND ESTUARINE CUES

Postlarvae (megalopae) of the blue crab Callinectes sapidus (Rathbun) are transported from shelf/coastal areas into estuaries where they met amorphose (molt) to the first crab stage. This study tested the hypoth esis of Wolcott & DeVries (1994; Mar. Ecol. Prog. Ser. 109: 157-163) t hat metamorphosis is delayed in offshore water and accelerated by cues associated with estuaries. The effects of offshore water, estuarine w ater, adult blue crab odors, eelgrass Zostera marina and salinity were tested by measuring the time until molting. Test megalopae were colle cted as they entered an estuary. Molting was slowest in offshore water , faster in estuarine water and fastest in the presence of eelgrass. A dult odors had no effect on molting, however, a decrease in salinity d ecreased molting time. These results support the hypothesis and indica te blue crab megalopae should preferentially undergo metamorphosis in estuarine seagrass beds.