EARLY-LIFE HISTORY OF HEMIGRAPSUS-SANGUINEUS, A NON-INDIGENOUS CRAB IN THE MIDDLE ATLANTIC BIGHT (USA)

The Japanese shore crab Hemigrapsus sanguineus (de Haan) was recently introduced to the northeast coast of the USA. The crab has established intertidal populations extending throughout the Middle Atlantic Eight . This study defines early-life-history characteristics that are germa ne to range extension in this species. Results of the investigation sh owed that the spawning season of H, sanguineus continues for at least 4 mo in the southern Middle Atlantic Eight. This is considerably longe r than the spawning seasons of co-occurring native crabs. Eggs Batch a bout 14 d after extrusion, and females have the potential to produce s everal broods each year. Zoeal larvae are tolerant of a wide range of temperature/salinity combinations, and mean duration of zoeal developm ent ranges from approximately 16 d at 25 degrees C to 55 d at 15 degre es C. At 25 degrees C zoeae are capable of development to the megalopa stage at salinities as low as 15 parts per thousand. At lower tempera tures the zoeae require salinities above 20 parts per thousand. The me galopa stage appears to have more stringent temperature/salinity requi rements, which may restrict H, sanguineus to rocky shores of the coast al ocean and the adjacent high-salinity regions of the estuary. Under these conditions megalopae molt to the first juvenile stage in approxi mately 25 d post hatching. Newly metamorphosed crabs reach the fifth j uvenile instar in 35 d. Dry-weight growth of zoeal larvae and early st age juveniles is exponential at respective rates of 23 and 8 % of body weight per day.