EARLY LIFE HISTORY OF THE OYSTER CRAB, PINNOTHERES OSTREUM (SAY)

¹ Virginia Fisheries Laboratory, Yorktown

1. The early stages of Pinnotheres ostreum have been reared in the laboratory from the egg to the first crab.

2. There are four zoeal stages and one megalops stage. The four zoeal instars are distinguished by having 4, 6, 8, and 10 swimming hairs on the exopodites of both maxillipeds.

3. The time required for development from the early egg (from orange-colored egg mass) to the first crab instar was 38 days. From hatching to the first crab required 25 days.

4. The first crab being only 0.6 mm. wide, at least one more instar must intervene before P. ostreum reaches the "first stage" described by Stauber as the youngest crabs which invade the oyster.

5. Oyster crabs are widely distributed and abundant in Virginia waters. They tend to keep oyster meats in relatively poor condition, but have never been observed to cause mortality of oysters in Virginia.