Abstract
The objects of this study are to clarify the temporal and areal distribution of larvae of Pinnixa rathbuni in Ise Bay and its neighbouring coastal waters, and to determine to what extent the final ecdysis into megalops takes place in water without drifting into the oceanic environment.
The larvae were found in November to March of the following year. Early zoeal larvae appeazed at first abundantly in November, and then abundant megalops were found in February of the next year, with the result that the length of the larval period in the plankton was approximately 120 days. This period is from two to four times that required for the larval development of the pinnotherid crabs synbiotic with invertebrates.
The larvae were found abundantly in Ise Bay and Mikawa Bay, but they were not met with in the open coastal and oceanic waters except the area near the mouth of the bays. This suggests that the larval dispersal into the open coastal and oceanic region does not considerably influence the loss of the larval population from the bays.
