Growth characteristics of the early juveniles of Aplysia juliana collected in a cold season were investigated. The juveniles in the earliest stage examined were 0.47-0.49 mm in maximum shell length, corresponding to approximately 3.7-fold of that of the veliger hatched. On the basis of their morphological and behavioral features, the earliest juveniles collected were defined to be immediately after metamorphosis. The juveniles cast off the larval operculum when their shells reached the length of 1.05-1.28 mm. Adult features such as the flat shell, parapodia, folded cephalic tentacles, rhinophores and amber body color develop with the growth of the juveniles. The captured juveniles which completed the metamorphosis, cast off the operculum and developed aforementioned adult features, were far larger in body size than those reported for several species of aplysiids in culture. This seems due to the effect of low temperature in the field where the juvenile in this species grows.
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