Abstract
Aplysia juliana at different growth stages from the hatched veliger to the adult was investigated to clarify ontogenetic allometries of the maximum shell length to the expanded body length, of the maximum shell length to the maximum aperture breadth, of the maximum shell length to the maximum aperture length, and of the maximum aperture length to the maximum aperture breadth. The relation between the shell length and the body length was expressed by two straight lines which intersected at a fairly grown juvenile stage causing the loss of larval operculum. This indicates that, in the planktonic veligers and the operculum-bearing early juveniles which have finished metamorphosis, the shell length increases in proportion to the body length. Whereas, in the juveniles after the loss of operculum and the adults, the body grows at a faster rate than the shell. On the other hand, both of the relations between the aperture length and the shell length and between the aperture breadth and the aperture length were expressed by three straight lines which intersected at the metamorphic stage and at a juvenile stage slightly after the loss of operculum. However, the relation between the aperture breadth and the shell length was expressed by a straight line throughout the life cycle of the animal.
