飼育下におけるアマミホシゾラフグの卵と仔稚魚の成長およびフグ科他種との比較

抄録

Torquigener albomaculosus has been found at depths of 10–30 m on the southern coast of Amami-Oshima Island, Kogoshima Prefecture, and at 100 m off Hamahika-jima Island, Okinawa Prefecture. However, there have been no reports on the morphology and pigmentation of the larvae and juveniles. Eggs of To. albomaculosus were collected from the southern coast of Kakeroma-jima Island, Kagoshima Prefecture, at a depth of 32 m, and development of eggs, larvae, and juveniles were observed in captivity. Comparisons were made with previous reports on the development of pufferfish species inhabiting Japan and adjacent seas. Eggs were 0.96 ± 0.02 mm (n = 20) in size, spherical in shape, colorless, transparent, demersal, and adhesive. Immediately after hatching, larvae were 2.43 ± 0.08 mm (n = 11) in total length and the number of myomeres was 8 + 11 = 19. Dendritic melanophores were present on the dorsal surfaces of the head and body, dorsal and ventral sides of the abdominal cavity, but were absent from the caudal region. The mouth and anus had already opened but the yolk still remained. The yolk was absorbed within 2 days of hatching. At 19 days after hatching, ossification of teeth began in the upper and lower jaws. Simple small spinules appeared on the gill covers and abdomen. They were pointed at the distal end and not divided. Black melanophores were distributed from the snout to the region between dorsal- and anal-fin bases, absent from the caudal region. The larvae became juveniles 36 days after hatching. At 61 days after hatching, the sides and dorsal surface of the body were silver, the ventral surface was yellow, and the area covered by small spinules extended posteriorly beyond the dorsal and anal fins. The larvae and juveniles of To. albomaculosus can be distinguished from those of other pufferfishes inhabiting the waters around Japan by the absence of black melanophores on the caudal region, the distribution and development process of small spinules, and body color.