On the development of eggs and rearing of larvae of a puffer, Fugu (Higanfugu) pardalis (Temminck et Schlegel)

Fugu pardalis (Temminck et Schlegel) is a common puffer in Japan, abundantly caught near shore in March. The artificial insemination of this fish was carried out on March 10 and March 25, 1955, at Meinohama, Fukuoka City, and the hatched larvae were reared in glass jars, fed only with the brine shrimp (Artemia) naupli. The egg is demersal and strongly adhesive, and spherical in shape, measuring 1.17～1.32 mm in diameter. The yolk is light yellowish, with one cluster of small oil-globules, each measuring 0.008～0.036 mm in diameter. A wavy network pattern is observed on the surface of the egg membrane. The fundamental process of development is much the same with the other teleostean eggs (Plate 12, 1～11 ). Hatching took place from 21 to 40 days after insemination at the water temperature 11.0～17.0℃, and most of the larvae emerged from the egg head first (Fig. 1), although in a few cases the tail came first. Newly hatched larvae (Plate 12, 12,13), measuring 2.64～3.20 mm in total length, with myotome number 9～10+13～18=23～27, have large yolk sac, containing oil-globules. The melanophores were distributed on the head and yolk surface, especially on the anterior portion of the tail. Grass green pigment cells were found on similar places as the melanophores, except on the yolk surface. The larvae entirely consumed the yolk in a week, and the remained oil-globules in 10 days. About 5～15％ of the reared larvae survived 3 weeks. In 50 days after hatching, one of the reared larvae attained 13.09 mm in total length, with the small granules all over the skin except the snout and caudal peduncle. Abnormal larvae (Fig. 4), with extraordinary swelled skin, were found from 2 to 7 weeks after hatching.1. 福岡市能古島に於ける1955年のヒガンフグの産卵期は3月中・下旬で, 成魚は岸近く集つて産卵すると思われた, 人工授精は3月10日と3月25日とに行つた. 2. 卵は直径1.17～1.32mmのほぼ球形をなした粘着卵で, 卵黄の一端には小油球群があり, 厚い卵膜表面には網目をした波状の小搬がある. 3. 親魚孕卵数は 36,000～166,000 で一度に産出されると考えられる. 4. 卵は比重の変化に対し抵抗が強い. 水槽中では水温11.0～17.0℃ で21日後より孵化が始まつたが, 天然でもほぼこれに近い日数を要すると思われる. 仔魚は多く頭部を先にして卵より出る. 5. 孵化直後の仔魚は全長2.64～3.20mmで黒色胞は頭頂・吻端・腹部・肛門後方等に発達し, 黄緑色胞も腹部を除きほぼ同じ場所にある. 6. 仔魚は約1週間で卵黄を, 10日間で油球を吸収し終り, 22日後迄に約 5～15％ が生残つた. 7. 仔魚の黒色胞は尾柄部に於いて特に発達し, 黒褐色の色胞が背部・腹面等体の大部を占め, 黄緑色胞は全身に分布する. 8. 餌としては熱帯魚飼育に用いる Brine shrimp (Artemia) の nauplius 幼生のみを与え, 最長62日間飼育できたが成長の最もよかつた例は50日後に全長13.09mmの稚魚になつた. 9. 全長 12.24～13.09mm の稚魚は吻の各側の鼻孔は未だ2箇にならず, 背鰭・胸鰭・尾鰭に黒色胞があり, 吻端部及び尾柄部を除く皮膚全面に小瘤状物がある. 10. 飼育中Fig.4に示す如き異常に膨れた仔魚が現われた. これらは孵化後2週間から7週間の仔魚に見られ, 一度膨れると元に戻らずに多く2週間以内に死んだがこの原因は不明である