胎生魚夕ケノコメバルの卵発生と仔魚期

Abstract

Sebtases oblongus GUNTHER is a common viviparous scorpaenid fish in Japan. From November to December, 1955 and 1956, the author reared female parent fish incubating fertilized eggs, and observed the development in the egg squeezed from the parent fish. Spawned larvae were also reared for about one month in a glass jar, feeding the brine-shrimp nauplii. On November 23, 1956, a female parent fish (210mm in total length) bearing developing eggs at 16-cell stage (Fig. 1) was caught and kept in an aquarium. In 7 days after being caught, this fish abnormally released all the eggs at 27-myotome stage. On November 29, 1956, another female (208mm) with developing eggs at more advanced stage (Fig. 6) was caught and kept in an aquarium. In 171/2 days after being caught this fish naturally spawned larvae in the tank. Fertilized eggs at the early developing stages are spherical in shape, measuring 1.55-1.60mm in diameter, with a number of orange oil-grobules. In the coures of development, the eggs became larger and changed in shape (Figs. 1-8). Newly spawned larvae (including the one of Fig. 9), measuring 7.25-7.50mm in total length had 27 (8+19) myotomes and swam freely in the glass jar. The melanophores and small xanthophores were distributed on the top of head, on the back of trunk, around the intestine tube, and on the middle part of the tail, but none on the pectoral fins. In 5 or 6 days after being spawned, the larva (7.20mm) consumed all the yolk and began to eat the brine-shrimp nauplii. In 25-30 days after being spawned, the larvae (including the one of Fig. 12), measuring 12-14mm in total length, reached the end of the post-larval stage. All the fins were well formed with a complete set of fin rays (D, VIII-13-14, A, 111-7, P, 16, V, 1-5).