マフグの成熟促進,卵内発生と飼育による仔稚魚の形態

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The induction of ovarian maturation and early development of the puffer Takifugu por-phyreus (Temminck et Schlegel) are described. The brood fish were collected off the coast of Shozanbetsu in northwestern Hokkaido in late June 1986. To each 1kg of body weight of the female, 6mg of acetone-dried pituitary of silver carp was injected to induce ovarian matu-ration, which took place in 79 to 96h at a water temperature of 14.2-15.6°C. The eggs obtained by hormone injection were artificially fertilized with milt from a collected male. The incubation period was about 142h at a water temperature of 15.3-21.0°C. The hatched larvae were fed with rotifers Artemia nauplii and fish meat, and reared for a period of 216 days. The eggs were spherical, 1.28±0.04mm in diameter, demersal and adhesive, nontrans-parent and milky white, containing a cluster of small oil-globules. Newly hatched larvae, measuring 2.53±0.09mm TL, had 8+15=23 myomeres. Absorption of the yolk was completed four days after hatching, when the larvae attained 3.42±0.17mm TL. In a 20-day-old specimen, 13mm TL, the complements of fin rays were completed on all the fins and fish reached the juvenile stage. At the early stage of the juvenile, puffers attacked each other violently and injured the caudal fins of their opponents.