On the egg development and hatched larvae of a Scorpaenoid fish, Pterois lunulata Temminck et Schlegel

Pternis lunulata Temminck et Schlegel is a well known Scorpaenoid fish by its beautiful coloration and poisonous spines. It is widely distributed in tropical Pacific extending to southern Japan. The authors carried out artificial insemination of this fish on August 28, 1954, at Tamanoura Cho, Goto Islands, Nagasaki Prefecture, Kyushu, and observed the egg development and hatched larvae. The ovary of this fish was composed of two egg masses, one of which consisted of fully matured eggs inbedded in a gelatinous substance, the other was of immature eggs without gelatinous substance and situated inner part of the former. It seemed to us that the matured egg mass would be spawned, as some previous authors reported, in a pair of egg balloons. The presence of the immature egg mass, seemed to denote the repeated spawning by the same female in one season. The egg and the gelatinous substance are colorless, transparent and bouyant. The shape of the egg is almost spherical, measuring 0.81～0.83 mm in diameter, with a single oil globule measuring 0.16～0.17 mm in diameter. The hatching took place in 24 hours at the water temperature 27～30℃, when the entire egg was still without pigment. The newly hatched larva was 1.52～1.58 mm in total length with the myotomes 11+16=27 (vertebral number of this fish is 9+15=24) (Fig. 1, g). Two days after hatching the larva attained 2.3～2.5 mm in total length, when the first appearance of the melanophores was observed on the eyes and middle of the tail (Fig. 1, i). In 4 days the yolk and oil globule were entirely consumed but the length of the larva did not change. The pectoral fins were well developed, fan like in shape. marginally pigmented by the melanophores. Number of myotomes was 8+18=26 (Fig. 1, j). The larva 12 hours or more after hatching showed peculiar deformation as is shown in Fig. 1, h, when preserved in 10 % formalin solution.ミノカサゴ Pterois lunulata Temminck et Schlegel はフサカサゴ科 Scorpaenidae に属する魚で, 本州中部以南から太平洋の温, 熱帯域の岩礁性沿岸に棲息し, 全長270mm に達する. 美麗な色彩と毒棘を持つている事によりよく知られている. 我国近海に産するミノカサゴ属の魚は本種のほかに3種が知られているが, 何れも産卵については知られていないようである. 筆者水戸は1954年(昭和29年)8月に,長崎県五島玉之浦町に於いて本種の人工授精を行い, 卵の性質,卵内発生及び孵化仔魚を観察する機会を得たので報苦する