ナガサキススメダイの飼育水槽における蕃殖と初期発生

本田, 晴朗, 今井, 貞彦

In summer of 1972, Pomacentrus nagasakiensis TANAKA bred in the small aquariam in the labolatory.Two 60 lit-acrilite tanks with the circulating devices were used. They were preliminary set forspawning by some rocks and coral blocks. Two pairs of the fishes were selected from the specimenscollected at Sakurajima in Kagoshima bay.One of the pairs lived together for 66 days, and bred 18 times, and the other for 20 days and 4times. In the aquarium the male showed some agressiveness, but the territory kept by him was narrowaround his nest. Spawning occured with the intervals of 3 or 4 days. Eggs were deposited undersideof ceiling of the nest cave and were fertilized immediately by the male.The shape of egg was ellipsoid, measured about 2.3×1.1mm. Incubations took about 3 and halfdays at 27~29°C. Throughout the period the eggs were guarded only by the male.The eggs hatched at evening soon after the sunset. The larvae were cultured in a 500 lit-tank,feeding with fertilized eggs of Heliocidaris, Brachionus plicatilis and Artemia naupli. After 15 to 20 daysthey became benthic. But all of them died within a month after hatching.

1. 1972年夏,鹿児島湾産のナガサキスズメダイPomacentrus nagasakiensisの成魚を各1対づつ,2個の60 litの小型水槽で飼育した。そのうち1対は66日間に18回産卵し,他の1対は20日間に4回産卵した。2. 二次性徴としては雄魚がやや大きく後頭部が多少凸出しているていどで大差がないが,外部生殖器には明らかな差がみとめられる。3. 他のスズメダイのように雄魚が主導的に営巣,求愛して雌に産卵させ孵化までの保護にあたる。水槽内では闘争を行なうが天然水域での闘争性は余りいちじるしくない。4. 卵は長径2.3mm,短径1.1mm内外のナス型で長軸の一端に附着糸叢を持つ。1回に数百個乃至数千個が産み出される。5. 卵は26-29°Cで約3.5ないし5.5日で孵化する。産卵は午前中に行なわれ,孵化するのは必らず日没直後である。6. 孵化直後の仔魚は全長2.8mm内外,約3000尾の仔魚を先づムラサキウニ幼生,ひきつづきシオミズツボワムシ,アルテミアの順に給餌飼育した。7. 仔魚は始め表層で生活し孵化後2週間内外から中層に移る。飼育日数27日で最後の1個体が死亡したが,なお色彩的には底生魚として特色を示すには至らなかった。

ナガサキススメダイの飼育水槽における蕃殖と初期発生

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