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トビハゼの卵発生および稚仔の飼育


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Title: トビハゼの卵発生および稚仔の飼育
Other Titles: Egg Development and Rearing Experiments of the Larvae of the Mud Skipper, Periophthalmus cantonensis
Authors: 小林, 知吉 / 道津, 喜衛 / 三浦, 信男
Authors (alternative): Kobayashi, Tomokichi / Dotsu, Yoshie / Miura, Nobuo
Issue Date: Aug-1972
Publisher: 長崎大学水産学部
Citation: 長崎大学水産学部研究報告, v.33, pp.49-62; 1972
Abstract: The artificial insemination of the eggs of the mud skipper, Periophthalmus cantonensis (Osbeck), collected from the mouth of the River Honmyo, Isahaya City (Lat. 32°51.5'N, Long. 130°5.2'E) on July 23, 1970 and induced the ovulation of the gonad by injection of the gonadotrophic hormone, Synahorin, was carried out. The artificially fertilized egg was demersal adhesive one provided with an ellipsoid chorion, measuring 0.94 mm in long axis and 0.64 mm in short axis, and it was smaller than the egg which collected from the nest in the River Honmyo which measured 1.14 mm and 0.74 mm. The light yellow yolk included many tiny oil globules which would not be united into a large globule until hatching. In the late developing stages, the embryo moved and freely changed its head to face the free tip of the chorion (normal egg) or to the basal end with a boundle of adhesive filaments (agrippa egg). Five rearing experiments of the larvae newly hatched from the eggs collected from the nests in the River Honmyo were carried out in 1970 and 1971. The rearing larvae were fed one after another with the larvae of the oyster, the rotifer, the sprash copepod, minced raw fish meat and formula food for aquarium fishes as the fish grew. The newly hatched larva, being 2.84 mm in total length, spent the planktonic life and grew to the 11.5 mm postlarva in 30 days. The 14 mm juvenile, reared for 45 days after hatching, entered into the bottom life. The 15mm early young changed its life into the amphibious mode. The pelvic fins first developed in the 8 mm postlarva in the planktonic life, and they were united to form a cup-like shape in the 14 mm juvenile that entered the bottom life. The fins were separated from each other at the posterior part by a deep notch formed in the posterior margin when the fish grew to the 31mm young. The scales first developed in the 14mm young as a longitudinal dotted line at the middle of the body sides and spread to the dorsal side as the fish grew. / 1970年6月23日に,長崎県諌早市本明川川口で採集した成熟トビハゼに性腺刺戟ホルモン(シナホリン)とビタミンE剤(ユベラ)を注射してその排卵を促し,その魚から得た完熟卵および精子を用いて湿導法によって人工授精を行なった。人工授精卵は,沈性付着卵で,卵膜は楕円体をなし,その長径は0.94mm,短径0.64mmで,天然卵(長径1.14mm,短径0.74mm)と比べるとやや小さかった。卵膜の基部には付着糸そうを備えており,淡黄色をした油球内には,同色の多数の小油球があるが,この油球群は,卵がふ化するまで合一して大油球となることはない。卵発生後期になって胚体が動きだすと,胚体は卵膜内でときどき体を回転させ,その頭部を卵膜の先端部へ向けたり(正常卵),基部へ向けたり(逆子卵)してその方向が定まらない。ふ化時間は,水温19-20℃で約7日間であった。ふ化直後の仔魚は生時の全長が2.84mmで,なおかなりの卵黄を持っており,約4日間でそれを吸収する。天然卵からふ化した仔魚に,その成長に従って,マガキの幼生,シオミズツボワムシ,シオダマリミジンコ,生の魚肉の砕肉,熱帯魚用の配合餌料の順に餌を与えて,1970,1971年の両年に,60-85日間飼育した結果によると,トビハゼの仔魚は,ふ化後約30日間浮遊生活を送り,全長11.5mm(固定標本)を越える大きさに達した後期仔魚末期にしだいに底生生活に移り,更に,ふ化後約50日を経た全長15mmほどの初期若魚期に両生生活を始める。トビハゼの幼期における各鰭の形成をみると,尾,臀,第2背,腹,胸,第1背鰭の順で完成をみるが,それらの形成は,幼期におけるトビハゼの成長に伴なう生態の変化と関連が深い。腹鰭は,浮遊生活を送る全長約8mmの仔魚で形成が始まり,左右両鰭が合一した盃状のものとなるが,若魚期になってトビハゼが底生,更には両生生活に移ると共に,円形をした腹鰭の後縁に欠刻が生じ,成長と共に深くなって,二次的に,左右分離型の腹鰭となる。鱗は,全長約15mmの両生生活初期の若魚で,最初に,その体側中央線上に1縦列をなして現われ,成長に伴って体背側方へ広がってゆく。
URI: http://hdl.handle.net/10069/31073
ISSN: 05471427
Type: Departmental Bulletin Paper
Text Version: publisher
Appears in Collections:第33号

Citable URI : http://hdl.handle.net/10069/31073

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