著者

松本 清二 岩田 勝哉

出版者

The Ichthyological Society of Japan

雑誌

魚類学雑誌 (ISSN:00215090)

巻号頁・発行日

vol.44, no.1, pp.35-41, 1997-05-26 (Released:2010-06-28)

参考文献数

13

被引用文献数

1

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Paternal egg guarding and mouthbrooding of larvae and juveniles were observed in the swamp-eel, Monopterus albus. In aquaria, the male guarded and cared for eggs in the bubble nest floating inside a plastic tube (5 cm in dia-meter, 50 cm in length). It was suggested that spawning and fertilization occurred outside the nest tube, and that the male carried the fertilized eggs (ca. 4 mm in diameter) in his mouth and inserted them into the bubble mass. Until the hatching of larvae (7-8 days after spawning), the male frequently added fresh bubbles into the bubble mass. As soon as the larvae (18-21 mm in TL) hatched and emerged from the bubble nest, the male sucked them into his mouth. Fifty juveniles (32-37 mm in TL) and two yolk-sac larvae (22 mm in TL) were released from the mouth of a male collected from a natural habitat. Those juveniles were retrieved by the male, some of them voluntarily returning to the male's mouth. The mouthbrooding male frequently performed pumping behavior (i.e., inflating and deflating the buccopharyngeal cavity), thereby acquiring to take fresh air. Eggs removed from the bubble nest successfully hatched only when directly exposed to aeration. In addition, only about 40% of the hatched larvae survived more than 10 days when they were kept in well-aerated water without the male parent. These suggest that both the bubble nest and mouthbrooding are indispensable for successful development and survival of eggs and larvae in this species, which inhabits swamps and paddy fields.

著者

松本 清二

出版者

橿原市昆虫館

雑誌

奨励研究

巻号頁・発行日

2010

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我々はこれまでのタウナギの繁殖性態の観察結果やタウナギの食性に着目し、次のような仮説をたてた。タウナギは魚類や水生動物をはじめ多種多様な動物を餌とする捕食者であり、共食いも頻繁に認められている。繁殖期雄は巣を構え訪問してくる雌には求愛するが、接近する雄には激しく噛み付き、それがもとで雄は死亡することもある。また、雄間での共食いも少なからず見られている。このような状況で、もし小型の雄の死亡率(雄間闘争や雄間での共食いによる)が高いなら、小型の時期は雄であることより雌でいることのほうが有利となるかも知れない。死亡率の性差による性転換を予測するモデルも出されている。この小型個体の雌雄での死亡率の差異が、本種の雌性先熟を引き起こす進化要因なのかも知れない。われわれは、タウナギの性転換を説明するために、「雌雄での死亡率の差異仮説」を考えた。本仮説のように小型魚の雄がいない場合,検証のための実験観察の実施は難しい。奈良県下で確認されているタウナギは、個体群毎で性転換サイズが大きく異なる。最小魚サイズの個体群では約30cmの小さな雄がいる一方、最大サイズの個体群では雄は60cmを超える。本実験ではこの特性を利用し、自然状態では共存していない大きさの異なる雄を用いることで実験を行った。水田を仕切った半自然状態の複数の実験池で、これらの大小の雄を入れ繁殖生態、なわばり行動、死亡率,共食いなどを観察した。仮説からの予想は(1)小型雄の高い死亡率と大型雄の低い死亡率、(2)雄間競争により小型雄が繁殖巣をもてないこと、(3)小型雄と同サイズの雌は産卵成功をあげること(4)小型雌の死亡率は高くはないこと、などであった。観察結果は、予想(1)大型の死亡率が10%であったのに対して小型のそれは10%と同様であった。予想(2)で小型雄が巣を持つことはなかった。予想(3)では、繁殖巣をつくった大型雄が2個体と少なく、しかも産卵できたのは1個体であり確認できなかった。予想(4)では、小型個体の性差が等しく著しい結果は得られなかった。この原因は、実験個体の雄が1m近い大型個体を使用した。そのため、広い縄張りが必要となり観察池が小さすぎた。そのため繁殖行動が大型雄2個体でしか観察できず、顕著な行動を観察できなかった。今後、観察池を改善し研究を進めたい。

著者

松本 清二 永井 伸夫 今西 塩一 蓮池 宏一 幸田 正典

出版者

一般社団法人 日本生態学会

雑誌

日本生態学会誌 (ISSN:00215007)

巻号頁・発行日

vol.48, no.2, pp.107-116, 1998-08-25 (Released:2017-05-25)

参考文献数

20

被引用文献数

1

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At the beginning of this century, the swamp-eel Monopterus albus was introduced from Korea to an area of Nara Prefecture, located at or near one of the origins of the Kizu, Yamato and Yoshino River Systems. Our samplings were carried out between 1988 and 1997 and information offered by farmers was confirmed that the fish was distributed in the three river systems. Furthermore, a comparison between our results and previous reports clearly shows that the fish has expanded its distribution range. Closer surveys revealed that the fish did not occur at higher altitudes which were isolated from lowland fields providing a habitat for the fish, even though both area were cconnected by rivers. In contrast, it occured in paddy fields on both sides of passes which the fields traversed. The fish seems to be a poor swimmer because of its degenerate fins. These facts suggest that its wide distribution range is due to its high dispersal ability and some extrinsic factors as suggested below: 1) ability to breathe air, which enables it to leave bodies of water; 2) release at or near the origins of the three river systems; 3) abundance of contiguous paddy fields which are suitable habitats for the fish.

著者

久米 智 松井 志穂 中谷 康弘 松本 清二

出版者

一般社団法人 日本環境教育学会

雑誌

環境教育 (ISSN:09172866)

巻号頁・発行日

vol.22, no.3, pp.3_14-21, 2013 (Released:2015-03-25)

参考文献数

2

被引用文献数

2

著者

松本 清二 岩田 勝哉

出版者

The Ichthyological Society of Japan

雑誌

魚類學雜誌 (ISSN:00215090)

巻号頁・発行日

vol.44, no.1, pp.35-41, 1997-05-26

被引用文献数

1

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Paternal egg guarding and mouthbrooding of larvae and juveniles were observed in the swamp-eel, <I>Monopterus albus</I>. In aquaria, the male guarded and cared for eggs in the bubble nest floating inside a plastic tube (5 cm in dia-meter, 50 cm in length). It was suggested that spawning and fertilization occurred outside the nest tube, and that the male carried the fertilized eggs (ca. 4 mm in diameter) in his mouth and inserted them into the bubble mass. Until the hatching of larvae (7-8 days after spawning), the male frequently added fresh bubbles into the bubble mass. As soon as the larvae (18-21 mm in TL) hatched and emerged from the bubble nest, the male sucked them into his mouth. Fifty juveniles (32-37 mm in TL) and two yolk-sac larvae (22 mm in TL) were released from the mouth of a male collected from a natural habitat. Those juveniles were retrieved by the male, some of them voluntarily returning to the male's mouth. The mouthbrooding male frequently performed pumping behavior (i.e., inflating and deflating the buccopharyngeal cavity), thereby acquiring to take fresh air. Eggs removed from the bubble nest successfully hatched only when directly exposed to aeration. In addition, only about 40% of the hatched larvae survived more than 10 days when they were kept in well-aerated water without the male parent. These suggest that both the bubble nest and mouthbrooding are indispensable for successful development and survival of eggs and larvae in this species, which inhabits swamps and paddy fields.