Positive buoyancy in eel leptocephali: an adaptation for life in the ocean surface layer
Positive buoyancy in eel leptocephali: an adaptation for life in the ocean surface layer
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DOI：
10.1007/s00227-008-1123-8
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发表时间：
2009-02
期刊：
影响因子：
2.4
通讯作者：
K. Tsukamoto;Y. Yamada;A. Okamura;T. Kaneko;Hideki Tanaka;Michael J. Miller;N. Horie;N. Mikawa
中科院分区：
文献类型：
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作者：
K. Tsukamoto;Y. Yamada;A. Okamura;T. Kaneko;Hideki Tanaka;Michael J. Miller;N. Horie;N. Mikawa
许多浮游生物具有适应能力，例如漂浮物或较轻的物质，以获得浮力，帮助它们留在海洋表层，在那里进行光合作用初级生产，食物最丰富。几乎完全透明的鳗鱼幼虫，称为细头鱼，是表层浮游群落的独特成员，但人们对它们的生态和生理知之甚少。我们对浮游动物的比重进行了比较研究，包括海洋无脊椎动物 7 个门的 25 个类群和薄头动物（脊椎动物）的 6 个类群，以广泛了解日本鳗鱼卵和幼虫阶段的浮力。各种新捕捞的海洋无脊椎动物类群的比重值差异很大，从 1.020 到 1.425，但细头类的比重值最低 (1.028-1.043)。人工养殖的活体薄头鱼具有更大的浮力，比重为1.019-1.025，接近或低于海水，其浮力在早期生命史的不同阶段表现出个体发生的变化。细头鱼似乎具有独特的浮力控制机制，通过遍布身体表面的氯细胞通过填充其身体的透明胶状糖胺聚糖的细胞外基质中所含的体液进行渗透调节。这种适应可能是它们生存的关键因素，帮助它们留在食物颗粒最丰富的表层，同时可以透明地躲避捕食者。鳗鱼卵、细头鳗和玻璃鳗的浮力的个体发生变化可能会增强它们幼体的存活、运输和招募到陆地淡水栖息地的能力。
Many planktonic organisms have adaptations such as floats or lighter substances to obtain buoyancy to help them remain in the surface layer of the ocean where photosynthetic primary production occurs and food is most abundant. The almost totally transparent eel larvae, called leptocephali, are a unique member of the planktonic community of the surface layer, but their ecology and physiology are poorly understood. We conducted a comparative study on the specific gravity of planktonic animals including 25 taxa of 7 phyla of marine invertebrates and 6 taxa of leptocephali (vertebrate) to gain a broad perspective on the buoyancy of the eggs and larval stages of the Japanese eel. The specific gravity values of the various freshly caught marine invertebrate taxa varied widely from 1.020 to 1.425, but leptocephali had some of the lowest values (1.028–1.043). Artificially cultured live leptocephali had even greater buoyancies with specific gravities of 1.019–1.025 that were close to or lower than seawater, and their buoyancy showed ontogenetic changes among the different early life history stages. Leptocephali appear to have a unique mechanism of buoyancy control by chloride cells all over body surface through osmoregulation of body fluid contained in the extracellular matrix of transparent gelatinous glycosaminoglycans filling their bodies. This adaptation is likely a key factor for their survival by helping them to remain in the surface layer where food particles are the most abundant, while being transparent for predator avoidance. The ontogenetic change in buoyancy of eel eggs, leptocephali and glass eels likely enhances their larval survival, transport, and recruitment to terrestrial freshwater habitats.