| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1995: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1994: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1993: ¥800,000 (Direct Cost: ¥800,000)
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| Research Abstract |
Gut contents of 585 letocephali comprising eight species of eels were examined from five families (Congridae, Muraenidae, Muraenesocidae, Nettastomatidae, and Ophichthidae). The larvae belonged leptocephalus(566 specimens)and the early metamorphic stage(19 specimens). Visible gut contents were recognized in 246 individuals among the eight species, regardless of developomental stage. Two kinds of visible objects, transparent(0.4 to1.2mm)and opaaque(20to380mum), were found in the gut of letocephali. From their morphological characteristics, the former and the latter were identified as larvacean houses and zooplankton fecal pellets, respectively. Furthermore, most fecal pellets in the gut were identified as oikopleurid larvacean's fecal pellets. No trace of the many other phytoplankton or zooplankton, which were found with leptocephali in the ambient waters and could be suitable-size food, was found in the gut of any leptocephalus. On the basis of the importance of larvacean houses in the diet of serveral species of leptocephalus larvae, it is proposed that the peculiar, large, fang-like teeth of leptocephali are used for feeding, and evolved to pierce and grasp the mucous houses of larvaceans.
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