Studies on diet of Anguilloid leptocephalus larvae

对5科(康氏鳗科、鳗科、鳗科、网鳗科、蛇鱼科)的8种鳗鱼共585尾的肠道内容物进行了观察。幼虫为细头型(566尾)和早期变态(19尾)。在8个物种中，有246个个体可识别出可见的肠道内容物，而不考虑发育阶段。可见物体有透明的(0.4~1.2 mm)和不透明的(20~380 mm)两种。根据形态特征，前者和后者分别被鉴定为幼虫室和浮游动物粪便颗粒。此外，肠道中的大多数粪便颗粒被鉴定为圆环类幼虫的粪便颗粒。其他许多浮游植物或浮游动物的踪迹，在任何细头藻的肠道中都没有发现，这些浮游植物和浮游动物在周围水域中被发现，可能是合适大小的食物。根据幼虫房在几种头节幼虫食性中的重要性，提出了利用头节独特的大而尖牙取食，并进化为刺穿和抓住幼虫粘液室的观点。

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.