狹首幼生為海鰱總目下物種仔魚期的統稱，過去因為外觀特異而被當作一個獨立屬，後方被確認為海鰱總目物種之仔稚魚。它們的身體透明且體側具有“W”字型肌節，部分物種體表可以觀察到不同排列方式的黑色素胞。由於與成魚的外觀差異甚大，難以精確鑑定其物種。本研究使用形態與分子特徵進行台灣西南海域常見狹首幼生以及成鰻之物種鑑定。形態鑑定的結果，確認有13個不同形態型，其中有9個能鑑定至種，分別為微鰭新蛇鰻、台灣絲尾海鰻、大錐體糯鰻、似米克氏錐體糯鰻、大眼錐體糯鰻、網格深海糯鰻、新種深海尾鰻、大頭糯鰻以及狹尾糯鰻，其餘4個分別為錐體糯鰻屬、蚓鰻屬之物種。其中台灣絲尾海鰻狹首幼生能透過不同的吻部形態，進一步區分為三個不同生長階段。大部分錐體糯鰻屬的狹首幼生具有接近轉變期的特徵，因此色素胞分佈有明顯差異。DNA生命條碼鑑定將79條基因序列序列區分為11個不同物種，其中7個可比對至成魚樣本。本研究整合台灣西南海域鰻魚之狹首幼生及成魚的形態與DNA生命條碼比對結果，首次確認並描述多個鰻魚物種之狹首幼生形態，並建立台灣西南海域常見狹首幼生的物種檢索表。

“ Leptocephali ” is a collective term for the fish larvae under the superorder Elopomorpha. They were treated as an independent genus because of their distinct morphology and confirmed to be larvae of the superorder Elopomorpha. Their bodies are transparent with many W-shaped myomeres and various pigmentations. The morphology of leptocephali is extremely different from their adults which makes the identification less accurate. In this study, both morphological and DNA barcoding are used for comparing leptocephali and adults of the common eels collected from Southwestern Taiwan. Thirteen morphological types are recognized and nine of them can be identified to species, including Neenchelys parvipectoralis, Gavialiceps taiwanensis, Ariosoma majus, Ariosoma aff. meeki, Ariosoma megalops, Bathycongrus retrotinctus, Bathyuroconger sp., Conger microcephalus and Uroconger lepturus. The other four are members of Ariosoma and Moringua. The leptocephali of Gavialiceps taiwanensis can be divided into three different life stages based on the snout developments. In addition, most of Ariosoma specimens are approaching the metamorphosis and their pigmentations are quite different. DNA barcoding study confirmed eleven different lineages, seven of them match the adults collected from Taiwan. This study combined morphological features and DNA barcoding of leptocephali and adults of common eels occurring in the southwestern Taiwan. The leptocephali of some species are confirmed and described for the first time. A key for identifying the common leptocephali in Taiwan is provided.

壹、前言 1
貳、材料與方法 6
參、結果 11
肆、討論 43
伍、結論 52
陸、參考文獻 54

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