Genetic identification of two types of Ariosoma leptocephali

Comparisons of genetic sequences of the mitochondrial DNA 16S rRNA gene were used to match two species of congrid eels of the genus Ariosoma to two established Ariosoma-types of leptocephali. 18 Ariosoma sp. 7 leptocephali (40-151mmTL) were matched with an A. major adult (333mmTL) collected from Tosa Bay of eastern Japan with 0.2-0.7% sequence differences, and 1 Ariosoma sp. 8 leptocephalus (330mmTL) was matched with two A. shiroanago adults (317 and 320mmTL) also from Tosa Bay with no sequence difference. Ariosoma sp. 7 leptocephali have been collected in many regions of the western North Pacific (WNP), and the leptocephali from both the East China Sea and the WNP were matched with A. major, suggesting that the leptocephali of this species are widely distributed in the region. The leptocephali of Ariosoma sp. 8 appear to be much less common in most areas that have been sampled recently