Taxonomical review of Auxis（Scombridae, Pisces）larvae using collections around Tosa Bay, Japan
2019 Volume 57 Issue 1-2 Pages 43-50
Details
2019 Volume 57 Issue 1-2 Pages 43-50
Larvae of Auxis collected around Tosa Bay from May 2002 to May 2018 could be distinguished into two types primarily by the pigmentation patterns on the caudal peduncle. Type-A Auxis larvae possess a row of pigmentation along the midlateral line in all larval stages, while type-B does not. Little morphometric differentiation was found until the flexion stage in both types, but at the postflexion type-A showed significantly larger head［36.8% BL(mean）］, larger mouth（24.1%）, shorter vent to anal-fin length（17.7%）and deeper body（27.8%）than type-B (34.8, 21.5, 19.0, 25.9%, respectively）. These observed differences indicate the validity of the pigmentation row in distinguishing Auxis larvae. Between the two types, type-B larvae（n = 795） were more abundant than type-A（n = 21）in Tosa Bay. Based on this distribution pattern and shallower body depth, type-B larvae could be considered as A. rochei and type-A with a deeper body as A. thazard.
