Larval and juvenile development of Lestidiops sphyraenopsis Hubbs, 1916 (Aulopiformes: Paralepididae) in the western North Pacific, with a reexamination of the holotype of Stemonosudis molesta (Marshall, 1955)

The early life stages of Lestidiops sphyraenopsis (Paralepididae) are described on the basis of 14 specimens [7.8 mm in notochord length (NL)-88.6mm in standard length (SL)] collected from the western North Pacific, and the holotype of Stemonosudis molesta is reexamined. Larval L. sphyraenopsis occurred in the Kuroshio waters, and juveniles were taken in the Kuroshio-Oyashio transition waters. Diagnostic characters of larval and juvenile L. sphyraenopsis are 96-101 myomeres; 27-31 anal fin rays; 4-9 peritoneal pigment sections in larvae (7.8mm NL-27.3mm SL); dorsal and anal pigment patches present; and anus located anterior to a vertical through dorsal fin origin. Stemonosudis molesta, known only from the holotype from the South Pacific, is similar to immature specimens of L. sphyraenopsis, but can be clearly distinguished from the latter by having higher vertebral counts (105 vs. 96-101) and by morphometric and pigment differences. Consequently, S. molesta is a valid species, and the distribution of L. sphyraenopsis is restricted to the North Pacific.