The first description of larvae and comments on the taxonomy of Stichaeus ochriamkini Taranetz, 1935 (Perciformes: Stichaeidae)

Stichaeus ochriamkini (Stichaeidae) is common in the northern Japan Sea and the southern Okhotsk Sea. Among the five known representatives of the genus Stichaeus, early ontogenesis is the least studied in S. ochriamkini. In this study, the authors provide the first description of all larval stages of this species. In the north-western Japan Sea, larvae are found in plankton from early April to early June. S. ochriamkini larvae can be identified using the following characters: postanal-lateral pigment (PLP) lines present on the sides of the caudal part of the body and run along the anterior edge of hypaxial myomeres; 14-15 abdominal vertebrae; 32-34 rays in the anal fin; larvae disappear from plankton at a body length of L-T > 25.0 mm (L-S > 20 mm). Larvae of S. ochriamkini are very similar to larvae of Stichaeus punctatus. The melanin pigmentation in larvae of both species shows similar patterns of development. In the genus Stichaeus Reinhardt, 1836, two groups of species are distinguished by the presence/absence of PLP lines in larvae, and by significant divergence (clearly exceeding the species level) in the COI mtDNA gene. It is suggested the differences between these species groups is recognized at the generic level. Thus, the genus Stichaeus Reinhardt, 1836 should include S. punctatus and S. ochriamkini, whereas the other three species should be placed in the genus Dinogunellus Herzenstein, 1890: Dinogunellus fuscus, Dinogunellus nozawae and Dinogunellus grigorjewi.

Automated summary

In this study, the authors provide the first description of all larval stages of Stichaeus ochriamkini and find that it is very similar to Stichaeus punctatus in larvae form. Based on the COI mtDNA gene and larval characteristics, it is suggested to classify them into different genera.