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

Abstract

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 LT > 25.0 mm (LS > 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.

First description of larvae of Radulinopsis derzhavini Soldatov et Lindberg, 1930 (Scorpaeniformes: Psychrolutidae) with remarks on melanin colouration and relationships with related species

“…To describe larvae, four stages of development were used (Kendall et al, 1984) based on the differences in the presence of yolk sac and the degree of notochord flexion during the formation of the caudal fin skeleton: yolk sac, preflexion, flexion, and postflexion (Balanov et al, 2022; Kendall et al, 1984). Photographs were taken through a Stereo Discovery V12 stereomicroscope (Zeiss).…”

“…In total, 182 specimens (L S 3.6-8.0 mm) were collected. The method for collecting larvae is described elsewhere (Balanov et al, 2020(Balanov et al, , 2022Sokolovskaya et al, 2010). We also used data from six individuals (L S 3.8-10.0 mm) reared from a developing egg mass (Table 1).…”