The relationships of Stichaeus nozawae (Jordan et Snyder, 1902) and Stichaeus grigorievi (Herzenstein, 1890) (Pisces: Stichaeidae) inferred from the data of genetic and karyological analyses and ultrastructural study of spermatozoa

Abstract

A complex study, including genetic and karyological approaches, as well as an analysis of the ultrastructural organization of spermatozoa of the Nozawa’s prickleback Stichaeus nozawae (Jordan et Snyder, 1902) and Grigorev’s prickleback S. grigorievi (Herzenstein, 1890) from Vostok Bay, Sea of Japan, is considered in the present work. The species exhibit differences in the spermatozoon head width and flagellum length. These characters are species-specific and, along with morphological traits, can be used as a proof of the validity of the species under study. The similarity between S. nozawae and S. grigorievi, as established based on genetic and karyological analyses (2n = 48, NF = 70, localization of nucleolar organizers), does not correspond to inter-species differences in morphological and biological characters. The lack of variations in DNA and the chromosome set that are suitable for species differentiation, between Nozawa’s and Grigorev’s pricklebacks is an evidence for the evolutionary adolescence of these species.