The Applicability of Pigmentation as a Diagnostic Character to Identify Larvae of Sand Lances of the Genus Ammodytes (Actinopterygii: Ammondytidae) Inhabiting the Sea of Japan

The development of melanin pigmentation is described in larvae of the Pacific sand lance Ammodytes hexapterus Pallas, 1814 from Peter the Great Bay, identified by phylogenetic analysis using the mtDNA cytochrome oxidase subunit I (COI) gene. No essential differences from A. japonicus larvae collected in the Yellow Sea and A. heian larvae collected in the Sea of Japan in the surface pigmentation were found, either in the number of its elements or in the time and pattern of development. The presence of the internal row of melanophores located above the notochord is shown, which already becomes evident at the flexion stage and is clearly visible in living material of A. hexapterus juveniles. It was not previously reported for any of the considered species of the genus. One can conclude that the melanin pigmentation of A. hexapterus larvae is not significantly different from that of larvae of other Ammodytes species from the Sea of Japan. Therefore, melanin pigmentation alone cannot be used for reliable identification without the use of countable characteristics such as the number of myomeres or vertebrae at later stages, which have previously shown more distinct differences.