New descriptions of four larval lanternfish species and cryptic diversity of Benthosema pterotum (Pisces: Myctophidae) from the Northwest Pacific

Abstract Although there have been many studies on the taxonomy of lanternfishes, morphological similarities during larval and juvenile stages make it difficult to identify species and understand their early life histories. During an ichthyoplankton survey in the Northwest Pacific (East Sea, East China Sea) between 2017 and 2020, a research vessel from the National Institute of Fisheries Science collected larvae and juveniles that belonged to the family Myctophidae using a bongo net. To accurately identify species, mtDNA sequences encoding cytochrome c oxidase subunit I and 16S ribosomal RNA were obtained and compared with those of adult voucher specimens. These comparisons led to the identification of four previously unknown larval lanternfish species ( Diaphus chrysorhynchus , Diaphus suborbitalis , Diaphus watasei and Lampanyctus fernae ), which are described here for the first time. The authors also describe the cryptic diversity of Benthosema pterotum and provide identification keys for 10 species of larval lanternfish, in accordance with their developmental stages.