Is Luciogobius dormitoris (Perciformes: Gobiidae) a valid species? Comparative morphology of two subterranean species of the genus Luciogobius

Luciogobius dormitoris is a subterranean gobiid species known only from its holotype. The species has been distinguished from the morphologically similar L. pallidus by its deeper body and the absence of lower jaw protrusion beyond the upper jaw. However, comprehensive morphological data for this species have not been reported previously, and morphological comparisons with the highly variable L. pallidus remain insufficient. In the present study, we conducted detailed morphological comparisons between the holotype of L. dormitoris and several specimens of L. pallidus , for which genetic characteristics were clarified using partial mitochondrial cytochrome b (cyt b ) gene sequences. The holotype of L. dormitoris , along with two specimens (TKPM-P 27391 and OMNH-P 41491), exhibited deeper and wider bodies than the other comparative specimens. OMNH-P 41491 showed morphological characteristics closely matching those of the holotype of L. dormitoris ; however, its cyt b sequence was entirely nested within the genetic variation of L. pallidus . Although L. dormitoris may represent a conspecific taxon of L. pallidus , the possibility of mitochondrial introgression between the two species cannot be ruled out. Therefore, genome-wide analyses, particularly focusing on OMNH-P 41491 and related specimens, are needed to clarify the taxonomic relationship between L. dormitoris and L. pallidus .