Morphology, molecular systematics and phylogeography of the Spine-cheek Gudgeon, Eleotris acanthopomus (Teleostei: Eleotridae) from the north-western Indian Ocean

General morphology, cephalic sensory papillae pattern, postcranial osteology, phylogenetic placement, phylogeographic pattern, and distribution of Eleotris acanthopomus Bleeker, 1853 (Teleostei: Gobiiformes: Eleotridae) from the north-western Indian Ocean (Arabian Sea) are described. The cephalic papillae pattern follows the 'open' opercular pattern, and the cheek pattern '2.4'. The vertebral column includes 10 abdominal and 14-15 caudal vertebrae, for a total vertebral count of 24-25. Corroborating the morphological results, DNA barcoding based on mitochondrial COI confirmed that the specimens collected from the Arabian Sea coastal area are conspecific with E. acanthopomus from other Indo-Pacific localities. Eleotris acanthopomus from the Arabian Sea shows the closest phylogenetic relationship to E. pellegrini (11.9% K2P genetic distance). The presence of E. acanthopomus in the coastal area of the Arabian Sea represents the first record of this genus and species for the northern Indian Ocean and markedly expands its known geographical distribution range. A preliminary phylogeographic analysis of the newly collected E. acanthopomus haplotype from the Arabian Sea and archived haplotypes from other Indo-Pacific localities suggests that extensive dispersal occurs among regional populations, most probably during the pelagic larval stage.