A New Species of the Paradise Goby (Rhinogobius, Gobiidae) from Inland Freshwaters of Korea

Fishes of the genus Rhinogobius are widely distributed across the Korean Peninsula, including inland freshwater systems and Jeju Island. While recent international taxonomic databases have synonymized several East Asian populations under R. similis, our integrative analysis reveals that certain Korean populations are phenotypically and genetically distinct. Here, we describe these unique populations as a new species, Rhinogobius koreensis sp. nov. This species is distinguished from its congeners by a suite of morphological characteristics: a relatively small body size (approximately 40.0 mm standard length (SL)), adult males possessing broad yellow transverse stripes on the dorsal and caudal fins, and seven to eight reddish-brown longitudinal stripes on the caudal fin. Diagnostic features also include numerous yellow spots on the mid-lateral scales, several short transverse rows in row a, and a uniserial row in the posterior half of row c of the cutaneous sensory papillae on the cheek. Furthermore, R. koreensis is morphometrically distinguished from its closely related congeners by a narrower body width at the anal fin origin (13.0% SL), shorter pectoral fin (23.2% SL), longer caudal fin (24.7% SL), larger eye diameter (25.2% head length (HL)), narrow interorbital width (3.8% HL), and a shorter snout (31.0% HL). Phylogenetic analysis based on mitochondrial DNA confirms that the Korean R. koreensis population forms a robust, monophyletic clade distinct from those in Japan and China, supporting its recognition as a separate evolutionary unit despite low interspecific genetic distances.