Species Diversity, Diagnostic Characters and Distribution of Tubenose Gobies of the Genus Proterorhinus (Gobiidae): Revalidation of the Caspian Species Proterorhinus blennioides

As a result of comparative morphological studies and molecular analysis, the tubenose gobies from the Southwestern Caspian Sea were confirmed and redescribed as a separate species, the small-eyed Caspian tubenose goby Proterorhinus blennioides, previously described by Kessler in 1877. This species is distinguished from all other species of tubenose gobies by its small eyes, with the horizontal diameter usually less than 20% of the head length, often almost equal to or even less than the interorbital distance. Unlike the other studied Caspian tubenose gobies, P. blennioides is characterized by a predominance of 13½ branched rays in the anal fin (versus 14½ branched rays), a large preanal distance, usually exceeding 56% SL (instead of usually not reaching 56% SL), and a shorter anal fin base, often not reaching 30% SL (instead of frequently exceeding 30% SL). Genetically a revalidated species P. blennioides is a sister taxon to P. marmoratus sensu stricto having a large distance (p-distance = 0.12 ± 0.014 in COI mtDNA). Both species form a deeply divergent sister clade to all other Proterorhinus spp. The goby P. blennioides is distributed along ca. 400 km along the coastline between Baku and Anzali Wetlands.