New Morphological and Molecular Data on the Southern Ninespine Stickleback, Pungitius platygaster (Gasterosteidae) from Southern Caspian Sea Basin

Being a group of popular model organisms in eco-evolutionary biology, genetic, and genomic research studies, the genus Pungitius with 12 species is the most species-rich genus in the stickleback family Gasterosteidae including the Caspian nine-spine stickleback, Pungitius platygaster (Kessler, 1859), the only known species from southern Caspian Sea basin. Here, the new data based on morphological and molecular characters of the mtDNA COI barcode region, and current distribution range of P. platygaster is presented. These data confirm the validity of P. platygaster among its congeners, being sister clade to P. hellenicus from Greece. Morphologically, it is distinguished from the other congeneric species by complete pelvic girdle, 8−11 dorsal spines, and presence of large lateral scutes. The Caspian nine-spine stickleback is found in several closely placed freshwater and brackish waterbodies in the southern Caspian Sea.