A new species of salamander of the genus Hynobius (Amphibia, Caudata, Hynobiidae) from South Korea

We describe a new species of lentic-breeding Hynobius salamander from the Naro Islands, near the village of Bongraemyeon, Goheung-gun, Jeollanam-do, South Korea, on the basis of results of morphological, ecological and genetic analyses. Hynobius unisacculus sp. nov. is distinguished from its congeners by a combination of the following morphological attributes: (1) comparatively small size (adult SVL up to 61 mm; range 38.3-60.3 mm in males and 37.5-59.9 mm in females); (2) relatively slender short limbs; tips of fore-and hindlimbs adpressed on body never meeting, but separated by a large gap (gap of -3.0 to -1.5 costal folds in males and -3.5 to -1.5 in females); (3) comparatively short tail (TL/SVL ratio in adult males varying from 0.54-0.98, in adult females from 0.55 to 0.89), tail flattened and with a low dorsal fin extending to the posterior one-third of tail length; (4) usually 11 (occasionally 12) costal grooves; (5) in adults, dark brown dorsum with indistinct bronze or dark copper spots, lighter greyish-white or pinkish belly; (6) well developed fifth toe; (7) comparatively shallow vomerine tooth series with 13-23 vomerine teeth; (8) small, pigmented ova, located in one, occasionally two, strings in a small, curved egg sac with folded envelope, lacking distinct mucous stalks or whiptail-like structures on both ends. The molecular differentiation among Korean Hynobius is high; Hynobius unisacculus sp. nov. is genetically highly divergent from the morphologically similar H. leechii, H. yangi and H. quelpaertensis: pairwise distances are 9.7%, 9.1% and 8.0% of sequence divergence at the COI mtDNA gene respectively, and 10.9%, 10.9% and 9.4% of sequence divergence at the cyt b mtDNA gene, respectively. At present, the new species is known from coastal areas and offshore islands in southeastern part of Jeollanam-do in South Korea. We suggest the species should be considered as Vulnerable (Vu2a) in accordance with IUCN's Red List categories. Our study supports the presence of undiagnosed taxonomic diversity among Korean Hynobius.