Wednesday, November 30, 2011

[Herpetology • 2011] Opisthotropis cucae • A new aquatic snake Opisthotropis (Natricidae) from the Central Highlands of Vietnam

A new species of the snake genus Opisthotropis Günther, 1872, Opisthotropis cucae sp. nov., is described from Kon Tum Plateau in central Vietnam. It is distinguished from any other Opisthotropis species by the combination of the following characters: (1) dorsal scales entirely smooth, in 23–19–19 rows; (2) 191 ventrals; (3) 1 loreal, in contact with internasal; (4) 7 supralabials, 5th entering orbit; (4) dorsum uniformly greyish-brown without bands or crossbars, with an irregular separation between dark dorsum and venter, greyish-yellow speckled with dark grey. An extended comparison with other species of the genus Opisthotropis species is provided together with a key to the known species of the genus. Opisthotropis cucae sp. nov. is the third new mountain stream snake described from Vietnam in the past decade. The grammatical gender of the genus Opisthotropis is discussed; this genus is feminine.

Key words: Natricidae, Opisthotropis cucae sp. nov., snake, taxonomy, Vietnam

As tectonic movements in Southeast Asia altered the topography opportunities for speciation increased. Isolation of mountains by valleys, the formation of new drainage systems, and alternating changes in grasslands and forests provided opportunities for restricting gene flow and in other cases brought long separated populations together.The stream snakes of the genus Opisthotropis have speciated in many of the streams to become localized endemics. There are 19 species in the genus and most have a poorly known natural history. Most are found in China and Indochina (Thailand, Vietnam, Laos, Cambodia), but species occur from Sumatra to the Philippines.

Only one species is known to exceed a meter in length, most are 0.4 to 0.6 m. Scale ornamentation is unusual with many species having smooth scales over most of the body and keeled scales on the posterior portion of the body, a pattern seen in a few other aquatic and semi-aquatic snakes. And, the keels may be normal looking, serrated, or in some composed of rows of tiny tubercles. Most are probably eating fish, but a few eat crustaceans, and it seems likely that some are more aquatic than others - spending most of their lives in the water and perhaps leaving the water only to lay their eggs.

Patrick David at the Muséum National d’Histoire Naturelle and colleagues have now described Opisthotropis cucae based on an adult female, from Chu Mom Ray National Park, Sa Thay District, Kon Tum Province, Vietnam. The snake was found at 740 m above sea level in secondary evergreen forest and was collected at night (21:30) under water in a rocky stream. The new species is named in honor of Mrs HO Thu Cuc at the Institute of Ecology and Biological Resources in Hanoi, for having collected the holotype and for her long lasting contributions to the herpetology of Vietnam. This the seventh species of Opisthotropis known from Vietnam.
David, P., Pham, T. C., Nguyen, Q. T. & Ziegler T. 2011. A new species of the genus Opisthotropis Günther, 1872 (Squamata: Natricidae) from the highlands of Kon Tum Province, Vietnam. Zootaxa. 2758: 43–56: