Opisthotropis zhaoermii, a new species of snake from western Hunan, China

The specific epithet of the new species, zhaoermii, is derived from the name of an internationally renowned Chinese herpetologist, Prof. Er-Mi Zhao, who unfortu

The specific epithet of the new species, zhaoermii, is derived from the name of an internationally renowned Chinese herpetologist, Prof. Er-Mi Zhao, who unfortunately passed away on 24 December 2016. Designation of this specific epithet honors his great contribution to herpetological research in China, specifically to his contribution to the taxonomy of Opisthotropis Günther, 1872, including the first description of the sister species, O. cheni Zhao, 1999 in 1999.

In 2007, 3 specimens were collected from Guzhang, western Hunan, China by Prof. Jia-Tang Li’s lab, from Chengdu Institute of Biology, Chinese Academy of Sciences. Researchers found that these specimens of Opisthotropis represents an undescribed species based on both mitochondrial DNA and morphological data, they first described and named the new species as O. zhaoermii. This species is only known from the type locality presently.

The Southeast Asian genus Opisthotropis is distributed across southern China and Southeast Asia, and inhabits flowing streams or waterfalls. Currently, the genus Opisthotropis includes 22 species, with 12 currently recorded in China, this group of animals are non-venomous and aquatic snakes. Many aspects of this specious group still remain poorly-knowned because of their mysterious life, some of the described species are known from only a handful of specimens even a single holotype from the type locality. Although some researchers have focused on their taxonomy recently, many areas in southern China remaining under-surveyed in regard to Opisthotropis diversity.

The new species is morphologically most similar and genetically most closely related to O. cheni and O. latouchii (Boulenger, 1899), but the new species was strongly recovered as a monophyletic clade (BPP=1.00; BSP=100) within Opisthotropis and possesses considerable genetic divergence (p-distance 5.1%–16.7%). After detailed morphological comparisons from topotypes of O. cheni and O. latouchii, they found the new species can be differentiated from all other congeners by a combination of the following morphological characters: (1) body size large (total length 514–586 mm) and strongly built; (2) dorsal scale rows 17 throughout, feebly keeled anteriorly and moderately keeled posteriorly; (3) ventral scales 147–152, subcaudal scales 54–62; (4) preocular absent, loreal elongated and touching orbit; (5) supralabials 8–9, fifth and sixth entering obit; (6) anterior temporals short, length 1.74–2.04 times longer than width; (7) maxillary teeth subequal, 28–30; (8) dorsal surface of head with distinct irregular yellow stripes and markings edged with ochre; (9) body with clear black and yellow longitudinal streaks, partly fused to several lighter patches or thicker stripes anteriorly; and (10) venter pale yellow, with asymmetric blackish speckles along outer margin.

The description of the new species adds a thirteenth species of the genus Opisthotropis occurs in China. Seven new species were found in the past ten years, thus the genus is understudied and likely still contains cryptic diversity. Although a few recent taxonomic works have revealed surprising endemism and cryptic diversity within the genus, these studies have focused on areas around the Fujian-Guangdong Coast Subregion of southern China, Red River Delta and Kon Tum Plateau of Vietnam. This work highlights the underestimated diversity of the genus in the Yangtze River Basin. In addition, an updated diagnostic key to all members of the genus Opisthotropis was provided to facilitate taxonomic work. Recommendations on the ecological study for the group were provided to investigate the possible ecological speciation mechanisms of the group in the future.

This study was supported by the Southeast Asia Biodiversity Research Institute, Chinese Academy of Science, the Frontier Science Key Research Programs of CAS, the Youth Innovation Promotion Association of CAS, and the National Natural Science Foundation of China. This research was published on the journal Zoological Research entitled A new species of the Southeast Asian genus Opisthotropis (Serpentes: Colubridae: Natricinae) from western Hunan, China,  the first author of this article is Jin-Long Ren, graduate student from Chengdu Institute of Biology, Chinese Academy of Sciences.

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Opisthotropis zhaoermii 

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General and close-up views of Opisthotropis zhaoermii holotype CIB109999 (Fig A, B, adult female) and paratype CIB109998 (Fig. C, D, adult male) in life

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Dorsal and ventral views of Opisthotropis zhaoermii holotype CIB109999 (Fig A, B, adult female) and paratype CIB109998 (Fig. C, D, adult male)

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Lateral head (column 1), dorsal head (column 2), and ventral head (column 3) comparisons of Opisthotropis zhaoermii (row A), O. cheni (row B), and O. latouchii (row C)

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Anterior dorsal (column 1), dorsolateral (column 2), and ventral coloration (column 3) comparisons of Opisthotropis zhaoermii (row A), O. cheni (row B), and O. latouchii (row C)