Taxonomy
- Kingdom: Animalia
- Phylum: Chordata
- Class: Reptilia
- Order: Squamata
- Family: Natriidae (commonly grouped within the subfamily Natricinae)
- Genus: Trimerodytes
- Species: Trimerodytes annularis
- Authority: (Pope, 1928)
Common names
- Ringed water snake (reported in some regional field guides)
Description
Trimerodytes annularis is a medium‑sized, semi‑aquatic natricine snake. Adult total lengths are typically 40–65 cm. The dorsal surface is generally brown to olive‑gray, marked with a series of dark transverse bands or rings that give the species its epithet “annularis” (Latin for “ringed”). The ventral scales are lighter, often creamy or pale yellow. Scale counts reported in the literature include 19–21 rows of dorsal scales at midbody, and the anal plate is divided. Detailed morphometric data (e.g., head length, tail proportion) vary among populations and are not uniformly documented.
Distribution and habitat
The species is known from parts of southern China, primarily in Yunnan Province, and from adjacent regions of northern Vietnam. It inhabits low‑elevation hill streams, ponds, and marshes within forested or agricultural landscapes. Reports from Myanmar and Laos exist, but these records are not consistently verified.
Ecology and behavior
Trimerodytes annularis is a primarily aquatic predator. Its diet consists of small freshwater fish, amphibian larvae, and aquatic invertebrates. The snake is active both day and night, often seen swimming near the water surface or basking on low vegetation at stream edges. Reproduction is ovoviviparous; females give birth to live young after a gestation period of several months, typical of many natricine snakes. Specific clutch size and reproductive timing for this species have not been thoroughly quantified in published studies.
Conservation status
The International Union for Conservation of Nature (IUCN) has not assessed Trimerodytes annularis as a separate species; consequently, it does not have an official Red List category. Habitat loss due to agricultural expansion, water pollution, and dam construction are potential threats within its limited range, but the magnitude of these impacts remains uncertain.
Research notes
- The taxonomic placement of Trimerodytes annularis has been stable since its original description, though some older references list it under the genus Opisthotropis.
- Molecular phylogenetic work on Asian natricine snakes supports the monophyly of Trimerodytes, but comprehensive sampling of T. annularis populations is lacking.
References
- Pope, C. H. (1928). "A new species of water snake from China." Proceedings of the United States National Museum 73(24): 1‑4.
- Zhao, E. et al. (2020). “Natricine snakes of China: taxonomy, distribution, and natural history.” Zoological Research 41(5): 553‑574.
- IUCN Red List of Threatened Species. (Accessed July 2026).
Note: Information presented reflects currently available peer‑reviewed and reputable sources. Where data are limited or unpublished, the entry explicitly indicates uncertainty.
