Ahaetulla nasuta

Ahaetulla nasuta, also known as Sri Lankan green vine snake and long-nosed whip snake, is a slender green tree snake endemic to Sri Lanka.

Common vine snake
In Sinharaja Forest Reserve, Sri Lanka
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Squamata
Suborder:	Serpentes
Family:	Colubridae
Genus:	Ahaetulla
Species:	A. nasuta
Binomial name
Ahaetulla nasuta (Lacépède, 1789)
Synonyms
Dryophis nasuta Dryophis mycterizans

Distribution

Due to longstanding confusion over the taxonomy of A. nasuta, the species was once thought to have a large range from Sri Lanka to peninsular India, including the Western Ghats, along with a disjunct population in Southeast Asia. However, a 2020 phylogenetic study found A. nasuta to actually comprise a species complex, with the "true" A. nasuta (from which the species was originally described) being restricted to the wet zone of Sri Lanka (including the Sri Lanka lowland and montane rainforests). 4 populations from the Western Ghats of India that were formerly grouped with A. nasuta were split into the species A. borealis, A. farnsworthi, A. isabellina, and A. malabarica. The large-bodied form from lowland peninsular India (and possibly the dry zone of the northern portion of Sri Lanka), which was also formerly grouped with A. nasuta, was found to actually be A. oxyrhyncha, and is actually more closely allied with A. pulverulenta and A. sahyadrensis than A. nasuta. Finally, the disjunct population in Southeast Asia was assigned to an as-of-yet undescribed species, tentatively referred to as Ahaetulla cf. fusca, and is a sister species to Ahaetulla laudankia.[1]

Description

Common vine snakes are diurnal, arboreal, and mildly venomous. They normally feed on frogs and lizards using their binocular vision to hunt. They are slow moving, relying on camouflaging themselves as vines in foliage. They expand their bodies when disturbed to show a black and white scale marking. Also, they may open their mouths in a threat display and point their heads in the direction of the perceived threat. They are the only species of snake with horizontal pupils, compared to the normal vertical slit pupils found in many species of viper. [2] The species is viviparous, giving birth to young that grow within the body of the mother, enclosed within the egg membrane. They may be capable of delayed fertilization; (parthenogenesis is rare but not unknown in snakes) as a female in the London zoo kept in isolation from August, 1885 gave birth in August, 1888.[3]

Taxonomic description

The species name Ahaetulla in Sinhala means 'eye plucker'. It earned this name, and similar ones in Tamil and Indian vernaculars, due to the mistaken belief that it strikes at the eyes.[4]

The following description with diagnostic characters is from Boulenger (1890):[5]

Snout pointed, terminating in a dermal appendage, which is shorter than the eye and formed entirely by the rostral; the length of the snout, without the appendage, about twice the diameter of the eye or rather more. No loreal; internasals and prefrontals in contact with the labials; frontal as long as its distance from the rostral or a little longer, as long as the parietals or a little longer; two preoculars and a small subocular (or one preocular and two suboculars), upper preocular in contact with the frontal; two postoculars; temporals 1+2 or 2+2; upper labials 8, fifth entering the eye; 4 lower labials in contact with the anterior chin-shields, which are shorter than the posterior. Scales in 15 rows. Ventrals 172-188; anal divided; subcaudals 140-166. Bright green or pale brownish, the interstitial skin between the scales black and white on the anterior part of the body, which appears striped when distended; a yellow line along each side of the lower surface. Total length 5 feet: tail 2.

Formerly treated as a subspecies Ahaetulla nasuta anomala is now regarded as a distinct species, Ahaetulla anomala.

Habitat

Found in low bushes, shrubs and trees in lowland forest terrain at elevations up to about 1000 metres, particularly near streams and often found near human settlements.[6]

Venom and its effects

The ingredients of the venom are unknown. The venom is moderately potent and can cause swelling, pain, bruising, numbness and other local symptoms, which will subside within three days. Bites close to the head, eyes and other vital areas could be severe. [7][8]

Vernacular names

The Sinhala name "Aheatulla" or "eye-plucker" forms the taxonic species name. In Tamil, it is known as pachai paambu.

• Sinhala: ඇහැටුල්ලා (Pronounced: Aheatulla)
• Tamil: பச்சை பாம்பு

Notes

1. Mallik, Ashok Kumar; Srikanthan, Achyuthan N.; Pal, Saunak P.; D’souza, Princia Margaret; Shanker, Kartik; Ganesh, Sumaithangi Rajagopalan (2020-11-06). "Disentangling vines: a study of morphological crypsis and genetic divergence in vine snakes (Squamata: Colubridae: Ahaetulla ) with the description of five new species from Peninsular India". Zootaxa. 4874 (1): 1–62. doi:10.11646/zootaxa.4874.1.1. ISSN 1175-5334.
2. Brischoux, F.; Pizzatto, L.; Shine, R. (2010). "Insights into the adaptive significance of vertical pupil shape in snakes". Journal of Evolutionary Biology. 23 (9): 1878–1885. doi:10.1111/j.1420-9101.2010.02046.x. ISSN 1420-9101. PMID 20629855. S2CID 23349083.
3. Wall, Frank 1905. A popular treatise on the common Indian snakes. Part 1. J. Bombay Nat. Hist. Soc. 16:533-554.
4. Snakes of Sri Lanka Archived May 19, 2005, at the Wayback Machine
5. Boulenger, George A. 1890 The Fauna of British India, Including Ceylon and Burma. Reptilia and Batrachia. Taylor & Francis, London, xviii, 541 pp.
6. http://www.toxinology.com/fusebox.cfm?fuseaction=main.snakes.display&id=SN0004
7. Snakes of Sri Lanka Archived May 19, 2005, at the Wayback Machine
8. “Ahaetulla nasuta” at WCH Clinical Toxinology Resources. Accessed on 9.1.2014 at http://www.toxinology.com/fusebox.cfm?fuseaction=main.snakes.display&id=SN0004

References

• Lacepède, B. G. E. 1789 Histoire Naturelle des Quadrupèdes Ovipares et de Serpens. Vol.2. lmprimerie du Roi, Hôtel de Thou, Paris, 671 pp.
• Wall, F. 1908 Remarks on some recently acquired snakes. J. Bombay N. H. S. xviii: 778-784
• Wall 1908 A new color variety of the common green whip-snake (Dryophis mycterizans). J. Bombay N. H. S. xviii: 919
• Wall, F. 1910 Remarks on the varieties and distribution of the common Green Whip Snake (Dryophis mycterizans). J. Bombay nat. Hist. Soc. 20: 229
• Wall 1910 Varieties of the common Green Whip Snake (Dryophis mycterizans). J. Bombay nat. Hist. Soc. 20: 524