Ahaetulla

Ahaetulla, commonly referred to as Asian vine snakes or Asian whip snakes, is a genus of colubrid snakes distributed throughout tropical Asia. They are considered by some scientists to be mildly venomous and are what is commonly termed as 'rear-fanged' or more appropriately, opisthoglyphous, meaning their enlarged teeth or fangs, intended to aid in venom delivery, are located in the back of the upper jaw, instead of in the front as they are in vipers or cobras. As colubrids, Ahaetulla do not possess a true venom gland or a sophisticated venom delivery system. The Duvernoy's gland of this genus, homologous to the venom gland of true venomous snakes, produces a secretion which, though not well studied, is considered not to be medically significant to humans.

Ahaetulla
Ahaetulla dispar
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Suborder: Serpentes
Family: Colubridae
Subfamily: Ahaetuliinae
Genus: Ahaetulla
Link, 1807

Green-colored members of this genus are often referred to as green vine snakes. They are not to be confused with the "green vine snake" Oxybelis fulgidus, which convergently appears very similar but is found in Central and South America.

Taxonomy

Their closest relative is the monotypic genus Proahaetulla, which Ahaetulla diverged from in the mid-Oligocene. From here, the clade containing Proahaetulla and Ahaetulla is a sister group to the genus Dryophiops, and the clade containing all three of these genera is a sister group to the clade containing the bronzeback snakes (Dendrelaphis) and flying snakes (Chrysopelea).[1]

In 2020, an analysis of Ahaetulla nasuta, Ahaetulla dispar, and Ahaetulla pulverulenta throughout their range found them to represent species complexes containing several undescribed or formerly synonymized species, leading to the description of A. borealis, A. farnsworthi, A. malabarica, A. travancorica, and A. sahyadrensis, as well as the resurrection of A. oxyrhyncha and A. isabellina. Ahaetulla nasuta and Ahaetulla pulverulenta, formerly considered to have much wider ranges, are now considered endemic to Sri Lanka.[2][3]

Geographic range

They are found from Sri Lanka and India to China and much of Southeast Asia. Sri Lanka and the Western Ghats of India are major hotspots of diversity for the genus, with 10 of the 17 currently-described species being endemic to these regions.[4]

Species

The taxonomy of vine snakes is not well-documented, and literature varies widely, but there are 17 currently accepted species in the genus Ahaetulla:[4]

Several undescribed species (including the Southeast Asian Ahaetulla formerly assigned to A. nasuta) still likely remain in these complexes[2]

Ahaetulla prasina, showing keyhole shaped pupil

Description

All Ahaetulla species are characterized by thin, elongated bodies, with extremely long tails and a sharply triangular shaped head. They are primarily green in color, but can vary quite a bit to yellows, oranges, greys, and browns. They can have black and/or white patterning, or can be solid in color. Their eyes are almost unique in the reptile world, having keen binocular vision and keyhole shaped pupils, being similar in this aspect with twig snakes, who also have keyhole shaped pupils.

Etymology

The genus name Ahaetulla comes from the Sinhalese name ehetulla for Ahaetulla nasuta, which means 'eye plucker' or 'eye striker.[5]

Vernacular names

The sinhala name "Aheatulla" or "eye-plucker" forms the taxonomic genus name. In Tamil, it is known as pachai paambu, in Malayalam it is known as pachila paambu, in Telugu it is known as Pasarika Paamu, in Marathi, it is known as shelati snake, and in Kannada it is known as Hasiru Haavu. There are dozens of other vernacular names for this snake genus within its range.[6][7]

  • Sinhala: ඇහැටුල්ලා (Pronounced: Aheatulla)
  • Telugu: పచ్చారి పాము.
  • Bengali: লাউডগা.
  • Odia: ଲାଉଡଙ୍କିଆ
  • Kannada: ಹಸಿರು ಹಾವು, ಹಸಿರು ಬಳ್ಳಿ ಹಾವು.
  • Gujarati: લીલવણ, માળણ.
  • Marathi हरणटोळ, शेलाटी[8]
  • Tamil: பச்சை பாம்பு
  • Malayalam: പച്ചില പാമ്പ്,കൺകൊത്തി
  • Telugu: పసరికా పాము

Behavior

They are primarily diurnal and arboreal, living in humid rainforests. Their diet consists mainly of lizards, but sometimes frogs and rodents are also consumed. Ahaetulla fronticincta, however, feeds exclusively on fish, striking its prey from branches overhanging water. Ahaetulla venom is not considered to be dangerous to humans, but serves to cause paralysis in their fast moving prey choices. They are ovoviviparous.

Ahaetulla prasina, showing rear-set fang

In captivity

Ahaetulla species are not yet frequently captive bred, as are many of the more popular snakes in the reptile keeping hobby. They are suitable for more advanced keepers, requiring a humid arboreal habitat and a diet of lizards as they rarely switch to rodents. Without proper husbandry, they are prone to health issues and stress.

References
  1. Mallik, Ashok Kumar; Achyuthan, N. Srikanthan; Ganesh, Sumaithangi R.; Pal, Saunak P.; Vijayakumar, S. P.; Shanker, Kartik (2019-07-17). "Discovery of a deeply divergent new lineage of vine snake (Colubridae: Ahaetuliinae: Proahaetulla gen. nov.) from the southern Western Ghats of Peninsular India with a revised key for Ahaetuliinae". PLOS ONE. 14 (7): e0218851. Bibcode:2019PLoSO..1418851M. doi:10.1371/journal.pone.0218851. ISSN 1932-6203. PMC 6636718. PMID 31314800.
  2. 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): zootaxa.4874.1.1. doi:10.11646/zootaxa.4874.1.1. ISSN 1175-5334. PMID 33311335.
  3. Kumar, Chethan (November 13, 2020). "IISc researchers discover 5 new species of vine snakes". The Times of India. Retrieved 2020-11-15.
  4. "Search results | The Reptile Database". reptile-database.reptarium.cz. Retrieved 2020-12-25.
  5. Wall, Frank (1921). Ophidia Taprobanica or the Snakes of Ceylon. Ceylon: Government Press. p. 291.
  6. Snakes by Dr. P. J. Deoras, Bombay.
  7. Chapter 4 Result and discussion - Shodhganga
  8. Ajanta Minerals Dist. Gadchiroli (Maharashtra)
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