Species of Thailand
Beaked sea snake
Hydrophis schistosus, François Marie Daudin, 1803
(In Thai: งูคออ่อนปากจงอย, ngu kor orn paak ja-ngoy)
Enhydrina schistosa, commonly known as the beaked sea snake, hook-nosed sea snake, common sea snake, or the Valakadyn sea snake, is a highly venomous species of sea snake common throughout the tropical Indo-Pacific. This species is implicated in more than 50% of all bites caused by sea snakes, as well as the majority of envenomings and fatalities.
The rostral scale is longer than broad, and is in contact with four shields; frontal more long than broad, shorter than the parietals; nasals in contact with the two anterior labials; sometimes partially divided; one pre- and one or two postoculars; temporals l–3; seven or eight upper labials, fourth or third and fourth entering the eye, the last sometimes divided; anterior chin-shields rather indistinct, separated. Scales with a tubercle or keel, in 50–70 rows; ventrals 230–314, slightly enlarged. The snake is usually uniformly dark grey above; sides and lower parts whitish. Young specimens olive or grey with black transverse bands, broadest in the middle. Length of head and body 1110 mm; tail 190 mm.
The name valakadyn is from the Malayalam and Tamil word Vala kadiyan meaning net biter.
It is found in the Arabian Sea and Persian Gulf (off Oman), south of the Seychelles and Madagascar, the seas off South Asia (Pakistan, India and Bangladesh), Southeast Asia (Myanmar (formerly Burma), Thailand, Vietnam).
Snakes from Australia (Northern Territory and Queensland) and New Guinea are now provisionally identified as Enhydrina zweifeli, due to DNA test that have shown they are not related to Enhydrina schistosa.
Habitat and behavior
These snakes are generally found in the coast and coastal islands of India. They are amongst the most common of the 20 kinds of sea snakes found in that region.
They are active both during the day and at night. They are able to dive up to 100 m and stay underwater for a maximum of five hours before resurfacing. Sea snakes are equipped with glands to eliminate excess salt. They are venomous and notably aggressive, with some herpetologists describing them as "cantankerous and savage". About 1.5 milligrams of its venom is estimated to be lethal.
Their principal food is fish.
The venom of this species is made up of highly potent neurotoxins and myotoxins. This widespread species is responsible for the vast majority of deaths from sea snake bites (up to 90% of all sea snake bites). The value is 0.1125 mg/kg based on toxicology studies. The average venom yield per bite is approximately 7.9–9.0 mg, while the lethal human dose is estimated to be 1.5 mg.
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- Hydrophis schistosus
- Beaked sea snake
- Common seasnake
- Hook-nosed sea snake
- Valakadyn sea snake
- French: Enhydrine ardoisee
- Thai: งูคออ่อนปากจงอย, ngu kor orn paak ja-ngoy
- Enhydrina schistosus, Tanya Chan-Ard et al. (2015)
- Enhydrina schistosa, Van Stanley Bartholomew Wallach et al. (2014)
- Hydrophis schistosus, K.L. Sanders et al. (2012)
- Enhydrina schistosa, Arne Redsted Rasmussen et al. (2011)
- Enhydrina schistosa, S. Wilson & G. Swan (2010)
- Enhydrina schistosa, Harold Cogger (2000)
- Enhydrina schistosa, John C. Murphy & Merel J. Cox & Harold K. Voris (1999)
- Enhydrina schistosa, Merel J. Cox et al. (1998)
- Disteira schistosa, Arne Redsted Rasmussen (1997)
- Enhydrina schistosa, Frank Glaw & Miguel Vences (1994)
- Disteira schistosa, Alice Georgie Cruickshank Grandison (1978)
- Disteira schistosa, Samuel Booker McDowell (1972)
- Enhydrina schistosa, Malcolm Arthur Smith (1943)
- Enhydrina valakadyen, Frank Wall (1921)
- Enhydrina valakadien, H. Gadow (1909)
- Enhydrina valakadyn, Leonhard Hess Stejneger (1907)
- Enhydrina velakadien, Stanley Smyth Flower (1899)
- Enhydrina valakadien, George Albert Boulenger (1896)
- Enhydrina schistosa, John Van Denburgh (1895)
- Enhydrina vikadien, Oskar Boettger (1892)
- Enhydrina valakadien, George Albert Boulenger (1890)
- Hydrophis schistosus, Giorgio Jan (1872)
- Hydrophis fasciatus, Giorgio Jan (1872)
- Enhydrina valakadyen, Ferdinand Stoliczka (1870)
- Enhydrina schistosa, Ferdinand Stoliczka (1870)
- Hydrophis schistosa, Johann Gustav Fischer (1856)
- Hydrophis schistosus, André Marie Constant Duméril & Gabriel Bibron (1854)
- Thalassophis werneri, Karl Patterson Schmidt (1852)
- Enhydrina valakadyen, John Edward Gray (1849)
- Hydrophis bengalensis, John Edward Gray (1842)
- Hydrophis subfasciata, John Edward Gray (1842)
- Hydrophis schistosa, Hermann Schlegel (1837)
- Polyodontes annulatus, René-Primevère Lesson (1834)
- Disteira russelii, Leopold Fitzinger (1827)
- Hydrus valakadyn, Friedrich Boie (1827)
- Hydrophis schistosus, François Marie Daudin (1803)
Least Concern (IUCN3.1)