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The ‘beaked’ or ‘hook-nosed’ sea snakes in the genus Enhydrina are among the most distinctive and widely distributed viviparous (live-bearing) sea snakes. They are distinguished from all other sea snakes by an extremely long and narrow (rather than triangular) mental (chin) scale that is largely concealed in a deep notch between the lower jaws.
The dangerously venomous Beaked Sea Snake (Enhydrina schistosa) occurs in the Persian Gulf, Arabian Sea, Madagascar, Iran, Pakistan, India, Sri Lanka, Malaysia north to the Philippines, Singapore, west coast of Thailand, Gulf of Thailand, Vietnam, Indonesia, and Australian region (including waters of New Guinea Island, excluding Western Australian waters).
In Australia, these snakes are reportedly often found in rivers, but it is unclear whether these are brackish waters of the tidal basins or freshwater farther from the estuaries. In Thailand, these snakes are also reported to occur in estuaries and rivers as well as in coastal waters, but, again, it is not clear how far upstream they travel. Enhydrina schistosa reportedly prefer waters at a depth from less than 5 m to a maximum around 30 m. They are active during both day and night.
The “beaked sea snake” is abundant in coastal and inshore habitats throughout the Asian and Australian regions, where it is responsible for the large majority of recorded deaths and injuries from sea snake bites. Analyses by Ukuwela et al. (2013) of five independent mitochondrial and nuclear loci for populations spanning Australia, Indonesia and Sri Lanka indicate that this nominal species actually consists of two distinct lineages in Asia and Australia--and that these are not closest relatives. As a result, Ukuwela et al. elevated Australian ‘‘E. schistosa’’ to full species status, provisionally referred to as Enhydrina zweifeli. Convergence in the characteristic "beaked" morphology of these species is probably associated with the wide gape required to accommodate their spiny prey.
The recognition of cryptic species potentially has important implications for snakebite management given the medical importance of beaked sea snakes and the fact that the only sea snake anti-venom available is raised against Malaysian E. schistosa. Variation among snake venoms has a strong phylogenetic component, and the venom of the two Enhydrina populations has been shown to have a similar overall composition, but different specific isoforms--although both the Asian and Australian forms are highly toxic. However, a key aspect of sea snake venom evolution, which has prevented the confusion of these two cryptic species from having catastrophic medical impacts, is that all sea snake venoms are very streamlined due to feeding on a single higher taxon (bony fish). Consequently, all sea snake venoms tested to date have been well neutralized by the only available antivenom.
de Silva et al. (2011) reported preliminary observations on the sex, reproductive status, and reproduction of six species of hydrophiine sea snakes (including Enhydrina schistosa) collected as fishing bycatch in different coastal regions of Sri Lanka.
Ward (2000) studied sea snake bycatch by trawlers pursuing prawns off northern Australia. This bycatch included a small number of Enhydrina schistosa.
(Leviton et al. 2003; Ukuwela et al. 2013 and references therein)
Mental scute small, partly concealed within mental groove. 3-4 maxillary teeth behind fangs; 5-6 palatine teeth, palatine teeth larger than pterygoid teeth. No suborbital stripe; young dark gray above, whitish below, with dark gray or black annuli (pattern disappears in adults, which are uniform gray in color). Scales around body variable: in Bay of Bengal, scales around neck males 43-52, females 48-55; scales around midbody males 53-60, females 55-65; scales somewhat imbricate or juxtaposed, with short central keel; ventrals 262-322; preanal scales only slightly enlarged. Total length 1400 m, tail length 180 mm (but rarely exceeding 1100 mm total length).
Kharin and Czeblukov (2009) give the range of Enhydrina schistosa as Persian Gulf, Arabian Sea, Madagascar, Iran, Pakistan, India, Sri Lanka, Malaysia, Singapore, west coast of Thailand, Gulf of Thailand, Vietnam, Indonesia, and Australian region (including waters of New Guinea Island; except Western Australian waters).
Leviton et al. (2003) give the range of Enhydrina schistosa as of Enhydrina schistosa as Persian Gulf east to Indonesia, New Guinea and northern Australia, and north from Malaysia to the Philippines, including Myanmar coastal waters (two specimens Ayeyarwady Division coastal waters).
வலைக்கடியன்/வலைகடியன்(Hook nosed sea snake) (Enhydrina schistosa[1]) என்பது இந்தியாவின் கடற்கரைகளின் அருகில் காணப்படுகின்ற ஒரு வகை கடற்பாம்பாகும். நச்சுத் தன்மையுடைய இந்த பாம்பு கடித்தால் மனிதன் இறந்துவிட நேரிடும். இவை தரைப் பாம்புகள் போலின்றி நீரில் வாழும் தன்மையுடையன. இதன் குட்டைவால் பக்கங்களில் தட்டையாகத் துடுப்பு வடிவானது. மூக்குத்துளைகள் மேற்புறம் திறப்புள்ளவை. மூடுசவ்வுகள் அமைந்தவை. இவை அதிகமாக மீன்களையே உணவாக உட்கொள்கின்றன. இவை நீரில் குட்டி போட்டு இனப்பெருக்கம் செய்கின்றன.
வலைக்கடியன்/வலைகடியன்(Hook nosed sea snake) (Enhydrina schistosa) என்பது இந்தியாவின் கடற்கரைகளின் அருகில் காணப்படுகின்ற ஒரு வகை கடற்பாம்பாகும். நச்சுத் தன்மையுடைய இந்த பாம்பு கடித்தால் மனிதன் இறந்துவிட நேரிடும். இவை தரைப் பாம்புகள் போலின்றி நீரில் வாழும் தன்மையுடையன. இதன் குட்டைவால் பக்கங்களில் தட்டையாகத் துடுப்பு வடிவானது. மூக்குத்துளைகள் மேற்புறம் திறப்புள்ளவை. மூடுசவ்வுகள் அமைந்தவை. இவை அதிகமாக மீன்களையே உணவாக உட்கொள்கின்றன. இவை நீரில் குட்டி போட்டு இனப்பெருக்கம் செய்கின்றன.
Enhydrina schistosa, commonly known as the beaked sea snake, hook-nosed sea snake, common sea snake, or the Valakadeyan 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.[1]
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.[2]
The name valakadyn is from the Malayalam and Tamil word Vala kadiyan meaning net biter.[3]
It is found in the Arabian Sea and Persian Gulf (Bahrain, Iran, Iraq, Kuwait, Oman, Qatar, Saudi Arabia and United Arab Emirates),[4] south of the Seychelles and Madagascar, the seas off South Asia (Pakistan, India (coasts from Gujarat to West Bengal and Andaman & Nicobar Island), Sri Lanka and Bangladesh),[4] Southeast Asia (Myanmar, Thailand, Vietnam).
Snakes from Australia (Northern Territory and Queensland) and New Guinea are now provisionally identified as Enhydrina zweifeli, due to DNA tests that have shown they are not related to Enhydrina schistosa.[5][6]
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".[7] 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.[8] This widespread species is responsible for the vast majority of deaths from sea snake bites (up to 90% of all sea snake bites).[9] The LD50 value is 0.1125 mg/kg based on toxicology studies.[10][11] 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.[8]
A hook-nosed sea snake seen on Arossim Beach, South Goa, India. This snake was found in a fishing net and later released to the sea. Enhydrina schistosa, commonly known as the beaked sea snake, hook-nosed sea snake, common sea snake, or the Valakadeyan 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.
Hydrophis schistosus Hydrophis generoko animalia da. Narrastien barruko Elapidae familian sailkatuta dago.
Hydrophis schistosus Hydrophis generoko animalia da. Narrastien barruko Elapidae familian sailkatuta dago.
Hydrophis schistosus ou serpent marin à bec est une espèce de serpents de la famille des Elapidae[1].
Cette espèce marine se rencontre[1] :
Ce serpent marin est vivipare et venimeux[1].
Sa taille totale atteint 1,5 à 3 m de long[2].
Sa robe varie de bleu-gris à gris-noir. Ce serpent de mer possède une queue aplatie.
Il est ichtyophage.
En 2019, deux de ces reptiles aquatiques ont été photographiés à 245 et 239 mètres de profondeur [2].
Son venin avec une dose létale médiane de 0,112 5 mg/kg mesurée chez la souris[1] fait de ce serpent l'un des plus venimeux. Cependant, plutôt craintif, il préfère fuir plutôt que d'attaquer.
Enhydrina schistosa chamada de cobra-marinha-comum, cobra-marinha-de-nariz-de-gancho ou cobra-marinha-de-valakadyn é uma cobra marinha.
Alegadamente tem a dose de peçonha (veneno) mais letal do mundo.
Encontra-se no Mar da Arábia e Golfo Pérsico ao largo de Oman, a sul das Seychelles e Madagáscar, ao largo da costa da Ásia Meridional (Paquistão, Índia e Bangladesh), Sudeste Asiático (Mianmar, Tailândia, Vietname), Austrália e Nova Guiné.
Hydrus valakadyn Boie, 1827
Disteira russelii Fitzinger, 1827
Polyodontes annulatus Lesson, 1834
Hydrophis schistosa Schlegel, 1837
Hydrophis subfasciata Gray, 1842
Hydrophis bengalensis Gray, 1842
Enhydrina valakadyen Gray, 1849
Thalassophis werneri Schmidt, 1852
Enhydrina schistosus Bibron & Duméril, 1854
Hydrophis fasciatus Jan, 1872
Enhydrina valakadien Boulenger, 1890
Enhydrina vikadien Boettger, 1892
Enhydrina velakadien Flower, 1899
Enhydrina valakadyn Stejneger, 1907
Mornár nosatý (lat. Enhydrina schistosa) je jedovatý morský had z čeľade koralovcovitých. Je prudko jedovatý, zodpovedný za 9 z 10 ľudských úmrtí na následky uhryznutia morským hadom. Napriek jeho silnému jedu sa často stáva potravou pobrežných predátorov, ako sú ryby a korkodíly.
Mornár nosatý dorastá do dĺžky 1 až 1,5 m a váži zvyčajne do 2 kg. Má svetlosivé sfarbenie s nevýraznými modrosivými pruhmi. Oplýva štíhlym telom, ostro zakončenou hlavou a veslovitým chvostom. Má malé zuby, menšie ako 4 mm, ale dokáže roztvoriť čeľuste tak široko, že zvládne prehltnúť aj veľkú korisť.
Žije a loví v plytkej kalnej vode popri pobreží, v mangrovových močiaroch, riekach a v ich ústí. Je rozšírený vo veľkom areáli Indického oceána a západ Pacifiku, od Perzského zálivu po sever Austrálie.
Je to agresívny a ľahko vyprovokovateľný druh živiaci sa prevažne rybami a krevetami. Korisť si hľadá čuchom a hmatom. Tak ako všetky rybami sa živiace hady aj on počká, kým korisť prestane bojovať a potom ju prehltne hlavou napred.
Každú sezónu rodia mornáre nosaté až 30 mláďat. Ich úmrtnosť je vysoká, takže iba malé percento jedincov sa dožije reprodukčného veku. Väčšinu mornárov usmrtia predátory alebo sa zapletú do sietí na krevety.
Jed v jednom uhryznutí tohto druhu je dostatočný na usmrtenie 50 ľudí, čo predstavuje v porovnaní so suchozemskými hadmi, napríklad kobra kráľovská alebo koralovce až dvojnásobok. K uhryznutiu dochádza prevažne pri brodení alebo lovení rýb v kalných vodách. O počte obetí, ktoré podľahli jedu mornára nosatého, neexistujú dôveryhodné záznamy.
Commons ponúka multimediálne súbory na tému Mornár nosatý
Wikidruhy ponúkajú informácie na tému Mornár nosatý
Mornár nosatý (lat. Enhydrina schistosa) je jedovatý morský had z čeľade koralovcovitých. Je prudko jedovatý, zodpovedný za 9 z 10 ľudských úmrtí na následky uhryznutia morským hadom. Napriek jeho silnému jedu sa často stáva potravou pobrežných predátorov, ako sú ryby a korkodíly.
