Theyellow-bellied sea snake (Hydrophis platurus) is an extremelyvenomousspecies of snake from the subfamilyHydrophiinae (the sea snakes) found intropical oceanic waters around the world except for theAtlantic Ocean. For many years, it was placed in themonotypicgenusPelamis, but recent molecular evidence indicates it lies within the genusHydrophis.
In 1766,Linnaeus published the original description of the yellow-bellied sea snake, naming itAnguis platura (Anguis meaning snake). In 1803,François Marie Daudin created the newgenusPelamis and assigned thisspecies to it, referring to it asPelamis platuros. In 1842, Gray described what he thought was a new species and called itPelamis ornata (subsequentlyP. ornata became a synonym ofP. platura). The commonly used genus namePelamis is derived from theAncient Greek word for "tunny fish", which presumably refers to the habitat or what Daudin thought they ate. The specific nameplaturus is a combination of the Ancient Greek wordsplatys "flat" andoura "tail", referring to the flattened tail. The wordPelamis is a feminine noun and means young or small tunny fish. In 1872,Stoliczka introduced the namePelamis platurus (still the most used scientific name by scientists today), but used the incorrect ending-us instead of-a which a feminine noun requires.[5] A few recent examples exist of scientists' beginning to use the grammatically correct namePelamis platura, e.g., Bohme 2003 and the Reptile Database with its page headedPelamis platura (Linnaeus, 1766), which includes an extensive synonymy of the different scientific names which have been used for the yellow-bellied sea snake.[6] The same rules apply for the most recent taxonomic name ofHydrophis platurus.
To further complicate thenomenclature, the taxonomic status of sea snakes is still under review, with recent authors suggesting a dismantling ofmonotypic genera, such asPelamis, in favour of a single genus,Hydrophis, in order to reduceparaphyly and better reflectphylogenetic relationships.[7]
Other common names are yellowbelly sea snake or pelagic sea snake.[citation needed]
Hydrophis platurus, a front-fanged venomous snake, related to the brown snakes, cobras and taipans (Elapidae)
The yellow-bellied sea snake, as the name implies, has a distinctive bicolor pattern with a yellow underbelly and brown back, making it easily distinguishable from other sea snakespecies. Yellow-bellied sea snakes, like many other species of sea snake, are fully adapted to living their whole lives at sea: mating, eating and giving birth to live young (ovoviviparous). Adaptations to aquatic life include the reducedventral scale size, laterally compressed body and paddle-tail for swimming,[11][12] valved nostrils andpalatine seal for excluding seawater, andcutaneous gas exchange for prolonging dive times.[12][13][14] Thisspecies can uptake up to 33% of itsoxygen requirements through theskin while diving and swimming at the surface of the water.[15] Sea snakes also have a special saltgland located in the lower jaw that was formerly believed to filter out salt from the surrounding seawater[16] but has been found not to be used for that purpose, as sea snakes drink fresh water only.[17]
The body of this snake is compressed, with the posterior less than half the diameter of the neck; the body scales are juxtaposed, subquadrangular in shape, and in 23–47 rows around the thickest part of the body; ventral scales, 264–406 in number, are very small and, if distinct, divided by a latitudinalgroove, but usually are indistinguishable from adjacent body scales. The head is narrow, with an elongated snout; head shields are entire, nostrils are superior, and nasal shields are in contact with one another; the prefrontal scale is in contact with second upper labial; one or two preoculars, two or three postoculars, and two or three small anterior temporals are present; seven or eight upper labials are found, with four or five below the eye, but separated from the border by a subocular. Colors of the snake are variable, but most often distinctly bicolored, black above, yellow or brown below, with the dorsal and ventral colors sharply demarcated from one another; ventrally, there may be a series of black spots or bars on the yellow or brown background, or the yellow may extend dorsally so there is only a narrow middorsal black stripe, or a series of black crossbars.[18] Total length for males is up to 720 mm (28 in), for females up to 880 mm (35 in); tail length for males is up to 80 mm (3.1 in), females up to 90 mm (3.5 in).
The yellow-bellied sea snake is one of the most widely distributed snakes in the world.[19] It is completelypelagic and is often observed on oceanic drift lines, using surface currents and storms to move around the ocean.[20] Their distribution appears to be largely determined by favourable water temperatures,oceanic currents and recent formation ofland bridges that have blocked farther dispersal.
The yellow-bellied sea snake has an extensive distribution covering the entire tropicalIndo-Pacific, as well as extending toCosta Rica, southernCalifornia, and northernPeru.[21][22] It is the only sea snake to have reached theHawaiian Islands.[23] The favoured habitat for hunting and reproduction includes free floating mats of sea kelp occurring in the Indian Ocean. The species is the most commonly beached sea snake on the coast ofSouthwest Australia, including records at beaches near metropolitan areas.[24] It is also reported from Christmas Island and Cocos (Keeling) Islands (Australia).[25]
The yellow-bellied sea snake requires a minimum of 16–18 °C (61–64 °F) to survive, long-term.[26] However, the species has been reported in colder waters of the Pacific, such as the coasts of southern California, Mexico,Tasmania, andNew Zealand,[27] the latter being a country that would otherwise be free of snakes were it not for the infrequent strandings of yellow-bellied sea snakes andbanded sea kraits.[28] Nonetheless, these wayward individuals make the yellow-bellied sea snake the most commonly-seen snake (and sea snake) in New Zealand, to the degree that the species is considerednative (indigenous) to New Zealand and worthy of protection under theWildlife Act 1953.[29] These colder water occurrences are believed to be linked toEl Niño, among other severe weather events, possibly creating unusually strong, new ocean currents that transport the snakes far off-course.[30][31][32][33] In October 2015, a beached yellow-bellied sea snake was reported and photographed inVentura County, California, well outside its normal range, for the first time in 30 years.[31] A few months later, in January 2016, a stranded individual was found inCoronado, California, washed-up on Coronado Beach's north end (better known as Dog Beach), just south ofNaval Air Station North Island (NASNI). The specimen was subsequently transported to and examined at theScripps Institute of Oceanography,La Jolla.[34]
The yellow-bellied sea snake is the only sea snake to have been found in the Atlantic Ocean, although only in limited circumstances. The yellow-bellied sea snake's occurrence into the Atlantic is not considered a part of its native range, but rather a dispersal from its native Pacific range.[35]
Hydrophis platurus xanthos
The yellow-bellied sea snake has been found in all the countries ofAfrica's eastern coast and all eastern islands, like Djibouti, Eritrea, Kenya, Madagascar, Mauritius, Mayotte, Mozambique, Réunion, Seychelles, Somalia, South Africa and Tanzania.[25] On the African Atlantic coast they have been reported to occur in theBenguela Current, with specimens found along the coasts ofSouth Africa andNamibia.[36][37]
The yellow-bellied sea snake has also been found in theColombian Caribbean four separate times, making it the only sea snake to be found in theCaribbean Sea. However these occurrences are believed to be the result of human activity, be it ship discharge, intentional release or via thePanama Canal, as it is not considered a part of their native range. This is due to theland bridge between North and South America, theIsthmus of Panama, which formed from about 10 million years ago to 3 million years ago[38] (i.e.,continental drift), acting as adispersal barrier and preventing entry into the Caribbean Sea from the Pacific Ocean. The man-madePanama Canal has not made a crossing of the isthmus possible presumably because it isfresh water.[39]
Due to the wide distribution of the species and relative lack ofdispersal barriers, it has been assumed that individuals from different localities represent a single breedingpopulation (i.e., highgene flow). However, a study that usedhaplotype networks in two populations fromCosta Rica suggests that shallow genetic population structure exists, which reflects variation in colour patterns (brown and yellow inGolfo de Papagayo and completely yellow inGolfo Dulce).[40]
The yellow-bellied sea snake can live its entire adult life in the open ocean
Contrary to past beliefs, sea snakes require fresh water to survive and the yellow-bellied sea snake drinksprecipitation that forms on the surface of sea water.[41] This species has been reported to survive severe dehydration of up to 7 months during seasonal drought.[42]
Yellow-bellied sea snakes breed in warm waters; they areovoviviparous with a gestation period around 6 months. According toDitmars, females bear live young intidal pools.[43] They move poorly on land due to their smaller belly scales that form aventralkeel.[13] They are sometimes observed in large aggregations of thousands on the surface of the water in oceanicdrift lines, which has been proposed as a strategy to catch prey.[44] They hunt by floating on the surface of the water to attractpelagic fish that are seeking shelter; prey are captured via a backwards swimming motion and rapid lunge of the jaws.[20] The ability to swim backwards is an unusual and distinguishing characteristic of this species.[24] Heatwole proposed that these snakes find their prey bysensing the vibration generated by fish movement. These snakes are not considered aggressive but will defend themselves if threatened.[45]
Thevenom of this species is highly potent, like that of othersea snakes.[46] Bites are rare and the most common victims are fishermen who try to get them out offishing nets.[47] The subcutaneousLD50 of the venom is 0.067 mg/kg and the venom yield per bite is 1.0–4.0 mg.[48][49] Yellow-bellied sea snake venom contains several differentneurotoxins and two other isotoxins.[50] Juvenile and adult specimens have the same toxin compounds in their venom however juvenile venom is on average less concentrated.[51]
Sea snake venom can cause damage toskeletal muscle with consequentmyoglobinuria, neuromuscularparalysis or directrenal damage. The venoms of significant species of sea snake are neutralised with Commonwealth Serum Laboratories Ltd (of Melbourne, Australia) sea snake (Enhydrina schistosa) antivenom.[52][53] If that preparation is not available,tiger snake or polyvalent antivenom should be used. No deaths have been recorded from bites in Australian waters.[54][55] TheE. schistosa antivenom was tested specifically onPelamus platurus, and it effectively neutralised the venom.[56]
^Guinea, M.; Lukoschek, V.; Cogger, H.; Rasmussen, A.; Murphy, J.; Lane, A.; Sanders, K.; Lobo, A.; Gatus, J.; Limpus, C.; Milton, D.; Courtney, T.; Read, M.; Fletcher, E.; Marsh, D.; White, M.-D.; Heatwole, H.; Alcala, A.; Voris, H.; Karns, D. (2017)."Hydrophis platurus".IUCN Red List of Threatened Species.2010 e.T176738A115883818.{{cite iucn}}: |volume= / |date= mismatch (help)
^Boulenger, G.A. 1896.Catalogue of the Snakes in the British Museum (Natural History). Volume III., Containing the Colubridæ (Opisthoglyphæ and Proteroglyphæ)... Trustees of the British Museum (Natural History). London. pp. 266–268.
^Pyron, R. Alexander; Burbrink, Frank T.; Colli, Guarino R.; de Oca, Adrian Nieto Montes; Vitt, Laurie J.; Kuczynski, Caitlin A.; Wiens, John J. (2011-02-01). "The phylogeny of advanced snakes (Colubroidea), with discovery of a new subfamily and comparison of support methods for likelihood trees".Molecular Phylogenetics and Evolution.58 (2):329–342.Bibcode:2011MolPE..58..329P.doi:10.1016/j.ympev.2010.11.006.ISSN1095-9513.PMID21074626.
^Sanders, Kate L.; Lee, Michael S. Y.; Mumpuni; Bertozzi, Terry; Rasmussen, Arne R. (2013-03-01). "Multilocus phylogeny and recent rapid radiation of the viviparous sea snakes (Elapidae: Hydrophiinae)".Molecular Phylogenetics and Evolution.66 (3):575–591.Bibcode:2013MolPE..66..575S.doi:10.1016/j.ympev.2012.09.021.PMID23026811.
^abBrowne-Cooper, R.; Bush, B.; Maryan, B.; Robinson, D. (2007).Reptiles and frogs in the bush: southwestern Australia. University of Western Australia Press. p. 273.ISBN978-1-920694-74-6.
^Harvey B Lillywhite, Coleman M Sheehy, Harold Heatwole, François Brischoux, David W Steadman; "Why Are There No Sea Snakes in the Atlantic?",BioScience, Volume 68, Issue 1, 1 January 2018, Pages 15–24,https://doi.org/10.1093/biosci/bix132
^Sexton, Owen J. (1967-01-01). "Population Changes in a Tropical Lizard Anolis limifrons on Barro Colorado Island, Panama Canal Zone".Copeia.1967 (1):219–222.doi:10.2307/1442198.JSTOR1442198.
^Also see references inThe Living Shores of Southern Africa, Margo and George Branch, pp. 130–131, Macmillan South Africa (Publishers), Johannesburg and "Snake versus Man"Johan Marais, pp. 50–51, C. Struik Publishers, Cape Town.
^Cañas, Carlos A.; Castaño-Valencia, Santiago; Castro-Herrera, Fernando (September 2022). "Biological and medical aspects related to the yellow-bellied sea snake Hydrophis platurus (Linnaeus, 1766): A view from Colombia".Travel Medicine and Infectious Disease.49 102410.doi:10.1016/j.tmaid.2022.102410.ISSN1477-8939.PMID35934312.
^Mori, Nobuhiro & Ishizaki, Hiroyuki & Tu, Anthony. (1989). "Isolation and Characterization of Pelamis platurus (Yellow-bellied Sea Snake) Postsynaptic Isoneurotoxin".The Journal of Pharmacy and Pharmacology. 41. 331-4. 10.1111/j.2042-7158.1989.tb06466.x.
^Durban J, Sasa M, Calvete JJ. Venom gland transcriptomics and microRNA profiling of juvenile and adult yellow-bellied sea snake, hydrophis platurus, from playa del coco (guanacaste, costa rica). Toxicon 2018;153:96–105.
Ditmars, Raymond L. (1936).The Reptiles of North America. New York: Doubleday, Doran & Co. p. 476.
Hecht, M. K.; Kropach, C.; Hecht, B. M. (1974). "Distribution of the yellow-bellied sea snakePelamis platurus, and its significance in relation to the fossil record".Herpetologica.30:387–395.
Kropach, C. 1975 The yellow-bellied sea snake,Pelamis, in the eastern Pacific. pp. 185–213 in: Dunson, W., ed., The Biology of Sea Snakes. Univ. Park Press, Baltimore, xi + 530 pp.
Smith, M.A. 1943.The Fauna of British India, Ceylon and Burma, including the Whole of the Indo-Chinese Sub-region. Reptiles and Amphibians. Vol. III. – Serpentes. Taylor & Francis. London. 583 pp.
