The yellow-bellied sea snake (''Hydrophis platurus'') is a highly

venomous Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through a wound by means of a bite, sting, or similar action. The toxin is delivered through a specially evolved ''venom apparatus'', such as fangs or a sti ...

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of snake from the subfamily

Hydrophiinae Hydrophiinae is a subfamily of venomous snakes in the family Elapidae. It contains most sea snakes and many genera of venomous land snakes found in Australasia, such as the taipans (''Oxyuranus''), tiger snakes (''Notechis''), brown snakes (' ...

(the sea snakes) found in

tropical The tropics are the regions of Earth surrounding the equator, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's ax ...

oceanic waters around the world except for the

Atlantic Ocean The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...

. For many years, it was placed in the

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unisp ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

''Pelamis'', but recent molecular evidence indicates it lies within the genus ''

Hydrophis ''Hydrophis'' is a genus of sea snakes, venomous snakes in the subfamily Hydrophiinae of the Family (biology), family Elapidae. Species in the genus ''Hydrophis'' are typically found in Indo-Australian and Southeast Asian waters. Currently, arou ...

''.

Taxonomy

In 1766,

Linnaeus Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...

published the original description of the yellow-bellied sea snake, naming it ''Anguis platura'' (''Anguis'' meaning snake). In 1803,

François Marie Daudin François Marie Daudin (; 29 August 1776 in Paris – 30 November 1803 in Paris) was a French zoologist. Biography With legs paralyzed by childhood disease, he studied physics and natural history but ended up being devoted to the latter. Daudin w ...

created the new

''Pelamis'' and assigned this

to it, referring to it as ''Pelamis platuros''. In 1842, Gray described what he thought was a new species and called it ''Pelamis ornata'' (subsequently ''P. ornata'' became a synonym of ''P. platura''). The commonly used genus name ''Pelamis'' is derived from the

Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

word for "tunny fish", which presumably refers to the habitat or what Daudin thought they ate. The specific name ''platurus'' is a combination of the Ancient Greek words ''platys'' "flat" and ''oura'' "tail", referring to the flattened tail. The word ''Pelamis'' is a feminine noun and means young or small tunny fish. In 1872, Stoliczka introduced the name ''Pelamis platurus'' (still the most used scientific name by scientists today), but used the incorrect ending ''-us'' instead of ''-a'' which a feminine noun requires. A few recent examples exist of scientists' beginning to use the grammatically correct name ''Pelamis platura'', e.g., Bohme 2003 and the Reptile Database with its page headed ''Pelamis platura'' (Linnaeus, 1766), which includes an extensive synonymy of the different scientific names which have been used for the yellow-bellied sea snake. The same rules apply for the most recent taxonomic name of ''Hydrophis platurus''. To further complicate the

nomenclature Nomenclature (, ) is a system of names or terms, or the rules for forming these terms in a particular field of arts or sciences. (The theoretical field studying nomenclature is sometimes referred to as ''onymology'' or ''taxonymy'' ). The principl ...

, the taxonomic status of sea snakes is still under review, with recent authors suggesting a dismantling of

genera, such as ''Pelamis'', in favour of a single genus, ''

'', in order to reduce

paraphyly Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...

and better reflect

phylogenetic relationship In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as Computational phylogenetics, phylogenetic inference. It infers the relationship among organ ...

s. Other common names are yellowbelly sea snake or pelagic sea snake.

Evolution

Sea snakes are a

monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...

group (

) that diverged from the front-fanged

Australasia Australasia is a subregion of Oceania, comprising Australia, New Zealand (overlapping with Polynesia), and sometimes including New Guinea and surrounding islands (overlapping with Melanesia). The term is used in a number of different context ...

snakes (

Elapidae Elapidae (, commonly known as elapids , from , variant of "sea-fish") is a family of snakes characterized by their permanently erect fangs at the front of the mouth. Most elapids are venomous, with the exception of the genus '' Emydocephalus ...

) about 10 million years ago. The yellow-bellied sea snake is a part of the rapidly radiating

group.

Description

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 snake

. 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 Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a "bridging" form of reproduction between egg-laying oviparity, oviparous and live-bearing viviparity, viviparous reproduction. Ovoviviparous animals possess embryos that develo ...

). Adaptations to aquatic life include the reduced

ventral Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

scale size, laterally compressed body and paddle-tail for swimming, valved nostrils and

palatine A palatine or palatinus (Latin; : ''palatini''; cf. derivative spellings below) is a high-level official attached to imperial or royal courts in Europe since Roman Empire, Roman times.

seal for excluding seawater, and

cutaneous gas exchange Cutaneous respiration, or cutaneous gas exchange (sometimes called skin breathing), is a form of respiration in which gas exchange occurs across the skin or outer integument of an organism rather than gills or lungs. Cutaneous respiration may be th ...

for prolonging dive times. This

can uptake up to 33% of its

oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...

requirements through the

skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other animal coverings, such as the arthropod exoskeleton, have different ...

while diving and swimming at the surface of the water. Sea snakes also have a special salt

gland A gland is a Cell (biology), cell or an Organ (biology), organ in an animal's body that produces and secretes different substances that the organism needs, either into the bloodstream or into a body cavity or outer surface. A gland may also funct ...

located in the lower jaw that was formerly believed to filter out salt from the surrounding seawater but has been found not to be used for that purpose, as sea snakes drink fresh water only. :''See

snake scales Snakes, like other reptiles, have skin covered in scales.Boulenger, George A. 1890 The Fauna of British India. p. 1 Snakes are entirely covered with scales or scutes of various shapes and sizes, known as snakeskin as a whole. A scale protects ...

for terminology used here''

Morphology

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 latitudinal groove, 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. Total length for males is up to , for females up to ; tail length for males is up to , females up to .

Distribution and habitat

The yellow-bellied sea snake is one of the most widely distributed snakes in the world. It is completely

pelagic The pelagic zone consists of the water column of the open ocean and can be further divided into regions by depth. The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or water column between the sur ...

and is often observed on oceanic drift lines, using surface currents and storms to move around the ocean. Their distribution appears to be largely determined by favourable water temperatures, oceanic currents and recent formation of

land bridge In biogeography, a land bridge is an isthmus or wider land connection between otherwise separate areas, over which animals and plants are able to cross and colonize new lands. A land bridge can be created by marine regression, in which sea le ...

s that have blocked farther dispersal. Pelamis platura yellow form Costa Rica

The yellow-bellied sea snake has an extensive distribution covering the entire tropical

Indo-Pacific The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the ...

, as well as extending to

Costa Rica Costa Rica, officially the Republic of Costa Rica, is a country in Central America. It borders Nicaragua to the north, the Caribbean Sea to the northeast, Panama to the southeast, and the Pacific Ocean to the southwest, as well as Maritime bo ...

, southern

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

, and northern

Peru Peru, officially the Republic of Peru, is a country in western South America. It is bordered in the north by Ecuador and Colombia, in the east by Brazil, in the southeast by Bolivia, in the south by Chile, and in the south and west by the Pac ...

. It is the only sea snake to have reached the

Hawaiian Islands The Hawaiian Islands () are an archipelago of eight major volcanic islands, several atolls, and numerous smaller islets in the Pacific Ocean, North Pacific Ocean, extending some from the Hawaii (island), island of Hawaii in the south to nort ...

. 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 of

Southwest Australia Southwest Australia is a biogeographic region in Western Australia. It includes the Mediterranean-climate area of southwestern Australia, which is home to a diverse and distinctive flora and fauna. The region is also known as the Southwest Au ...

, including records at beaches near metropolitan areas. It is also reported from Christmas Island and Cocos (Keeling) Islands (Australia). The yellow-bellied sea snake requires a minimum of to survive, long-term. However, the species has been reported in colder waters of the Pacific, such as the coasts of southern California, Mexico,

Tasmania Tasmania (; palawa kani: ''Lutruwita'') is an island States and territories of Australia, state of Australia. It is located to the south of the Mainland Australia, Australian mainland, and is separated from it by the Bass Strait. The sta ...

, and

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

, the latter being a country that would otherwise be free of snakes were it not for the infrequent strandings of yellow-bellied sea snakes and banded sea kraits. 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 considered

native Native may refer to: People * '' Jus sanguinis'', nationality by blood * '' Jus soli'', nationality by location of birth * Indigenous peoples, peoples with a set of specific rights based on their historical ties to a particular territory ** Nat ...

(indigenous) to New Zealand and worthy of protection under the

Wildlife Act 1953 Wildlife Act 1953 is an Act of Parliament in New Zealand. Under the act, the majority of native New Zealand vertebrate species are protected by law, and may not be hunted, killed, eaten or possessed. Violations may be punished with fines of up t ...

. These colder water occurrences are believed to be linked to

El Niño EL, El or el may refer to: Arts and entertainment Fictional entities * El, a character from the manga series ''Shugo Chara!'' by Peach-Pit * Eleven (''Stranger Things'') (El), a fictional character in the TV series ''Stranger Things'' * El, fami ...

, among other severe weather events, possibly creating unusually strong, new ocean currents that transport the snakes far off-course. In October 2015, a beached yellow-bellied sea snake was reported and photographed in

Ventura County, California Ventura County () is a County (United States), county located in Southern California, the southern part of the U.S. state of California. As of the 2020 United States census, 2020 census, the population was 843,843. The largest city is Oxnard, Ca ...

, well outside its normal range, for the first time in 30 years. A few months later, in January 2016, a stranded individual was found in

Coronado, California Coronado (Spanish language, Spanish for "Crowned") is a resort town, resort city in San Diego County, California, United States, across San Diego Bay from downtown San Diego. It was founded in the 1880s and incorporated in 1890. Its population ...

, washed-up on Coronado Beach's north end (better known as Dog Beach), just south of

Naval Air Station North Island Naval Air Station North Island or NAS North Island , at the north end of the Coronado peninsula on San Diego Bay in San Diego, California, is part of the largest aerospace-industrial complex in the United States Navy – Naval Base Coronado (N ...

(NASNI). The specimen was subsequently transported to and examined at the

Scripps Institute of Oceanography Scripps Institution of Oceanography (SIO) is the center for oceanography and Earth science at the University of California, San Diego. Its main campus is located in La Jolla, California, La Jolla, with additional facilities in Point Loma, San Die ...

La Jolla La Jolla ( , ) is a hilly, seaside neighborhood in San Diego, California, occupying of curving coastline along the Pacific Ocean. The population reported in the 2010 census was 46,781. The climate is mild, with an average daily temperature o ...

. 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. Hydrophis platurus xanthos 103019572

The yellow-bellied sea snake has been found in all the countries of Africa's eastern coast and all eastern islands, like Djibouti, Eritrea, Kenya, Madagascar, Mauritius, Mayotte, Mozambique, Réunion, Seychelles, Somalia, South Africa and Tanzania. On the African Atlantic coast they have been reported to occur in the

Benguela Current The Benguela Current is the broad, northward flowing ocean current that forms the eastern portion of the South Atlantic Ocean gyre. The current extends from roughly Cape Point in the south, to the position of the Angola-Benguela Front in the no ...

, with specimens found along the coasts of

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...

and

Namibia Namibia, officially the Republic of Namibia, is a country on the west coast of Southern Africa. Its borders include the Atlantic Ocean to the west, Angola and Zambia to the north, Botswana to the east and South Africa to the south; in the no ...

. The yellow-bellied sea snake has also been found in the

Colombia Colombia, officially the Republic of Colombia, is a country primarily located in South America with Insular region of Colombia, insular regions in North America. The Colombian mainland is bordered by the Caribbean Sea to the north, Venezuel ...

n Caribbean four separate times, making it the only sea snake to be found in the

Caribbean Sea The Caribbean Sea is a sea of the Atlantic Ocean, North Atlantic Ocean in the tropics of the Western Hemisphere, located south of the Gulf of Mexico and southwest of the Sargasso Sea. It is bounded by the Greater Antilles to the north from Cuba ...

. However these occurrences are believed to be the result of human activity, be it ship discharge, intentional release or via the

Panama Canal The Panama Canal () is an artificial waterway in Panama that connects the Caribbean Sea with the Pacific Ocean. It cuts across the narrowest point of the Isthmus of Panama, and is a Channel (geography), conduit for maritime trade between th ...

, as it is not considered a part of their native range. This is due to the

between North and South America, the

Isthmus of Panama The Isthmus of Panama, historically known as the Isthmus of Darien, is the narrow strip of land that lies between the Caribbean Sea and the Pacific Ocean, linking North America, North and South America. The country of Panama is located on the i ...

, which formed from about 10 million years ago to 3 million years ago (i.e.,

continental drift Continental drift is a highly supported scientific theory, originating in the early 20th century, that Earth's continents move or drift relative to each other over geologic time. The theory of continental drift has since been validated and inc ...

), acting as a dispersal barrier and preventing entry into the Caribbean Sea from the Pacific Ocean. The man-made

has not made a crossing of the isthmus possible presumably because it is

fresh water Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salt (chemistry), salts and other total dissolved solids. The term excludes seawater and brackish water, but it does include ...

. Due to the wide distribution of the species and relative lack of dispersal barriers, it has been assumed that individuals from different localities represent a single breeding

population Population is a set of humans or other organisms in a given region or area. Governments conduct a census to quantify the resident population size within a given jurisdiction. The term is also applied to non-human animals, microorganisms, and pl ...

(i.e., high

gene flow In population genetics, gene flow (also known as migration and allele flow) is the transfer of genetic variation, genetic material from one population to another. If the rate of gene flow is high enough, then two populations will have equivalent ...

). However, a study that used

haplotype A haplotype (haploid genotype) is a group of alleles in an organism that are inherited together from a single parent. Many organisms contain genetic material (DNA) which is inherited from two parents. Normally these organisms have their DNA orga ...

networks in two populations from

suggests that shallow genetic population structure exists, which reflects variation in colour patterns (brown and yellow in Golfo de Papagayo and completely yellow in Golfo Dulce).

Behaviour

Contrary to past beliefs, sea snakes require fresh water to survive and the yellow-bellied sea snake drinks

precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls from clouds due to gravitational pull. The main forms of precipitation include drizzle, rain, rain and snow mixed ("sleet" in Commonwe ...

that forms on the surface of sea water. This species has been reported to survive severe dehydration of up to 7 months during seasonal drought. Yellow-bellied sea snakes breed in warm waters; they are

with a gestation period around 6 months. According to Ditmars, females bear live young in

tidal pools A tide pool or rock pool is a shallow pool of seawater that forms on the rocky intertidal shore. These pools typically range from a few inches to a few feet deep and a few feet across. Many of these pools exist as separate bodies of water only ...

. They move poorly on land due to their smaller belly scales that form a

keel The keel is the bottom-most longitudinal structural element of a watercraft, important for stability. On some sailboats, it may have a fluid dynamics, hydrodynamic and counterbalancing purpose as well. The keel laying, laying of the keel is often ...

. They are sometimes observed in large aggregations of thousands on the surface of the water in oceanic drift lines, which has been proposed as a strategy to catch prey. They hunt by floating on the surface of the water to attract

pelagic fish Pelagic fish live in the pelagic zone of ocean or lake waters—being neither close to the bottom nor near the shore—in contrast with demersal fish that live on or near the bottom, and reef fish that are associated with coral reefs. ...

that are seeking shelter; prey are captured via a backwards swimming motion and rapid lunge of the jaws. The ability to swim backwards is an unusual and distinguishing characteristic of this species. Heatwole proposed that these snakes find their prey by sensing the vibration generated by fish movement. These snakes are not considered aggressive but will defend themselves if threatened.

Venom

The

venom Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through a wound by means of a bite, sting, or similar action. The toxin is delivered through a specially evolved ''venom apparatus'', such as fangs or a sti ...

of this species is highly potent, like that of other

sea snakes Sea snakes, or coral reef snakes, are elapid snakes that inhabit marine environments for most or all of their lives. They belong to two subfamilies, Hydrophiinae and Laticaudinae. Hydrophiinae also includes Australasian terrestrial snakes, w ...

. Bites are rare and the most common victims are fishermen who try to get them out of

fishing net A fishing net or fish net is a net (device), net used for fishing. Fishing nets work by serving as an improvised fish trap, and some are indeed rigged as traps (e.g. #Fyke nets, fyke nets). They are usually wide open when deployed (e.g. by cast ...

s. The subcutaneous of the venom is 0.067 mg/kg and the venom yield per bite is 1.0–4.0 mg. Yellow-bellied sea snake venom contains several different

neurotoxin Neurotoxins are toxins that are destructive to nervous tissue, nerve tissue (causing neurotoxicity). Neurotoxins are an extensive class of exogenous chemical neurological insult (medical), insultsSpencer 2000 that can adversely affect function ...

s and two other isotoxins. Juvenile and adult specimens have the same toxin compounds in their venom however juvenile venom is on average less concentrated.

Antivenom

Sea snake venom can cause damage to

skeletal muscle Skeletal muscle (commonly referred to as muscle) is one of the three types of vertebrate muscle tissue, the others being cardiac muscle and smooth muscle. They are part of the somatic nervous system, voluntary muscular system and typically are a ...

with consequent

myoglobinuria Myoglobinuria is the presence of myoglobin in the urine, which usually results from rhabdomyolysis or muscle injury. Myoglobin is present in muscle cells as a reserve of oxygen. Signs and symptoms Signs and symptoms of myoglobinuria are usua ...

, neuromuscular

paralysis Paralysis (: paralyses; also known as plegia) is a loss of Motor skill, motor function in one or more Skeletal muscle, muscles. Paralysis can also be accompanied by a loss of feeling (sensory loss) in the affected area if there is sensory d ...

or direct

renal In humans, the kidneys are two reddish-brown bean-shaped blood-filtering organs that are a multilobar, multipapillary form of mammalian kidneys, usually without signs of external lobulation. They are located on the left and right in the retrop ...

damage. The venoms of significant species of sea snake are neutralised with Commonwealth Serum Laboratories Ltd (of Melbourne, Australia) sea snake ('' Enhydrina schistosa'') antivenom. If that preparation is not available,

tiger snake The tiger snake (''Notechis scutatus'') is a large and highly venomous snake of southern Australia, including its coastal islands and Tasmania. These snakes are often observed and locally well known by their banding, black and yellow like a ti ...

or polyvalent antivenom should be used. No deaths have been recorded from bites in Australian waters. The ''E. schistosa'' antivenom was tested specifically on ''Pelamus platurus'', and it effectively neutralised the venom.http://www.ajtmh.org/cgi/content/abstract/23/1/135 Published 1973. Accessed May 2008.

Cited references

Other sources

* * * * 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.

External links

Pelagic Sea Snakes and the animals that live on them
Life is Short but Snakes are Long {{Taxonbar, from=Q1247379 Reptiles described in 1766 Taxa named by Carl Linnaeus Hydrophis Reptiles of Pakistan Reptiles of New Zealand Reptiles of Western Australia Snakes of Japan Reptiles of Mexico Reptiles of Iran Reptiles of Guatemala Reptiles of Hawaii Snakes of Australia