Yellow-lipped sea krait

{{speciesbox

|image = Banded Sea Krait (Laticauda colubrina) (14641328165).jpg

|image_caption = Yellow-lipped sea krait in Malaysia

|status = LC

|status_system = IUCN3.1

|status_ref = {{cite iucn |author=Lane, A. |author2=Guinea, M. |author3=Gatus, J. |author4=Lobo, A. |date=2010 |title=Laticauda colubrina |volume=2010 |page=e.T176750A7296975 |doi=10.2305/IUCN.UK.2010-4.RLTS.T176750A7296975.en |access-date=19 November 2021}}

|genus = Laticauda

|species = colubrina

|authority = (Schneider, 1799)

|synonyms = *Hydrus colubrinus {{small|Schneider, 1799}}

Platurus colubrinus {{small|— Wagler, 1830}}
Hydrophis colubrinus {{small|— Schlegel, 1837}}
Laticauda colubrina {{small|— Stejneger, 1907}}

|synonyms_ref = {{NRDB species|genus=Laticauda |species=colubrina }}

|range_map = Distribution of Laticauda colubrina.svg

}}

The yellow-lipped sea krait (Laticauda colubrina), also known as the banded sea krait or colubrine sea krait, is a species of highly venomous snake found in tropical Indo-Pacific oceanic waters. The snake has distinctive black stripes and a yellow snout, with a paddle-like tail for use in swimming.

It spends much of its time under water to hunt, but returns to land to digest, rest, and reproduce. It has very potent neurotoxic venom, which it uses to prey on eels and small fish. Because of its affinity to land, the yellow-lipped sea krait often encounters humans, but the snake is not aggressive and only attacks when feeling threatened.

Description

{{multiple image

| align = left

| direction = vertical

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| image1 = Serpiente marina de hocico ancho (Laticauda colubrina), Anilao, Filipinas, 2023-08-23, DD 04.jpg

| alt1 = A photo of the head of L. colubrina, showing its characteristic yellow snout

| image2 = Laticauda colubrina (Zamboanguita) 3.jpg

| alt2 = A photo of the tail of L. colubrina, showing its paddle-like tail

| footer = The characteristic yellow snout and paddle-like tail of L. colubrina, Zamboanguita, Philippines

}}The head of a yellow-lipped sea krait is black, with lateral nostrils and an undivided rostral scale. The upper lip and snout are characteristically colored yellow, and the yellow color extends backward on each side of the head above the eye to the temporal scales.

File:LaticaudaColubrinaSmith.jpg

The body of the snake is subcylindrical, and is taller than it is wide. Its upper surface is typically a shade of blueish gray, while the belly is yellowish, with wide ventral scales that stretch from a third to more than half of the width of the body. Black rings of about uniform width are present throughout the length of the snake, but the rings narrow or are interrupted at the belly. The midbody is covered with 21 to 25 longitudinal rows of imbricated (overlapping) dorsal scales. The dorsal and lateral scales can be used to differentiate between this species and the similar yellow-lipped New Caledonian sea krait, which typically has fewer rows of scales and scales that narrow or fail to meet (versus the yellow-lipped sea krait's ventrally meeting dark bands).{{Cite Q|Q58629017}} The tail of the snake is paddle-shaped and adapted to swimming.{{Cite journal|last1=Shine|first1=R.|last2=Shetty|first2=S.|date=2001-03-01|title=Moving in two worlds: aquatic and terrestrial locomotion in sea snakes (Laticauda colubrina, Laticaudidae)|journal=Journal of Evolutionary Biology|language=en|volume=14|issue=2|pages=338–346|doi=10.1046/j.1420-9101.2001.00265.x|s2cid=82676695|issn=1420-9101|doi-access=}}

On average, the total length of a male is {{Convert|875|mm|ftin|abbr=on}} long, with a {{Convert|13|cm|in|abbr=on}} long tail. Females are significantly larger, with an average total length of {{Convert|1.42|m|ftin|abbr=on}} and a tail length of {{Convert|145|mm|in|abbr=on}}.{{cite book|title=The Fauna of British India, Ceylon and Burma, Including the Whole of the Indo-Chinese Sub-region.|author=Smith, M.A.|publisher=Secretary of State for India. (Taylor and Francis, printers)|year=1943|volume=Reptilia and Amphibia. Vol. III.—Serpentes|location=London|page=443|author-link=Malcolm Arthur Smith|title-link=The Fauna of British India, including Ceylon and Burma}}

Distribution and habitat

The yellow-lipped sea krait is widespread throughout the eastern Indian Ocean and Western Pacific. It can be found from the eastern coast of India, along the coast of the Bay of Bengal in Bangladesh, Myanmar, and other parts of Southeast Asia, to the Malay Archipelago and to some parts of southern China, Taiwan, and the Ryukyu Islands of Japan. The species is also common near Fiji and other Pacific islands within its range. Vagrant individuals have been recorded in Australia, New Caledonia, and New Zealand. Six specimens have been found around the North Island of New Zealand between 1880 and 2005, suspected to have come from populations based in Fiji and Tonga. It is the most common sea krait identified in New Zealand, and second-most seen sea snake after the yellow-bellied sea snake - common enough to be considered a native species, protected under the Wildlife Act 1953.

Venom

The venom of this elapid, L. colubrina, is a very powerful neurotoxic protein, with a subcutaneous LD₅₀ in mice of 0.45 mg/kg body weight.{{Cite journal|last=Levey|first=Harold A.|date=1969-05-01|title=Toxicity of the venom of the sea-snake, Laticauda colubrina, with observations on a Malay 'folk cure'|journal=Toxicon|volume=6|issue=4|pages=269–276|doi=10.1016/0041-0101(69)90095-6|pmid=5805121|bibcode=1969Txcn....6..269L }} The venom is an α-neurotoxin that disrupts synapses by competing with acetylcholine for receptors on the postsynaptic membrane, similar to erabutoxins and α-bungarotoxins.{{Cite journal|last1=Sato|first1=S.|last2=Yoshida|first2=H.|last3=Abe|first3=H.|last4=Tamiya|first4=N.|date=1969-10-01|title=Properties and biosynthesis of a neurotoxic protein of the venoms of sea snakes Laticauda laticaudata and Laticauda colubrina|journal=Biochemical Journal|language=en|volume=115|issue=1|pages=85–90|doi=10.1042/bj1150085|issn=0264-6021|pmid=5346371|pmc=1185071}} In mice, lethal venom doses cause lethargy, flaccid paralysis, and convulsions in quick succession before death. Dogs injected with lethal doses produced symptoms consistent with fatal hypertension and cyanosis observed in human sea snake bite victims.

Some varieties of eels, which are a primary food source for yellow-lipped sea kraits, may have coevolved resistance to yellow-lipped sea krait venom.{{Cite journal|last1=Heatwole|first1=Harold|last2=Poran|first2=Naomie S.|date=1995-01-01|title=Resistances of Sympatric and Allopatric Eels to Sea Snake Venoms|journal=Copeia|volume=1995|issue=1|pages=136–147|doi=10.2307/1446808|jstor=1446808}} Gymnothorax moray eels taken from the Caribbean, where yellow-lipped sea kraits are not endemic, died after injection with doses as small as 0.1 mg/kg body weight, but Gymnothorax individuals taken from New Guinea, where yellow-lipped sea kraits are endemic, were able to tolerate doses as large as 75 mg/kg without severe injury.{{Cite journal|last1=Heatwole|first1=Harold|last2=Powell|first2=Judy|date=1998-05-08|title=Resistance of eels (Gymnothorax) to the venom of sea kraits (Laticauda colubrina): a test of coevolution|journal=Toxicon|volume=36|issue=4|pages=619–625|doi=10.1016/S0041-0101(97)00081-0|pmid=9643474|bibcode=1998Txcn...36..619H }}

Behavior

File:Sea Snake eating Moray Eel, Fiji (Laticauda colubrina vs. Gymnothorax sp.).webm]]

Yellow-lipped sea kraits are semiaquatic. Juveniles stay in water and on adjacent coasts, but adults are able to move further inland and spend half their time on land and half in the ocean. Adult males are more terrestrially active during mating and hunt in shallower water, requiring more terrestrial locomotive ability. Adult females, though, are less active on land during mating and hunt in deeper water, requiring more aquatic locomotive ability. Because males are smaller, they crawl and swim faster than females.

Body adaptations, especially a paddle-like tail, help yellow-lipped sea kraits to swim. These adaptations are also found in more distantly related sea snakes (Hydrophiinae) because of convergent evolution, but because of the differences in motion between crawling and swimming, these same adaptations impede the snake's terrestrial motion. On dry land, a yellow-lipped sea krait can still move, but typically at only slightly more than a fifth of its swimming speed. In contrast, most sea snakes other than Laticauda spp. are virtually stranded on dry land.

When hunting, yellow-lipped sea kraits frequently head into deep water far from land, but return to land to digest meals, shed skin, and reproduce. Individuals return to their specific home islands, exhibiting philopatry. When yellow-lipped sea kraits on Fijian islands were relocated to different islands 5.3 km away, all recaptured individuals were found on their home islands in an average of 30.7 days.{{Cite journal|last1=Shetty|first1=Sohan|last2=Shine|first2=Richard|date=2002-01-01|title=Philopatry and Homing Behavior of Sea Snakes (Laticauda colubrina) from Two Adjacent Islands in Fiji|journal=Conservation Biology|volume=16|issue=5|pages=1422–1426|doi=10.1046/j.1523-1739.2002.00515.x|jstor=3095337|bibcode=2002ConBi..16.1422S |s2cid=86013129 }}

Yellow-lipped sea kraits collected near the tip of Borneo had heavy tick infections.{{Cite web|url=http://tracc-borneo.org/2011/03/sea-snake-parasites-1/|title=Sea snake parasites – 1|last1=Clark|first1=M.|last2=Oakley|first2=S.|date=2011-03-08|website=Tropical Research and Conservation Centre|archive-url=https://web.archive.org/web/20160304091418/http://tracc-borneo.org/2011/03/sea-snake-parasites-1/|archive-date=2016-03-04|url-status=dead|access-date=2016-08-20}}

=Hunting and diet=

Hunting is often performed alone, but L. colubrina kraits may also do so in large numbers in the company of hunting parties of giant trevally and goatfish. This cooperative hunting technique is similar to that of the moray eel, with the yellow-lipped sea kraits flushing out prey from narrow crevices and holes, and the trevally and goatfish feeding on fleeing prey.{{cite episode |title=Shallow Seas |series=Planet Earth |credits=Produced by Mark Brownlow |network=BBC |station=BBC One |airdate=2006-11-26}}

While probing crevices with their heads, yellow-lipped sea kraits are unable to observe approaching predators and can be vulnerable. The snakes can deter predators, such as larger fish, sharks, and birds, by fooling them into thinking that their tail is their head, because the color and movement of the tail is similar to that of the snake's head. For example, the lateral aspect of the tail corresponds to the dorsal view of the head.{{Cite journal | last1 = Rasmussen | first1 = A.R. | last2 = Elmberg | first2 = J. | doi = 10.1111/j.1439-0485.2009.00318.x | title = 'Head for my tail': A new hypothesis to explain how venomous sea snakes avoid becoming prey | journal = Marine Ecology | volume = 30 | issue = 4 | pages = 385–390| year = 2009 }}{{cite news |url=http://news.bbc.co.uk/2/hi/science/nature/8184364.stm |title=Sea snake's two-headed illusion |date=6 August 2009 |work=BBC News |access-date=7 October 2012}}

Yellow-lipped sea kraits primarily feed on varieties of eels (of the families Congridae, Muraenidae, and Ophichthidae), but also eat small fish (including those of the families Pomacentridae and Synodontidae). Males and females exhibit sexual dimorphism in hunting behavior, as adult females, which are significantly larger than males, prefer to hunt in deeper water for larger conger eels, while adult males hunt in shallower water for smaller moray eels. In addition, females hunt for only one prey item per foraging bout, while males often hunt for multiple items.{{Cite journal|last1=Shetty|first1=S.|last2=Shine|first2=R.|date=2002-02-01|title=Sexual divergence in diets and morphology in Fijian sea snakes Laticauda colubrina (Laticaudinae)|journal=Australian Ecology|language=en|volume=27|issue=1|pages=77–84|doi=10.1046/j.1442-9993.2002.01161.x|bibcode=2002AusEc..27...77S |issn=1442-9993}} After hunting, yellow-lipped sea kraits return to land to digest their prey.

=Courtship and reproduction=

File:Banded sea kraits mating (8017106628).jpg

The yellow-lipped sea krait is oviparous, meaning it lays eggs that develop outside of the body.

Each year during the warmer months of September through December, males gather on land and in the water around gently sloping areas at high tide. Males prefer to mate with larger females because they produce larger and more offspring.{{Cite journal|last1=Shetty|first1=Sohan|last2=Shine|first2=Richard|date=2002-01-01|title=Activity Patterns of Yellow-Lipped Sea Kraits (Laticauda colubrina) on a Fijian Island|journal=Copeia|volume=2002|issue=1|pages=77–85|doi=10.1643/0045-8511(2002)002[0077:apoyls]2.0.co;2|jstor=1447926|s2cid=55800239 }}

When a male detects a female, he chases the female and begins courtship. Females are larger and slower than males, and many males escort and intertwine around a single female. The males then align their bodies with the female and rhythmically contract; the resulting mass of snakes can remain nearly motionless for several days.{{Cite journal|last1=Shetty|first1=Sohan|last2=Shine|first2=Richard|date=2002-01-01|title=The Mating System of Yellow-Lipped Sea Kraits (Laticauda colubrina: Laticaudidae)|journal=Herpetologica|volume=58|issue=2|pages=170–180|doi=10.1655/0018-0831(2002)058[0170:tmsoys]2.0.co;2|jstor=3893192|s2cid=86240716 }} After courtship, the snakes copulate for about an average of two hours.

The female yellow-lipped sea kraits then lay as many as 10 eggs per clutch. The eggs are deposited in crevices where they remain until hatching.{{Cite book|title=Sea Snake Toxicology|last=Guinea|first=Michael L.|publisher=Singapore Univ. Press|year=1994|isbn=978-9971-69-193-6|editor-last=Gopalakrishnakone|editor-first=Ponnampalam|pages=212–233|chapter=Sea snakes of Fiji and Niue}} These eggs are very rarely found in the wild; only two nests have been definitively reported throughout the entire range of the species.

=Interaction with humans=

Because yellow-lipped sea kraits spend much of their time on land, they are often encountered by humans. They are frequently found in the water intake and exhaust pipes of boats. They are also attracted to light and can be distracted by artificial sources of light, including hotels and other buildings, on coasts.

Fewer bites from this species are recorded compared to other venomous species such as cobras and vipers, as it is less aggressive and tends to avoid humans.{{cite web |url=http://animaldiversity.ummz.umich.edu/accounts/Laticauda_colubrina/ |title=Laticauda colubrina Colubrine or yellow-lipped sea krait|work=Animal Diversity Web |publisher=University of Michigan Museum of Zoology}} If they do bite, it is usually in self-defense when accidentally grabbed. Most sea snake bites occur when fishermen attempt to untangle the snakes from their fishing nets.{{cite news|url=https://books.google.com/books?id=0JkKOFIj5pgC|title=Introduction to Marine Biology|date=2009|publisher=Cengage Learning|last2=Small|first2=James|page=307|isbn=978-0-495-56197-2|last3=Turner|first3=Richard|first1=George|last1=Karleskint}}

In the Philippines, yellow-lipped sea kraits are caught for their skin and meat; the meat is smoked and exported for use in Japanese cuisine. The smoked meat of a related Laticauda species, the black-banded sea krait, is used in Okinawan cuisine to make irabu-jiru ({{langx|ja|イラブー汁}}, irabu soup).{{cite web |url=http://en.okinawa2go.jp/u/gourmet/1g8p1vfsa9mvik |title=Sea snake soup (Irabu-jiru) |website=En.okinawa2go.jp |department=Okinawa Gourmet Guide |access-date=2016-07-17 |url-status=dead |archive-url= https://web.archive.org/web/20170226094430/https://en.okinawa2go.jp/u/gourmet/1g8p1vfsa9mvik |archive-date=26 February 2017}}