Laticauda colubrina

Laticauda colubrina
Banded sea krait in Malaysia
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Suborder: Serpentes
Family: Elapidae
Subfamily: Laticaudinae
Genus: Laticauda
Species: L. colubrina
Binomial name
Laticauda colubrina
(Schneider, 1799)
Synonyms[2]
  • Hydrus colubrinus
    Schneider, 1799
  • Platurus colubrinus
    — Wagler, 1830
  • Hydrophis colubrinus
    — Schlegel, 1837
  • Laticauda colubrina
    — Stejneger, 1907

Laticauda colubrina, commonly known as the banded sea krait, colubrine sea krait, or yellow-lipped sea krait, is a species of venomous sea 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 underwater in order 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 their affinity to land, banded sea kraits often encounter humans, but the snakes are not aggressive and only attack in self-defense.

Description

A photo of the head of L. colubrina, showing its characteristic yellow snout
A photo of the tail of L. colubrina, showing its paddle-like tail
The characteristic yellow snout and paddle-like tail of L. colubrina, Zamboanguita, Philippines

The head of a banded 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.[3]

The body of the snake is subcylindrical, and is taller than it is wide. It has an upper surface that 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 imbricate (overlapping) dorsal scales.[3] The tail of the snake is paddle-shaped and adapted to swimming.[4]

On average, the total length of a male krait is 875 mm (34.4 in) long, with a 130 mm (5.1 in) long tail. Females are significantly larger, with an average total length of 1,420 mm (56 in) and a tail length of 145 mm (5.7 in).[3]

Range and habitat

The banded 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 on Fiji and other Pacific islands within its range. Vagrant individuals have been recorded in Australia, New Caledonia, and New Zealand.[1]

Venom

The venom of this elapid is a very powerful neurotoxic protein, with a subcutaneous LD50 in mice of 0.45 mg/kg body weight.[5] 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.[6] In mice, lethal venom doses caused 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.[5]

Some varieties of eels, which are a primary food source for sea kraits, may have coevolved resistance to banded sea krait venom.[7] Gymnothorax moray eels taken from the Caribbean, where the banded sea krait is not present, died after injection with doses as small as 0.1 mg/kg body weight, but Gymnothorax individuals taken from New Guinea, where banded sea kraits are endemic, were able to tolerate doses as large as 75 mg/kg without severe injury.[8]

Behavior

Banded sea krait swallowing a moray eel

Banded sea kraits are semiaquatic. Juveniles stay in water and on adjacent coast, 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. On the other hand, adult females 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.[4]

Body adaptations, especially a paddle-like tail, help banded sea kraits to swim. These adaptations are also found in more distantly related sea snakes (Hydrophiinae) because of convergent evolution. However, because of the differences in motion between crawling and swimming, these same adaptations impede the snake's terrestrial motion. On dry land, a banded sea krait can still move, but, on average, at only slightly more than a fifth of its swimming speed. In contrast, most other non-Laticauda sea snakes are virtually stranded on dry land.[4]

When hunting, sea kraits frequently head into deep water far from land, but return to land in order to digest, shed skin, and reproduce. Individual kraits return to their specific home islands, exhibiting philopatry. One study found that when 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.[9]

Banded sea kraits collected near the tip of Borneo had heavy tick infections.[10]

Hunting and diet

Hunting is often performed alone, but the snakes 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 kraits flushing out prey from narrow crevices and holes, and the trevally and goatfish feeding on fleeing prey.[11]

While probing crevices with their head, 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.[12][13]

Kraits primarily feed on varieties of eels, but also eat small fish. Male and female kraits 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.[4][14] After hunting, the kraits return to land in order to digest their prey.[9]

Courtship and reproduction

Multiple banded sea kraits mating

The banded sea krait is oviparious, meaning it lays eggs that develop outside of the body.[1]

Each year during the warmer months of September through December, male banded sea kraits gather on land and in the water around gently sloping areas at high tide. Male kraits prefer to mate with larger female kraits because they produce larger and more offspring.[15]

When a male detects a female, it chases the female and begins courtship. Female kraits are larger and slower than males, and many males will 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.[15][16] After courtship, the snakes copulate for about an average of two hours.[15]

The female kraits then lay as many as 10 eggs per clutch. The eggs are deposited in crevices where they remain until hatching.[17] These eggs are very rarely found in the wild; only two nests have been definitively reported throughout the entire range of the species.[1]

Interaction with humans

Irabu-jiru (Japanese: イラブー汁, irabu soup) made from smoked black-banded sea krait

Because these 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.[17] Kraits are also attracted to light and can be distracted by artificial sources of light, including hotels and other buildings, on coasts.[1]

There are fewer recorded bites from this species compared to other venomous species such as cobras and vipers as it is less aggressive and tends to avoid humans.[18] 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.[19]

In the Philippines, banded sea kraits are caught for their skin and meat; the meat is smoked and exported for use in Japanese cuisine.[1] The smoked meat of a related Laticauda species, the black-banded sea krait, is used in Okinawan cuisine to make irabu-jiru (Japanese: イラブー汁, irabu soup).[20]

See also

References

  1. 1 2 3 4 5 6 Lane, A.; Guinea, M.; Gatus, J.; Lobo, A. (2010). "Laticauda colubrina". IUCN Red List of Threatened Species. Version 2012.1. International Union for Conservation of Nature. Retrieved 7 October 2012.
  2. ↑ "Laticauda colubrina ". The Reptile Database. www.reptile-database.org.
  3. 1 2 3 Smith, M.A. (1943). The Fauna of British India, Ceylon and Burma, Including the Whole of the Indo-Chinese Sub-region. Reptilia and Amphibia, Vol. III.—Serpentes. London: Secretary of State for India. (Taylor and Francis, printers). p. 443.
  4. 1 2 3 4 Shine, R.; Shetty, S. (2001-03-01). "Moving in two worlds: aquatic and terrestrial locomotion in sea snakes (Laticauda colubrina, Laticaudidae)". Journal of Evolutionary Biology. 14 (2): 338–346. doi:10.1046/j.1420-9101.2001.00265.x. ISSN 1420-9101.
  5. 1 2 Levey, Harold A. (1969-05-01). "Toxicity of the venom of the sea-snake, Laticauda colubrina, with observations on a Malay 'folk cure'". Toxicon. 6 (4): 269–276. doi:10.1016/0041-0101(69)90095-6.
  6. ↑ Sato, S.; Yoshida, H.; Abe, H.; Tamiya, N. (1969-10-01). "Properties and biosynthesis of a neurotoxic protein of the venoms of sea snakes Laticauda laticaudata and Laticauda colubrina". Biochemical Journal. 115 (1): 85–90. doi:10.1042/bj1150085. ISSN 0264-6021. PMC 1185071Freely accessible. PMID 5346371.
  7. ↑ Heatwole, Harold; Poran, Naomie S. (1995-01-01). "Resistances of Sympatric and Allopatric Eels to Sea Snake Venoms". Copeia. 1995 (1): 136–147. doi:10.2307/1446808. JSTOR 1446808.
  8. ↑ Heatwole, Harold; Powell, Judy (1998-05-08). "Resistance of eels (Gymnothorax) to the venom of sea kraits (Laticauda colubrina): a test of coevolution". Toxicon. 36 (4): 619–625. doi:10.1016/S0041-0101(97)00081-0. PMID 9643474.
  9. 1 2 Shetty, Sohan; Shine, Richard (2002-01-01). "Philopatry and Homing Behavior of Sea Snakes (Laticauda colubrina) from Two Adjacent Islands in Fiji". Conservation Biology. 16 (5): 1422–1426. doi:10.1046/j.1523-1739.2002.00515.x. JSTOR 3095337.
  10. ↑ Clark, M.; Oakley, S. (2011-03-08). "Sea snake parasites – 1". Tropical Research and Conservation Centre. Archived from the original on 2016-03-04. Retrieved 2016-08-20.
  11. ↑ Produced by Mark Brownlow (2006-11-26). "Shallow Seas". Planet Earth. BBC. BBC One.
  12. ↑ Rasmussen, A.R.; Elmberg, J. (2009). "'Head for my tail': A new hypothesis to explain how venomous sea snakes avoid becoming prey". Marine Ecology. 30 (4): 385–390. doi:10.1111/j.1439-0485.2009.00318.x.
  13. ↑ "Sea snake's two-headed illusion". BBC News. 6 August 2009. Retrieved 7 October 2012.
  14. ↑ Shetty, S.; Shine, R. (2002-02-01). "Sexual divergence in diets and morphology in Fijian sea snakes Laticauda colubrina (Laticaudinae)". Austral Ecology. 27 (1): 77–84. doi:10.1046/j.1442-9993.2002.01161.x. ISSN 1442-9993.
  15. 1 2 3 Shetty, Sohan; Shine, Richard (2002-01-01). "Activity Patterns of Yellow-Lipped Sea Kraits (Laticauda colubrina) on a Fijian Island". Copeia. 2002 (1): 77–85. doi:10.1643/0045-8511(2002)002[0077:apoyls]2.0.co;2. JSTOR 1447926.
  16. ↑ Shetty, Sohan; Shine, Richard (2002-01-01). "The Mating System of Yellow-Lipped Sea Kraits (Laticauda colubrina: Laticaudidae)". Herpetologica. 58 (2): 170–180. doi:10.1655/0018-0831(2002)058[0170:tmsoys]2.0.co;2. JSTOR 3893192.
  17. 1 2 Guinea, Michael L. (1994). "Sea snakes of Fiji and Niue". In Gopalakrishnakone, Ponnampalam. Sea snake toxicology. Singapore Univ. Press. pp. 212–233. ISBN 9971-69-193-0.
  18. ↑ "Laticauda colubrina Colubrine or yellow-lipped sea krait". Animal Diversity Web. University of Michigan Museum of Zoology.
  19. ↑ Karleskint, George; Small, James; Turner, Richard (2009). "Introduction to Marine Biology". Cengage Learning. p. 307. ISBN 978-0-495-56197-2.
  20. ↑ "Okinawa Gourmet Guide : Sea snake soup (Irabu-jiru) | Website of Okinawa Sightseeing information Okinawa2Go!". En.okinawa2go.jp. Retrieved 2016-07-17.

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