Sea kraits are a genus of venomous elapid sea snakes (subfamily: Laticaudinae), Laticauda. They are semiaquatic, and retain the wide ventral scales typical of terrestrial snakes for moving on land, but also have paddle-shaped tails for swimming. Unlike fully aquatic ovoviviparous sea snakes, sea kraits are oviparous and must come to land to digest prey and lay eggs. They also have independent evolutionary origins into aquatic habitats, with sea kraits diverging earlier from other Australasian elapids. Thus, sea kraits and sea snakes are an example of convergent evolution into aquatic habitats within the Hydrophiinae snakes. Sea kraits are also often confused with land kraits (genus Bungarus), which are not aquatic.
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Sea kraits are semiaquatic, so have morphological adaptations to both land and sea. Laticauda species show traits intermediate between those of sea snakes and terrestrial elapids. They have a vertically flattened and paddle-shaped tail (similar to sea snakes) and laterally positioned nostrils and broad, laterally expanded ventral scales (similar to terrestrial elapids). Their body has a striped pattern, nasal scales are separated by inter-nasals scales, and the maxillary bone extends forwards beyond the palatine bone. Members of Laticauda can grow to 1.5 m (4.9 ft) long.
Laticauda species are found throughout the South and Southeast Asian islands spreading from India in the west, north as far as Japan, and southeast to Fiji. The species occasionally wanders south to the Eastern coast of Australia and New Zealand (Laticauda colubrina being the most common example in New Zealand), however no known locally breeding populations are known to exist in these areas. Sea kraits typically live in the littoral zone of coastal waters and are semi-terrestrial, spending time ashore and in shallow waters, as well as around coral reefs.
Laticauda species are often active at night, which is when they prefer to hunt. Though they possess highly toxic venom, these snakes are usually shy and reclusive, and in New Caledonia, where they are called tricot rayé ("stripey sweater"), children play with them. Bites are rare, but must be treated immediately. Bites are more likely to occur under low light conditions (night), and when the snake is roughly handled (e.g. grabbed "hard") while in the water, or having been abruptly taken from the water. When these snakes are on land, bites are extremely rare.  Black-banded sea kraits, numbering in the hundreds, form hunting alliances with yellow goatfish and bluefin trevally, flushing potential prey from narrow crannies in a reef the same way some moray eels do. Sea kraits are capable of diving up to 80 m deep in a single hunting trip. They have a remarkable ability to climb up vertical rocks of their coastal limestone habitats.
Laticauda females are oviparous, and they return to land to mate and lay eggs. Several males form a mating ball around the female, twitching their bodies in what is termed "caudocephalic waves". Though these animals can occur in high densities in suitable locations, nests of eggs are very rarely encountered, suggesting specific nesting conditions need to be met.
Species and taxonomyEdit
- Laticauda colubrina (Schneider, 1799) – yellow-lipped sea krait
- Laticauda crockeri Slevin, 1934 – Crocker's sea snake
- Laticauda frontalis (De Vis, 1905)
- Laticauda guineai Heatwole, Busack & Cogger, 2005 – Guinea's sea krait
- Laticauda laticaudata (Linnaeus, 1758) – blue-lipped sea krait
- Laticauda saintgironsi Cogger & Heatwole, 2006 – New Caledonian sea krait
- Laticauda schistorhyncha (Günther, 1874) – katuali or Niue sea krait
- Laticauda semifasciata (Reinwardt in Schlegel, 1837) – black-banded sea krait
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- 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. S2CID 82676695.
- Brischoux, François; Kato, Akiko; Ropert-Coudert, Yan; Shine, Richard (2010-10-30). "Swimming speed variation in amphibious seasnakes (Laticaudinae): A search for underlying mechanisms". Journal of Experimental Marine Biology and Ecology. 394 (1–2): 116–122. doi:10.1016/j.jembe.2010.08.001.
- Shine, Richard; Shetty, Sohan (2002). "Activity Patterns of Yellow-Lipped Sea Kraits (Laticauda colubrina) on a Fijian Island". Copeia 2002 (1): 77-85.
- Gill, B.J.; Whitaker, A.H. (2014). "Records of sea-kraits (Serpentes: Laticaudidae: Laticauda) in New Zealand". Records of the Auckland Museum. 49: 39–42. ISSN 1174-9202.
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- Sea krait slithering on coastal rocks. https://www.youtube.com/watch?v=KAe69AlIvR4