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The sea snake subfamily Laticaudinae consists of a single genus with eight named species, based on morphological characters. Lane and Shine (2011) investigated the phylogenetic relationships of species within this genus using microsatellite and mtDNA markers. Two major clades were identified, the yellow-banded and blue-banded sea kraits. Although these snakes forage in the water, they spend about half their time in terrestrial habitats. All (or nearly all) laticaudine sea snakes rely on small islands as oviposition (egg-laying) sites, but the snakes in the two major lineages differ in their use of marine vs. terrestrial habitats. Individuals of the blue-banded sea krait clade rarely venture more than a few meters inland. In contrast, yellow-banded sea kraits are adept at terrestrial locomotion, and are frequently found in the interior of small coral islets.

The two most widespread laticaudines, the blue-banded (Laticauda laticaudata) and yellow-banded (Laticauda colubrina) sea kraits, are broadly distributed from the waters of continental southeastern Asia to the southwestern Pacific. The yellow-banded sea krait clade includes, in addition to the widespread L. colubrina, L. guineai (found in a small region of southern Papua New Guinea), L. saintgironsi (endemic to New Caledonia, where it is common), and L. frontalis (a dwarf species endemic to Vanuatu, where it is sympatric with L. colubrina). A 6th Laticauda species, L. crockeri, is known only as an isolated population in the slightly brackish waters of Lake Te-nggano on Rennell Island, Solomon Islands. Finally, L. semifasciata (occurring from southern Japan southward through Taiwan and the Philippines to some eastern islands of Indonesia) and L. schistorhynchus (known only from Niue Island, Tonga, and Samoa, 6500 km east of the range of L. semifasciata) have sometimes been segregated into a distinct genus, Pseudolaticauda.

Sea kraits are all (or nearly all) egg-layers, with a clutch size of 4 to 19. The thin-shelled eggs are laid terrestrially and the shells have a high permeability to oxygen, three times that of chicken eggs and nine times that of the eggs of an iguanid lizard; permeability to water is also high.

Growth is rapid in young sea kraits but tapers off after sexual maturity is reached (about 18 months in males and 18–30 months in females) and slows down earlier in males than in females.

When not foraging for food, sea kraits come ashore, often in large numbers on small offshore islands sequestered from terrestrial predators. There they rest, digest their food, slough their skin, mate, and oviposit. They are active mainly at night and at dusk, with courtship taking place in the morning. By day, the snakes thermoregulate by shuttling from sun to shade, but in the afternoon they often seek shelter.

Courtship can involve a number of males attending a female simultaneously. The male lies adjacent to the female and contracts his body in pulses of undulating spasms, up to 20 pulses per minute; prior to copulation he may rub his chin against the female’s head.

Unlike most sea snakes, sea kraits have retained their broad gastrosteges (large ventral scales), which helps them crawl effectively on land. They share with other sea snakes the aquatic adaptation of a flattened, paddle-shaped tail. As noted above, the members of the colubrina species complex are more terrestrial than are other Laticauda. Laticauda colubrina is the most terrestrial of all and is a good climber. It spends approximately half its time in each medium, on a roughly 10-day cycle, and transfers between land and sea most often at high tides, especially at night, sometimes in cohorts. Females spend more time on land than do males. It is likely that the combination of appropriate terrestrial shelter and coral reefs for foraging are required for a habitat to be suitable. Laticauda colubrina is quite site-specific and will home if re-located.

Perhaps because of its partial terrestriality, L. colubrina often has ectoparasitic ticks; it also is parasitized by cestode and  trematode flatworms, lung mites and nematode roundworms, and lung mites and may have a superficial growth of algae

Sea kraits have powerful neurotoxic venoms. Death of prey is caused by irreversible presynaptic and postsynaptic blocking of neuromuscular transmission. However, despite being highly venomous, sea kraits are known for their docility and reluctance to bite humans defensively, although humans have been bitten.

(Heatwole et al. 2005 and references therein)


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