Cobras, mambas, sea snakes and one fish-egg eater that gave up venom
The elapid family runs from an 18-centimetre white-lipped snake to the king cobra, the longest venomous snake on Earth at up to 5.85 metres. Its roughly 360 species share fixed hollow fangs at the front of the mouth, yet one genus has abandoned venom entirely to dine on fish eggs.
Elapids live across the tropics and subtropics, mostly in the Southern Hemisphere, with land species in Asia, Africa, Australia and the Americas and marine species in the Indian Ocean and south-west Pacific. The family spans 55 genera and over 170 subspecies. Most land forms resemble ordinary colubrid snakes: slim, smooth-scaled, quick, round-pupilled and usually egg-laying. Australia's death adders break the pattern, looking and behaving like vipers, with stout bodies, keeled scales, cat-like pupils, live birth and a patient ambush style.
Venom flows from glands near the back of the upper jaw through a pair of enlarged hollow front teeth, usually with just one working fang per side. Taipans, mambas, the king cobra and death adders carry long fangs on mobile jaws and strike fast, and spitting cobras can squirt venom through forward-facing openings. The chemistry is mostly nerve-targeting, built around PLA2 enzymes and three-finger toxins, with some species adding heart or cell-damaging compounds. The exception is Emydocephalus, whose leftover fangs produce nothing because it feeds on fish eggs.
Lifestyles vary widely. Some, such as African mambas and Australian broad-headed snakes, live in trees; others burrow in wet or dry soils. Diets can be broad or strikingly narrow; the king cobra and kraits eat mostly other snakes. When threatened, cobras and mambas rear up, flare a hood and hiss, whereas kraits coil and tuck their heads beneath their bodies.
Sea snakes have gone furthest. All have paddle-shaped tails and can excrete salt, and most have flattened bodies, nostrils on top of the snout, shrunken belly scales that make them clumsy on land, and live young. They can also absorb oxygen through the skin; the yellow-bellied sea snake covers about 20 percent of its needs that way, stretching its dives, and ranges across the Pacific to Central and South America. Sea kraits remain partly terrestrial, coming ashore to lay eggs and digest meals.
Source: Elapidae
