Elapidae


Elapidae is a family of venomous snakes characterized by hollow, permanently erect, relatively short fangs in the front of the mouth that channel venom into their prey. Elapids are endemic to tropical and subtropical regions around the world, with terrestrial forms in Asia, Australia, Africa, and the Americas alongside marine forms in the Pacific and Indian Oceans. Members of the family have a wide range of sizes, from the white-lipped snake to the king cobra. Most species have neurotoxins in their venom, while some may contain other toxic components in various proportions. The family includes 56 genera with some 360 species and some 170 subspecies.

Description

Appearance

elapids look similar to the Colubridae; almost all have long, slender bodies with smooth scales, a head covered with large shields and not always distinct from the neck, and eyes with round pupils. In addition, their behavior is usually quite active, and most are oviparous. Exceptions to all these generalizations occur: e.g. the death adders include short and fat, rough-scaled, very broad-headed, cat-eyed, live-bearing, sluggish ambush predators with partly fragmented head shields.
Sea snakes, sometimes considered to be a separate family, have adapted to a marine way of life in different ways and to various degrees. All have evolved paddle-like tails for swimming and the ability to excrete salt. Most also have laterally compressed bodies, their ventral scales are much reduced in size, their nostrils are located dorsally, and they give birth to live young. The reduction in ventral scaling has greatly diminished their land mobility, but aids in swimming.
Members of this family have a wide range of sizes. Drysdalia species are small serpents typically and down to in length. Cobras, mambas, and taipans are mid- to large sized snakes which can reach or above. The king cobra is the world's longest venomous snake with a maximum length of and an average mass of.

Behavior

Most elapids are terrestrial, while some are strongly arboreal. Many species are more or less specialized burrowers in either humid or arid environments. Some species have very generalised diets, but many taxa have narrow prey preferences and correlated morphological specializations, for example feeding almost exclusively on other serpents. Elapids may display a series of warning signs if provoked, either obviously or subtly. Cobras and mambas lift their inferior body parts, expand hoods, and hiss if threatened; kraits often curl up before hiding their heads down their bodies.
In general, sea snakes are able to respire through their skin. Experiments with the yellow-bellied sea snake, Hydrophis platurus, have shown that this species can satisfy about 20% of its oxygen requirements in this manner, allowing for prolonged dives. The sea kraits are the sea snakes least adapted to aquatic life. Their bodies are less compressed laterally, and they have thicker bodies and ventral scaling. Because of this, they are capable of some land movement. They spend much of their time on land, where they lay their eggs and digest prey.

Dentition

All elapids have a pair of proteroglyphous fangs to inject venom from glands located towards the rear of the upper jaw. The fangs, which are enlarged and hollow, are the first two teeth on each maxillary bone. Usually only one fang is in place on each side at any time. The maxilla is intermediate in both length and mobility between typical colubrids and viperids. When the mouth is closed, the fangs fit into grooved slots in the buccal floor and usually below the front edge of the eye and are angled backwards; some elapids have long fangs on quite mobile maxillae and can make fast strikes. A few species are capable of spraying their venom from forward-facing holes in their fangs for defense, as exemplified by spitting cobras. Venom may cause intense pain, if not blindness, upon contact with eyes.

Distribution

Terrestrial elapids are found worldwide in tropical and subtropical regions, mostly in the Southern Hemisphere. Most prefer humid tropical environments, and so are not found in the Sahara or Middle East, although some can be found in Mexican and Australian deserts. Sea snakes occur mainly in the Indian Ocean and the south-west Pacific. They occupy coastal waters and shallows, and are common in coral reefs. However, the range of Hydrophis platurus extends across the Pacific to the coasts of Central and South America.

Venom

Venoms of species in the Elapidae are mainly neurotoxic for immobilizing prey and defense.The main group of toxins are PLA2 and Three finger toxins. Other toxic components in some species comprise cardiotoxins and cytotoxins, which cause heart dysfunctions and cellular damage, respectively. Bites from all the members of this family are potentially fatal, some of which are even considered to be the world's most venomous snakes based upon their murine values, such as the taipans. Large species, mambas and cobras included, are dangerous for their capability of injecting high quantities of venom upon single envenomation and/or striking at a high position proximal to the victim's brain, which is vulnerable to neurotoxicity. Antivenom is promptly required to be administrated if bitten by any elapids. Venom of spitting cobras is more cytotoxic rather than neurotoxic. It damages local cells, especially those in eyes, which are purposely targeted by the snakes. The venom may cause intense pain if not blindness upon contact with eyes. It is not lethal on skin if no wound provides any chance for the toxins to make contact with the blood. Specific antivenoms are the only cure to treat elapidae bites. There are commercial monovalent and polyvalent antivenoms for Mambas, Cobras, Najas, and some other important elapids. Recently, experimental antivenoms based on recombinant toxins have a shown that is feasible to create antivenoms with a wide spectrum of coverage.

Taxonomy

The table below lists out all of the elapid genera and no subfamilies. In the past, many subfamilies were recognized, or have been suggested for the Elapidae, including the Elapinae, Hydrophiinae, Micrurinae, Acanthophiinae, and the Laticaudinae. Currently, none are universally recognized. Molecular evidence via techniques like karyotyping, protein electrophoretic analyses, immunological distance and DNA sequencing, suggests reciprocal monopholoy of two groups: African, Asian, and New World Elapinae versus Australasian and marine Hydrophiinae. The Australian terrestrial elapids are technically 'hydrophiines', although they are not sea snakes. It is believed that the Laticauda and the 'true sea snakes' evolved separately from Australasian land snakes. Asian cobras, coral snakes, and American coral snakes also appear to be monophyletic, while African cobras do not.
The type genus for the Elapidae was originally Elaps, but the group was moved to another family. In contrast to what is typical of botany, the family Elapidae was not renamed. In the meantime, Elaps was renamed Homoroselaps and moved back to the Elapidae. However, Nagy et al. regard it as a sister taxon to Atractaspis, which should have been assigned to the Atractaspidinae.
GenusTaxon
author
SpeciesSubspecies*Common
name
Geographic
range
AcanthophisDaudin, 180370death addersAustralia, New Guinea, Indonesia
AipysurusLacépède, 180471olive sea snakesTimor Sea, South China Sea, Gulf of Thailand, and coasts of Australia, New Caledonia, Loyalty Islands, southern New Guinea, Indonesia, western Malaysia and Vietnam
AntaioserpensWells & Wellington, 198520burrowing snakesAustralia
AspidelapsFitzinger, 184324shieldnose cobrasSouth Africa, Namibia, southern Angola, Botswana, Zimbabwe, Mozambique
AspidomorphusFitzinger, 184333collared addersNew Guinea
AustrelapsWorrell, 196330copperheadsAustralia
BoulengerinaDollo, 188621water cobrasCameroon, Gabon, the Democratic Republic of the Congo, Congo, the Central African Republic, Tanzania, Equatorial Guinea, Rwanda, Burundi, Zambia
BrachyurophisGünther, 186370shovel-nosed snakesAustralia
BungarusDaudin, 1803124kraitsIndia, Myanmar, Nepal, Vietnam, Afghanistan, Pakistan, Sri Lanka, Bangladesh, Cambodia, Indonesia, Peninsular Malaysia, Singapore, Taiwan, Thailand
CacophisGünther, 186340rainforest crowned snakesAustralia
CalliophisGray, 1834811Oriental coral snakesIndia, Bangladesh, Sri Lanka, Nepal, Indonesia, Cambodia, Malaysia, Singapore, Thailand, Burma, Brunei, the Philippines, Vietnam, Laos, southern China, Japan, Taiwan
CryptophisWorrell, 196150Australia and Papua New Guinea
DemansiaGray, 184292whipsnakesNew Guinea, continental Australia
DendroaspisSchlegel, 184841mambasSub-Saharan Africa
DenisoniaKrefft, 186920ornamental snakesCentral Queensland and central northern New South Wales, Australia
DrysdaliaWorrell, 196130southeastern grass snakesSouthern Australia
EchiopsisFitzinger, 184310bardickSouthern Australia
ElapognathusBoulenger, 189620southwestern grass snakesWestern Australia
ElapsoideaBocage, 1866107African or venomous garter snakes Sub-Saharan Africa
EmydocephalusKrefft, 186930turtlehead sea snakesThe coasts of Timor, New Caledonia, Australia, and in the Southeast Asian Sea along the coasts of China, Taiwan, Japan, and the Ryukyu Islands
EnhydrinaGray, 184920beaked sea snakesIn the Persian Gulf, south to the Seychelles and Madagascar,
Southeast Asian Sea, Australia, New Guinea and Papua New Guinea
EphalophisM.A. Smith, 193110Grey's mudsnakeNorthwestern Australia
FurinaA.M.C. Duméril, 185350pale-naped snakesMainland Australia, southern New Guinea, Aru Islands
HemachatusFleming, 182210rinkhals/ring-necked spitting cobraSouth Africa, Zimbabwe, Lesotho, Swaziland
HemiaspisFitzinger, 186120swamp snakesEastern Australia
HemibungarusW. Peters, 186230Barred coral snakesPhilippines
HomoroselapsJan, 185820harlequin snakesSouth Africa
HoplocephalusWagler, 183030broad-headed snakesEastern Australia
HydrelapsBoulenger, 189610Port Darwin mudsnakeNorthern Australia, southern New Guinea
HydrophisLatreille In Sonnini & Latreille, 1801343sea snakesIndoaustralian and Southeast Asian waters.
Incongruelaps10Riversleigh, Australia
LaticaudaLaurenti, 176850sea kraitsSoutheast Asian and Indo-Australian waters
LoveridgelapsMcDowell, 197010Solomons small-eyed snakeSolomon Islands
MicropechisBoulenger, 189610New Guinea small-eyed snakeNew Guinea
MicruroidesK.P. Schmidt, 192812Western coral snakesUnited States, Mexico
MicrurusWagler, 18248054coral snakesSouthern North America, South America
NajaLaurenti, 1768363cobrasAfrica, Asia
Neelaps10Australia
NotechisBoulenger, 189620tiger snakesSouthern Australia, including many offshore islands
OgmodonW. Peters, 186410bolaFiji
OphiophagusGünther, 186410King CobraBangladesh, Myanmar, Cambodia, China, India, Andaman Islands, Indonesia, Laos, Thailand, Vietnam, western Malaysia, the Philippines
OxyuranusKinghorn, 192332taipansAustralia, New Guinea
ParahydrophisBurger & Natsuno, 197410Northern mangrove sea snakeNorthern Australia, southern New Guinea
ParapistocalamusRoux, 193410Hediger's snakeBougainville Island, Solomons
ParasutaWorrell, 196160Australia
ParoplocephalusKeogh, Scott, and Scanlon, 200010Lake Cronin snakeWestern Australia
PseudechisWagler, 183070black snakes Australia
PseudohajeGünther, 185820tree cobrasAngola, Burundi, Cameroon, Central African Republic, Democratic Republic of the Congo, Congo, Gabon, Ghana, Kenya, Nigeria, Rwanda, Uganda, Sierra Leone, Liberia, Ivory Coast, Togo, Nigeria
PseudonajaGünther, 185882venomous brown snakes Australia
RhinoplocephalusF. Müller, 188510Australian small-eyed snakesSouthern and eastern Australia, southern New Guinea
SalomonelapsMcDowell, 197010Solomons coral snakeSolomon Islands
SimoselapsJan, 1859133Australian coral snakesMainland Australia
SinomicrurusSlowinski, Boundy, & Lawson, 200177Asia
SutaWorrell, 196140hooded snakes Australia
ThalassophisP. Schmidt, 185210anomalous sea snakeSouth Chinese Sea, Indian Ocean
ToxicocalamusBoulenger, 1896110New Guinea forest snakesNew Guinea
TropidechisGünther, 186320rough-scaled snakeEastern Australia
VermicellaGray in Günther, 185860bandy-bandiesAustralia
WalterinnesiaLataste, 188720black desert cobraEgypt, Israel, Lebanon, Syria, Jordan, Iraq, Iran, Kuwait, Saudi Arabia, Turkey

* Not including the nominate subspecies