Acanthophis
Encyclopedia
Acanthophis is a genus
of elapid
snake
s. Commonly called death adders, they are native to Australia
, New Guinea
and nearby islands, and are among the most venomous snake
s in the world. The name of the genus derives from the Ancient Greek
acanthos/ἄκανθος "spine" and ophis/ὄφις "snake", referring to the spine on the death adder's tail.
Seven species are listed by ITIS
, though it remains unclear how many species
this genus includes, with figures ranging from 4 to 15 species being quoted (see Taxonomy).
-like in appearance, having a short, robust body, triangular
shaped heads and small subocular scale
s. They also have vertical pupil
s and many small scales on the top of the head. Their fangs are also longer and more mobile than for most other elapids, although still far from the size seen in some of the true vipers. Despite their name and appearance, they are not vipers at all. This is a case of convergent evolution
.
They normally take 2–3 years to reach adult size. Females are generally slightly larger than the males. They can also be easily distinguished from other Australian snakes because of a small, worm like lure on the end of their tail, which is used to attract prey. Most have large bands around their bodies, though the color itself is variable, depending on their locality. Colors are usually black, grey or red and yellow, but also include brown and greenish-grey.
and when wiggled is easily mistaken for a grub or worm. An unsuspecting bird or mammal will eventually notice the 'easy lunch' and attempt to seize it. Only then will the death adder move, lashing out with the quickest strike of any snake in the world. A death adder can go from a strike position, to strike and envenoming their prey, and back to strike position again, in less than 0.15 of a second.
of the venom was reported as 0.4–0.5 mg/kg subcutaneous and it is completely neurotoxic
, containing neither haemotoxins nor myotoxin
s, unlike most venomous snakes.
A bite from a death adder can cause paralysis
which seems minor at first but can cause death from a complete respiratory
shutdown in six hours. Symptoms of envenomation can be reversed through the use of death adder antivenom, or using anticholinesterases, which break the synaptic blockade
by making acetylcholine
more available to the parasympathetic nervous system, thus mitigating the effects of the venom.
Before antivenom was introduced, it is reported that about 50% of death adder bites were fatal. Deaths are much rarer nowadays as the anti-venom is widely available and the progression of envenomation symptoms is slow.
family, they are really members of the Elapidae
family, being more closely related to cobra
s, mamba
s, and coral snake
s.
It remains unclear how many species
this genus
includes. Traditionally, only A. antarcticus, A. praelongus and A. pyrrhus have been recognized. In 1998 five new species were described (A. barnetti, A. crotalusei, A. cummingi, A. wellsei and A. woolfi) and in 2002 an additional three were described (A. groenveldi, A. macgregori and A. yuwoni). These were received with scepticism, and only A. wellsi, where an extended description has been published, has been widely recognized. Further confusion exists over the death adders from Papua New Guinea
and Indonesia
. They have variously been placed in A. antarcticus or A. praelongus. In 2005 it was shown that neither is appropriate, and the New Guinea death adders fall into two main clade
s: The rather smooth-scaled A. laevis complex
(including death adders from Seram), and the rough-scaled A. rugosus complex. The latter can be divided into two sub-clades; one, A. rugosus sensu stricto, from southern New Guinea
, and a second, A. hawkei, from northern Queensland
and the Northern Territory
in Australia. It is likely some of these include more than one species, as populations included in e.g. A. laevis show extensive variation in both pattern and scalation.
* ) Not including the nominate subspecies.
T) Type species
.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of elapid
Elapidae
Elapidae is a family of venomous snakes found in tropical and subtropical regions around the world, terrestrially in Asia, Australia, Africa, North America and South America and aquatically in the Pacific and Indian Oceans...
snake
Snake
Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...
s. Commonly called death adders, they are native to Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, New Guinea
New Guinea
New Guinea is the world's second largest island, after Greenland, covering a land area of 786,000 km2. Located in the southwest Pacific Ocean, it lies geographically to the east of the Malay Archipelago, with which it is sometimes included as part of a greater Indo-Australian Archipelago...
and nearby islands, and are among the most venomous snake
Venomous snake
"Poisonous snake" redirects here. For true poisonous snakes, see Rhabdophis.Venomous snakes are snakes which have venom glands and specialized teeth for the injection of venom...
s in the world. The name of the genus derives from the Ancient Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
acanthos/ἄκανθος "spine" and ophis/ὄφις "snake", referring to the spine on the death adder's tail.
Seven species are listed by ITIS
Integrated Taxonomic Information System
The Integrated Taxonomic Information System is a partnership designed to provide consistent and reliable information on the taxonomy of biological species. ITIS was originally formed in 1996 as an interagency group within the U.S...
, though it remains unclear how many species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
this genus includes, with figures ranging from 4 to 15 species being quoted (see Taxonomy).
Description
Death adders are very viperViperidae
The Viperidae are a family of venomous snakes found all over the world, except in Antarctica, Australia, Ireland, Madagascar, Hawaii, various other isolated islands, and above the Arctic Circle. All have relatively long, hinged fangs that permit deep penetration and injection of venom. Four...
-like in appearance, having a short, robust body, triangular
Triangle
A triangle is one of the basic shapes of geometry: a polygon with three corners or vertices and three sides or edges which are line segments. A triangle with vertices A, B, and C is denoted ....
shaped heads and small subocular scale
Scale (zoology)
In most biological nomenclature, a scale is a small rigid plate that grows out of an animal's skin to provide protection. In lepidopteran species, scales are plates on the surface of the insect wing, and provide coloration...
s. They also have vertical pupil
Pupil
The pupil is a hole located in the center of the iris of the eye that allows light to enter the retina. It appears black because most of the light entering the pupil is absorbed by the tissues inside the eye. In humans the pupil is round, but other species, such as some cats, have slit pupils. In...
s and many small scales on the top of the head. Their fangs are also longer and more mobile than for most other elapids, although still far from the size seen in some of the true vipers. Despite their name and appearance, they are not vipers at all. This is a case of convergent evolution
Convergent evolution
Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. The wings are...
.
They normally take 2–3 years to reach adult size. Females are generally slightly larger than the males. They can also be easily distinguished from other Australian snakes because of a small, worm like lure on the end of their tail, which is used to attract prey. Most have large bands around their bodies, though the color itself is variable, depending on their locality. Colors are usually black, grey or red and yellow, but also include brown and greenish-grey.
Hunting
Unlike most snakes, death adders do not actively hunt, but rather lie in ambush and draw their prey to them. When hungry, death adders bury themselves amongst the substrate. This may be leaf litter, soil or sand, depending on their environment. The only part of themselves they expose are their head and their tail, both generally very well camouflaged. The end of the tail is used for caudal luringCaudal luring
Caudal luring is the use of tail movements employed by a predator to attract prey animals. It is a form of mimicry classified formally as aggressive mimicry, but perhaps better described by the term feeding mimicry. The behavior is employed by a number of snake species and allegedly by two lizards,...
and when wiggled is easily mistaken for a grub or worm. An unsuspecting bird or mammal will eventually notice the 'easy lunch' and attempt to seize it. Only then will the death adder move, lashing out with the quickest strike of any snake in the world. A death adder can go from a strike position, to strike and envenoming their prey, and back to strike position again, in less than 0.15 of a second.
Venom
Death adders can inject on average 40–100 mg of highly toxic venom with a bite. The LD50LD50
In toxicology, the median lethal dose, LD50 , LC50 or LCt50 of a toxin, radiation, or pathogen is the dose required to kill half the members of a tested population after a specified test duration...
of the venom was reported as 0.4–0.5 mg/kg subcutaneous and it is completely neurotoxic
Neurotoxin
A neurotoxin is a toxin that acts specifically on nerve cells , usually by interacting with membrane proteins such as ion channels. Some sources are more general, and define the effect of neurotoxins as occurring at nerve tissue...
, containing neither haemotoxins nor myotoxin
Myotoxin
Myotoxins are small, basic peptides found in snake venoms, such as in that of certain rattlesnakes. This involves a non-enzymatic mechanism that leads to severe muscle necrosis...
s, unlike most venomous snakes.
A bite from a death adder can cause paralysis
Paralysis
Paralysis is loss of muscle function for one or more muscles. Paralysis can be accompanied by a loss of feeling in the affected area if there is sensory damage as well as motor. A study conducted by the Christopher & Dana Reeve Foundation, suggests that about 1 in 50 people have been diagnosed...
which seems minor at first but can cause death from a complete respiratory
Respiration (physiology)
'In physiology, respiration is defined as the transport of oxygen from the outside air to the cells within tissues, and the transport of carbon dioxide in the opposite direction...
shutdown in six hours. Symptoms of envenomation can be reversed through the use of death adder antivenom, or using anticholinesterases, which break the synaptic blockade
Blockade
A blockade is an effort to cut off food, supplies, war material or communications from a particular area by force, either in part or totally. A blockade should not be confused with an embargo or sanctions, which are legal barriers to trade, and is distinct from a siege in that a blockade is usually...
by making acetylcholine
Acetylcholine
The chemical compound acetylcholine is a neurotransmitter in both the peripheral nervous system and central nervous system in many organisms including humans...
more available to the parasympathetic nervous system, thus mitigating the effects of the venom.
Before antivenom was introduced, it is reported that about 50% of death adder bites were fatal. Deaths are much rarer nowadays as the anti-venom is widely available and the progression of envenomation symptoms is slow.
Taxonomy
Although the death adders resemble vipers of the ViperidaeViperidae
The Viperidae are a family of venomous snakes found all over the world, except in Antarctica, Australia, Ireland, Madagascar, Hawaii, various other isolated islands, and above the Arctic Circle. All have relatively long, hinged fangs that permit deep penetration and injection of venom. Four...
family, they are really members of the Elapidae
Elapidae
Elapidae is a family of venomous snakes found in tropical and subtropical regions around the world, terrestrially in Asia, Australia, Africa, North America and South America and aquatically in the Pacific and Indian Oceans...
family, being more closely related to cobra
Cobra
Cobra is a venomous snake belonging to the family Elapidae. However, not all snakes commonly referred to as cobras are of the same genus, or even of the same family. The name is short for cobra capo or capa Snake, which is Portuguese for "snake with hood", or "hood-snake"...
s, mamba
Mamba
Mambas, of the genus Dendroaspis , are a group of highly venomous, fast-moving land-dwelling snakes of Africa. They belong to the family of Elapidae which includes cobras, coral snakes, taipans, brown snakes, tiger snakes, death adders, kraits and, debatably, sea snakes...
s, and coral snake
Coral snake
The coral snakes are a large group of elapid snakes that can be subdivided into two distinct groups, Old World coral snakes and New World coral snakes...
s.
It remains unclear how many species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
this genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
includes. Traditionally, only A. antarcticus, A. praelongus and A. pyrrhus have been recognized. In 1998 five new species were described (A. barnetti, A. crotalusei, A. cummingi, A. wellsei and A. woolfi) and in 2002 an additional three were described (A. groenveldi, A. macgregori and A. yuwoni). These were received with scepticism, and only A. wellsi, where an extended description has been published, has been widely recognized. Further confusion exists over the death adders from Papua New Guinea
Papua New Guinea
Papua New Guinea , officially the Independent State of Papua New Guinea, is a country in Oceania, occupying the eastern half of the island of New Guinea and numerous offshore islands...
and Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...
. They have variously been placed in A. antarcticus or A. praelongus. In 2005 it was shown that neither is appropriate, and the New Guinea death adders fall into two main clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
s: The rather smooth-scaled A. laevis complex
Species complex
A species complex is a group of closely related species, where the exact demarcation between species is often unclear or cryptic owing to their recent and usually still incomplete reproductive isolation. Ring species, superspecies and cryptic species complex are example of species complex...
(including death adders from Seram), and the rough-scaled A. rugosus complex. The latter can be divided into two sub-clades; one, A. rugosus sensu stricto, from southern New Guinea
New Guinea
New Guinea is the world's second largest island, after Greenland, covering a land area of 786,000 km2. Located in the southwest Pacific Ocean, it lies geographically to the east of the Malay Archipelago, with which it is sometimes included as part of a greater Indo-Australian Archipelago...
, and a second, A. hawkei, from northern Queensland
Queensland
Queensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...
and the Northern Territory
Northern Territory
The Northern Territory is a federal territory of Australia, occupying much of the centre of the mainland continent, as well as the central northern regions...
in Australia. It is likely some of these include more than one species, as populations included in e.g. A. laevis show extensive variation in both pattern and scalation.
Species
| Species | Authority | Subspecies* | Common name | Geographic range |
|---|---|---|---|---|
| A. antarcticusT | (Shaw, 1794) | 2 | Common death adder | Australia Australia Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area... |
| A. hawkei | Wells & Wellington, 1985 | 1 | Barkly Tableland death adder | Australia |
| A. laevis | Macleay William John Macleay Sir William John Macleay . was an Australian politician, zoologist and naturalist.-Early life:Macleay was born at Wick, Caithness, Scotland, second son of Kenneth Macleay of Keiss and his wife Barbara, née Horne... , 1878 |
None | Smooth-scaled death adder | Indonesia Indonesia Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an... , Papua New Guinea Papua New Guinea Papua New Guinea , officially the Independent State of Papua New Guinea, is a country in Oceania, occupying the eastern half of the island of New Guinea and numerous offshore islands... |
| A. praelongus | Ramsay Edward Pierson Ramsay Edward Pierson Ramsay was an Australian zoologist who specialised in ornithology.-Early life:Pierson was born in Dobroyd Estate, Long Cove, Sydney and educated at St Mark's Collegiate School, The King's School, Parramatta... , 1877 |
None | Northern death adder | Australia |
| A. pyrrhus | Boulenger George Albert Boulenger George Albert Boulenger FRS was a Belgian-British zoologist who identified over 2000 new animal species, chiefly fish, reptiles and amphibians.-Life:... , 1898 |
None | Desert death adder | Australia |
| A. rugosus | Loveridge, 1948 | None | Rough-scaled death adder | Australia, Indonesia |
| A. wellsi | Hoser Raymond Hoser Raymond Terrence Hoser is an Australian herpetologist, snake-catcher, and author. Since 1976 he has written books and articles about official corruption in Australia. He has also authored works on Australian frogs and reptiles and operates a snake handling business, Snakebusters, in Melbourne... , 1998 |
1 | Pilbara death adder | Australia |
T) Type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
.
External links
- A severe case of stomatitis (canker or mouthrot) in a Death Adder (Acanthophis antarcticus) associated with a reovirus infection. Boydii (Autumn 2004):16-17. Treatment
- Husbandry and breeding of Death Adders
- WCH Clinical Toxinology