Atheris Explained

Atheris is a genus of vipers known as bush vipers.[1] They are found only in tropical subsaharan Africa (excluding southern Africa) and many species have isolated and fragmented distributions due to their confinement to rain forests.[2] Like all other vipers, they are venomous. In an example of convergent evolution, they show many similarities to the arboreal pit vipers of Asia and South America.[1] Seventeen species are currently recognized.

Description

They are relatively small in size, with adults ranging in total length (body + tail) from 55cm (22inches) for A. katangensis to a maximum of 78cm (31inches) for A. squamigera.[1]

All species have a broad, triangular head that is distinct from the neck. The canthus is also distinct and the snout is broad. The crown is covered with small imbricate or smooth scales, none of which is enlarged. The eyes are relatively large with elliptical pupils. The eyes are separated from the supralabials by 1–3 scale rows and from the nasal by 2–3 scales.[2]

The body is slender, tapering, and slightly compressed. The dorsal scales are overlapping, strongly keeled and have apical pits. Laterally these are smaller than the middorsals. Midbody there are 14–36 rows of dorsal scales. There are 133–175 rounded ventral scales. The subcaudal scales are single and number 38–67.[1] [2] The tail is strongly prehensile and can support the body while suspended from a branch or a twig.[3]

Members of this genus come in a wide variety of colors and patterns, often within a single species. A. ceratophora and A. squamigera are particularly variable.

Location

They inhabit rainforest regions and forests, mostly in remote areas far from human activity.[1]

They are found in tropical subsaharan Africa, excluding southern Africa.Some species have only isolated populations, surviving in small sections of ancient rainforest. They once had a much wider distribution but are now declining.[1]

Conservation status

Some species are threatened by habitat destruction.[1] A major cause of illness and mortality in both caged and wild bush viper snakes is Snake fungal disease(SFD).[4]

Behavior

All species have extreme aggressive tendencies. All species are arboreal, although they can sometimes be found on or near the ground.

Diet

Atheris species have been known to prey upon a variety of small amphibians, lizards, rodents, birds, and even other snakes. Some species or populations may specialize in eating frogs, but most have been described as opportunistic feeders.[2] Prey is typically ambushed from a hanging position, held until it has succumbed to the venom, and then swallowed.

Reproduction

All Atheris species are ovoviviparous. Mating takes place in October and November, and the females give birth to live young in March and April.

Captivity

A. squamigera is reported to do very well in captivity, needing only arboreal access and having no particular temperature requirements. Captive specimens take mice and small birds.[2] However, there have been reports of cannibalism. Food may be refused during the African winter months of July and August.

Venom

Not much is known about their venom except that it is strongly hemotoxic, causing pain, swelling and blood clotting problems.[1] Until recently, their venom has often been regarded as less toxic than that of many other species, perhaps because bites are uncommon,[2] but this turned out not to be the case. There are now a number of reports of bites that have led to severe hemorrhaging.[5] [6] [7] One case was fatal.[2] Atheris-specific antivenom does not exist[1] and antivenom meant for bites from other species seem to have little effect, although Echis antivenom has been reported to have been of some help in a case of A. squamigera envenomation.[2] Symptomatic replacement therapy is applied due to the absence of an Atheris specific antivenom.[8]

Species

Image SpeciesTaxon author Subsp.* Common name Geographic range
A. acuminataBroadley, 19980Acuminate bush viperWestern Uganda
A. anisolepisMocquard, 18870Mayombe bush viperWest central Africa: Gabon, Congo, west DR Congo, north Angola
A. barbouri(Loveridge, 1930)0Barbour's short-headed viper, Uzungwe Mountain bush viperThe Udzungwa and Ukinga mountains in southern Tanzania
A. broadleyiD. Lawson, 19990Broadley's bush viper[9] Cameroon, Central African Republic, Nigeria, Congo
A. ceratophoraF. Werner, 18950Usambara eyelash viperThe Usambara and Uzungwe Mountains in Tanzania
A. chlorechisT(Pel, 1851)0West African bush viperWest Africa including Guinea-Bissau, Guinea, Sierra Leone, Liberia, Ivory Coast, Ghana, Togo, Benin, isolated locations in Nigeria, Cameroon, Equatorial Guinea, and Gabon
A. desaixiAshe, 19680Mount Kenya bush viper, Ashe's bush viperTwo isolated populations in Kenya: in the forests at Chuka, south-eastern Mount Kenya, and Igembe in the northern Nyambeni range
A. hirsutaR. Ernst & Rödel, 20020Tai hairy bush viperIvory Coast
A. hetfieldi[10] [11] Ceríaco, Marques, & Bauer, 20200Hetfield’s bush viperBioko island, Equatorial Guinea
A. hispidaLaurent, 19550African hairy bush viperCentral Africa: DR Congo, south-west Uganda, west Kenya
A. katangensisde Witte, 19530Katanga mountain bush viperRestricted to Upemba National Park, Shaba Province in eastern DR Congo
A. mabuensisBranch & Bayliss, 2009[12] 0Mount Mabu forest viperMount Mabu and Mount Namuli, northern Mozambique
A. matildaeMenegon, Davenport & Howell, 20110Matilda's horned vipersouth west Tanzania
A. mongoensisCollet & Trape, 20200Mongo hairy bush viperDemocratic Republic of Congo
A. nitscheiTornier, 19020Great Lakes bush viperCentral Africa from east DR Congo, Uganda and west Tanzania southward to north Malawi and north Zambia.
A. rungweensisBogert, 1940 0Mt. Rungwe bush viper southwestern Tanzania, northeastern Zambia, northern Malawi
A. squamigera(Hallowell, 1856)0Variable bush viperWest and central Africa: Ivory Coast and Ghana, eastward through southern Nigeria to Cameroon, southern Central African Republic, Gabon, Congo, DR Congo, northern Angola, Uganda, Tanzania (Rumanika Game Reserve), western Kenya, and Bioko Island
A. subocularisFischer, 18880Cameroon
T) Type species

Taxonomy

Other species may be encountered in literature, such as:

Until relatively recently, the following species, all of which are terrestrial, were also included in the genus Atheris:[2]

Together with Atheris, these three genera are sometimes referred to as the tribe Atherini.

Further reading

Notes and References

  1. Spawls S, Branch B (1995). The Dangerous Snakes of Africa. Ralph Curtis Books. Dubai: Oriental Press. 192 pp. .
  2. Mallow D, Ludwig D, Nilson G (2003). True Vipers: Natural History and Toxinology of Old World Vipers. Malabar, Florida: Krieger Publishing Company. 359 pp. .
  3. Mehrtens JM (1987). Living Snakes of the World in Color. New York: Sterling Publishers. 480 pp. .
  4. Díaz-Delgado . Josué . Marrow . Judilee C. . Flanagan . Joseph P. . Bauer . Kendra L. . Zhang . Meng . Rodrigues-Hoffmann . Aline . Groch . Katia R. . Gomez . Gabriel . Balamayooran . Gayathriy . Outbreak of Paranannizziopsis australasiensis Infection in Captive African Bush Vipers (Atheris squamigera) . Journal of Comparative Pathology . 20 March 2022 . 97–102 . en . 10.1016/j.jcpa.2020.10.004 . 1 November 2020. 181 . 33288159 . 227955419 .
  5. 10.1016/S0041-0101(98)00008-7 . Mebs D, Holada K, Kornalík F . Severe coagulopathy after a bite of a green bush viper (Atheris squamiger): case report and biochemical analysis of the venom . Toxicon . 36 . 10 . 1333–40 . October 1998 . 9723832 . etal.
  6. Top LJ, Tulleken JE, ((Ligtenberg JJM)), ((Meertens JHJM)), van der Werf TS, Zijlstra JG . Serious envenomation after a snakebite by a Western bush viper (Atheris chlorechis) in the Netherlands: a case report . Neth. J. Med. . 64 . 5 . 153–6 . 2006 . PDF . 16702615 .
  7. http://www.venomousreptiles.org/articles/28 Bitten by a Sedge Viper!
  8. Wang, He, et al. (2018). "Comparative Profiling of Three Atheris Snake Venoms: A. squamigera, A. nitschei and A. chlorechis ". The Protein Journal 37 (4): 353–360. doi:10.1007/s10930-018-9781-y.
  9. Beolens, Bo; Watkins, Michael; Grayson, Michael (2011). The Eponym Dictionary of Reptiles. Baltimore: Johns Hopkins University Press. xiii + 296 pp. . (Atheris broadleyi, p. 39).
  10. News: Maciel . Ana Rita . Investigadores portugueses dão o nome do vocalista dos Metallica a nova espécie de víbora africana . 5 September 2020 . . 2020-09-05.
  11. Web site: New venomous snake species named after Metallica's James Hetfield. August 28, 2020.
  12. Branch WR, Bayliss J . A new species of Atheris (Serpentes: Viperidae) from northern Mozambique . Zootaxa . 2113 . 41–54 . 2009. 10.11646/zootaxa.2113.1.2 .