Lachesis (genus)

''Lachesis'', also known as bushmasters,Campbell JA, Lamar WW. 2004. The Venomous Reptiles of the Western Hemisphere. 2 volumes. Comstock Publishing Associates, Ithaca and London. 870 pp. 1500 plates. . is a genus of venomous pit vipers found in forested areas of Central and South America. The generic name refers to one of the Three Fates, Lachesis, in Greek mythology who determined the length of the thread of life. Four species are currently recognized.

Description

Adults vary in length from , although some may grow to as much as , making it the longest venomous snake in the Western Hemisphere. Bushmasters are the longest type of viper in the world. ''L. muta'' is possibly the largest of the three species currently recognized, although more scant information suggest ''L. stenophrys'' broadly overlaps in size and may average at a similar size, while ''L. melanocephala'' and ''L. acrochorda'' are seemingly slightly smaller than the prior two species. Although they are not the heaviest vipers, being surpassed in mass by the Gaboon viper and the Eastern diamondback rattlesnake, large adults still can weigh up to . Bushmasters are sexually dimorphic in size, with males reaching larger sizes than females. The bushmaster's tail ends with a horny spine which sometimes vibrates when disturbed like rattlesnakes. This has led to some calling it 'the mute rattlesnake'.

Geographic range

Found in central and South America, including the island of Trinidad.List of Snakes of Trinidad and Tobago
a
Republic of Trinidad and Tobago Biodiversity Clearing House
. Accessed 25 October 2006.

Reproduction

Bushmasters lay eggs: about a dozen in an average clutch. The female reportedly remains with her eggs during incubation and may aggressively defend the nest if approached. The hatchlings average in length and are more colorful than the adults. ''Lachesis'' is thought to be unique among New World pit vipers by laying eggs rather than giving birth to live young, although some evidence suggests that the species '' Bothrocophias'' ''colombianus'' found in Colombia may do the same.

Venom

This snake is capable of multiple-bite strikes and the injection of large amounts of venom. Even the bite of a juvenile specimen can be fatal. However, this snake is rarely encountered so snakebite incidents are not common. The venom of ''Lachesis'' has several activities, such as the activation of plasminogen, leading to increased permeability of blood vessels, causing edema and lowering of blood pressure. It also has coagulant activity in which thrombin-like enzymes act on fibrinogen, forming small clots that settle in organs such as lungs and kidneys, obstructing capillary blood flow. Hemorrhagic activity is caused by metalloproteases, which damage capillary walls. Both coagulant and hemorrhagic activities act in combination, triggering local and systemic hemorrhagic disorders. Proteolytic activity is due to direct action of proteases (thrombin for example), metalloproteases, and important myotoxic and cytolytic factors. Myotoxic action occurs due to phospholipase generating an inflammatory infiltrate composed of polymorphonuclear leukocytes and macrophages around necrotic cells. Phospholipases can induce necrosis of skeletal muscle fibers. While the defibrinating action results in blood incoagolability, the venom also has a kininogen-like action; it causes the body to release substances such as bradykinin and kallikrein inducing hypotension. Bradykinin-enhancing peptides interfere with the bradykinin metabolism causing it to last longer in the blood, leading to lasting hypotension. The venom also has a neurotoxic action, isolated from basic phospholipase, that is capable of inducing irreversible blockage of neuromuscular transmission in vitro at as low concentrations as 1 mg / ml.

Species

''*) Not including the nominate subspecies.''

^T) Type species.

Taxonomy

Campbell and Lamar (2004) also recognize a fourth species, ''L. acrochorda'' (García, 1896), referring to it as the Chochoan bushmaster. It is found in western Panama and northwestern Colombia and Ecuador. Its evolutionary relationships are not certain, but ''Lachesis acrochorda'' is thought to be closer to the South American bushmaster ''L. muta'' than to the two Central American species ''L. stenophrys'' and ''L. melanocephala''. The snake is known to be one of the deadliest snakes in the world.

Cultural depictions

The bushmaster snake is the antagonist in the tenth episode of the old time radio show ''Escape''. The episode's title was "A Shipment of Mute Fate", and starred Jack Webb and Raymond Lawrence. It was broadcast on 15 October 1947. The story was also adapted for ''Suspense'' starring Jack Kelly, broadcast on January 6, 1957. Jack T. Colton killed a bushmaster in the film '' Romancing the Stone'' from 1984 when seeking shelter in a crashed plane.

The following weapons and military vehicles are named after this viper:
* M242 Bushmaster, a chain gun manufactured by Northrop Grumman Innovation Systems;
* Bushmaster IMV, an Australian infantry mobility vehicle;
* A variant of the amphibious Landing Vehicle Tracked introduced in 1944, the LVT-3 Bushmaster.

References

Further reading

* Eatherley, Dan. ''Bushmaster: Raymond Ditmars and the Hunt for the World's Largest Viper''. 2015 (Arcade: New York City)
* Mehrtens, J.M. ''Living Snakes of the World in Color''. New York: Sterling Publishers. 1987. 480 pp. .
* O'Shea, Mark. ''Venomous Snakes of the World''. Princeton University Press. 2005. 160 pp. .

External links

*

{{Taxonbar, from=Q766057

Snakes of South America
Snakes of Central America
Reptiles of Nicaragua
Snake genera
Taxa named by François Marie Daudin