Bothrops


 * Common names: lanceheads, American lanceheads, American lance-headed vipers. 

Bothrops is a genus of venomous pitvipers found in Central America, South America. Currently, 32 species are recognized. The generic name is derived from the Greek words bothros and ops that mean "pit" and "eye" or "face"; an allusion to the heat-sensitive loreal pit organs. Members of this genus are responsible for more human deaths in the Americas than any other group of venomous snakes.

Description
These snakes range from small, never growing to more than 50-70 cm, to large at over 200 cm in length. Most are characterized by having a sharp canthus rostralis and an unelevated snout.

The arrangement of the scales on top of the head is extremely variable; the number of intrasupraoculars may be anything from 3 to 14. Usually there are 7-9 supralabials and 9-11 sublabials. There are 21-29 midbody dorsal scales, 139-240 ventral scales and 30-86 subcaudals, which are generally divided.

Geographic range
Found in northeastern Mexico (Tamaulipas) southward through Central and South America to Argentina. Also occurs on the islands of Saint Lucia and Martinique in the Lesser Antilles, as well as on Ilha da Queimada Grande off the coast of Brazil.

Behavior
Most species are nocturnal, although a few that are found at higher altitudes are active during the day. Otherwise they may be seen on cloudy days or during periods of rain. Most are terrestrial, even though all are capable of climbing. One in particular, B. insularis, has a reputation for often being found in trees.

Venom
Members of this genus are responsible for more fatalities in the Americas than any other group of venomous snakes. In this regard, the most important species are B. asper, B. atrox and B. jararaca. Without treatment, the fatality rate is estimated to be about 7%, but with treatment this is reduced to 0.5-3%.

Typical symptoms of bothropic envenomation include immediate burning pain, dizziness, nausea, vomiting, sweating, headache, massive swelling of the bitten extremity, hemorrhagic blebs, local necrosis, bleeding from the nose and gums, ecchymosis, erythemia, hypotension, tachycardia, coagulopathy with hypofibrinogenemia and thrombocytopenia, hematemesis, melena, epistaxis, hematuria, intracerebral hemorrhage and renal failure secondary to hypotension and bilateral cortical necrosis. There is usually some discoloration around the bite site and rashes may develop on the torso or the extremities.

In general, death results from hypotension secondary to hypovolemia, renal failure and intracranial hemorrhage. Common complications include necrosis and renal failure secondary to hypovolemic shock and the toxic effects of the venom.

Species
*) Not including the nominate subspecies (typical form). T ) Type species.

Taxonomy
Other (new) species may be encountered in literature, such as:
 * B. alcatraz - Marques, Martins & Sazima, 2002. Range: Brazil (São Paulo). Common name: jararaca-de-Alcatrazes.
 * B. muriciensis - Ferrarezzi & Freire, 2001. Range: northeastern Brazil (Alagoas). Common name: Murici lancehead.