The Majestc Black Mamba
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Species: D. polylepis
The black mamba (Dendroaspis polylepis), also called the common black mamba or black-mouthed mamba, is the longest venomous snake in Africa, averaging around 2.5 to 3.2 m in length, and sometimes growing to lengths of 4.45 m (14.6 ft). It is named for the black colour of the inside of the mouth rather than the colour of its scales which varies from dull yellowish-green to a gun-metal grey. It is also the fastest snake in the world, capable of moving at 4.32 to 5.4 metres per second (16–20 km/h, 10–12 mph). The black mamba has a reputation for being very aggressive, but it usually attempts to flee from humans like most snakes, unless it is threatened. Without rapid and vigorous antivenom therapy, a bite from a black mamba is almost always fatal.
Black mambas breed only once a year. The breeding season begins in the spring, which occurs around the month of September in the African regions where these snakes occur, as much of sub-Saharan Africa is in the Southern Hemisphere. In this period, the males fight over females. Agonistic behaviour for black mambas involves wrestling matches in which opponents attempt to pin each other’s head repeatedly to the ground. Fights normally last a few minutes, but can extend to over an hour. The purpose of fighting is to secure mating rights to receptive females nearby during the breeding season. Beyond mating, males and females do not interact. Males locate a suitable female by following a scent trail. Upon finding his mate, he will thoroughly inspect her by flicking his forked tongue across her entire body. Males are equipped with two hemipenes. After a successful and prolonged copulation, the eggs develop in the female’s body for about 60 days. During this period, the female seeks a suitable place to lay the eggs. Females prefer using abandoned termite mounds as nests. Mature females lay between 15 and 25 eggs, which they hide very well and guard very aggressively. The eggs incubate for about 60 days before hatching. The hatchlings are about 50 centimetres (20 in) in length and are totally independent after leaving the eggs, hunting and fending for themselves from birth. Young hatchlings are as venomous as the adults, but do not deliver as much venom per bite as an adult snake would.
Mamba venom is made up mostly of dendrotoxins , fasciculins, and calciseptine. Being a protein of low molecular weight, the venom and its constituents are able to spread extraordinarily rapidly within the bitten tissue, so black mamba venom is the most rapid-acting of all snake venoms. The dendrotoxins disrupt the exogenous process of muscle contraction by means of the sodium potassium pump. Toxin K is a selective blocker of voltage-gated potassium channels, Toxin 1 inhibits the K+ channels at the pre and postsynaptic level in the intestinal smooth muscle. It inhibits Ca2+-sensitive K+ channels from rat skeletal muscle‚ incorporated into planar bilayers (Kd = 90 nM in 50 mM KCl), Toxin 3 inhibits M4 receptors, while Toxin 7 inhibits M1 receptors. The calciseptine is a 60 amino acid peptide which acts as a smooth muscle relaxant and an inhibitor of cardiac contractions. It blocks K+-induced contraction in aortic smooth muscle and spontaneous contraction of uterine muscle and portal vein. The venom is highly specific and virulently toxic. In one experiment, the death time of a mouse after subcutaneous injection of some toxins studied, was around seven minutes. However, black mamba venom can kill a mouse after 4.5 minutes.
Black mamba venom also contains proteins, mambalgins, which in mice act as an analgesic as strong as morphine, but without most of the side-effects. Mambalgins cause much less tolerance than morphine and no respiratory distress. They act through a completely different route, acid-sensing ion channels. Laboratory tests suggest that the pain-killing effect on humans may be similar, but this had not been tested as of October 2012. Researchers were puzzled about the advantage this substance could give the snakes.