Mamba (deep Learning Architecture)

Mambas are fast-moving, highly venomous snakes of the genus ''Dendroaspis'' (which literally means "tree asp") in the family Elapidae. Four extant species are recognised currently; three of those four species are essentially arboreal and green in colour, whereas the black mamba, ''Dendroaspis polylepis'', is largely terrestrial and generally brown or grey in colour. All are native to various regions in sub-Saharan Africa and all are feared throughout their ranges, especially the black mamba. In Africa there are many legends and stories about mambas. also at

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Behaviour

The three green species of mambas are arboreal, whereas the black mamba is largely terrestrial. All four species are active diurnal hunters, preying on birds, lizards, and small mammals. At nightfall some species, especially the terrestrial black mamba, shelter in a lair. A mamba may retain the same lair for years. Resembling a cobra, the threat display of a mamba includes rearing, opening the mouth and hissing. The black mamba's mouth is black within, which renders the threat more conspicuous. A rearing mamba has a narrower yet longer hood and tends to lean well forward, instead of standing erect as a cobra does.

Stories of black mambas that chase and attack humans are common, but in fact the snakes generally avoid contact with humans. Most apparent cases of pursuit probably are examples of where witnesses have mistaken the snake's attempt to retreat to its lair when a human happens to be in the way. The black mamba usually uses its speed to escape from threats, and humans actually are their main predators, rather than prey.

Venom

All mambas have medically significant venom, with dendrotoxins, short chain alpha-neurotoxins, cardiotoxins and fasciculins. There are multiple components in dendrotoxins with different targets:

*''Dendrotoxin 1'', which inhibits the K⁺ channels at the pre and post-synaptic level in the intestinal smooth muscle. It also inhibits Ca²⁺-sensitive K⁺ channels from rat skeletal muscle‚ incorporated into planar bilayers (Kd = 90 nM in 50 mM KCl).)
*''Dendrotoxin 3'', which inhibits acetylcholine M4 receptors.
*''Dendrotoxin 7'', commonly referred to as muscarinic toxin 7 (MT7) inhibits acetylcholine M1 receptors.
*''Dendrotoxin K'', structurally homologous to Kunitz-type proteinase inhibitors with activity as a selective blocker of voltage-gated potassium channels

Not only does toxicity determine severity of envenomation, but also venom yields, proximity of wounds to the CNS and depth of punctures. All the members are capable of causing rapid onsets of symptoms, with the black mamba being the most feared in the genus for having inflicted the worst bite prognosis as a result of its more terrestrial nature (more possible contact with humans), high defensiveness (tendency to deliver fatal bites instead of dry bites), large size (strike positions), higher average venom yields and potential toxicity (based upon experimental murine ). A lethality rate of 100% (or "near 100%") for "untreated" black mamba bites has been circulating among various sources, which is probably based upon a single medical record made during 1957 to 1963 when specific antivenom had yet been introduced. Seven out of seven victims succumbed to bites of this species who received non-specific polyvalent antivenom that had no effect on the species' toxins. However, more literatures have to be reviewed for the full picture, especially when the aforementioned record was made in a single district only. Generally speaking, there were 15 out of 35 people who received ineffective treatments died. A mamba-specific antivenom was introduced in 1962, followed by a fully polyvalent antivenom in 1971. Over this period, 5 of 38 people bitten by black mambas and given antivenom died.

Despite their fearsome reputation and often exaggerated notoriety, mamba envenomation occurs far less frequently than some other snakes', for instance the puff adder. Besides proximity to residences, behaviour of a given species is also a critical aspect when it comes to snakebite morbidities. Mambas are agile, usually fleeing from any confrontation with unambiguous threat display which allows early recognition of the serpent, avoiding escalation in tension.

Taxonomy

''Dendroaspis'', is derived from Ancient Greek ''déndron'' (''δένδρον''), meaning "tree", and ''aspis'' (''ασπίς''), which is understood to mean "shield", but also denotes "cobra" or simply "snake", in particular "snake with hood (shield)". Via Latin ''aspis'', it is the source of the English word "asp". In ancient texts, ''aspis'' or asp often referred to the Egyptian cobra (''Naja haje''), in reference to its shield-like hood. The genus was first described by the German naturalist Hermann Schlegel in 1848, with ''Elaps jamesonii'' as the type species. It was misspelt as ''Dendraspis'' by Dumeril in 1856, and generally uncorrected by subsequent authors. In 1936, Dutch herpetologist Leo Brongersma pointed out that the correct spelling was ''Dendroaspis'' but added that the name was invalid as Fitzinger had coined ''Dendraspis'' in 1843 for the king cobra and hence had priority. However, in 1962 German herpetologist Robert Mertens proposed that the 1843 description of ''Dendraspis'' by Fitzinger be suppressed due to its similarity to ''Dendroaspis'', and the confusion it would cause by its use.

Range and characteristics

Black mambas live in the savannas and rocky hills of southern and eastern Africa. They are Africa's longest venomous snake, reaching up to 14 feet in length, although 8.2 feet is more the average. They are also among the fastest snakes in the world, slithering at speeds of up to 12.5 miles per hour.

''* Including the nominate subspecies.''

^T Type species.

Phylogeny

A 2018 analysis of the venom of the mambas, as well as a 2016 genetic analysis, found the following cladogram representative of the relationship between the species.

Notes

References

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Muscarinic antagonists