![]() ![]() Measurements of LD 50 using dry venom mixed with 0.1% bovine serum albumin in saline are more consistent than the results obtained using saline alone. SC LD 50 is considered the most applicable to actual bites as only vipers with large fangs (such as large specimens from the genera Bitis, Bothrops, Crotalus, or Daboia) are capable of a truly intramuscular bite, snakebites rarely cause IV envenomation, and IP envenomation is even rarer. ![]() Smaller murine LD 50 values indicate venoms that are more toxic, and there have been numerous studies on snake venom with a variability of potency estimates. The result obtained depends on which of the four delivery sites is used for the injection: subcutis (SC), vein (IV), muscle or peritoneum (IP). Venom toxicities are compared by looking at the median lethal dose (usually using rodents as test animals and termed the murine LD 50), which is the dose of venom per unit body mass that kills half of the test animals that receive it. The world's most venomous snake, based on LD 50, is the inland taipan of Australia. Similarly, certain garter snakes from Oregon can retain toxins in their livers from ingesting rough-skinned newts. Keelback snakes are both venomous and poisonous – their poisons are stored in nuchal glands and are acquired by sequestering toxins from poisonous toads the snakes eat. While unusual, there are a few species of snake that are actually poisonous. Poisons must be ingested, inhaled or absorbed, while venom must be injected into the body by mechanical means. Venomous snakes are often said to be poisonous, but poison and venom are not the same thing. True vipers, including the Russell's viper, saw-scaled vipers, puff adders and pit vipers, including rattlesnakes, lanceheads and copperheads and cottonmouths. Sea snakes, taipans, brown snakes, coral snakes, kraits, death adders, tiger snakes, mambas, king cobras, cobras and more. Most are harmless, but others have potent venom and at least five species, including the boomslang, have caused human fatalities. Purple-glossed snakes, centipede eaters, burrowing asps, Revoil's short snake, Chilorhinophis, Hypoptophis, Homoroselaps, Macrelaps, Micrelaps, and more. Around a quarter of all snake species are identified as being venomous. This has been interpreted to mean venom in snakes originated more than once as the result of convergent evolution. There is not a single or special taxonomic group for venomous snakes. The Toxicofera hypothesis further implies that "nonvenomous" snake lineages have either lost the ability to produce venom (but may still have lingering venom pseudogenes), or actually do produce venom in small quantities, likely sufficient to help capture small prey but causing no harm to humans when bitten. Evidence has recently been presented for the Toxicofera hypothesis, that venom was present (in small amounts) in the ancestors of all snakes (as well as several lizard#Venom families) as "toxic saliva" and evolved to extremes in those snake families normally classified as venomous by parallel evolution. Snake venom is modified saliva used for prey immobilization and self-defense and is usually delivered through highly specialized teeth, hollow fangs, directly into the bloodstream or tissue of the target. The evolutionary history of venomous snakes can be traced back to as far as 28 million years ago. ![]()
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