Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through a wound by means of a bite, sting, or similar action. The toxin is delivered through a specially evolved venom apparatus, such as fangs or a stinger, in a process called envenomation.
Venom is often distinguished from poison, which is a toxin that is passively delivered by being ingested, inhaled, or absorbed through the skin, and toxungen, which is actively transferred to the external surface of another animal via a physical delivery mechanism.Venom has evolved in terrestrial and marine environments and in a wide variety of animals: both and prey, and both and . Venoms kill through the action of at least four major classes of toxin, namely necrosis and , which kill cells; , which affect nervous systems; , which damage muscles; and Hemotoxin, which disrupt Thrombus. Venomous animals cause tens of thousands of human deaths per year.
Venoms are often complex mixtures of toxins of differing types. Toxins from venom are used to treat a wide range of medical conditions including thrombosis, arthritis, and some . Studies in venomics are investigating the potential use of venom toxins for many other conditions.
Also, a number of animal species have been demonstrated to acquire venom toxins from other sources, notably from associated microbes, which may even inhabit their venom apparatuses.
Venoms adapt to their environment and victims, evolving to become maximally efficient on a predator's particular prey (particularly the precise within the prey). Consequently, some venoms may become specialized to an animal's standard diet.
Many have defensive venom glands associated with specialized bristles on the body called urtication. These are usually merely irritating, but those of the Lonomia moth can be fatal to humans.
Bees synthesize and employ an acidic venom (apitoxin) to defend their hives and food stores, whereas wasps use a chemically different venom to paralyse prey, so their prey remains alive to provision the food chambers of their young. The use of venom is much more widespread than just these examples; many other insects, such as Hemiptera and many , also produce venom. The ant species Polyrhachis dives uses venom topically for the sterilisation of pathogens.
Venom is found in a few other reptiles such as the Mexican beaded lizard, the gila monster, and some monitor lizards, including the Komodo dragon. Mass spectrometry showed that the mixture of proteins present in their venom is as complex as the mixture of proteins found in snake venom.Fry, B. G.; Wuster, W.; Ramjan, S. F. R.; Jackson, T.; Martelli, P.; Kini, R. M. 2003c. Analysis of Colubroidea snake venoms by liquid chromatography with mass spectrometry: Evolutionary and toxinological implications. Rapid Communications in Mass Spectrometry 17:2047-2062. Some lizards possess a venom gland; they form a hypothetical clade, Toxicofera, containing the suborders Serpentes and Iguania and the families Varanidae, Anguidae, and Helodermatidae.
A few species of living mammals are venomous, including , shrews, the European mole, , male , and . Shrews have venomous saliva and most likely evolved their trait similarly to snakes. The presence of tarsal spurs akin to those of the platypus in many non- Mammaliaformes groups suggests that venom was an ancestral characteristic among mammals.Jørn H. Hurum, Zhe-Xi Luo, and Zofia Kielan-Jaworowska, Were mammals originally venomous?, Acta Palaeontologica Polonica 51 (1), 2006: 1-11
Extensive research on platypuses shows that their toxin was initially formed from gene duplication, but data provides evidence that the further evolution of platypus venom does not rely as much on gene duplication as was once thought. Modified sweat glands are what evolved into platypus venom glands. Although it is proven that reptile and platypus venom have independently evolved, it is thought that there are certain protein structures that are favored to evolve into toxic molecules. This provides more evidence of why venom has become a homoplastic trait and why very different animals have convergently evolved.
In medicine, snake venom proteins are used to treat conditions including thrombosis, arthritis, and some . Gila monster venom contains exenatide, used to treat type 2 diabetes. extracted from fire ant venom has demonstrated biomedical applications, ranging from cancer treatment to psoriasis.
A branch of science, venomics, has been established to study the proteins associated with venom and how individual components of venom can be used for pharmaceutical means.
The California ground squirrel has varying degrees of resistance to the venom of the Northern Pacific rattlesnake. The resistance involves toxin scavenging and depends on the population. Where rattlesnake populations are denser, squirrel resistance is higher. Rattlesnakes have responded locally by increasing the effectiveness of their venom.
The of the Americas are constrictors that prey on many venomous snakes.
They have evolved resistance which does not vary with age or exposure. They are immune to the venom of snakes in their immediate environment, like copperheads, cottonmouths, and North American rattlesnakes, but not to the venom of, for example, king cobras or black mambas.Among marine animals, eels are resistant to sea snake venoms, which contain complex mixtures of neurotoxins, myotoxins, and nephrotoxins, varying according to species. Eels are especially resistant to the venom of sea snakes that specialise in feeding on them, implying coevolution; non-prey fishes have little resistance to sea snake venom.
Clownfish always live among the tentacles of venomous (an obligatory symbiosis for the fish), and are resistant to their venom. Only 10 known species of anemones are hosts to clownfish and only certain pairs of anemones and clownfish are compatible. All sea anemones produce venoms delivered through discharging and mucous secretions. The toxins are composed of peptides and proteins. They are used to acquire prey and to deter predators by causing pain, loss of muscular coordination, and tissue damage. Clownfish have a protective mucus that acts as a chemical camouflage or macromolecular mimicry preventing "not self" recognition by the sea anemone and nematocyst discharge. Clownfish may acclimate their mucus to resemble that of a specific species of sea anemone.
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