This article is about animals that inject venom. For animals poisonous on contact or when ingested, see
list of poisonous animals.
Numerous animal species naturally produce chemical toxins which are used to kill or incapacitate prey or as a defense against predators.
Venomous animals actively deliver their toxins (called
venom) into their target through a specially designed mechanism, such as a
bite or
sting, by using a venom apparatus, such as
fangs or a
stinger, in a processes called
envenomation.[1][2]
They are often distinguished from
poisonous animals, which instead passively deliver their toxins (called
poison) to their victims upon contact such as through inhalation, absorption through the skin, or after being ingested.[1][2][3] The only difference between venomous animals and poisonous animals is how they deliver the toxins.[3] This list deals exclusively with venomous animals.
Venoms have adapted to serve a wide variety of purposes. Their intended effects can range from mild fleeting discomfort to paralysis and death, and they may be highly selective in which species they target, often making them harmless to all but a few specific organisms; what may be fatal to one species may be totally insignificant to another species. Because the definition of "venomous" can be extremely broad, this list includes only those animals with venom that is known or suspected to be medically significant for humans or domestic animals.
Strictly speaking, all spiders and scorpions possess venom, though only a handful are dangerous to humans. Spiders typically deliver their venom with a bite from piercing, fang-like
chelicerae; scorpions sting their victims with a long, curved
stinger mounted on the
telson.
All
widow spiders (Latrodectus spp.), including the black widows, button spiders, Australian
redback spider (L. hasseltii), and the endangered
katipō of New Zealand (L. katipo)
Of more than a thousand known species of
scorpion, only a few dozen have venom that is dangerous to humans,[6] most notably the
bark scorpions, including:
The
remipedeXibalbanus tulumensis is a centipede-like
crustacean that lives in underground
anchialine caves of Mexico and Central America. Although blind, it is a formidable predator and feeds on the shrimp that share its underground pools.[7]
Mollusks
Cone snails of the family
Conidae are a diverse group of predatory marine
gastropods, mostly tropical in distribution, which hunt and immobilize prey using a modified harpoon-like
radular tooth that can deliver neurotoxic
conopeptides. All cone snails are venomous, though the danger posed to humans varies widely by species.
Many species of
octopus,
squid, and
cuttlefish make use of venom when hunting their prey.
The
blue-ringed octopodes (Hapalochlaena spp.) produce
tetrodotoxin, which is extremely toxic to even the healthiest adult humans, though the number of actual fatalities they have caused is far lower than the number caused by spiders and snakes, with which human contact is more common.[8]
Cnidarians
Jellyfish sting using microscopic cells called
nematocysts, which are capsules full of venom expelled through a microscopic lance. Contact with a jellyfish tentacle can trigger millions of nematocysts to pierce the skin and inject venom.[9]
Chaetognathans, known as arrow worms, use the grasping spines in front of their mouth to catch prey and inject them with
tetrodotoxin produced by symbiotic bacteria.[11][12]
Annelids
Glyceridae, also called bloodworms, is a family of carnivorous
polychaete worms which have an eversible proboscis equipped with four jaws connected to venom glands, used for killing the invertebrates they feed on.[13]
Some scientists have proposed that Sinornithosaurus had a venomous bite, but recent evidence suggests otherwise.[16]
Amphibians
Though there are numerous
poisonous amphibian species capable of secreting lethal toxins through their skin, relatively few amphibians are truly venomous.
Only a few modern mammal species are capable of producing venom; they are likely the last living examples of what was once a more common trait among the mammals. The definition of "venomous" becomes less distinct here, however, and whether some species are truly venomous is still debated.
^Gianechini, F.A., Agnolín, F.L. and Ezcurra, M.D. (2010). "A reassessment of the purported venom delivery system of the bird-like raptor Sinornithosaurus." Paläontologische Zeitschrift, in press.
doi:
10.1007/s12542-010-0074-9