Venom
Introduction
Venom is a type of poison, specifically a cocktail of proteins and peptides, produced by certain types of animals such as snakes, spiders, and scorpions. It is used primarily for immobilizing prey and for self-defense. Venom is injected into victims by means of a bite or sting. This distinguishes it from poison, which is ingested or inhaled. Venom has evolved in a wide variety of animals, both predators and prey, and both vertebrates and invertebrates.
Evolution of Venom
Venom has evolved on numerous separate occasions across the animal kingdom. It is thought to have first appeared in animals some 500 million years ago. Venom is a costly adaptation. Its production and delivery systems, such as fangs and stingers, require significant resources. This has led to the evolution of venom in a diverse array of species including mammals, fish, reptiles, and insects.
Venomous Animals
There are many types of venomous animals, including snakes, spiders, scorpions, cone snails, and some types of fish. Venomous snakes include species from the families Viperidae (vipers), Elapidae (cobras and kraits), and some Colubridae. Venomous spiders include the black widow, brown recluse, and the Australian funnel-web. Scorpions, particularly those from the family Buthidae, are known for their venomous sting. The cone snails, fish such as stonefish and stingrays, and some octopuses produce venom.
Composition of Venom
Venom is a complex mixture of proteins and peptides. These components can vary widely between different species, and even between different individuals within the same species. Some venoms also contain a variety of other components, such as enzymes, lipids, biogenic amines, and other small molecules.
Mechanisms of Action
Venom exerts its effects by disrupting normal physiological processes. It can affect the nervous system, cardiovascular system, and muscle tissue, among other things. Some venoms contain neurotoxins, which disrupt the nervous system by blocking nerve signals or by damaging nerve tissue. Other venoms contain cytotoxins, which kill cells, or hemotoxins, which affect the blood and cardiovascular system.
Medical Uses of Venom
Despite its harmful effects, venom has also been used for medical purposes. Some venom peptides are used as pharmaceutical drugs. For example, the venom of the Gila monster, a venomous lizard, has been used to develop a drug for the treatment of type 2 diabetes. Other venom-derived drugs are used for the treatment of conditions such as hypertension, heart failure, and chronic pain.