A venom is a poison or mixture of poisons secreted by an animal for predation or self defence. These mixtures can be impressively complex, involving several dozen different proteins and, on occasion (e.g. the komodo dragon) symbiotic/commensual bacteria as well. Venom is usually delivered by a bite or sting and doesn't normally include skin secretions or blood borne antifeedants.
Venoms are most commonly found in arthropods of various kinds, followed by reptiles and then fish - only a few species of molluscs, mammals and amphibians have been found to use venoms and to date no birds at all.
Due to the complexity of many venoms, they are frequently classified by their effect on the target. Common examples would include:
- Nerve toxins: Interfere with neurological activity in the target, causing temporary or permanent paralysis, often leading to death by interfering with breathing in more complex organisms. Frequently used by species that want to use their target as a place to lay eggs.
- Conversion agents: Cause structural breakdown of living tissue in the target - often used to make prey more easily digestable.
- Blood agents: interfere with the circulation or efficacy of the target's blood, sometimes by attacking the heart muscle or arterial muscles and sometimes by destroying or coagulating blood cells.
- Metabolic toxins: true poisons that disrupt basic biochemistry in the cells around the bite area.
Again, due to the complexity of many venoms, a given bite may deliver several of these effects.
Antidotes - more specifically antivenoms - are available for many more common forms, and accquired immunity is possible in some cases, but both can turn out to be dangerous restricted to a given species … from a given geographical area.
There is also considerable scientific interest in many compounds found in venoms for medical use - as anticoagulants, immune regulators and other, more obscure uses.
Game and Story Use
- Lots of RPG monsters have venoms … very few adventures are set around hunting them for it.
- Older than print as a source of applied poisons - Heracles made significant use of the blood of the Lernaean Hydra (not technically a venom, but the creature did have toxic breath which would probably count).
- A lot of venoms are significantly painful - some primitive tribes use the enduring of painful but non-fatal venoms as part of initiation rites.