Snake venom is modified saliva, delivered through fangs to immobilise or kill prey as quickly as possible. It is mostly protein and varies both between species and within a particular species depending on age, season and temperature.
Insects such as bees and ants use modified egg-laying devices to sting their victims and inject the venom, while cane toad poison is produced by modified salivary glands and excreted onto the skin as a defensive measure.
Venoms can contain a variety of different toxins:
- Neurotoxins - that act specifically on nerve cells to produce paralysis
- Myotoxins - that damage muscle cells to prevent prey from escaping
- Procoagulants - overstimulate blood clotting leading to a shortage of clotting factors so that the prey cannot stop bleeding
Land snakes feed on a range of animals and birds, so scientists think that these snakes need a diverse array of toxins in their venom. Sea snakes, on the other hand, tend to have a more restricted diet, feeding only on fish. The toxins in these snakes have now been shown to be less diverse than those in terrestrial snakes, suggesting that the venom may vary depending on the type of prey.
Contributed by R. Brooks. Last updated: October 2007
