Physiology of Snake Venom

by Evan Eskew

Snakes, especially those that are venomous, are a subject of fear and fascination for many people. In fact, the relationship between humans and venomous snakes appears to have influenced our evolutionary past; some scientists hypothesize that the threat of dangerous snakes led to the refinement of neurological skills in early anthropoids (Isbell, 2006), so in some sense venomous snakes may have helped make us what we are today.

The venomous cottonmouth (Agkistrodon piscivorus) in a defensive posture. Photo by Evan Eskew.

Venomous animals are defined as those that inject toxins into other animals by means of “spurs, stingers, spines, or teeth” (Greene, 1997). Venomous snakes have traditionally been categorized into two main groups, elapids and vipers, which are defined by the type of fangs the snake has for venom injection. Elapids are characterized by relatively immobile fangs and comprise approximately 330 species including the cobras, mambas, seakraits, and coral snakes. In contrast, vipers have highly movable fangs that fold flat against the roof of the mouth when not in use. Rattlesnakes and adders are among the nearly 230 species of vipers (Greene, 1997). Recent work suggests that the organization of venomous snakes may be much more complex as there are some species of venomous colubrids (a group of snakes that are for the most part non-venomous) and a distinct third group of venomous snakes apart from the elapids and vipers: the atractaspidids or stilleto snakes (Greene, 1997; Jackson, 2003).

The website aims to review the vast literature concerning venomous snakes with particular emphasis on the physiology of venom. Major topic headings are listed at the left of this page along with additional resources pertaining to venomous snakes and a list of the scientific literature referenced throughout the website.