Week 6 - Venom Introduction

Venom

  • It bites you and you die
  • Causes internal bleeding
  • Can activate blood clotting
    • Causes stroke/heart attack
  • Have toxins that damage cells
  • Venom is the mode of delivery - same as poison, just injected
Types of venom
  1. Proteolytic

   

  1. Contains proteolytic enzymes that degrade tissue structures
  2. Breaks down blood vessel walls and muscle tissue
    1. Hemotoxic

   

  1. Destroys red blood cells as well as tissues and organs
  2. Can also cause blood clotting or prevent clotting
  3. Results in cardiovascular failure, loss of limb, and internal bleeding
    1. Neurotoxic

   

  1. Hinders nerve impulses around the body
    1. Cytotoxic

   

  1. Kills cells
  2. Can result in loss of limb function and other disabilities
  3. Severely damages skin and tissues
Evolution of venom
  • Due to dramatic changes in habitat/lifestyle
  • Evolved from an old ancestor or individually
  • First snakes were constrictors
  • Constrictors in jungles
    • Allow them to hide
  • Prevents prey from escaping, stops return attacks, begins digestion
  • Evolved independently in more than 100 animal lineages
  • Each type of venom is encoded by a single gene, so they can be compared gene by gene to determine how they’re related to each other
  • Venom composition can be adaptive to the prey being targeted
  • Venoms evolved from other proteins that had functions such as:
    • Immune system proteins that attack bacteria invading the body
    • Digestive enzymes
  • Genes can duplicate, allowing them to make more of a protein; then one copy can mutate for a different function, or to be made in a different place (eg. mouth rather than pancreas)
Case Study: Shrew
  • 2 species are venomous
    • Eurasian water shrew
    • The short-tail shrew
  • The saliva is the poisonous part
  • Deliver it via a groove in their teeth
  • Used to subdue and paralyze prey
    • Small insects, earthworms, and sometimes mice
  • Ineffective of larger animals
  • Not used as a means of defence
  • Used to preserve their prey and keep it fresher for longer
    • Especially useful in winter when food accessibility is harder