Meeting Abstract
When organisms possess chemical defenses, their predators may eventually evolve resistance to their toxins. Eastern Indigo Snakes (Drymarchon couperi; EIS) subdue and consume a variety of pitviper species and it has been suggested EIS possess a physiological resistance to their venom. In this study, we formally investigated this hypothesis by using microassays that measured the ability of EIS blood sera to inhibit A) hemolytic and B) snake venom metalloproteinase (SVMP) activity of Copperhead (Agkistrodon contortrix) venom. To serve as controls, we also tested the inhibitory ability of sera from inbred House Mice (Mus musculus) and from a snake that does not feed on pitvipers, the Checkered Gartersnake (Thamnophis marcianus). As expected, mouse sera exhibited little effect on the activity of either class of toxins tested. However, sera from both EIS and gartersnakes inhibited over 60% of SVMP activity. EIS sera also inhibited 78% of venom hemolytic activity, while gartersnake sera failed to inhibit these toxins. Our results demonstrate that EIS serum is indeed capable of inhibiting two of the primary classes of toxins found in Copperhead venom, suggesting that EIS may possess physiological resistance to venom upon injection. Because we documented resistance to hemolytic components of pitviper venom within EIS but not gartersnakes, we speculate this resistance may be driven by antagonistic interaction while resistance to SVMP may be relatively widespread among snakes and not necessarily related to the diet and ecology of extant species.
