The Cost of Making Venom

Acanthophis antarcticus, Petra Karstedt Wikimedia

Speculation and studies on the energy cost of snakes producing venom are of interest because they are tied to the idea that snakes meter their venom during bites. However, only one study has attempted to examine the metabolic cost of replenishing venom in snakes. McCue (2006) showed that venom expenditure increased the metabolic rate in three pit vipers by 11% increase during the first 72 hour of replenishment. Now Anna Pinto and colleagues from James Cook University use flow-through respirometry, to examine changes in the metabolic rate of the Australia elapid known as the Death Adder, Acanthophis antarcticus. They measure metabolism after venom expenditure and feeding as well as during preparation for shedding in an effort to establish a comparison for the energetic expenditures made during these common physiological processes. The snakes used were a captive group of six siblings and their parents. The authors found venom expenditure was associated with an abrupt and distinct increase in metabolism during the first 12 h after venom extraction, followed by a slow return to resting levels and they found that snakes appear to spread out the expenditure of energy of to replace the venom over time and the metabolic rate may stay up for a much longer time period than was measured in the study. However, 54% of total costs are made during the first day first day of venom replenishment, and the metabolic rate stayed only slightly above the resting metabolism during the subsequent five days. Suggesting that the activation of venom gland epithelium including the up regulation of protein synthesis was the main expense in venom production and it occurs in the first day after the venom was expelled.  Pinto and colleagues found that the cost of replenishing venom increased the snake's resting metabolism by 69%, while feeding (minus the venom expenditure) increased the metabolic rate 169%, and his was considerably lower than the cost of shedding, which increased the snake's metabolism 126% above the resting rate for 13 days (this is 17 times greater than the energy used to replace the venom). Thus, their results suggest that total costs of venom replenishment are relatively small when compared to costs of digestion and shedding.

Literature
Pintor, A. F. V., A. K. Krockenberger and J. E. Seymour. 2010. Costs of venom production in the common death adder (Acanthophis antarcticus). Toxicon, 56(6):1035-1042.

McCue, M. D., 2006. Cost of producing venom in three North American pitviper species. Copeia 2006, 818–825.

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