Toxicity and metabolic costs of the Atlantic stingray (Dasyatis sabina) venom delivery system in relation to its role in life history

The Atlantic stingray (Dasyatis sabina) venomous spine is thought to be primarily a defensive adaptation, but may also play key roles in reproduction and conspecific social interactions. This study quantified metabolic costs associated with the venom delivery system, venom toxicity (LC50), and routine resting metabolism for Atlantic stingrays. Respirometry trials estimated an average routine resting metabolism for Atlantic stingrays of 0.484 kcal g(-1) h(-1); whereas the average metabolic rate of the venomous delivery system was 0.000162 kcal g(-1) h(-1), or 0.04% of the fish's resting rate. Ballistic bomb calorimetry revealed an average spine caloric density of 0.238 kcal per gram of spine. Acute toxicity tests using sheepshead minnow, Cyprinodon variegates, as a surrogate, determined a venom LC50 value of 0.181 mg protein g fish(-1). When compared with other venomous species, where venom is used primarily for defense and prey capture, the low toxicity and low metabolic cost of the Atlantic stingray's venomous system suggests that defense is not the primary purpose of the venomous spine. (C) 2011 Elsevier B.V. All rights reserved.