The kinematics of envenomation by the yellow stingray, Urobatis jamaicensis

摘要

The yellow stingray, Urobatis jamaicensis (Cuvier 1817), is a common saltwater stingray species that can administer a fast, venomous sting, usually as the result of being inadvertently stepped upon. This species has been studied by a number of investigators, however, little is known about the kinematics of its strike, or the strike of any other ray species. High-speed cinematography was used to film vertical strikes catalyzed by a foot-like apparatus used to pin the animal down. The average maximum velocity of 213.15 cm/s was found to occur 61.3% through the total strike; strikes lasted, on average, 0.23 s. The average maximum acceleration was determined to be 3067.34 cm/s/s. To accomplish a successful envenomation, a stingray will arc its tail upward then depress the tip of its tail to reveal the venomous spine, forming an angle with the tail with a mean of 35.73 degrees. This angle appears, on average, at a point 58.8% through the path of the strike, or just before the maximum velocity. Morphological analyses determined that this angle is accomplished by a significant reduction in the dorso-ventral height of the vertebral column, as well as spacing between haemal arches and processes, creating a "hinge-like" feature that allows the tail-tip to flex away from the spine. Yellow stingrays are morphologically and behaviorally adapted to deploy their venomous spine as a mean of defense against threats, and a better understanding of this mechanism may aid in the prevention and treatment of stingray-inflicted wounds in humans.