DEUFEL, A.*; CUNDALL, D.: Feeding in stiletto snakes

Stiletto snakes (Atractaspis) resemble vipers in having a short maxilla bearing a long fang associated with a large venom gland. Previous studies of Atractaspis have described an unusual envenomation strategy in which one fang is unilaterally everted from the closed mouth and stabbed into the prey by a posteroventral jerk of the head. Prior anatomical descriptions suggest that the head of Atractaspis is designed for increased cranial kinesis through liberation of both ends of the pterygoid. We combined video records of A. bibroni feeding on live prey inside a narrow tunnel with electrical stimulation of anesthetized snakes and dissection of preserved specimens to show that the apparent design for increased cranial kinesis is constrained minimally by maxillary-prefrontal relationships that limit pterygoid movement. Liberation of the palatine from the pterygoid precludes prey transport using the “pterygoid walk” because of the absence of a palatine protraction mechanism. Atractaspis has to rely on a relatively inefficient transport mechanism in which the snake forces its head over the prey with lateral rotations around a vertical axis. As the prey enters the esophagus A. bibroni switches to bilateral head and anterior trunk extension and compression, a mechanism that can make use of the palatine teeth. It remains unresolved how an upper jaw with high kinetic potential of the medial elements could evolve together with a lateral upper jaw with limited kinetic potential. Nevertheless, the unusual feeding apparatus of Atractaspis appears to be ideally suited for prey capture in small spaces.