Meeting Abstract

50.4  Jan. 6  The spatial distribution of venom spat by cobras WESTHOFF, Guido*; BOETIG, Melissa; YOUNG, Bruce/A.; University of Bonn; Washburn University; Washburn University bruce.young@washburn.edu

Venom spitting has evolved independently in multiple lineages of cobras. Within the spitting cobras this defensive behavior spans a considerable range; some species expulse strong streams of venom capable of traveling well over a meter through the air, while other species produce a �mist� of venom that is limited in both volume and distance covered. Previous studies have shown that the same specimen can produce different spatial distributions or patterns of spat venom. Given that the corneal surface is the only external body area affected by contact with the venom, and that these distribution patterns impact the likelihood of spat venom contacting the cornea, the spatial distribution of the venom could be under selective pressure. We explored three competing hypotheses for the determinant of the spatial distribution of spat venom: 1) morphological specializations within the venom fang; 2) physiological performance of the propulsive muscle, and 3) kinematic displacement of the head during venom expulsion. To explore the morphological hypothesis we examined the fangs of several species of spitting and non-spitting cobras using SEM. The other two hypotheses were explored experimentally. Bipolar EMG leads were implanted into the skeletal muscle surrounding the venom gland. Standard and high-speed digital videography was used to document the distance between the cobra and the target (one of the authors) as well as the kinematic displacement of the cobra’s head during venom expulsion.