Functional Bases of the Spatial Dispersal of Venom during Cobra “Spitting” (original) (raw)

Analyses of venom spitting in African cobras (Elapidae: Serpentes)

African Zoology, 2005

Abstract: The venom spat by four spitting cobras (Naja nigricollis, N. pallida, N. mossambica and Hemachatus haemachatus) was caught using perspex plates. Densiometric analysis of the spat venom revealed low levels of variation in volume among successive spits. The dispersal patterns formed by the spat venom were divided into two basic classes, both of which were produced by all four species. The low levels of variation in venom volume, coupled with the variation in venom dispersal pattern, suggests a complexity to the regulation of venom flow in spitting cobras beyond simply neuromuscular control of the extrinsic venom gland.

Experimental pathophysiology of systemic alterations induced by Bothrops asper snake venom

Toxicon, 2009

Moderate and severe envenomations by the snake Bothrops asper provoke systemic alterations, such as systemic bleeding, coagulopathy, hypovolemia, hemodynamic instability and shock, and acute renal failure. Systemic hemorrhage is a typical finding of these envenomations, and is primarily caused by the action of P-III snake venom metalloproteinases (SVMPs). This venom also contains a thrombin-like serine proteinase and a prothrombin-activating P-III SVMP, both of which cause defibrin(ogen)ation. Thrombocytopenia, predominantly induced by a C-type lectin-like protein, and platelet hypoaggregation, caused by the two defibrin(ogen)ating enzymes, also contribute to hemostatic disturbances, which potentiate the systemic bleeding induced by hemorrhagic SVMPs. Cardiovascular disturbances leading to shock are due to the combined effects of hemorrhagic toxins, other venom components that increase vascular permeability, the action of hypotensive agents in the venom and of endogenous mediators, and the potential cardiotoxic effect of some toxins. Renal alterations are likely to be caused by direct cytotoxicity of venom components in the kidney, and by renal ischemia resultant from hypovolemia and hypoperfusion. Lethality induced by B. asper venom is the consequence of several combined effects among which the action of P-III SVMPs is especially relevant.