Venom characteristics as an indicator of hybridization between Crotalus viridis viridis and Crotalus scutulatus scutulatus in New Mexico

Abstract

One hundred and thirteen venoms from 46 populations of Crotalus viridis viridis were screened by immunodiffusion for protein toxins antigenically similar to the phospholipase A2 (PLA) toxin 'Mojave toxin', using a polyclonal antibody to it's basic PLA subunit. Venom i.p. LD50 values in mice were recorded from 22 of the 46 populations. The venoms of three of 14 specimens from southwest (S.W.) New Mexico and one specimen from northern Arizona were immunologically positive by the immunodiffusion tests and produced low LD50 values (0.38-0.65 mg/kg) compared to all immunologically negative venoms (0.9-5.5 mg/kg). These four specimens were morphologically typical for C. v. viridis and their venoms were the only samples of 15 southern New Mexico specimens examined by reverse phase HPLC to exhibit peaks corresponding to the acidic and basic subunits of Mojave toxin. Alkaline polyacrylamide gel electrophoresis (PAGE) analysis of the recombined subunit peaks from the C.v. viridis venom from the S.W. New Mexico specimens showed more similarity to Mojave toxin from C.s. scutulatus venom than to similar toxins in C.v. concolor venom. The combined results of the immunodiffusion, lethal toxicity tests, HPLC profiles and PAGE analysis strongly suggest that the venoms of the three New Mexico specimens contain Mojave toxin(s), as a result of some previous hybridization with C.s. scutulatus. The northern Arizona specimen likely contains 'concolor toxin' through integration with C.v. concolor in its' genetic background.