Lethal factors and enzymes in the secretion from Duvernoy's gland of three colubrid snakes

Secretion from Duvernoy's gland of the colubrid snakes Malpolon, Spalerosophis, and Thamnophis was obtained by pilocarpine stimulation and tested for lethality and selected enzymatic activities. Pools of secretion from Malpolon and Spalerosophis were fractionated by gel filtration, and several major active fractions were examined. The secretion from Malpolon had an LD₅₀ of 6.5 μg/gm in mice; two lethal fractions with LD₅₀'s of 2.75 μg/gm and 4.5 μg/gm were isolated. One of these fractions appears to be a basic phospholipase A with a molecular weight of about 17,000. Spalerosophis had a secretion with an LD₅₀ of 2.75 μg/gm in mice; one main lethal fraction with an LD₅₀ of 2.5 μg/gm was isolated. Secretion from Thamnophis had an LD₅₀ of 33.3 μg/gm; it was not fractionated owing to a paucity of material. At least two of the snake species examined have toxic secretions that may be important during feeding by killing or weakening and helping to subdue the struggling prey.