title: One scorpion, two venoms: prevenom of Parabuthus transvaalicus acts as an alternative type of venom with distinct mechanism of action.
abstract: Scorpion venom is a complex mixture of salts, small molecules, peptides, and proteins. Scorpions employ this valuable tool in several sophisticated ways for subduing prey, deterring predators, and possibly during mating. Here, a subtle but clever strategy of venom utilization by scorpions is reported. Scorpions secrete a small quantity of transparent venom when initially stimulated that we propose to name prevenom. If secretion continues, a cloudy and dense venom that is white in color is subsequently released. The prevenom contains a combination of high K(+) salt and several peptides including some that block rectifying K(+) channels and elicit significant pain and toxicity because of a massive local depolarization. The presence of high extracellular K(+) in the prevenom can depolarize cells and also decrease the local electrochemical gradient making it more difficult to reestablish the resting potential. When this positive change to the K(+) equilibrium potential is combined with the blockage of rectifying K(+) channels, this further delays the recovery of the resting potential, causing a prolonged effect. We propose that the prevenom of scorpions is used as a highly efficacious predator deterrent and for immobilizing small prey while conserving metabolically expensive venom until a certain level of stimuli is reached, after which the venom is secreted.
authors.affiliation: Department of Entomology, Chemistry and Superfund Analytical Laboratory, Molecular Biosciences, School of Veterinary Medicine, and Chemical Engineering and Materials Science, University of California, Davis, CA 95616, USA.
authors.forename: Bora
authors.initials: B
authors.lastname: Inceoglu
authors.forename: Jozsef
authors.initials: J
authors.lastname: Lango
authors.forename: Jie
authors.initials: J
authors.lastname: Jing
authors.forename: Lili
authors.initials: L
authors.lastname: Chen
authors.forename: Fuat
authors.initials: F
authors.lastname: Doymaz
authors.forename: Isaac N
authors.initials: IN
authors.lastname: Pessah
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Hammock
mesh_terms: D000818:Animals; D001681:Biological Assay; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D004305:Dose-Response Relationship, Drug; D007313:Insecta; D007477:Ions; D013058:Mass Spectrometry; D051379:Mice; D011188:Potassium / Q000378:metabolism; D012604:Scorpion Venoms / Q000737:chemistry* / Q000378:metabolism*; D012605:Scorpions / Q000502:physiology*; D013997:Time Factors
chemical_list: D007477:Ions; D012604:Scorpion Venoms; D011188:Potassium