Investigating the chemical profile of regenerated scorpion (Parabuthus transvaalicus) venom in relation to metabolic cost and toxicity.

We investigated the biochemical profile of regenerated venom of the scorpion Parabuthus transvaalicus in relation to its metabolic cost and toxicity. Using a closed-system respirometer, we compared oxygen consumption between milked and unmilked scorpions to determine the metabolic costs associated with the first 192 h of subsequent venom synthesis. Milked scorpions had a substantially (21%) higher mean metabolic rate than unmilked scorpions, with the largest increases in oxygen consumption occurring at approximately 120 h, 162 h, and 186 h post-milking. Lethality tests in crickets indicated that toxicity of the regenerated venom returned to normal levels within 4 d after milking. However, the chemical profile of the regenerated venom, as evaluated by FPLC and MALDI-TOF mass spectrometry, suggested that regeneration of different venom components was asynchronous. Some peptides regenerated quickly, particularly those associated with the scorpion's "prevenom," whereas others required much or all of this time period for regeneration. This asynchrony could explain the different spikes detected in oxygen consumption of milked scorpions as various peptides and other venom components were resynthesized. These observations confirm the relatively high metabolic cost of venom regeneration and suggest that greater venom complexity can be associated with higher costs of venom production.

Denim clothing reduces venom expenditure by rattlesnakes striking defensively at model human limbs.

STUDY OBJECTIVE: Venomous snakebites can be painful, costly, and potentially life threatening. We seek to learn whether ordinary clothing (denim material from blue jeans) interferes with the kinematics of venom delivery, thereby reducing the amount of venom injected by a representative viper into a human limb. METHODS: In a laboratory study, we used model human limbs (warm, saline solution-filled gloves) to elicit defensive strikes from small and large southern Pacific rattlesnakes (Crotalus oreganus helleri). Each snake was videotaped biting a bare glove and a denim-covered glove. RESULTS: The snakes injected significantly less venom into denim-covered gloves than bare gloves during defensive strikes, with a 60% reduction for small snakes and 66% for large snakes. Latency to bite, number of bites, and duration of fang contact during the bite were similar for the 2 glove types, suggesting that the 2 targets elicited similar defensive behaviors and strikes. Several findings suggested that denim interfered with venom delivery, including the high proportion of dry bites for denim-covered gloves and the large quantity of venom spilled harmlessly on the denim cover. Large rattlesnakes struck more readily, maintained longer fang contact during the bite, and delivered 26 to 41 times more venom into gloves than small snakes. CONCLUSION: In our model, denim clothing proved effective at reducing venom injection by both small and large rattlesnakes. Wearing long denim pants as an alternative to shorts may provide a simple, low-cost means of reducing the severity of snakebites.

Cost of venom regeneration in Parabuthus transvaalicus (Arachnida: Buthidae).

Scorpion venom has many components, but is mainly made up of water, salts, small molecules, peptides, and proteins. One can reasonably assume that the production and storage of this complex secretion is an expensive metabolic investment. However, to date, no study has addressed the costs associated with the regeneration of venom by scorpions. Using a closed-system respirometer, we examined the difference in oxygen consumption between milked and unmilked scorpions to determine the metabolic costs associated with the first 72 h of subsequent venom synthesis. During this time period, milked scorpions had a significantly higher (39%) metabolic rate than unmilked scorpions. The regenerated venom from a second milking had significantly lower (74%) protein concentration, suggesting that venom regeneration was incomplete after 72 h. The protein content in the regenerated venom was not correlated with oxygen consumption. The significant increase in oxygen consumption after milking supports existing hypotheses about the metabolic cost associated with venom regeneration and provides further insight on why scorpions appear to be judicious in their stinger use.