Replenishing venom takes time and energy - so it pays to be stingy with stings. According to researchers at the Australian National Institute of Tropical Health and Medicine, scorpions adapt their bodies, their behavior, and even the composition of their venom, for efficient control of prey and predators. In an open-acccess article published online on June 6, 2019 in Frontiers in Ecology and Evolution, the scientists say it's not just the size of the stinger, but also how it's used that matters. "Scorpions can store only a limited volume of venom, that takes time and energy to replenish after use," says lead author Edward Evans, PhD. "Meanwhile the scorpion has a reduced capacity to capture prey or defend against predators, so the costs of venom use are two-fold." As a result, over 400 million years of evolution, scorpions have developed a variety of strategies to minimize venom use. The most obvious of these is to avoid using venom at all. "Research has shown the lighter, faster male specimens of one species are more likely to flee from danger compared to the heavier-bodied females, rather than expend energy using toxins," notes Dr. Evans. "Others -- particularly burrowing species -- depend instead on their large claws or 'pedipalps,” and have a small, seldom-used stinging apparatus." When immobility, threat, or lively prey forces venom use, scorpions can adjust the volume they inject - both within each sting and through the application of multiple stings. "Scorpions can hold prey in their pedipalps and judiciously apply stings, just until it stops struggling." At the other extreme, when the survival stakes are high, some species abandon precision and spray their venom through the air.
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