Scorpions adapt their stinging, stingers and sting contents to minimize costs of venom use

phys.org | 10/12/2017 | Staff
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Figure 1. Morphological comparison of four Australian scorpions. (A) Australobuthus xerolimniorum (Buthidae) (B) Lychas buchari (Buthidae) (C) Hormurus waigiensis (Hormuridae) (D) Urodacus sp. (Urodacidae). A. xerolimniorum and L. buchari are more vagrant and active foragers, and have evolved relatively small chelicerae and thick powerful tails. H. waigiensis and Urodacus sp. are burrowing species, and have evolved larger chelicerae and smaller stinging apparatuses. Photographs by Edward Evans.

Replenishing venom takes time and energy—so it pays to be stingy with stings.

Researchers - National - Institute - Tropical - Health

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.

Writing in Frontiers in Ecology and Evolution, they say it's not just the size of the stinger, but also how it's used that matters.

Scorpions - Volume - Venom - Time - Energy

"Scorpions can store only a limited volume of venom, that takes time and energy to replenish after use," says lead author Edward Evans. "Meanwhile the scorpion has a reduced capacity to capture prey or defend against predators, so the costs of venom use are twofold."

As a result, over 400 million years of evolution scorpions have developed a variety of strategies to minimize venom use.

Venom

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 Evans. "Others—particularly burrowing species—depend instead on their large claws or 'pedipalps," and have a small, seldom-used stinging apparatus."

Immobility - Threat - Forces - Venom - Use

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."

Extreme - Survival

At the other extreme, when the survival...
(Excerpt) Read more at: phys.org
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