12 April, 2010

Sting use in prey capture

One of the conclusions from my master thesis many years ago was that sting use is probably costly for scorpions and because of this they will only use their stinger if the prey is large and/or the prey resists capture.

Now, Martin Edmunds and Richard Sibly have published a similar study with similar conclusions, using Hadrurus spadix Stahnke, 1940 (Caraboctonicae).

Since venom is costly to produce and stinging is not obligatory in prey capture for scorpions, the need to optimize use of resources suggests that venom should be reserved for prey that cannot otherwise be overpowered, (i.e., larger and/or more active prey). In accordance with these predictions, sting use by Hadrurus spadix Stahnke 1940 increased with prey size, reaching 100% once prey items were longer than the scorpion’s pedipalp patella length, and with prey activity, which we manipulated by varying prey temperature. Surprisingly, the scorpions were slower to capture less active (cooler) prey than those that exhibited higher rates of activity. We suggest this is because prey are located by vibrations in the substrate, with less active prey producing fewer vibrations.

Edmunds MC, Sibly RM. Optimal sting use in the feeding behavior of the scorpion Hadrurus spadix. Journal of Arachnology. 2010;38(1):123-5. [Subscription required for fulltext, but free fulltext after 12 months].

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