Morphology as a predictor of venom potency in scorpions

Forde, Alannah
Scorpionism is a global health concern with estimates of over 1 million annual envenomation cases, resulting in over 3,000 deaths each year, mostly amongst children below the age of 15 years old from rural communities in developing countries. Although all scorpions are venomous, those responsible for severe envenomations represent less than 2% (<50 taxa) of all known scorpion species. Little is known about the drivers of scorpion venom potency. One widely held view is that smaller scorpions with less well-developed chelae possess the most potent venoms. While this perception is often used as a guide for medical intervention, it has yet to be tested in a formal comparative framework. Here we use a phylogenetic comparative analysis of 36 scorpion species to test whether scorpion venom potency, as measured using LD50, is related to scorpion body size and morphology. We find a positive relationship between LD50 and scorpion total length, supporting the perception that smaller scorpions possess more potent venoms. We also found that, independent of body size, scorpion species with long narrow chelae have higher venom potencies compared to species with more robust chelae. These results not only support the general perception of scorpion morphology and potency but also the presence of an ecology trade-off with scorpions either selected for well-developed chelae or more potent venoms. Testing patterns of venom variations in scorpions contributes to both our ecological understanding and our ability to address the global health burden of scorpionism. We hope that our findings will help nonexperts, including children, to identify medically significant scorpions occurring in their vicinity, so a relevant treatment plan can be administered to the victim in case of envenomation.
NUI Galway
Publisher DOI
Attribution-NonCommercial-NoDerivs 3.0 Ireland