Medical Research Council - London Institute of Medical Sciences

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What's Your Poison?
02 November 2013

What's Your Poison?

This six-eyed crab spider is a stealthy predator. One of the Sicariidae family, it coats its legs with soil particles below ground as camouflage, and scrambles upwards at the first sign of prey. Despite being relatively small – its body‘s about two centimetres long – Sicarius ornatus has a deadly bite. It contains a toxin – SMase D – that eats away at the membranes of nerve cells, kills skin cells and ruptures blood cells inside veins and arteries. These tissue-destroying effects are known as loxoscelism, a condition first associated with Loxosceles, another Sicariidae spider, which give over 5000 poisonous bites to humans every year. Investigating chemical similarities and differences between these spiders’ venoms (which both carry SMase D) brings hope for designing suitable antivenoms, but also a warning: humans rarely come into contact with Sicarius ornatus, and we’d be wise to leave them lurking in the dry forests and deserts of South America.

Written by John Ankers

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