Urchin 'Urting

Stepping on a sea urchin is very painful. I did it once (Ibiza, 1992) and a good-natured waiter poured vinegar on my heel to take away the pain. I assumed it was just the needle-like spines that hurt. But now – thanks to a team of scientists in Brazil looking into the toxins of Echinometra lucunter (pictured) – I see I was wrong. The researchers found that an enzyme called cathepsin B/X present in the urchin’s spines causes a painful inflammatory response in humans. Not only that, they discovered that this enzyme is also involved in regenerating the urchin’s spines, a hard matrix of calcium and magnesium carbonate, when broken. So there you go, this unforgiving enzyme that provides the urchin with a double whammy: reducing me to tears as a toxin while enabling the urchin to rearm and wait for the next unsuspecting holidaymaker.

Written by Nick Kennedy

• Image by Dwayne Meadows on Wikimedia Commons
• NOAA Photo Library
• Originally published under a Creative Commons Licence (BY 2.0)
• Research published in the Journal of Venomous Animals and Toxins including Tropical Diseases, December 2013