Tuesday, 26 July 2011
The bay of Sao Francisco do Sul in Santa Catarina, southern Brazil, is a calm and tranquil place, but when we visited on Sunday there were one or two dangers to be aware of. About 30 jellyfish had washed up on the beach.
A study in 1999-2002 found that 76% of jellyfish stings in Santa Catarina* occured at times of high southerly winds, when they are driven inshore from the deep sea. Jellyfish are known locally as "agua vivas" or "living water" and you can see why, these extraordinary creatures are virtually transparent and don't resemble any other creature.
But scattered around the beach these foot wide disks were also rather reminescent of land mines, and that too has some sense, they pack a powerful punch. Stinging cells known as nematocysts inject powerful toxins and they can cause intense pain, as anyone who has been stung can testify. This is how they kill their prey. Several jellyfish on the beach had dead crabs attached, but whether they had been caught out at sea, or killed trying to feed on the beach, it was hard to say.
If you are stung you should wash the wound, but not with fresh water, this will burst any nematocysts still in the wound. Vinegar works, but yes, the urban myth of using urine will also work too at a punch. Better is go to a hospital and get an injection of dexamethosome.
Which species these are I cannot say, but the commonest on the beaches of Santa Catarina is reported to be Olindias sambaquiensis* - hopefully so as it only causes relatively mild, local, symptoms. Unless you are a crab.
*The occurrence of jellyfish stings on the Santa Catarina coast, southern Brazil
Resgalla et al 2005. Brazilian Journal of Oceanography, 53, 183-186.