Expert: Walter Hintz - 1/7/2007

Question
I live in Central California, and one day last summer I took my family to the Kern River to escape the heat. My girlfriend was holding my 5 year old daughter, playing in slow water near the grassy shoreline, well out of the current. Just as they'd entered, my daughter began to whimper, then complain loudly that something was stinging her legs. Upon exam, we noticed faint reddish lines on her legs and torso. My girlfriend, too, had stings, but there was no evidence of what had caused them. Described as similar to bullnettle, the stinging faded after maybe 10 minutes, but my curoisity hasn't yet. As a lifelong local
resident, I've used the river a lot, and know many others who do, too, but I have never heard anyone relate a similar experience. After initial research, I think what they were stung by was a freshwater cousin to the jellyfish. Do you concur? Do populations of these animals inhabit such waters? Could there have been a great population "bloom" that only makes them noticable for a short period of time? Perhaps this explains the lack of local knowledge?
Please educate me-I really would like clarification to see if I'm guessing right.
Thank-you.

Answer
 Hi phildoe
There is a single species of freshwater jellyfish called Craspedacusta sowerbii. They are found in almost every state and I have collected them in Ohio.  They are most common in deep lakes and quarries.  I checked the distribution and found no record of them in Kern River CA.  That does not mean they are not there and they do have population explosions.  Can they sting? There is no real evidence that C. sowerbii stings people although some people have made claims to the otherwise. In the hydroid stage they are extremely small as is the medusa which is about the size of a quarter. In light of this I would suggest another reason for the stinging of your daughter.