zoo folds back onto itself

[dnh]

One of my zoos regularly folds back on itself. See photo:
http://home.wideopenwest.com/~dh972/...back%20zoo.jpg
Does anyone know why it is doing that? It is normally spread out about the size of a quarter or a little larger.
(This is my first attempt at a photo, so I hope it works!)

 

[nas19320]

Palythoa's tend to do that sometimes. I have read many different theories as to why but from what I have found they are nothing more than theories. Bottom line is I don't think anyone knows for sure but its generally is not a problem.