Crypsis
While being completely sessile as adults, Rhabdastrella globostellata does blend easily with the surrounding environment so that, at first, it can be hard to distinguish (as seen below). Variation in colour (from tan to dark brown) and shape (globular, with apical depressions) means there are no two identical specimens observed (a simple image search gives a good idea of the variation observed in field).
Image: in field specimen of Rhabdastrella globostellata located in the lagoon of Heron Island (2011). |