invertebrate with arms protruding from rock

[BayAreaSteve]

I have a few of these critters with black and white alternating striped "arms" that stick out of holes in the rocks. They seem to be increasing and do not move altho the arms remind me of brittle stars. There is one in the center of the pic and one on the upper right. They are about 1/2 inch with multiple arms protruding from the rock Anyone have an idea of what they might be? BTW have been enjoying the podcasts catching up with old ones and appreciate all the great stuff on TR. Thanks. Steve

[JustDavidP]

tiny brittle stars.. neat critters

[BayAreaSteve]

they look like stars (at least the arms) but they never move from the same hole in the rock day or night that I can see and the arms wave in the current like they are filter feeders. Wouldn't they move at some point if serpent stars?

[JustDavidP]

Not necessarily. Looking at your picture, I'm about 99.9% sure that they are the tiny brittle stars that many of us get as hitch hikers in our system. To be more specific, they are Ophiactis spp.

They are great scavengers BECAUSE of the fact that they can get into these little holes in the rock and help clean them out of debris. If, in fact, a Ophiactis finds that one nook or cranny is the perfect "real estate", they may not leave at all, or just leave during dark (they are subject to predation) to roam just inches away. They tend to keep their little townhouses within view so they don't get any "squatters" taking it away from them.

When I say "prime real estate", I mean that the size of the hole, system water flow, YOUR feeding patterns, etc. all come together for them. If it is this good a spot, they may just stick their legs out and "fish" when there is food in the column.

Dave

[lReef lKeeper]

i agree with Dave, i believe they are in the micro star genre.

[BayAreaSteve]

thanks for the info. very helpful