Since brittle stars are so inconspicuous, it may seem that they are of little significance. Ophiuroids are so cryptic and difficult to spot, you might think that even fish can't find them. Ophiuroids are extremely popular prey items for fish and invertebrates like crabs. Though there doesn't appear to be very much to eat inside an ophiuroid, we know that they are eaten because parts of arms compose a large percentage of the gut contents of fish. In these relationships, both the brittle star and the host animal benefit.
Sponges survive by filtering water and capturing small food particles.
After a time, the surface of the sponge may become clogged with particles that are too large to efficiency of the sponge's feeding currents. The rest of the brittle star remains safely hidden inside the sponge. The brittle star removes the large debris clogging the sponge and consumes it. So, the sponge is cleaned, and the ophiuroid gets a meal and a safe place to live. Burrowing ophiuroids are also very important because of their role in bioturbation, or stirring up the sediment.