We had a squat lobster sighting today on the Crinoid feather star during feeding time. Sorry for the poor quality photos.
"Crinoids eat a range of microscopic particles, ranging from diatoms, foraminifera, unicellular algae, small crustaceans, larvae and detritus." from http://palaeo.gly.bris.ac.uk/Palaeofiles/Fossilgroups/Crinoidea/page2.html
I recently received an email from a Biology student working with Crinoids. He says that the squat lobsters use the Crinoids, which may be toxic, to hid from predators. Squat lobsters also steal food from the Crinoid. My squat lobsters all eat large pieces of Mysis shrimp without the help of a Crinoid. I don't think they require Crinoids for survival, because I've had my Galathea inflata since November 2007, and it has increased in size by about 25%.
I think I may have seen the squat lobster "combing" through the Crinoids feathery arms. Since it is difficult to feed these sea stars in captivity, I wonder if the squat lobster will increase its chance of starvation in my aquarium. Chuck Raabe has a little section on these squat lobsters and says they are "Klepto-parasites that don't directly harm the host but steal its food." I'll have to try to think of a way to keep the squat lobster well fed so it doesn't steal too much from the feather star. Or I could relocate the squat lobster. I don't know anyone who has kept one of these Crinoids in an aquarium for longer than six months, so if I make it past that point, I will be satisfied.
I want to make a point to say that I did not purchase this Crinoid. I do not recommend purchasing animals from your local shop that have a poor survival rate in captivity. That will just encourage your local shop to order and sell more of them. It is for the same reason I do not encourage purchasing an animal from a shop just to "rescue" it from poor conditions there. I would never attempt to keep an impossible creature like this one if it was not accidentally imported (hitchhiked) and then given to me to care for.
Also check out these lovely Crinoid commensals photos.
Check out this little cutie, he looks just like my squat lobster!