A relatively small number of species shelter in sea urchins or crinoids. Whether this relationship is obligate (clingfish always with a sea urchin or crinoid) or facultative (clingfish sometimes with a sea urchin or crinoid) varies with species. In some, only young clingfish are obligate and gradually move away as they become adult. Three clingfish species, the Australian "Cochleoceps bicolor" and "C. orientalis", and the warm East Atlantic "Diplecogaster tonstricula", are cleaner fish that will cling onto the bodies of larger fish.