ABSTRACT
The external surfaces of most echinoderms have some features in common, e.g. tube feet, spines, and mucus-secreting glands, but asteroids and echinoids also have pedicellariae. Pedicellariae are small pincer-like organs with movable jaws known as valves. The most outstanding feature of pedicellariae is their independent reflex behavior mediated by their own sensory cells, neuropil and muscles. Pedicellarial research has progressed broadly in line with other anatomical and physiological investigations of echinoderms. The difficulty in analysing function is that pedicellariae are diverse in form, capricious in behavior, and have not lent themselves to detailed electrophysiological study. Asteroid pedicellariae are poorly understood and little has been published regarding the distribution of their sensory cells. Pedicellariae are an attractive preparation for the behavioral neurobiologist because of the inbuilt reflex arc and the fact that in many echinoids they will function quite freely when detached from the test.
