ABSTRACT
The crinoid feeding mechanism relies on environmentally produced water movements to carry suspended food particles to the extended tube feet which are the primary food capturing organs. Crinoids with relatively shorter, more closely spaced tube-feet occur on elevated perches and utilize a filtration fan feeding posture. The tube-foot feeding mechanism has been used to extract the smaller size fractions of the plankton and suspended matter. The principal axes of crinoid feeding niches appear to be type of substratum, elevation above substratum, feeding periodicity, and water movement regime. Assignment of crinoids to the correct trophic category depends upon a clear understanding of the basic food gathering mechanism. In living comatulid crinoids of the family Comasteridae the proximal pinnules are specialized in the possession of teeth on the distal segments which form a terminal comb. The morphology of the tube-feet of crinoids has been studied in detail in only a few species.
