Comprehensive DescriptionRead full entry The crinoid echinoderms
are the only living echinoderms that may be stalked. Those
commonly known as "sea lilies" retain a stalk thoughout their
lives and are sessile (attached to the substrate); those known
as "feather stars" (order Comatulida), such as Poliometra
prolixa, retain a stalk through a post-larval pentacrinoid
stage, but later lose the stalk and are able to move about. All
living crinoids have flexible feather-like arms and show at at
least some evidence of pentamerous (5-part) radial symmetry. The
arms bear reproductive organs as well as extensions of the water
vascular system that serve for food capture and respiration.
Crinoids orient in life with the oral surface uppermost, away
from the substrate; both mouth and anus are on the oral surface.
(Messing and Dearborn 1990) Poliometra prolixa has brown to
yellow arms, red to yellow pinnules (tiny side branches on the
arms), and white cirri (flexible appendages with which the
animal attaches to objects or t