Most stalked crinoid
fossils depict spindly, plantlike animals anchored to sea floor rocks, explains earth scientist William Ausich, coauthor of a study in Geologica Acta.
The stalked crinoid spends most of its time sitting and catching food with the flowerlike wheel of feathery arms that have earned it and its relatives the nickname sea lilies.
A stalked crinoid pulled itself along the bottom briskly enough for a viewer to notice.
Two decades ago, Baumiller and Messing independently documented movement by some stalked crinoids. Baumiller observed creeping stalks in a lab.
Specimens of the stalked crinoid Metacrinus rotundus Carpenter, 1882, were dredged from depths of 100-150 m in Suruga Bay off Numazu, Japan.
The simultaneous measurement of isotonic contraction and tissue stiffness revealed that the arm of a stalked crinoid from which arm muscles had been removed simultaneously shortened and changed in stiffness in response to chemical stimulation.
We have reported shortening and force development in arm joints from which the muscles have been removed in the stalked crinoid Metacrinus rotundus and also in the stalkless crinoid Oxycomanthus japonica (Birenheide and Motokawa, 1996, 1998).
Several species of stalked crinoid were observed from Johnson-Sea-Link (JSL) submersibles at depths ranging from 400 to 900 m in the northern Bahamas (see map in Young, 1992).
A photographic survey of a population of the stalked crinoid Diplocrinus (Annacrinus) wyvillethomsoni (Echinodermata) from the bathyal slope of the Bay of Biscay.
rotundus may not even represent all members of the stalked crinoids
, the class to which the species belongs.
This result is particularly interesting because the evolutionary success of the comatulid crinoids has been attributed to morphological changes that increased arm flexibility relative to the stalked crinoids (Meyer and Macurda, 1977).
Passive orientation of entire organisms has been described in gorgonian corals (Theodor and Denizot, 1965; Wainwright and Dillon, 1969) and in stalked crinoids (Baumiller and Plotnick, 1989), although the mechanisms differ in these two systems.