Comprehensive Description

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Comprehensive Description

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 the seabottom) (Clark 1970, cited in Messing and Dearborn 1990). This species has a northern distribution; it is unknown south of Greenland and reaches North America only off Baffin and Ellesmere Islands in the Canadian Arctic. Messing and Dearborn give the distribution of P. prolixa as: "East of the Taimyr Peninsula westward to Novaya Zemlya; Spitzbergen; Norway north of latitude 62 to 63°N westward along the Faeroe Ridge to northern Iceland; Greenland; Baffin Bay and Davis Straits." It occurs from 20 to 1960 meters at temperatures from -1.97 to +2.0°C. This species is found mainly in soft mud or clay, sometimes on mud with sand or gravel. (Messing and Dearborn 1990)

Hansson (1999) lists the distribution of P. prolixa as off Norway (Slope 61 to 62°); along and north of Wyville Thomsom Ridge; all but southern Iceland; eastern, southern, and western Greenland; Barents Sea; Spitsbergen; Kara Sea; Laptev Sea - Taimyr Peninsula.


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© Shapiro, Leo

Source: EOL Rapid Response Team


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