Hathrometra sarsii

(Düben and Koren, 1846)

This is a slender and fragile species, which is very liable to throw off its arms on being taken out of the water; good, complete specimens are therefore rather difficult to obtain.

Body centro-dorsal subconical, with numerous, crowded cirrus sockets. Arms rarely longer than 85 mm. Cirri numerous, with ca. 20 (14-23) joints; those on the apex of centro-dorsal smaller and with fewer joints. Pinnule 1, much elongated, composed of 30-40 segments; a few of the basal segments are short, the following becoming slender and greatly elongated. Pinnule 2 very much shorter, with only a few joints. Colour in life greyish, with indistinct, brown transverse bands.

The first developmental stages are unknown, but probably the eggs are free. In the pentacrinoid stage they have a long and slender stalk composed of up to ca. 40 very slenmder segments. The pentacrinoid has a remarkably large anal cone. The young feather-star does not detach itself until a rather late stage, when 20-30 cirri have appeared and the arms have 5-6 pinnules on each side.

This is a free-moving species of sheltered habitats after the pentacrinoid has detached itself from its stalk.

Northern parts of the North Sea: Norway north 70 (Oksfjord), Shetlands, between Scotland and Faeroes. Known to have a bathrymetrical distribution, 28-1783 metres, from S.W. of Ireland to the Shetlands, from depths of ca. 300-500 m.

An ecotype or variety of this species occurs at the east coast of N. America. It is distinguisehd by a somewhat larger numbers of cirrus-segments (mostly 27-30), and is, upon the whole, somewhat larger: arms are usually 85-100 mm long.