(Saint-Joseph, 1888)
Description:
A scale-worm with a body of uniform width. Dorsal and ventral surfaces smooth.
Prostomium bilobed, without peaks, with a median antenna, a pair of lateral antennae, laterally inserted, and a pair of palps. Two pairs of eyes, the anterior pair in front of the line of greatest width, the posterior pair near the rear margin.
First segment bearing chaetae and a pair of dorsal and ventral tentacular cirri. Scales overlap, covering the body. The first pair of scales are round with sparse fringing papillae, the rest oval to kidney-shaped, with smooth margins; the surfaces with a patch of small tubercles.
Notopodia are small mounds with a ventral acicular ligule and numerous chaetae.
Notopodial chaetae are spinose with blunt tips. Neuropodia are well developed with an anterior acicular ligule and chaetae.
Neuropodial chaetae are spinose on the terminal quarter, with bidentate tips, a few in lower position with unidentate tips (M. arenicolae-detail).
Size:
Up to 20 mm for 36 chaetigers.
Colour:
Greenish black in life.
Habitat:
Littoral and sublittoral to 220 m. Found in the tubes or burrows of polychaetes such as Arenicola marina and Neoamphitrite figulus .
Distribution:
Arctic, North Pacific, Northeast Atlantic up to southern North Sea.
Remark:
This species has been confused with many other species such as Malmgrenia lunulata .