Claus, 1890
Description
Carapace of female subrectangular with a slight anterior taper [C.hyalophyllum-fem-lat]. The height about 50% of the length, the dorsal margin nearly straight, ventral margin slightly concave. Postero-dorsal corner a blunt right angle. Posterior margin curving abruptly into the ventral margin. Male carapace lateral aspect less tapered, the rostra straighter, shoulder vaults more developed [C.hyalophyllum-male-lat]. In both sexes, in ventral aspect, rostra taper, antero-ventral margins beneath the incisure bowed, carrying longitudinal striae [C.hyalophyllum-fem-vent; C.hyalophyllum-male-vent]. Left asymmetrical gland opening just anterior to posterior end of the hinge. Right asymmetrical gland opening at the postero-ventral corner with immediately dorsally 1-3 additional lateral gland cells.
Female, frontal organ stem extending just beyond first antenna, capitulum slightly down-turned, ending in a curved point. First antenna segmentation obscure, second podomere carrying a long plumose dorsal seta, "e" seta is almost three times longer than sensory setae [C.hyalophyllum-1].
Male, frontal organ capitulum finely spinose over basal half, ends in a point [C.hyalophyllum-3]. First antenna, "a" seta nearly as long as the limb, "c" seta minute, the "b" and "d" setae only just shorter than "e" seta, "e" seta armature 24-25 pairs of squat spines which, basally, are succeeded by a further 26-27 alternating spines [C.hyalophyllum-4]. Second antenna endopodite, "b" seta carrying tuft of long hairs at midpoint, right-hand hook appendage bent through two angles [C.hyalophyllum-5], lefthand bent through one.
Size
Female 1.55-1.80 mm, male 1.50-1.65 mm carapace length.
Depth range
Extensive vertical migrant from mesopelagic depths to the bottom of the epipelagic zone at night.
Distribution in the North Sea
No information available.
World distribution
Recorded from all oceans. In the Atlantic it is known from 60°N-48°, where it may also occur >60°N according to Poulsen (1977).
[After Angel, 2000]