Eualus gaimardii

(H. Milne-Edwards, 1837)

Description
Rostrum curving upwards slightly, depth variable; twice length of antennular peduncle; five to seven dorsal teeth, three to five ventral teeth.
Carapace with antennal and pterygostomian spines.
Stylocerite acutely pointed, 0.66 x length of antennular peduncle or little more.
Scaphocerite about twice the length of antennular peduncle, outer border straight becoming concave towards apex; apical spine not exceeding lamellar portion. Third maxilliped equal to or slightly shorter than scaphocerite; epipod and exopod present.
Mandible with molar and incisor process, and two-segmented palp.
Pereiopods 1 and 2 with epipods, reduced setobranch on pereiopod 3. Carpus of pereiopod 2 seven-segmented. Pleonite 4 with acute ventro-posterior spine.
Telson with three to five pairs of lateral spines.

Remarks
The rostrum of this species varies considerably in shape and armature — illustrated by Dons (1915). Two forms of E. gaimardii were noted by Holthuis (1947). E. gaimardii forma gaimardii is a southern form with pleonite 3 smooth and rounded in both males and females. E. gaimardii forma belcheri (Bell, 1855) is a northern form, in which the posterior-median part of pleonite 3 in males bears a strong tubercle, which ends in a curved hook. The females have only a blunt, but distinct tubercle.

Size
Length up to 100 mm, usually 60-70 mm.

Colour
Pale, translucent, with brownish-red markings on carapace and pleon.

Ecology
Hyperbenthic species, may swim up at night, mostly confined to the nepheloid layer; adults may get caught with pelagic sampling. Ovigerous females occur from January to April, although the breeding period may be longer.

Depth range
Down to about 10-200 m.

Distribution in the North Sea
Adults reported from southwestern and northern North Sea, British NE coasts.

World distribution
A circumpolar species, reaching its southern limits around northern Britain. It ranges from W Greenland, Jan Mayen, Spitzbergen, Franz Josef Land, N and W Norway, White Sea, Barents Sea, Siberia and Alaska southwards to Cape Cod (Massachusetts), the Firth of Forth and the Clyde Sea area.

[mainly after Smaldon, 1993]

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