(Couch, 1856)
Description
— Generic features. General form somewhat short and thick. Carapace with very short triangular rostrum; posterior margin emarginate.
Antennal scale with outer margin naked, usually ending in a spine.
Endopods of the thoracic limbs moderately long with the combined carpopropodus divided into four to five subsegments; dactylus with a strong nail. Pleopods in the female small, rudimentary; in the male the first two pairs are rudimentary as in the female but larger; third pair with large sympod, simple unsegmented or two-segmented endopod and the exopod, if present, extremely small and knob-like; fourth pair with a two-segmented sympod; endopod small, two-segmented; exopod long, five- or six-segmented with two long modified setae on the distal segments; fifth pair well developed, biramous, multiarticulate and natatory. Uropod long and narrow; inner margin of endopod armed with a row of spines.
Telson small and narrow, with a cleft which is armed with a close row of teeth or truncate, with or without a slight median emargination.
Marsupium consisting of a pair of large brood lamellae on each of the seventh and eighth thoracic segments and a very small anterior pair on the sixth segment.
— Species. Carapace with very short triangular rostrum; posterior margin emarginate. Antennal scale rather small, extending only slightly beyond the eyes and about the same length as the antennular peduncle. broadly lanceolate; proximal portion of the outer margin naked the unarmed portion not ending in a tooth.
Eyes very large, nearly globular extending well beyond the lateral margins of the carapace eyestalks very small pigment of cornea black.
First thoracic limb with eight well developed lobes from the second and third segments of the endopod but the lobe from the second and third segments of the endopod but the lobe from the fourth segment only very slightly produced. Third to the eighth thoracic limb with four or five subsegments in the carpoprodus, first subsegment the longest; outer distal angles of the subsegments armed with stiff setae which are spinous on one side only. Pleopods of the male first two pairs similar to those of the female but stronger and larger. Third pair with the sympod large endopod short unsegmented and armed with a few plumose setae; exopod extremely small, reduced to a small knob. Fourth pair with small two-segmented endopod; exopod six-segmented, penultimate segment bearing on its outer distal angle an extremely long setae which is armed along one side with small spines along one side. These terminally with a shorter seta with small spines along one side. These two long setae form a kind of weak pincers. Fifth pair with small two-segmented sympod biramous multiarticulate natatory.
Telson short, about equal in length to the last abdominal segment; lateral margins almost straight converging slightly distally, armed on the distal half of the margin with seven to ten small spines; telson cleft to about one-fourth of its length cleft widely open and armed along its margins with a close row of teeth apical lobes very convex on their inner margins and armed distally with a single long strong spine; no median setae.
Uropods with exopod slender, about half as long again as the telson; endopod shorter armed on the inner margin with a row of 10-12 graduated spines which extend from the statocyst for about three quarters of the length of the uropod.
Colour
Clear bright red or orange.
Size
Up to 8-10 mm.
Depth range
Shallow waters; hyperbenthic: 5-20 m.
Remarks
This species closely resembles H. abyssicola but may be distinguished from it by its more robust build an shorter length; the extremely black eyes, the fewer spines on the inner margins of the endopod of the uropod and the fewer spines on the lateral margins of the telson.
Hemimysis lamornae is a bottom-living shallow-water form living close inshore in the shade of overhanging rocks or among laminaria. It leaves the bottom during the hours of darkness and becomes pelagic in mid-water. It is easily recognised by its vivid red colour and black eyes. Although it has been taken at several places around the North Sea, it is by no means common.
Distribution in the North Sea
North Sea, W off Norway, Skagerrak, at bottom, shallow.
World distribution
Atlantic: ?- 64°N; Baltic, Mediterranean, Black Sea; coastal to shelf.
[After Tattersall and Tattersall, 1951]