(Pallas, 1766)
Description
Body slender. Antenna 1 extending well beyond article 3 of the peduncle of antenna 2; there is a single large aesthetasc, not a pair, at the distal end of the aesthetasc series on the antenna 1. Antenna 2 flagellum longer than the peduncle, about a quarter of the body length. Cephalon subquadrate, eyes dorsolateral, prominent. Coxal plates narrow, only those of pereion segments 5, 6 and 7 reaching the posterior border. Pereiopods all more or less alike. Pleon of two complete segments, and one partial suture in the pleotelson. Pleotelson with the sides subparallel, slightly keeled posteriorly in the mid-dorsal line; posterior border with a single, median tooth, hardly acute, and with obtuse lateral corners. Uropods uniramous.
Colour mostly uniformly green or brown sometimes with white markings; females often darker than males.
Size
Males recognisable from about 5 mm body length, ranging to 15 mm; adult females from 6 to 10 mm.
Depth range/habitat
A brackish water species, among intertidal algae in sheltered estuaries or where streams flow over the shore, and also in sheltered brackish pools at or above high water mark.
Distribution in the North Sea
All North Sea, including the Baltic Sea, the Gulf of Bothnia and the Gulf of Finland.
World distribution
Recorded from Norway to the Mediterranean.