Lekanesphaera hookeri

(Leach, 1814)

Body oval in outline, readily rolling into a ball. Antenna 1 with 2 to 10 aesthetascs. Maxillipede palp with prominent lobes fringed with smooth setae on articles 2 to 4. Five anterior pleon segments all fused; sixth pleon segment fused with the telson as a pleotelson which articulates freely with the pleon. Coxal plates of pereion segments 2 to 7 fused with the segments. Pereiopod 1 with up to about 20 smooth setae on ischium and on merus; setae absent from distal region of propodus. Pleotelson rounded or only slightly acute at the apex, without a mid-ventral respiratory channel and posterior border not notched. Pleotelson with two longitudinal rows of elongate tubercles, one on each side of the mid-line; posterior border not extending beyond uropods. Uropods lateral, with the expod and endopod subequal in length, endopod rounded at the apex. Uropods with the outer border of exopod almost smooth. No sexual dimorphism.
Sexes recognizable at about 3 to 5 mm body length, males reaching 10.5 mm and females 8.5 mm.

Found at the head of sheltered estuaries, nearer the limit of EHWS than Lekanesphaera rugicauda . In brackish ditches and sometimes taken on banks of river channel.

Patchily distributed in Britain and absent from the northeast. Ranges from the Mediterranean northwards to northern Scotland and then eastwards into the southern Baltic as far as southeast Sweden.