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(Forskål, 1775)

—Generic. Antennular flagellum (a1) of male seven- to eight-segmented, first segment inflated, long, and densely haired. Antennal flagellum (a2) of male with many segments, long and thin, or rudimentary.
Pereiopod 5 with thick, inflated carpus and claw shaped propodus, together forming a grasping hand. Uropods well developed. Gills on thoracomeres 4-6.
Abdomen of male stubby compared to female. Pleomeres with very broad epimeres
— Specific. Female: length of cephalon and pereion together little more than length of pleon and urosome together. Head twice as high as long; height somewhat more than the length of thoracomeres 1-6 together. Pereion 7 somewhat longer than pleonite 1. Distal half of last antennular (a1) segment beset with hairs. Pereiopod 5 longer than pereiopod 4; basis of pereiopod 5 with postero-distal spine, ischium with antero-distal spine; merus twice as long as ischium. Carpus with long anterior extension. Propodus little shorter than the hind margin of the carpus. Propodus with a median hump on the inner (=anterior) margin. Pereiopods 6-7 equal in length. Anterior edge of ischium hatchet-formed. Epimeres of pleon with sharp, slightly curved spine-like ventero-distal corners. Uropod 2 with inner branch shorter, or as long as outer branch. Last gill as long as second segment of pereiopod 7.
Male: length of cephalon and pereion together equal the length of pleon and urosome together. Head frontally protruded; length longer than total length of thoracomeres 1-5 (but not more than 1-6 together). First segment of antennular flagellum (a1) not reaching beyond top of head. Antenna (a2) rudimentary. Pereion 7 as long as pereion 5+6.
Epimeres of pleon posteriorly elongated into wide, lancet-like plates. Carpus of pereiopod 5 similar as in female but front margin is relatively shorter. A small tooth frontal of the distal knob. Hump on propodus only weakly developed. Uropod 2 with inner branch more slender and shorter than outer branch.

Length female 16-40 mm, male 8-10 mm.

Depth range
Surface to deep water.

Possible hosts in the North Sea
Pyrosoma (Subphylum Tunicata), Beroe (Phylum Ctenophora). See for references Harbison et al., 1977. Also associated with Order Salpida and Order Doliolida.

Distribution in the North Sea
Possibly in the northern North Sea

World distribution
Temperate and (sub)tropical waters of Atlantic Ocean (range ca. 61°N-50°S) including the Mediterranean, Pacific Ocean (range ca. 36°N-55°S), Indian Ocean.

Phronima sedentaria