Jassa herdmani

(Walker, 1893)

Description:
Antenna overlaps antenna 2 to about 50-75% of the length of segment 5.
Antenna 2: segment 5 and flagellum, posterior margin without plumose setae, simple filter setae about 50% the length of those of the juvenile; flagellum 5-segmented, the last, minute segment 1 is 45% of full length.
Gnathopod 1: coxal margins, anterior 98% of dorsal length, ventral margin sinuous; basis, anterior and posterior margins with only a few minute setae; carpus, posterior lobe 50% of anterior margin length, without an anterodistal setal cluster; propodus, palm convex; dactyl cusped along most of posterior margin, with 2 rows of facial striations.
Gnathopod 2: coxal margins, anterior 28% and posterior 50% of ventral length, ventral margin sinuous and convex; gill small; basis, anterolateral flange without long filter setae; carpus, posterior lobe without distal seta; propodus, anterior margin without setae proximally, palmar setae throughout most of palm, thumb 18% of propodus length, distally squared, posterior margin evenly concave to location of defining setae, setae quite closely approximated, accompanied by 3 spines; dactyl, inner margin with a strongly pronounced protuberance extending into palmar incision.
Pereiopods 3 coxa, greatest depth posterior of centre; basis, anterior margin sinuous, not broadly convex; merus, anterior marginal setae single and evenly spaced, 33-50% of segment width, segment width 87% of length; carpus fully overlapped by menis; propodus, width 55% of length.
Peracopods 5-7: propodus not expanded anteriorly; dactyl without fringe of setae along anterior margin, without facial striations.
Plecopods: with 2 peduncular coupling hooks.
Uropod 1: peduncle, posteroventral spinous process underlying 40% of inner ramus, inner and outer rami with 4 and 7 mid-dorsal spines, respectively, terminating in fringe of cusps ventral to apical spine group.
Uropod 2: peduncle, posteroventral spinous process underlying 5% of inner ramus.
Uropod 3: outer ramus with 2 sequential, closely approximated cusps proximal to basally immersed, dorsally recurved spine, additional numerous small cusps proximally, and 1 seta originating at insertion of recurved spine; inner ramus with only the single apical spine.
Telson setose only at lateral cusps.

Size:
Male 3.3-9.5 mm and female 4.9-7.3 mm.

Habitat:
Depth range from 0 to 8 metres.

Distribution:
Norway, Ireland, England, Denmark, Atlantic coast, Algeria.

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