Marine Species Identification Portal : Hyperia medusarum

(Müller, 1776)

Description
— Generic. Head much shorter than high, with truncated front. Female with very short antennae (a1, a2) of equal length. Pereion of female humped.
Mandible with large and minutely striated molar process; last two segments of mandibular palp of equal length. Maxillar palp spatula-shaped, but not very broad. Outer plate of maxilliped broad lancet-shaped, the inner margin with bundles of short chaeta. Carpus of first gnathopod sometimes, and carpus of second gnathopod always with process, together with propodus forming a sort of chela. Carpus of second gnathopod with longer process than the carpus of first gnathopod. Pereiopods 3-7 short, firm, and of about equal shape. Uropods broad, with wide branches. Telson large.
— Specific. Generally resembling Hyperia galba , but with longer gnathopods. Epimeres of pleon with pointed postero-ventral margins. Female with very small antenna (a2).
Gnathopods 1-2 almost as long as pereiopods 3-7, with densely haired carpus. Carpus of first gnathopod without a process; carpus of second gnathopod with a very short process. Propodus of both gnathopods long and oval. Dactylus very small and short, even shorter than the adjacent spines.
Pereiopods 3-4 with hind margin beset with saetae.

Colour
Red brown.

Size
Length 8-20 mm.

Depth range
200-1800 m.

Possible hosts in the North Sea
Medusae, Rhizostoma pulmo, Cyanea capillata, Aurelia (all Phylum Cnidaria), Pleurobrachia, Beroe (both Phylum Ctenophora). See for references Harbison et al., 1977.

Distribution in the North Sea
Possibly northern North Sea.

World distribution
North Atlantic Ocean, including Arctic waters; North Pacific Ocean.

Hyperia medusarum