Description: Members of Infraorder Physicephalata usually have a pereon which is not spherically inflated and is about the same width as the pleon. They usually have large eyes. The antennae of males and females differ in shape. Pereopods 1 and 2 are usually chelate or subchelate. Members of Superfamily Phronimoidea have antennae which extend from the front of the head. Antennae are short in females but long in males. Members of Family Hyperiidae usually have dark pigment, and a head which is large and rather spherical, larger than the first somite of the pereon. The eyes occupy much of the head and touch each other dorsally (photo). The uropods have free rami (photo). Members of genus Hyperoche have all pereonsomites and coxal plates free. The head is large and semicircular. The eyes cover the entire dorsal and lateral surfaces of the head. Antenna 1 has 3 segments in its peduncle, and in females it is longer than antenna 2. Antennae 2 have 4 segments in the peduncle in females. The chelae on pereopods 1 and 2 are formed from segments 5 & 6 of the legs, rather than segments 6 & 7. The 7th segment is small and projects from the chela. The fifth segment of pereopods 1 & 2 (the fixed claw of the chelae) is laterally compressed, knife-shaped, and has small teeth along the anterior margin. Hyperoche medusorum is the type species for this genus. It has the posterior distal angle of epimerons 2 & 3 slightly acute rather than rounded or straight. The anterior distal angle of the 6th segments of pereopods 1 & 2 is not stretched out above the claw. The posterior margin of the 5th & 6th segments of pereopods 3 & 4 have small teeth. Total length usually not more than 5-6 mm but up to 15 mm for females.
Geographical Range: Bipolar: In the North Pacific from Japan through the Okhotsk and Bering Seas and Alaska down to the Gulf of California. From the Arctic Ocean it extends into the North Atlantic down to Ireland and Labrador and to Chesapeake Bay. In the Southern Ocean it has been found near the South Georgia Islands, SW Africa south of 25 degrees S, off Argentina, and off southern New Zealand.
Depth Range: Epipelagic (upper 30 m), but caught at 1100 m in the Gulf of California (Gasca and Haddock, 2004)
Habitat: Parasitic on gelatinous organisms
Biology/Natural History: Adults of this species parasitizes several species of ctenophores such as Pleurobrachia and Mnemiopsis, as well as medusae such as Cyanea capillata. One of the prey items consumed by the free-swimming juveniles are fish larvae such as Pacific Herring (Westerhagen and Rosenthal, 1976). The juvenile amphipods can occur in high numbers so their impact on the fish larvae may be substantial. Juveniles can often be found sitting on the exumbrella of hydromedusae such as Tiaropsis, Sarsia, Phialidium, and Polyorchis.
Some authors claim that hyperiid amphipods are second in numbers in the plankton only to copepods and euphausiids.
Merresunters (1976) gathered large numbers of juveniles at the Pacific Biological Station, Nanaimo, Vancouver Island, Canada by suspending a 300 watt bulb over the water at the station dock at night and scooping them up as they aggregated in the light. The species is common in Departure Bay (near Nanaimo) in April and May.
Spicer and Morritt (1995) studied the blood of this and several other species of Hyperiidean amphipods and concluded that their blood contains no hemocyanin.
Adults of Family Hyperiidae usually are strongly sexually
Vinogradov et al., 1982
Bowman, T.E., 1953. The systematics and distribution of pelagic amphipods of the families Vibiliidae, paraphronimidae, Hyperiidae, Dairellidae, and Phrosinnidae from the northeastern Pacific. Ph.D. thesis, University of California, Los Angeles. 430 pp.
Bowman, T.E., C.D. Meyers, and S.D. Hicks, 1963. Notes on associations between hyperiid amphipods and medusae in Chesapeake and Narranansett Bays and the Niantic River. Chesapeake Science 4: pp 141-146
Gasca, Rebeca and Steven H.D. Haddock, 2004. Associations between gelatinous zooplankton and hyperiid amphipods (Crustacea: Peracarida) in the Gulf of California. Hydrobiologia 530/531: pp 529-535
Hurley, D.E., 1956. Bathypelagic and other Hyperiidae from Californian waters. Allan Hancock Foundation Occasional Paper 18. 25 pp.
Laval, P., 1980. Hyperiid amphipods as crustacean parasitoids associated with gelatinous zooplankton. Oceanography and Marine Biology Annual Review 18: pp 11-56
Lorz, H.V. and W.G. Pearcy, 1975. Distribution of hyperiid amphipods off the Oregon coast. Journal of the Fisheries Research Board of Canada 32: pp 1442-1447
Sorarrain, Dora R., Fernando Ramirez, and Hermes Mianzan, 2001. Hyperoche medusarum (Kroyer, 1838) (Amphipods, Hyperiidae) and Mnemiopsis McCradyi (Mayer, 1910) (Ctenophora): a new host and first record of this association for the southwestern Atlantic. Crustaceana 74:4 pp 407-410
Spicer, John I. and David Morritt, 1995. Oxygen carriage by the haemolymph of Hyperiid Amphipods. Journal of the Marine Biological Association of the United Kingdom 75:4 pp 997-998
Westerhagen, H. von, 1976. Some aspects of the biology of the hyperiid amphipod Hyperoche medusarum. Helgolander wissenschaft Merresunters 28: pp 43-50
Westerhagen, Hein von, and Harold Rosenthal, 1976. Predator-prey relationship between Pacific Herring, Clupea harengus pallasi, larvae and a predatory Hyperiid amphipod, Hyperoche medusarum. Fishery Bulletin 74:3 pp 669-674
Westerhagen, H. von, H. Rosenthal, and G. Furstenberg, 1979. Factors influencing predation of Hyperoche medusarum (Hyperiida: Amphipoda) on larvae of the Pacific Herring Clupea harengus pallasi. Marine Biology 51: pp 195-201
General Notes and Observations: Locations, abundances, unusual behaviors:
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