Hyperia medusarum (O.F. MÜller, 1776)

Size: Length varies from 9-15 mm, individuals in the Arctic reach up to 20 mm, individuals in Antarctica may surpass 20 mm.

Range: Abundant in the Puget Sound, also found in deep water worldwide.

Habitat: They are associated with cnidarians and ctenpohores. In the Puget Sound, they have been found on Pleurobrachia bachei, Phacellophora camtschatica, Aurelia labiata, and Aequoria victoria.

Misidentification: Hyperia galba. The head length of H. galba is shorter than the combined length of somites I and II. The combined length of somites I and II of H. medusarum is equal to the head length. Pereopods III and IV of H. galba have setae on the fifth segment. Hyerpia medusarum has spines of variable length on the fourth and fifth segments of pereopods III and IV.

Life History: Eggs are laid on the medusa. Juveniles stay on the host and eat bits of the host’s prey. Juveniles and adults also eat the host, primarily the tentacles and gonads. Males are better equipped for swimming and adults spend some time off of the host. Hyperia medusarum is a parasitoid.

Predators: Many fish including Oncorhynchuys spp. (http://www.fish.washington.edu/Publications/pdfs/0311.pdf), and Zaprora silenus (http://www.afsc.noaa.gov/abl/Oilspill/pdfs/ffdchap1.pdf). Cnidarian eating animals such as Dermochelys coriacea, the leatherback turtle (http://islands.bio.miami.edu/index.html).

Links:

The Amphipod Homepage: http://web.odu.edu/sci/biology/amphome/

Species Profile: http://www.nwrc.usgs.gov/publications/specindex.htm.

References:

Laval, P., 1980. Hyperiid amphipods as crustacean parasitoids associated with gelatinous zooplankton. Oceanography and Marine Biology Annual Review, 18:11-51.

Vinogradov, M.E., A.F. Volkov, & T.N. Semenova, 1996. Hyperiid Amphipods (Amphipoda, Hyperiidea) of the World Oceans. Smithsonian Institution Libraries, Washington D.C., 650 pp.

Prepared by Emily Vlahovich, May 2004