hyperiid amphipod Hyperia macrocephala

Hyperia macrocephala is found in Antarctic coastal regions and South Georgia Island [1]. H. macrocephala is up to 2.9 centimeters long [1].



As shown here, Hyperia macrocephala can be found on the medusa Diplulmaris antarctica [3].

Hyperiid amphipods are found throughout the world oceans and are found from the surface down to abyssopelagic depths, though they have not been collected deeper than 7,000 meters [1]. Hyperiid amphipods are mostly commensals and parasitoids of gelatinous zooplankton like medusas, salps, and coelenterates; they are pelagic and none are benthic [1].


Side view of Hyperia macrocephala.

Hyperiid amphipods are highly variable in body morphology due to their lifestyle and encompass these body forms: near-spherical; needle- like; very large -- up to fourteen centimeters with eyes comprising up to 25% of the body; nearly sightless; house-constructors; and free-living pelagic [1].

The medusa Diplulmaris antarctica can also be infested with a hyperiid amphipod Hyperiella dilatata which sits with its dorsal (top) surface against the outside top of the medusa's bell, the exumbrellar surface [2]. The hyperiid amphipods are those white dots on the surface of the clear bell in the picture at left. Collectors have found up to 54 of these amphipods riding along, clinging tightly to the medusa. These riding amphipods are predominantly juveniles and females; this suggests that the medusa is both an amphipod mating platform (where females await more mobile males) and a predation refuge for juveniles and females [2]. The hyperiid amphipods do not appear to feed on the medusa and probably use it as a safe harbor between feeding forays [2]. The hyperiid amphipod Hyperiella dilatata grabs the pteropod Clione antarctica from the water and holds it to itself as a chemical defense against predation [6,7,9]. Predatory fish won't eat the amphipod/pteropod combination or the pteropod C. antarctica itself which has a chemical, pteroenone, which deters feeding [6,7,8,9]. C. antarctica preys on the shelled pteropod Limacina helicina which doesn't have pteroenone so it appears that C. antarctica synthesizes it as part of its metabolic processes [8,9].

Diplulmaris antarctica medusa which get close enough to the bottom in shallow water are prey to be captured by the tentacles of an anemone (Isotealia antarctica shown here) [4]. The struggle can continue for quite awhile. The medusa pulses its bell as it tries to swim away while the anemone slowly pulls the medusa into its mouth. The hyperiid amphipods hitchhiking on this medusa are going to get consumed by the anemone.

Other hyperiid amphipod predators are the nototheniid fish (Pagothenia borchgrevinki, Trematomus bernacchii, T. hansoni, T. centronotus) which eat Hyperiella dilatata [5,10].

1: Hyperiid Amphipods (Amphipoda, Hyperiidea) of the World Oceans. ME Vinogradov, AF Volkov, TN Semenova; scientific editor, D Siegel-Causey. Lebanon, NH : Science Publishers, 1996; 2: Polar Biology 11(1):19-25, 1990; 3: Pelagic Scyphomedusae (Scyphozoa: Coronatae and Semaeostomeae) of the Southern ocean. Ronald J. Larson. Washington, DC : American Geophysical Union, 1986; 4: Antarctic Ecology, Volume 1. MW Holdgate, ed. NY: Academic Press, 1970. pp244-258; 5: Polar Biology 8(1):49-54, 1987; 6: Journal of Organic Chemistry 60(3):780-782, 1995; 7: Nature 346(6283):462-464, 1990; 8: Antarctic Journal of the United States 29(5):151-153, 1994; 9: Marine Biology 122:271-277, 1995; 10: Environmental Biology of Fishes 36(3):313- 318, 1993

Text ©Peter Brueggeman. Photographs ©Canadian Museum of Nature (Kathleen Conlan), Uwe Kils, and Norbert Wu. Photographs may not be used in any form without the express written permission of Canadian Museum of Nature (Kathleen Conlan), Uwe Kils, and Norbert Wu. Norbert Wu no longer grants permission for uncompensated use of his photos under any circumstances whatsoever; want more info?