MBARI (Monterey Bay Aquarium Research Institute) | Weird and Wonderful: The barrel amphipod devours its host @MBARIvideo | Uploaded October 2021 | Updated October 2024, 19 hours ago.
The midwater is a vast expanse of water between the surface and the seafloor. There are no places for rest or refuge here. The barrel amphipod, Phronima sedentaria, is a shrimp-like crustacean that adapts by living inside the repurposed bodies of gelatinous animals, like salps and pyrosomes.

The amphipod uses its sharp claws to snag a salp, then rips out the soft tissues inside. But that salp is more than a meal—the amphipod carries around the carved-out carcass as its home. It even “remodels” its shelter by reshaping the barrel and secreting chemicals to toughen its tissues. Female barrel amphipods lay their eggs inside the salp and their hatchlings feast on the salp’s tissues.

MBARI researchers and their collaborators are studying the hitchhiking hyperiid amphipods that live on jellies and other gelatinous animals in the midwater. MBARI Adjunct Karen Osborn and her team at the Smithsonian’s National Museum of Natural History are examining the elaborate compound eyes of Phronima sedentaria and other midwater amphipods.


Common name: Barrel Amphipod
Scientific name: Phronima sedentaria
Reported depth range: surface–600 meters (2,000 feet)
Size: to 4 centimeters (1.5 inches)

Editor: Ted Blanco
Script writer: Larissa Lemon
Production team: Kyra Schlining, Susan von Thun, Nancy Jacobsen Stout

For more information see:
mbari.org/bioinspiration-2019-expedition
mbari.org/gulf-of-california-2015-mar-14

mbari.org/deep-piv-3d-flow

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