The seven-armed octopus, Haliphron atlanticus, has only been observed by MBARI’s remotely operated vehicles three times in 27 years. In this species, the male keeps the hectocotylized arm hidden so it appears to be missing, thus the common name. During the most recent encounter, the octopus was holding the bell of an egg-yolk jellyfish (Phacellophora camschatica) in its arms. The octopus had apparently eaten most of the tissue that would have been hanging down from the bell, but the ring of jellyfish tentacles was intact. It looked as though Haliphron had not only made a meal of the jelly, but was hanging onto it, perhaps for defense or for help in catching prey. Haliphron is a member of the family Argonautidae, and now four genera in the family have been observed having some kind of relationship with salps or jellyfish—living on, in, or with the jelly. We know very little about the diversity of the communities that live in the deep sea, but even less about what these organisms eat. Paradoxically many large animals like whales, manta rays, and ocean sunfish eat small or gelatinous plankton —drifting prey that are easier to catch than fast-swimming fishes. This large octopus is another example of this interesting adaptation to life in the open ocean: live slow, grow big. For more information see: www.mbari.org/a-giant-deep-sea-octopus-is-a-sucker-for-jellies/ For more information on jellyfish or to report sightings of jellyfish and other marine organisms, go to www.jellywatch.org Video producer: Susan von Thun Music: Steve Haddock Script and narration: Steve Haddock Production support: Danielle Haddock, Kyra Schlining, Linda Kuhnz, Lonny Lundsten, and Nancy Jacobsen Stout Special thanks to Jeffrey Milisen for use of his Tremoctopus image. Publication citation: Hoving, H.J.T. and Haddock, S.H.D. The giant deep-sea octopus Haliphron atlanticus forages on gelatinous fauna. Sci. Rep. 7, 44952; doi: 10.1038/srep44952 (2017). www.nature.com/articles/srep44952

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