Stygiomedusa gigantea is one of the largest invertebrate predators known in the ocean, yet little is understood about its ecology and behavior. Stygiomedusa lacks tentacles, but has four extraordinarily large oral arms that are presumably used to envelope prey. The swimming bell of this spectacular medusa can reach over one meter across with arms over ten meters long.

A symbiotic relationship between Stygiomedusa and the fish, Thalassobathia pelagica, was confirmed in 2003 when scientists from the Monterey Bay Aquarium Research Institute (MBARI) filmed the pair swimming together in the Gulf of California. The fish has adapted to using the medusa as a hiding place in its open ocean habitat.

In twentyseven years of scientific ROV surveys, researchers at MBARI have been lucky enough to observe this rare animal seven times, from depths of 750 meters down to 2187 meters.

Video editing & script: Kyra Schlining
Narration: Andrew Hamilton
Music: Heavy Water, APM Music, LLC
Production support: Nancy Jacobsen Stout, Linda Kuhnz, Lonny Lundsten, Susan vonThun, George Matsumoto, Steve Haddock, Kim FultonBennett

Data for map from: OBIS (2015) [Distribution records of Stygiomedusa gigantea (Brown, 1910)] [ID numbers for data sources: 1620; 2524; 2303; 500] (Available: Ocean Biogeographic Information System. Intergovernmental Oceanographic Commission of UNESCO. http://www.iobis.org. Accessed: 20151023)

For more information:
www.mbari.org

See also:
Drazen, J.C., and Robison, B.H. 2004. Direct observations of the association between a deepsea fish and a giant scyphomedusa. Journal of Marine and Freshwater Behaviour and Physiology (37): 209214.