2021 Annual Report
Photo by Steve Haddock

MBARI reveals a dazzling diversity of delicate drifters

Siphonophores (pronounced “sigh-fawn-oh-fours”) are colonial creatures made up of specialized segments that work together as one. They may not be familiar to most, but they’re abundant animals in the ocean. In fact, siphonophores are some of the most important predators in ocean ecosystems. Scientists have described about 175 siphonophore species. Most follow a similar body plan—a gas-filled float provides buoyancy, swimming bells propel the colony, and a central stem bears specialized parts for feeding, defense, and reproduction. Siphonophores are some of the longest animals in the world, with the giant siphonophore estimated to grow up to 40 meters (nearly 132 feet) long but only as big around as a broomstick. They capture prey with a curtain of stinging cells, allowing them to consume organisms much beefier than they are. From the surface to the seafloor, the ocean is home to many extraordinary siphonophores.

Most siphonophore species in the ocean are found in the deep sea and are poorly known because it is difficult to sample these delicate animals. This year, we partnered with Google Arts & Culture to showcase some of the most stunning species MBARI and our collaborators have encountered. It’s a must-see if you’re a siphono-fan like we are!


Dunn, C.W., P.R. Pugh, and S.H.D. Haddock (2005). Marrus claudanielis, a new species of deep-sea physonect siphonophore (Siphonophora, Physonectae). Bulletin of Marine Science, 76: 699-714.

Pugh, P.R. and S.H.D. Haddock (2016). A description of two new species of the genus Erenna (Siphonophora: Physonectae: Erennidae), with notes on recently collected specimens of other Erenna species. Zootaxa, 4189(3): 401-446. doi.org/10.11646/zootaxa.4189.3.1.

Haddock, S.H.D., C.W. Dunn, P.R. Pugh, and C.E. Schnitzler (2005). Bioluminescent and red fluorescent lures in a deep-sea siphonophore. Science, 309: 263.doi.org/10.1126/science.1110441.

The gossamer worm: An effective and elegant swimmer

This ethereal worm is a graceful swimmer that “dances'' through the midwater with the rhythmic paddling of its swimming legs.