animal Type
Maximum Size

30 cm

(12 inches)


500–1,500 m

(1,640–4,920 feet)



in the twilight (mesopelagic) and midnight (bathypelagic) zones



likely crustaceans and possibly small fishes


Northeastern Pacific Ocean

also known from northwestern Atlantic Ocean, and may be more widespread


This spectacular siphonophore is a sight to see.

Siphonophores (pronounced “sigh-fawn-oh-fours”) are colonial creatures made up of specialized segments that work together as one. Scientists have described some 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. Most siphonophores live far from the seafloor and call the endless expanse of the ocean’s midwater zone their home.

Because their delicate bodies can break apart at the slightest touch, siphonophores are hard to study. Thankfully, MBARI’s remotely operated vehicles (ROVs) give scientists the opportunity to get a close-up look at deep-sea siphonophores without damaging them. Our skilled pilots carefully maneuver the ROV to record stunning video of these delicate drifters. These observations complement specimens we gingerly collect with samplers on the ROV.

We’ve discovered a rainbow of siphonophores in the depths of Monterey Bay and beyond, like this stunningly scarlet species, Marrus claudanielis, described by MBARI researchers and their collaborators in 2005.


Video Clips


Burns, J.A., K. P. Becker, D. Casagrande, J. DanielsP. RobertsE. Orenstein, D. M. Vogt, Z. E. Teoh, R. Wood, A.H. Yin, B. Genot, D.F. Gruber, K. Katija, R.J. Wood, B.T. Phillips. 2024. An in situ digital synthesis strategy for the discovery and description of ocean life. Science Advances, 10(eadj4960).

Choy, C.A., S.H.D. Haddock, and B.H. Robison. 2017. Deep pelagic food web structure as revealed by in situ feeding observations. Proc Biol Sci, 284: 1–10.

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.

Munro, C., S. Siebert, F. Zapata, M. Howison, A. Damian-Serrano, S.H. Church, F.E. Goetz, P.R. Pugh, S.H.D. Haddock, and C.W. Dunn. 2018. Improved phylogenetic resolution within Siphonophora (Cnidaria) with implications for trait evolution. Molecular Phylogenetics and Evolution, 127: 823–833.