animal Type
Maximum Size

5 m

(16 feet) total length, possibly longer


600–1,800 m

(2,000–5,900 feet)



in the midnight (bathypelagic) zone


Gelatinous plankton

also fishes and crustaceans


North Pacific Ocean

California to Baja California, likely also occurs off Japan


In a world without boundaries, delicate drifters unfurl a curtain of tentacles to snag a meal.

The endless expanse of the ocean’s midnight zone offers plenty of room to stretch out. Here, some animals can grow to great lengths. Siphonophores are gelatinous animals composed of specialized parts growing together in a chain. The woolly siphonophore (Apolemia lanosa) is a shaggy species we often encounter in Monterey Bay. We know they can reach at least five meters (16 feet) in length, but other siphonophores can be as long as a blue whale!

We often encounter the woolly siphonophore in a spiral coil dangling a curtain of tentacles. Specialized stinging cells stun any unfortunate animal that blunders into those sprawling tentacles.

Recent work with our collaborators examined video observations of animals in the wild and stomach contents of specimens in the lab, revealing that Apolemia have a diverse diet. This group of siphonophores feasts on crustaceans, squids, worms, and fishes. While their close cousins are not picky about their meals, the woolly siphonophore prefers gelatinous animals—jellies, salps, and even other siphonophores. Their tentacles bear specialized branches called tentilla specifically adapted to adhere to slippery jellies.

For years, scientists classified all Apolemia as a single species. But a closer look at our video observations suggested there might be far more diversity in this group than we knew. DNA research confirmed our suspicions and in 2013 we described Apolemia lanosa

An unusually fluffy appearance distinguishes this species. Most siphonophores grow from a single zone along the stem, right below the swimming bells (nectophores). Apolemia are unique because they can grow at various points all along the stem. This abundance of growth zones can lead to a fuzzy appearance—most other siphonophores are more uniform and streamlined.

The woolly siphonophore is one of two new Apolemia species we discovered in Monterey Bay. Our team has worked with collaborators around the world to describe 11 previously unknown siphonophore species off the California coast—how many more still await discovery? 

Understanding and documenting deep-sea biodiversity is increasingly critical. Fishing pressure, pollution, and climate change all threaten the deep ocean. We urgently need to establish a baseline of what lives in the deep sea so we can monitor ongoing human impacts on this environment.


Video Clips


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.

Damian-Serrano, A., S.H.D. Haddock, and C.W. Dunn. 2021. The evolution of siphonophore tentilla for specialized prey capture in the open ocean. Proceedings of the National Academy of Sciences, 118: 1–9.

Damian-Serrano, A., E.D. Hetherington, C.A. Choy, S.H.D. Haddock, A. Lapides, and C.W. Dunn. 2022. Characterizing the secret diets of siphonophores (Cnidaria: Hydrozoa) using DNA metabarcoding. PLOS ONE, 17(e0267761): 1–24.

Gasca, R., and S.H. Haddock. 2016. The rare deep-living hyperiid amphipod Megalanceoloides remipes (Barnard, 1932): Complementary description and symbiosis. Zootaxa, 4178: 138–144.

Gasca, R., R. Hoover, and S.H.D. Haddock. 2014. New symbiotic associations of hyperiid amphipods (Peracarida) with gelatinous zooplankton in deep waters off California. Journal of the Marine Biological Association of the United Kingdom, 95: 503–511.

Haddock, S.H.D., and J.F. Case. 1999. Bioluminescence spectra of shallow and deep-sea gelatinous zooplankton: ctenophores, medusae and siphonophores. Marine Biology, 133: 571–582.

Hetherington, E.D., A. Damian-Serrano, S.H.D. Haddock, C.W. Dunn, and C.A. Choy. 2022. Integrating siphonophores into marine food-web ecology. Limnology and Oceanography Letters, 7: 81–95.

Siebert, S., P.R. Pugh, S.H.D. Haddock, and C.W. Dunn. 2013. Re-evaluation of characters in Apolemiidae (Siphonophora), with description of two new species from Monterey Bay, California. Zootaxa, 3702: 201–232.