animal Type
Maximum Size

15 cm

(6 inches) across


200–1,200 m

(660–3,900 feet)



seamounts, submarine canyons, and rocky outcroppings


Plankton and small crustaceans


Northeastern Pacific Ocean

from California to Mexico


This coral is one of the nicest neighbors you could hope for.

The mushroom soft coral (Heteropolypus ritteri) is one of the most common animals we see in the depths off the central coast of California. They are abundant on the jagged walls of Monterey Canyon and the rocky slopes of local seamounts. Fast currents running along the bottom can carry an abundance of plankton and other tiny bits of food. Heteropolypus extends delicate tentacles into the currents to snag a feast. When their tentacles are extended, they resemble a beautiful flower. When the tentacles are pulled in, they look more like their namesake—mushrooms.

A resident of rocky environments, the mushroom soft coral offers safe haven for small animals seeking protection. A snailfish may hide near the umbrellas of stinging tentacles. A shrimp might hang on to weather the storm of strong currents. A mother catshark may secure her egg cases to the coral’s sturdy trunk.

Unlike their close cousins in shallower waters, the mushroom soft coral spawns year round. Their larvae are large and have robust energy reserves to ensure their survival as the currents running along the seafloor carry them to new environments. But some of the larvae stay close to home—we sometimes see clusters of smaller corals alongside a big parent. Growth studies suggest this coral can live at least 25 years, perhaps even longer.

Some of our observations have sparked intriguing questions. For example, we have learned that when disturbed, the mushroom soft coral glows with a steady blue light, but we still do not know why Heteropolypus produces brilliant bioluminescence or how this light show affects their neighbors.

The abundance of mushroom soft corals and their diverse relationships with other bottom-dwelling animals tell us they are an important part of the seafloor community. But the intimate interactions among deep-sea animals only become apparent when we conduct regular surveys. We cannot protect what we do not understand. Our research is helping improve our baseline understanding of the largest environment on Earth, even if our encounters sometimes yield more questions than answers.

We still have a lot to learn about Heteropolypus, including how a changing seafloor environment will impact them and their neighbors. But we do know that a healthy ocean is one of the best ways to fight climate change. We must act quickly to safeguard Heteropolypus and other denizens of the deep. Understanding how our actions affect the ocean is an important first step. Share what you have learned, and help us grow our community of ocean champions. Together, we can protect the remarkable residents of the ocean’s depths.


Video Clips


Barry, J.P., H.G. Greene, D.L. Orange, C.H. Baxter, B.H. Robison, R.E. Kochevar, J.W. Nybakken, D.L. Reed, and C.M. McHugh. 1996. Biologic and geologic characteristics of cold seeps in Monterey Bay, California. Deep Sea Research Part I: Oceanographic Research Papers, 43: 1739–1762.

Bessho-Uehara, M., W. R. Francis, and S. Haddock. 2020. Biochemical characterization of diverse deep-sea anthozoan bioluminescence systems. Marine Biology, 167: 1–19.

Kogan, I., C.K. Paull, L. Kuhnz, E.J. Burton, S. Von Thun, H.G. Greene, and J. Barry. 2006. ATOC/Pioneer Seamount cable after 8 years on the seafloor: Observations and environmental impact. Continental Shelf Research, 26: 771–787.

Lundsten, L., J.P. Barry, G.M. Caillet, D.A. Clague, A. DeVogelaere, and J.B. Geller. 2009. Benthic invertebrate communities on three seamounts off southern and central California, USA. Marine Ecology Progress Series, 374: 23–32.

Martini, S., L. Kuhnz, J. Mallefet, and S.H.D. Haddock. 2019. Distribution and quantification of bioluminescence as an ecological trait in the deep sea benthos. Scientific Reports, 9(14654).