Animal Type
Maximum Size

15 cm

(6 inches)


500–5,000 m

(1,600–16,400 feet)



typically in the midnight (bathypelagic) zone



including gelatinous zooplankton and crustaceans




This regal resident of the midnight zone has unique adaptations to survive where food is scarce and predators are plentiful.

The deep-sea crown jelly (Atolla sp.) is one of the most common jellies in the ocean’s depths. Most have a distinctive elongated tentacle that can be up to six times the diameter of the jelly’s bell. Scientists suspect that characteristic trailing tentacle helps this jelly capture food. As a hungry Atolla pulses along, that long tentacle snags crustaceans or other prey.

But Atolla is not the only clever hunter in the deep sea. Predators lurk in the darkness, ready to pounce. The bright red bell helps keep Atolla hidden—in the deep sea, red appears black. If Atolla’s crimson camouflage does not work, this jelly sounds the alarm with pinwheels of brilliant blue bioluminescence. A burst of light in the dark water not only disorients predators but it also acts like a burglar alarm telling larger predators there is something interesting happening here. The threat of a bigger predator scares off any immediate danger, allowing the jelly to swim to safety.

Even one of the most common jellies in the deep sea still holds many secrets. Scientists currently recognize around 10 different species of Atolla. However, MBARI researchers recently discovered three varieties of crown jellies that look like Atolla, but lack the telltale trailing tentacle. They have named one of these new species Atolla reynoldsi, in honor of Jeff Reynolds, the first volunteer at MBARI’s education and conservation partner, the Monterey Bay Aquarium. Who knows what other discoveries still await us in the ocean’s mysterious midnight zone?



Video Clips


Matsumoto, G.I., L.M. Christianson, B.H. Robison, S.H.D. Haddock, and S.B. Johnson. 2022. Atolla reynoldsi sp. nov. (Cnidaria, Scyphozoa, Coronatae, Atollidae): A new species of coronate Scyphozoan found in the Eastern North Pacific Ocean. Animals, 12: 1–21.

Osborn, D.A., M.W. Silver, C.G. Castro, S.M. Bros, and F.P. Chavez. 2007. The habitat of mesopelagic scyphomedusae in Monterey Bay, California. Deep Sea Research Part I, 54(8): 1241–1255.