animal Type
Maximum Size

2.8 cm

(1 inch) across


1,000–3,300 m

(3,300–10,800 feet)



in the midnight (bathypelagic) zone




North Pacific Ocean

also known from the Arctic Ocean and Caribbean Sea


This jelly’s vibrant colors and far-out appearance clued scientists into a unique find.

Of all the jellies that call the ocean’s midnight zone home, the psychedelic jelly (Crossota millsae) is one of the most stunning. Its wildly colorful appearance—ruby red, bright orange, and electric purple—first tipped off scientists that they had found a previously unknown species.

But a closer look offered scientists another surprise: This species is one of a handful of jellies that bear live young.

The female psychedelic jelly broods her babies on those crimson canals that radiate out inside her bell. Mom carries more than a single baby at once. Her babies can all be different sizes, indicating different stages of development. The developing young get their nutrition from mom. In their shelter beneath her bell, the little jellies grow bigger and bigger, even sprouting tentacles while still attached to their mother. When the juvenile jelly outgrows its shelter, it pulses free and swims off to live on its own. As the juvenile grows, its lavender color fades, developing the tangerine pigmentation typical of adults.


Video Clips


Meech, M.E., C.E. Mills, S.H.D. Haddock, and R.W. Meech. 2021. Two swimming modes in Trachymedusae; bell kinematics and the role of giant axons. Journal of Experimental Biology, 224: 1–12.

Matsumoto, G.I., B. Bentlage, R. Sherlock, K. Walz, and B.H. Robison. 2020. “Little red jellies” in Monterey Bay, California (Cnidaria: Hydrozoa: Trachymedusae: Rhopalonematidae). Frontiers in Marine Science, 6: 1–14.