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Three giant bell jellies side by side in dark waters

Bell jelly

Polyorchis sp

Not on exhibit
Animal type
Invertebrates
Ecosystem
Coastal wetlands
Relatives
Hydroids, siphonophores, hydrocorals; Phylum: Cnidaria; Class: Hydrozoa
Diet
Zooplankton
Range
Nearshore waters of bays and harbors along the Pacific Coast
Size
Bell to about 2.5 inches (6.4 cm) in diameter

Meet the bell jelly

A bell jelly has a translucent bell and a clapper-shaped mouth stalk. This jelly has 100 or more wispy tentacles and red ocelli, or eyespots, which are sensitive to light. Bell jellies are vertical migrators, meaning they remain in dark, deep waters during the day and rise to the surface at night.

Did you know?

A bell jelly spends about half its time near the seafloor, where it feeds on small benthic (bottom-dwelling) creatures. Bell jellies often "hop" up from the seafloor to stir up sediments and uncover potential food. They swim to the surface and sink back down to the seafloor, a process that lets them collect plankton as they drift.

Conservation

Bell jellies used to be abundant in bays and estuaries along the West Coast, bur their populations are dwindling due to human activities like dredging, pollution, and collection for neurobiological research.

To understand the exact causes of population increases and decreases, we must know more about the life cycles of jellies.

Cool facts

  • Bell jellies respond to bright lights at night (such as camera flashes) and quickly swim away.
  • Since their red coloration disappears in deep water where light is low, bell jellies are virtually invisible to deep-sea predators.

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