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Comb Jellies

Sea walnuts, a type of comb jelly, have a colorless, walnut-shaped body. Two of the body lobes are longer than the rest. (Steven G. Johnson/Wikimedia Commons)
Sea walnuts, a type of comb jelly, have a colorless, walnut-shaped body. Two of the body lobes are longer than the rest. (Steven G. Johnson/Wikimedia Commons)

Comb jellies are transparent, jelly-like invertebrates with bright, iridescent color bands. They live near the water’s surface in the middle and lower Chesapeake Bay.

Two species of comb jellies can be found in the Chesapeake Bay:

  • Sea walnut, Mnemiopsis leidyi
  • Pink comb jelly, Beroe ovata

Appearance:

Comb jellies have transparent, jelly-like bodies with bright, iridescent color bands, which are made up of tiny hairs called combs. The bands divide the body into eight symmetrical parts. Sea walnuts have a colorless, walnut-shaped body, with two of their body lobes longer than the rest. Pink comb jellies have a sac- or egg-shaped body that is often tinted pinkish to reddish-brown. Comb jellies grow to about 4 inches.

Habitat:

Comb jellies live near the surface of both shallow and deep waters and swim by beating their combs rhythmically to push themselves forward. Sea walnuts often swim together in large swarms.

Range:

Sea walnuts are the more widely distributed species. They occur as far north as the Baltimore area. They are present year-round but are most common in spring and summer. Pink comb jellies can be found in late summer to autumn in the middle and lower Chesapeake Bay, south of Kent Island, Maryland.

Feeding:

Sea jellies are voracious feeders of planktonic organisms, including copepods and fish larvae. They can consume almost 500 copepods per hour. They eat by continuously pumping water into their body cavities.

Predators:

Even though they are both comb jellies, the pink comb jelly is a major predator of the sea walnut.

Reproduction and Life Cycle:

Spawning occurs at night when water temperatures warm to 66-73 degrees. Comb jellies have both male and female reproductive organs and can fertilize themselves. Each comb jelly releases about 8,000 eggs per spawn. Unlike jellyfish, comb jellies develop without distinctive larval and polypoid stages. Comb jelly species are difficult to distinguish from each other when they are young. Young are able to reproduce 13 days after hatching.

Other Facts:

  • Unlike jellyfish, comb jellies do not have stinging tentacles.
  • Comb jellies break apart when taken out of the water. If you find a comb jelly and would like to view its true shape, gently scoop it out of the water with a clear container and view it through the sides of the container.
  • When disturbed at night, the color bands of the sea walnut glow soft green.

  • Although sea nettles and other stinging jellyfish are more well-known, comb jellies are much more abundant in the Bay.

Sources and Additional Information:


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