Sea walnuts 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:
Transparent, jelly-like bodies
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. Two of the body lobes are longer than the rest.
Pink comb jellies have a sac- or egg-shaped body that is often tinted pinkish to reddish-brown
Grow to about 4 inches
Habitat:
Live near the surface of both shallow and deep waters
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:
Voracious feeders of planktonic organisms, including copepods and fish larvae
Can consume almost 500 copepods per hour
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:
Spawn 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 jellies 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, sea walnut color bands glow soft green
Although sea nettles and other stinging jellyfish are more well-known, comb jellies are much more abundant in the Bay
