Are the small, clear blobs that get caught in my net in the sound jellyfish? It doesn’t look like they have any tentacles.

March 2004

Comb jellies can easily be mistaken for jellyfish. (photo by Tim Blades)

Comb jellies can easily be mistaken for jellyfish. (photo by Tim Blades)

It’s possible they’re jellyfish, but it’s more likely they’re comb jellies. These floating spheres can easily be mistaken for jellyfish.

Comb jellies were once classified as jellyfish, but today are scientifically classified in a group of their own. They don’t sting, nor do they undergo the many developmental stages like jellyfish. They are exclusively marine animals (there are freshwater jellyfish) and can be found in tremendous numbers in all the oceans.

In general, comb jellies are small, colorless, sac-like or flat-bodied animals made up of two lobes. Some species can be tinted pinkish or brownish, but most are nearly invisible in water. These small drifters are noted for their beautiful iridescence. When disturbed, their glimmering light flashes as they move gracefully just beneath the surface.

The light is caused by the refraction of natural light during the day, but is most dramatic at night when the comb jelly’s chemical luminescence (much like fireflies) gives off eerie, vibrant flashes. This is best seen when the water is calm and clear and the jellies are just beneath the surface.

For closer inspection, comb jellies can be gently scooped up in a cupped hand or bucket. They are fragile and often occur in huge swarms. They may occupy a particular bay, inlet or sound, and may stay a few days or suddenly disappear.

Comb jellies move using cilia, also called combs, which are short, hair-like growths similar to our eyelashes. The cilia beat up and down to feebly propel the animal along. It is the refraction of light on the beating cilia that causes their beautiful iridescence.

Three types of comb jellies are common in North Carolina waters; Leidy’s comb jelly, Beroe’s comb jelly and the sea gooseberry. Comb jellies have both male and female sex organs and release eggs and sperm directly into the water.

Like jellyfish, comb jellies depend primarily on winds and currents for transportation and are frequently swept into bays and sounds. Out of water they are reduced to jiggley blobs. Voracious predators, the small orbs feed by swimming with mouths agape in search of tiny crustaceans, floating fish eggs and larvae of mollusks, crabs and echinoderms. As many as 126 oyster larvae have been found in a single comb jelly. Some comb jellies trail behind a pair of sticky tentacles to snare a meal. Others have large mouths or lobes around the mouth to funnel in prey, and some are cannibalistic.