Comb jelly, any of a large group of marine animals also known as ctenophores. Comb jellies, which range in length from three-fourths of an inch to more than 3 feet, have gelatinous, transparent bodies that may be spherical, oval, bell-shaped, or flat and ribbon-like. Running lengthwise along the body are eight bands of cilia, or swimming paddles. Although comb jellies can move through the water by beating their paddles rhythmically, they are weak swimmers and are often swept ashore by currents.
At one end of the body of the comb jelly is a mouth opening, and at the opposite end is a small sensory organ, or statocyst, which is used to maintain balance. Many comb jellies have two long branching tentacles near the statocyst. These tentacles, which are covered with sticky cells, usually trail through the water and capture small shrimp or fish that the animal eats. Some comb jellies, which feed on tiny plants and animals, have series of short tentacles around the mouth.
Many comb jellies are luminescent and emit flashes of blue or green light when disturbed. Although some of them are among the brightest of all marine animals, the light they emit is only 1/3000 of the light given off by a candle.
Comb jellies make up the phylum Ctenophora of the animal kingdom. This phylum comprises the classes Nuda and Tentaculata.
