Comb jellies are all free swimming and never go through alternation of generations as jellyfish do. There are approximately 100 known species of Ctenophores and all are restricted to marine environments. Lacking the bell that is present in most jellyfish, comb jellies rely on eight rows of cilia for locomotion. The name ctenophore comes from the Greek word for comb, cteno, referring to the rows or combs of cilia in the animal. The cilia wave in unison, enabling the comb jellies to move.
Ctenophores are the largest animals that use cilia for locomotion.
Comb jellies' bodies, translucent and very fragile, easily fall apart like jelly when picked up or caught in a net. Comb jellies are quite beautiful organisms, existing in an array of ethereal shapes. At night or in darkened water they are even more impressive. The rows of cilia are bioluminescent , creating a glowing underwater rainbow. Most have either one or two pairs of retractable tentacles that assist in catching food.