Like the true jellyfish, ctenophores are predators on a wide range of zooplankton. They also lack the stinging nematocysts of jellyfish and use other means for collecting food, including sticky tentacles, mucous-covered oral lobes and large mouths. Some groups less familiar to most people have also taken up a gelatinous existence. Among the more abundant gelatinous zooplankton are the various types of pelagic gastropods within the phylum Mollusca. Lacking a hard, dense shell and using modifications of the molluscan foot for locomotion, many of these swimming snails barely resemble their benthic relatives.
Few people are aware that some of the most common planktonic animals are gelatinous snails.
Predatory heteropods possess a single swimming fin to scull through the water while seeking prey. Pteropods use a pair of swimming wings, and some are known as sea butterflies due to the manner in which they flap them. One group of pteropods uses various styles of mucous nets to graze on phytoplankton and other small particles. Another group is predatory, using complex mouth structures to capture gelatinous prey. The tunicates are best known by the sessile benthic forms, the sea squirts.