Other zooplankton include cnidarians, ctenophores, chaetognaths, molluscs, arthropods, urochordates, and annelids such as polychaetes. Most animals are bilaterians, excluding sponges, ctenophores, placozoans and cnidarians. Hence ctenophores and cnidarians have traditionally been labelled diploblastic, along with sponges. Coelenterazine is found in radiolarians, ctenophores, cnidarians, squid, brittle stars, copepods, chaetognaths, fish, and shrimp. Hence, cnidarians and ctenophores have traditionally been labelled diploblastic, along with sponges. The jellyfish themselves feed mostly on zooplankton, small fish, ctenophores, and moon jellies. They generally feed on zooplankton, ctenophores, other jellies, and sometimes crustaceans. Occasionally, they are also seen feeding on gelatinous zooplankton such as hydromedusae and ctenophores. Others are members of gelatinous zooplankton such as "Beroe" ctenophores and various Scyphozoa (jellyfish). Solenogasters feed on cnidaria and ctenophores, either sucking their bodily fluids or eating their tissue. Many species of the jellyfish-like ctenophores have two tentacles, while some have none. The last common ancestor (LCA) of the ctenophores was hermaphroditic. One theory is that nerve nets may have developed independently in Ctenophores and Cnidarians. No ctenophores have been found in fresh water. Most ctenophores that live near the surface are mostly colorless and almost transparent.