Ctenophores are invertebrate marine animals commonly referred to as "comb jellies" and "sea walnuts." Fewer than 100 species of this phylum have been identified. All ctenophores have fragile, transparent bodies and eight rows of cilia called comb plates that they use to swim. Ctenophores are also characterized by the colloblasts found on the surface of their tentacles. These specialized glue cells secrete a sticky substance that helps ctenophores catch prey.