Chaetodontidae, or butterflyfishes, are among the most widely recognized coral reef fishes. Their vivid coloration and striking patterns make them popular in the aquarium trade, although some species are difficult to maintain in aquaria (see Economic Importance). The family contains 10 genera with 114 species, the majority in the genus Chaetodon. They occur mainly in tropical waters, most densely distributed in the Indo-West Pacific, but some occupy warm temperate waters (see Habitat). Members of this family vary considerably in terms of color, but all butterflyfishes share certain morphological traits such as a deep, laterally compressed body,   ctenoid scales that extend onto the soft-rayed portions of the dorsal and anal fins, and jaws that may be slightly or extremely elongated (see Physical Description). Jaw shape and size correlates with the type of prey consumed; some butterflyfishes feed upon small invertebrates or algae, others solely on   coral polyps (known as obligate corallivores), and still others upon zooplankton (see Food Habits). Butterflyfish are largely pair-forming, pelagic (in the water column) spawners (see Reproduction), and are unique among reef fishes in that the larvae pass through a stage termed tholychthys during which a bony sheath encases the head (see Development). As of 1994, five chaetodontid species were listed as vulnerable to extinction (see Conservation Status).