Molas are distinguished for their distinct morphological characters which include reduced/fused caudal elements, presence of a clavus in place of the caudal fin, absence of a swim bladder and a degenerate, cartilaginous skeleton (Ref. 86435). Adults are found on slopes adjacent to deep water where they come in for shelter and for seeking cleaner fishes. They are usually shy. However, they may become familiar with divers in some locations (Ref. 48637). Individuals often drift at the surface while lying on its side but can swim actively and are capable of directional movements otherwise (Ref. 86435). They swim upright and close to the surface. The dorsal fin often protrudes above the water. Females are larger than males (Ref. 86435). This species has been filmed in 480 m depth with the help of a camera equipped with baits (Lis Maclaren, pers. comm. 2005). Adults eat fishes, mollusks, zooplankton, jellyfish, crustaceans and brittle stars (Ref. 4925, 5951, 48637). A live colony of the cirripede Lepas anatifera
were found attached to the anterior portion of the sunfish's esophagus that was stranded in the south coast of Terceira Island, Azores Archipelago in 2004. This association has apparent advantages for the goose barnacles such as a regular intake of food and protection both from hydrodynamic hazards and from predators: but for the sunfish, it is not clear whether it is neutral, of advantage or causes feeding problems since the attachment may obstruct the sunfish's esophagus (Ref. 55063). The sunfish is registered as the heaviest bony fish and as the one with the most eggs in the Guinness Book of World Records (Ref. 6472). Generally this species is not used as food fish; some people consider it as a delicacy (Ref. 30573). The fish can be utilized fresh and can be broiled (Ref. 9988). Some parts of the fish are used in Chinese medicine (Ref. 12166). Molas may contain the same toxin as puffers and porcupine fish (Ref. 13513). They do not adapt well in captivity (Ref. 12382, 37040). Juveniles are victims of California sea lions in Monterey Bay (Ref. 37040).