Sunfish, or mola, develop their truncated, bullet-like shape because the back fin which they are born with simply never grows. Instead, it folds into itself as the enormous creature matures, creating a rounded rudder called a clavus. Mola in Latin means "millstone" and describes the ocean sunfish’s somewhat circular shape. They are a silvery color and have a rough skin texture.
The mola are the heaviest of all the bony fish, with large specimens reaching 14 feet (4.2 meters) vertically and 10 feet (3.1 meters) horizontally and weighing nearly 5,000 pounds (2,268 kilograms). Sharks and rays can be heavier, but they're cartilaginous fish.
Mola are found in temperate and tropical oceans around the world. They are frequently seen basking in the sun near the surface and are often mistaken for sharks when their huge dorsal fins emerge above the water. Their teeth are fused into a beak-like structure, and they are unable to fully close their relatively small mouths.
Ocean sunfish can become so infested with skin parasites, they will often invite small fish or even birds to feast on the pesky critters. They will even breach the surface up to 10 feet (3 meters) in the air and land with a splash in an attempt to shake the parasites.
They are clumsy swimmers, waggling their large dorsal and anal fins to move and steering with their clavus. Their food of choice is jellyfish, though they will eat small fish and huge amounts of zooplankton and algae as well. They are harmless to people, but can be very curious and will often approach divers.
Their population is considered stable, though they frequently get snagged in drift gill nets and can suffocate on sea trash, like plastic bags, which resemble jellyfish.
There are currently two recognized species in this genus:
- Sepkoski, Jack (2002). "A compendium of fossil marine animal genera". Bulletins of American Paleontology 364: 560. http://strata.ummp.lsa.umich.edu/jack/showgenera.php?taxon=611&rank=class. Retrieved 2008-01-08.
- Froese, Rainer, and Daniel Pauly, eds. (2012). Species of Mola in FishBase. October 2012 version.
<National Geographic Online>
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