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| Sunfish are generally thought to be a solitary fish, swimming freely in the ocean alone. However, certain sightings of molas in groups of more than tens have been reported. | Sunfish are generally thought to be a solitary fish, swimming freely in the ocean alone. However, certain sightings of molas in groups of more than tens have been reported. | ||
| Sometimes the molas are spotted floating sideways on the sea surface. Although most scientists are still puzzled at this behavior, it is commonly thought that they are basking in the sun. Some observers have seen sea birds such as gulls picking ectoparasites off basking sunfish. Breaching has also been observed. This is when sunfish jump out of the water as whales would. | Sometimes the molas are spotted floating sideways on the sea surface. Although most scientists are still puzzled at this behavior, it is commonly thought that they are basking in the sun. Some observers have seen sea birds such as gulls picking ectoparasites off basking sunfish. Breaching has also been observed. This is when sunfish jump out of the water as whales would. They are reported to jump ten feet out of the water. THis is probably done to dislodge parasites on their body. | ||
| ==Environmental Adaptations== | ==Environmental Adaptations== | ||
Revision as of 21:02, 29 June 2006
| Ocean Sunfish | |
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| |
| Conservation status | |
| Template:StatusSecure | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Tetraodontiformes |
| Family: | Molidae |
| Genus: | Mola |
| Species: | M. mola |
| Binomial name | |
| Mola mola (Linnaeus, 1758) | |
The Ocean Sunfish (Mola mola) is a unique pelagic fish, perhaps the most massive bony fish in the world (but not the longest one; that honor probably goes to the Oarfish, known as the king of herrings). Specimens of ocean sunfish have been observed up to 3.33 m (11 ft) in length and weighing up to 2,300 kg (5070 lb). Nonetheless, the ocean sunfish is dwarfed in size by the largest fish, the whale shark (a cartilaginous fish), which grows up to 20 m (65 ft, 7 in) and 34000 kg (75000 lb) in weight. A member of order Tetraodontiformes, the ocean sunfish has many derived characters and is the type species of its genus.
Physiology
Ocean Sunfish are commonly mistaken for sharks, as they often swim close to the surface and have dorsal fins that stick up out of the water in a shark-like fashion. However, Ocean Sunfish feed on jellyfishes and other gelatinous, soft bodied zooplankton (along with small fish and other marine life). They are found in warm and temperate zones of all oceans, including the Eastern Pacific and the eastern and western Atlantic. There are three to five species of Molas.
Because of their very short and stiff body, they have no more than 16 vertebra, and the spinal cord is no longer than 1/2 of an inch (under 15 mm long). A specimen of 200 kg may have a brain no bigger than a nut. Their unusual shape is due to the tail, which is present in the tiny larvae, but doesn't grow with the rest of the body. As the rest of the body grows to the enormous adult size, it 'wraps around' where the tail would normally be, giving the squared, 'cut-off' shape of the adult Mola tail.
Fin
Like the triggerfishes and pufferfishes it is related to, Mola mola uses its long, thin dorsal and anal fins for propulsion; it lacks a caudal fin (or 'tail fin'), having in its place a rudder-like structure, the clavus. Its fry resemble miniature pufferfish, a hint at the species's place in the evolutionary tree.
Toxin
While the flesh of the Ocean Sunfish is considered a delicacy by some, it contains neurotoxins similar to those of other poisonous tetraodontiformes.
Diet
Sunfish eat jellyfishes, salps, comb jellies, zooplankton, squid, and crustaceans. They live in the Eastern Pacific and Atlantic. Despite the soft and watery nature of their food, it is densely packed with proteins, vitamins and minerals, and occurs in vast swarms. This, and the Mola's huge appetite, is why Molas can grow larger than any other bony fish. Their predators are orcas, sea lions, dolphins and marlin. Molas can produce more than 300 million eggs, each about 2 to 3 mm large, more than any other known vertebrate. They are thought to live for over 10 years. Interestingly, the rough and leathery skin (a fibrous tissue up to 1.5 cm thick) of the Ocean Sunfish is host to more dermal parasites than that of any other marine creature.
Appearance
The ocean sunfish is described as a flat, oval fish with grooves on its body. It has a rounded “tail” known as a clavus instead of a caudal fin. The clavus is short and broad and it is formed by extensions of dorsal and anal fin rays. It clavus is wavy and has 8 to 9 ossicles and 12 fin rays. The ocean sunfish also has rough, sandpapery skin and can weigh up to 4927 pounds. It also has mucus on its skin and can grow to 11 feet long. Its average weight is one ton and its average size from the tip of the snout to the tip of its clavus is 6 feet. Vertically, from fin to fin, its average size is 11 feet. The ocean sunfish is taller than it is long and has large, high dorsal and anal fins, which are dark in color. Its tiny mouth cannot be closed and its top and bottom teeth are fused to form a beak. It has a round, bulging eye, and its skin is extremely thick and elastic. There is a definite line at the posterior where denticles on the skin change from extremely rough to very fine. Its pectoral fins are small, fan-shaped, and pointed up. It has 4 gills and a slit behind the last one is covered by a thin flap of skin near the pectoral fin called an operculum. Juveniles are silvery in color and adults are usually dark gray to white and have variations in mottling and spots. Some sunfish are brown. Sunfish are usually gray above, silvery gray to brown on the side, and paler or dusky below. It is able to change color rapidly from spotty to even-colored. Compared to a human, the ocean sunfish is huge!
Behavior
Sunfish are generally thought to be a solitary fish, swimming freely in the ocean alone. However, certain sightings of molas in groups of more than tens have been reported.
Sometimes the molas are spotted floating sideways on the sea surface. Although most scientists are still puzzled at this behavior, it is commonly thought that they are basking in the sun. Some observers have seen sea birds such as gulls picking ectoparasites off basking sunfish. Breaching has also been observed. This is when sunfish jump out of the water as whales would. They are reported to jump ten feet out of the water. THis is probably done to dislodge parasites on their body.
Environmental Adaptations
The sunfish uses its clavus as a rudder and may also steer with its ability to spit strong jets of water out of its mouth or gills. It sculls and is propelled by waving its dorsal and anal fins from side to side and it is a weak swimmer. It usually lets the current carry it. The water supports its enormous weight and its great size gives it safety. Its thick, leathery hide also protects it because it is made up of collagen fibers up to 6 inches thick. It often protects it from the stinging jellyfish, which it eats. Its top and bottom teeth are fused together to form a beak and it also has claw-like teeth in its throat, which are used to help it break up its food before it eats it. The function of its operculum is to keep parasites out of its body. It has a mouth that is perfect for slurping jellies and salps. It is lighter on the bottom of its body and darker above to camouflage better.
Name
The Ocean Sunfish is also known as the marine sunfish, the moon fish, or simply by its specific name, mola (Latin for "millstone", which it was said to resemble). It has various obsolete binomial synonyms; its original name was Tetraodon mola.
The freshwater sunfishes (family Centrarchidae) are unrelated; for other fishes known as "sunfish", see Sunfish.
References
External links
- Ocean Sunfish research and information, Tierney Thys, PhD
- Ocean Sunfish Photographs, Mike Johnson Marine Natural History Photography
- Ocean Sunfish Photographs, Phillip Colla Photography
- Ocean Sunfish, Mola mola, Natural History Photographs
- Ocean sunfish Photographs, Jens Kuhfs Photography