Ocean sunfish Temporal range: Middle Holocene–present (5,941–0 YBP) [1] | |
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Nordsøen Oceanarium, Denmark | |
Scientific classification ![]() | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Actinopterygii |
Order: | Tetraodontiformes |
Family: | Molidae |
Genus: | Mola |
Species: | M. mola |
Binomial name | |
Mola mola | |
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IUCN distribution of the ocean sunfish Extant (resident) | |
Synonyms [5] | |
List |
The ocean sunfish or common mola (Mola mola) is one of the largest bony fish in the world. It is the type species of the genus Mola, and one of five extant species in the family Molidae. [6] [7] It was once misidentified as the heaviest bony fish, which was actually a different and closely related species of sunfish, Mola alexandrini . [8] Adults typically weigh between 247 and 1,000 kg (545 and 2,205 lb). It is native to tropical and temperate waters around the world. It resembles a fish head without a tail, and its main body is flattened laterally. Sunfish can be as tall as they are long when their dorsal and ventral fins are extended.
Many areas of sunfish biology remain poorly understood,[ needs update ] and various research efforts are underway, including aerial surveys of populations, [9] satellite surveillance using pop-off satellite tags, [10] [9] genetic analysis of tissue samples, [10] and collection of amateur sighting data. [11]
Adult sunfish are vulnerable to few natural predators, but sea lions, killer whales, and sharks will consume them. Sunfish are considered a delicacy in some parts of the world, including Japan, Korea, and Taiwan. In the European Union, regulations ban the sale of fish and fishery products derived from the family Molidae. [12] Sunfish are frequently caught in gillnets.
Its common English name, sunfish, refers to the animal's habit of sunbathing at the surface of the sea.[ citation needed ] Its common names in Dutch, Portuguese, French, Spanish, Catalan, Italian, Russian, Greek, Hungarian, Norwegian, and German (maanvis, peixe lua, Poisson lune, pez luna, peix lluna, Pesce luna, рыба-луна, φεγγαρόψαρο, holdhal, månefisk and Mondfisch, respectively) mean "moon fish", in reference to its rounded shape. In German, the fish is also known as Schwimmender Kopf, or "swimming head". In Polish, it is named samogłów, meaning "head alone" or "only head", because it has no true tail. In Swedish and Danish it is known as klumpfisk, in Dutch klompvis, in Finnish möhkäkala, all of which mean "lump fish". The Chinese translation of its academic name is 翻車魚; fān chē yú, meaning "toppled wheel fish". Many of the sunfish's various names allude to its flattened shape.[ citation needed ]
It was originally classified in the pufferfish family as Tetraodon mola, [13] its epithet mola is Latin for "millstone", [14] which the fish resembles because of its gray color, rough texture, and rounded body. [15] It is now placed in its own genus Mola and family name Molidae [15] as the type species with two other species: Mola tecta and M. alexandrini (previously known as Mola ramsayi). [16] Extinct relatives of Mola mola lived in the Oligocene and Miocene epochs. [17] However, the earliest known fossil remains of Mola mola itself were found in archaeological middens dating to the Holocene epoch. [1]
The common name "sunfish" without qualifier is used to describe the marine family Molidae and the freshwater sunfish in the family Centrarchidae, which is unrelated to Molidae. On the other hand, the name "ocean sunfish" and "mola" refer only to the family Molidae. [6]
It shares many traits common to members in the order Tetraodontiformes including pufferfish, porcupinefish, and filefish like having a beak formed from four fused teeth; sunfish fry resemble spiky pufferfish more than they resemble adult molas. [18]
The caudal fin of the ocean sunfish is replaced by a rounded clavus, creating the body's distinct truncated shape. The body is flattened laterally, giving it a long oval shape when seen head-on. The pectoral fins are small and fan-shaped, while the dorsal fin and the anal fin are lengthened, often making the fish as tall as it is long. Specimens up to 3.3 m (10 ft 10 in) in height have been recorded. [19]
The mature ocean sunfish has an average length of 1.8 m (5 ft 11 in) and a fin-to-fin length of 2.5 m (8 ft 2 in)[ further explanation needed ]. The weight of mature specimens can range[ further explanation needed ] from 247 to 1,000 kg (545 to 2,205 lb), [6] [20] [21] but even larger individuals are not unheard of[ by whom? ]. The maximum size recorded is 3.3 m (10 ft 10 in) in length, [19] [22] and maximum weight recorded is 2,300 kg (5,100 lb). [22]
The spinal column of M. mola contains fewer vertebrae and is shorter in relation to the body than that of any other fish. [23] Although the sunfish descended from bony ancestors, its skeleton contains largely cartilaginous tissues, which are lighter than bone, allowing it to grow to sizes impractical for other bony fishes. [23] [24] Its teeth are fused into a beak-like structure, [25] which prevents them from being able to fully close their mouths, while also having pharyngeal teeth located in the throat. [26]
The sunfish lacks a swim bladder. [23] Some sources[ who? ] indicate the internal organs contain a concentrated neurotoxin, tetrodotoxin, like the organs of other poisonous tetraodontiformes, [25] while others dispute this claim. [10]
In the course of its evolution, the caudal fin (tail) of the sunfish disappeared, to be replaced by a lumpy pseudotail, the clavus. This structure is formed by the convergence of the dorsal and anal fins, [27] [28] and is used by the fish as a rudder. [29] The smooth-denticled clavus retains 12 fin rays and terminates in a number of rounded ossicles. [30]
Ocean sunfish often swim near the surface, and their protruding dorsal fins are sometimes mistaken for those of sharks. [31] However, the two can be distinguished by the motion of the fin. Unlike most fish, the sunfish swings its dorsal fin and anal fin in a characteristic sculling motion. [32]
Adult sunfish range from brown to silvery-grey or white, with a variety of region-specific mottled skin patterns. [6] Coloration is often darker on the dorsal surface, fading to a lighter shade ventrally as a form of countershading camouflage. M. mola also exhibits the ability to vary skin coloration from light to dark, especially when under attack. [6] The skin, which contains large amounts of reticulated collagen, can be up to 7.3 cm (2+3⁄4 in) thick on the ventral surface, and is covered by denticles and a layer of mucus instead of scales. The skin on the clavus is smoother than that on the body, where it can be as rough as sandpaper. [23]
More than 40 species of parasites may reside on the skin and internally, motivating the fish to seek relief in a number of ways. [6] [30] [ clarification needed ] One of the most frequent ocean sunfish parasites is the flatworm Accacoelium contortum . [33]
In temperate regions, drifting kelp fields harbor cleaner wrasses and other fish which remove parasites from the skin of visiting sunfish. In the tropics, M. mola solicits cleaning help from reef fishes. By basking on its side at the surface, the sunfish also allows seabirds to feed on parasites from its skin. Sunfish have been reported to breach, clearing the surface by approximately 3 m (10 ft), in an apparent effort to dislodge embedded parasites. [31] [34]
Ocean sunfish are native to the temperate and tropical waters of every ocean in the world. [23] Mola genotypes appear to vary widely between the Atlantic and Pacific, but genetic differences between individuals in the Northern and Southern hemispheres are minimal. [35]
Although early research suggested sunfish moved around mainly by drifting with ocean currents (which has resulted in the sunfish sometimes being characterized as a megaplankton [36] [37] ), individuals have been recorded swimming 26 km (16 mi) in a day at a cruising speed of 3.2 km/h (1.7 kn). [29]
While this might be the case most of the time, they are also capable of moving rapidly when feeding or avoiding predators, to the extent that they can vertically leap out of water. Contrary to the perception that sunfish spend much of their time basking at the surface, M. mola adults actually spend a large portion of their lives actively hunting at depths greater than 200 m (660 ft), occupying both the epipelagic and mesopelagic zones. [38]
Sunfish are most often found in water warmer than 10 °C (50 °F); [38] prolonged periods spent in water at temperatures of 12 °C (54 °F) or lower can lead to disorientation and eventual death. [32] Surface basking behavior, in which a sunfish swims on its side, presenting its largest profile to the sun, may be a method of "thermally recharging" following dives into deeper, colder water in order to feed. [35] [39] Sightings of the fish in colder waters outside of its usual habitat, such as those southwest of England, may be evidence of increasing marine temperatures. [40] [41]
Sunfish are usually found alone, but occasionally in pairs. [23]
The diet of the ocean sunfish was formerly thought to consist primarily of various jellyfish. However, genetic analysis reveals that sunfish are actually generalist predators that consume mostly small fish, fish larvae, squid, and crustaceans, with jellyfish and salps making up only around 15% of the diet. [42] Occasionally they will ingest eel grass. This range of food items indicates that the sunfish feeds at many levels, from the surface to deep water, and occasionally down to the seafloor in some areas. [6]
Ocean sunfish may live up to ten years in captivity, but their lifespan in a natural habitat has not yet been determined. [31] Their growth rate remains undetermined. However, a young specimen at the Monterey Bay Aquarium increased in weight from 26 to 399 kg (57 to 880 lb) and reached a height of nearly 1.8 m (5 ft 11 in) in 15 months. [32]
The sheer size and thick skin of an adult of the species deters many smaller predators, but younger fish are vulnerable to predation by bluefin tuna and mahi mahi. Adults are consumed by orca, sharks [23] and sea lions. [6] [32]
The mating practices of the ocean sunfish are poorly understood, but spawning areas have been suggested in the North Atlantic, South Atlantic, North Pacific, South Pacific, and Indian oceans. [23]
Females of the species can produce more eggs than any other known vertebrate, [6] up to 300 million at a time. Sunfish fry do not have the large pectoral fins and tail fin of their adult forms, but they have body spines uncharacteristic of adult sunfish, that disappear as they grow.
Females are estimated to be carrying as many as 300 million eggs at one time, more than any other known vertebrate. [6] [43] Sunfish eggs are released into the water and externally fertilized by sperm. [30]
Newly hatched sunfish larvae are only 2.5 mm (3⁄32 in) long and weigh less than one gram. They develop into fry that resemble miniature pufferfish, their close relatives. [30] [44] Young sunfish school for protection, but this behavior is abandoned as they grow. [45] The fry that survive can grow up to 60 million times their original weight before reaching adult proportions, [29] arguably the most extreme size growth of any vertebrate animal. [46] [47]
In 2016, researchers from China National Genebank and A*STAR Singapore, including Nobel laureate Sydney Brenner, sequenced the genome of the ocean sunfish and discovered several genes which might explain its fast growth rate and large body size. As member of the order Tetraodontiformes, like fugu, the sunfish has quite a compact genome, at 730 Mb in size. Analysis from this data suggests that sunfish and pufferfishes diverged approximately 68 million years ago, which corroborates the results of other recent studies based on smaller datasets. [48]
Despite their size, ocean sunfish are docile and pose no threat to human divers. [30] Injuries from sunfish are rare, although a slight danger exists from large sunfish leaping out of the water onto boats. In 2005, a 1 metre (3 feet 3 inches)-long sunfish landed on a 4-year-old boy when the fish leaped onto the boy's family's boat off the coast of Pembrokeshire, Wales. [49] Areas where they are commonly found are popular destinations for sport dives, and sunfish at some locations have reportedly become familiar with divers. [25] They are more of a problem to boaters than to swimmers, as they can pose a hazard to watercraft due to their large size and weight. Collisions with sunfish are common in some parts of the world and can cause damage to the hull of a boat, [50] or to the propellers of larger ships, as well as to the fish. [30]
The flesh of the ocean sunfish is considered a delicacy in some regions, the largest markets being Taiwan and Japan. All parts of the sunfish are used in cuisine, from the fins to the internal organs. [10] Some parts are used in some areas of traditional medicine. [25] Fishery products derived from sunfish are forbidden in the European Union according to Regulation (EC) No 853/2004 of the European Parliament and of the Council, as they contain toxins that are harmful to human health. [12]
Sunfish are accidentally but frequently caught in drift gillnet fisheries, making up nearly 30% of the total catch of the swordfish fishery employing drift gillnets in California. [29] The bycatch rate is even higher for the Mediterranean swordfish industry, with 71% to 90% of the total catch being sunfish. [10] [45]
A decrease in sunfish populations may be caused by more frequent bycatch and the increasing popularity of sunfish in human diet. [23] The fishery bycatch and destruction of ocean sunfish are unregulated worldwide. In some areas, the fish are "finned" by fishermen who regard them as worthless bait thieves; this process, in which the fins are cut off, results in the eventual death of the fish, because it can no longer propel itself without its dorsal and anal fins. [51] The species is also threatened by floating litter such as plastic bags which resemble jellyfish, a common prey item. Bags can choke and suffocate a fish or fill its stomach to the extent that it starves. [31]
Patterns of this fish are seen in sarongs worn by women in Lamalera, a village in the island of Lembata, in the Lesser Sunda Islands of Indonesia. [52]
Sunfish are not widely held in aquarium exhibits, due to the unique and demanding requirements of their care. Some Asian aquaria display them, particularly in Japan. [32] The Kaiyukan Aquarium in Osaka is one of few aquaria with Mola mola on display, where it is reportedly as popular an attraction as the larger whale sharks. [53] The Lisbon Oceanarium in Portugal has ocean sunfish showcased in the main tank, [54] and sunfish are also on display at the Denmark Nordsøen Oceanarium. [55]
In Kamogawa Sea World the ocean sunfish named Kukey, who started captivity in 1982, set a world record for captivity for 2,993 days, living for eight years. Kukey was 72 cm (2.36 ft) at the time of delivery, but was 187 cm (6.14 ft) in size at the time of death. [56] [57]
While the first ocean sunfish to be held in an aquarium in the United States is said to have arrived at the Monterey Bay Aquarium in August 1986, [58] other specimens have previously been held at other locations. Marineland of the Pacific, closed since 1987 and located on the Palos Verdes Peninsula in Los Angeles County, California, held at least one ocean sunfish by 1961, [59] and in 1964 held a 290-kilogram (650 lb) specimen, said to be the largest ever captured at that time. [60] However, another 450-kilogram (1,000 lb) specimen was brought alive to Marineland Studios Aquarium, near St. Augustine, Florida, in 1941. [61]
Because sunfish had not been kept in captivity on a large scale before, the staff at Monterey Bay was forced to innovate and create their own methods for capture, feeding, and parasite control. By 1998, these issues were overcome, and the aquarium was able to hold a specimen for more than a year, later releasing it after its weight increased by more than 14 times. [32] Mola mola has since become a permanent feature of the Open Sea exhibit. [29] Monterey Bay Aquarium's largest sunfish specimen was euthanized on February 14, 2008, after an extended period of poor health. [62]
A major concern to curators is preventive measures taken to keep specimens in captivity from injuring themselves by rubbing against the walls of a tank, since ocean sunfish cannot easily maneuver their bodies. [53] In a smaller tank, hanging a vinyl curtain has been used as a stopgap measure to convert a cuboid tank to a rounded shape and prevent the fish from scraping against the sides. A more effective solution is simply to provide enough room for the sunfish to swim in wide circles. [32] The tank must also be sufficiently deep to accommodate the vertical height of the sunfish, which may reach 3.2 m (10 ft 6 in). [19]
Feeding captive sunfish in a tank with faster-moving, more aggressive fish can also present a challenge. Eventually, the fish can be taught to respond to a floating target to be fed, [63] [ better source needed ] and to take food from the end of a pole or from human hands. [32]
The Tetraodontiformes are an order of highly derived ray-finned fish, also called the Plectognathi. Sometimes these are classified as a suborder of the order Perciformes. The Tetraodontiformes are represented by 10 extant families and at least 349 species overall; most are marine and dwell in and around tropical coral reefs, but a few species are found in freshwater streams and estuaries. They have no close relatives, and descend from a line of coral-dwelling species that emerged around 80 million years ago.
The Molidae comprise the family of the molas or ocean sunfishes, unusual fish whose bodies come to an end just behind the dorsal and anal fins, giving them a "half-fish" appearance. They are also the largest of the ray-finned bony fish, with the southern sunfish, Mola alexandrini, recorded at 4.6 m (15 ft) in length and 2,744 kg (6,049 lb) in weight.
Lancetfishes are large oceanic predatory fishes in the genus Alepisaurus in the monogeneric family Alepisauridae.
The Atlantic blue marlin is a species of marlin endemic to the Atlantic Ocean. It is closely related to, and usually considered conspecific with, the Indo-Pacific blue marlin, then simply called blue marlin. Some authorities consider both species distinct.
The Caesar grunt, also known as the black grunt, blacktail grunt, or redmouth grunt is a species of marine ray-finned fish, a grunt in the family Haemulidae. It is native to the western Atlantic Ocean
The pelagic stingray is a species of stingray in the family Dasyatidae, and the sole member of its genus. It is characterized by the wedge-like shape of its pectoral fin disc, which is much wider than long, as well as by the pointed teeth in both sexes, whip-like tail with extremely long tail spine, and uniform violet to blue-green coloration. It generally reaches 59 cm (23 in) in width. The pelagic stingray has a worldwide distribution in waters warmer than 19 °C (66 °F), and migrates seasonally to spend the summer closer to the continental shelf and at higher latitudes. The only stingray that almost exclusively inhabits the open ocean, this species is typically found in surface waters down to a depth of 100 m (330 ft). As a consequence of its midwater habits, its swimming style has evolved to feature more of a flapping motion of the pectoral fins, as opposed to the disc margin undulations used by other, bottom-dwelling stingrays.
A sunfish, also called a mola, is any fish in the genus Mola. The fish develop their truncated, bullet-like shape because the back fin, which is present at birth, never grows. Instead, it folds into itself as the 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 herring scad, is a common species of tropical marine fish in the jack family Carangidae. The species inhabits the surface waters of coastal regions throughout the Indo-West Pacific region, feeding on a variety of crustaceans and small fishes. It is the largest fish of the scad genus Alepes, growing to a recorded length of 56 cm. The herring scad is identified among the genus Alepes by its more numerous and smaller scutes and the number of gill rakers on the first arch. It is of minor importance to fisheries throughout its range.
Cantherhines dumerilii is a species of fish in the family Monacanthidae, the filefishes. Its common names include whitespotted filefish, barred filefish, orange-fin file, and yelloweye leatherjacket. It is distributed in the Indian and Pacific Oceans where it is found on coral reefs.
The humpback anglerfish is a species of black seadevil in the family of Melanocetidae, which means "black whale" in Greek. The species is named after James Yate Johnson, the English naturalist who discovered the first specimen in Madeira in 1863. The common names include anglerfish, viperfish and fangtoothfish.
The sharptail mola is a species of mola found circumglobally in tropical and temperate waters. It is similar in appearance to the ocean sunfish, but can be distinguished by the projection on its clavus (pseudo-tail). Other common names include sharpfin sunfish, point-tailed sunfish, and trunkfish. Rarely encountered, very little is known of the biology or life history of the sharptail mola. It has recently become important to commercial fisheries operating off eastern Taiwan. This species is the only member of its genus.
Like humans and other animals, fish suffer from diseases and parasites. Fish defences against disease are specific and non-specific. Non-specific defences include skin and scales, as well as the mucus layer secreted by the epidermis that traps microorganisms and inhibits their growth. If pathogens breach these defences, fish can develop inflammatory responses that increase the flow of blood to infected areas and deliver white blood cells that attempt to destroy the pathogens.
The giant sunfish or bumphead sunfish, , is a fish belonging to the family Molidae. It is closely related to the more widely known Mola mola, and is found in the Southern Hemisphere. With a specimen found dead near the Azores in 2021 weighing in at 2744 kg it is the largest extant bony fish species in terms of maximum recorded mass by a wide margin. It can be found basking on its side occasionally near the surface, which is thought to be used to re-heat themselves after diving in cold water for prey, recharge their oxygen stores, and attract gulls to free them of parasites.
The bluestriped grunt, also known as the boar grunt, golden grunt, humpback grunt, redmouth grunt, or yellow grunt, is a species of marine ray-finned fish, a grunt belonging to the family Haemulidae. It is found in the western Atlantic Ocean.
Haemulon flavolineatum, the French grunt, banana grunt, gold laced grunt, open-mouthed grunt, redmouth grunt, or yellow grunt, is a species of marine ray-finned fish, a grunt belonging to the family Haemulidae. It is native to the western Atlantic Ocean.
Guentherus is a genus of jellynose fishes, belonging to the Ateleopodidae family, with two recognized species:
Oxyjulis californica is a species of wrasse native to the eastern Pacific Ocean along the coasts of California and Baja California. Its distribution extends from Salt Point in Sonoma County, California, to southern central Baja California, near Cedros Island. It is a very common species; its common name in Spanish is señorita.
Mola tecta, the hoodwinker sunfish, belongs to the family Molidae and genus Mola. It is closely related to the more widely known ocean sunfish. The Latin word "tecta" means hidden. The word "hidden" was adopted for the name because the fish has blended in among other species of sunfish for a long time and has only been discovered recently. Discovered on a beach near Christchurch, New Zealand, in 2015, it was the first new species of sunfish to be identified in 130 years. Mola tecta are mostly discovered in the temperate region of the Southern Hemisphere in the water near Australia, New Zealand, Southern Chile and Southern Africa. It was first described by Marianne Nyegaard, a marine scientist who studied ocean sunfish for her PhD.
Marianne Nyegaard is a Danish marine biologist who specializes in the study of ocean sunfish. She is known for identifying the ocean sunfish species Mola tecta.
We thus conclude that the molid clavus is unequivocally formed by modified elements of the dorsal and anal fin and that the caudal fin is lost in molids.