Mola Fish

Mola fish are also known as ocean sunfish. Any fish in the Mola genus is known as a sunfish (or mola) (belonging to the family Molidae). Mola is a Latin word that means "millstone" and characterizes the form of the ocean sunfish.

Because their rear fin, which they are born with, never develops, the Mola fish have a truncated, bullet-like form. Instead, when the organism grows older, it folds in on itself, forming a clavus, a rounded rudder.

The mola is the heaviest of all the bony fish, reaching 14 feet (4.3 meters) vertically and 10 feet (3.0 meters) horizontally and weighing almost 5,000 pounds in big individuals (2,300 kg). Sharks and rays are cartilaginous fish, therefore they may be quite large. Mola may be found all over the world in temperate and tropical seas. 

They are commonly observed near the surface sunbathing in the sun, and their massive dorsal fins are commonly mistaken for sharks when they come above the water. Their teeth have fused into a beak-like shape, preventing them from fully closing their tiny jaws.

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Ocean sunfish may become so infected with parasites on their skin that they will often entice tiny fish or even birds to eat them. In an attempt to shake off the parasites, sunfish will break the surface up to 10 feet (3 meters) in the air.

They're awkward swimmers, guiding with their clavus and waggling their huge dorsal and anal fins to move. Jellyfish are their preferred diet, although they may also consume tiny fish, zooplankton, and algae in large quantities.

They are not dangerous to humans, although they are curious and frequently approach divers.

Though they are regularly trapped in drift gillnets and can choke on sea debris such as plastic bags, their population is thought to be steady (which resemble jellyfish). Let us learn more about the family of Mola- Molidae.

Molidae

The molas, or ocean sunfishes, belong to the Molidae family of fish, which have unique bodies that finish just beyond the dorsal and anal fins, giving them a "half-fish" look. The ocean sunfish Mola mola and southern sunfish Mola Alexandrini, both up to 4.6 m (15 ft) in length and 2,300 kg (5,100 lb) in weight, are the biggest of the ray-finned bony fish. Mola mola, for example, has only 16 vertebrae, the fewest of any fish. They also have no caudal bones, and their skeletons are mostly made of cartilage. There are no bone plates in the skin, but it is thick and dense like cartilage and very rough. They don't have swim bladders either. Molids primarily swim with their anal and dorsal fins, with the pectoral fins likely serving as stabilizers. They use a powerful jet of water squirted from their mouths or gills to steer. They may also make small changes to the anal or dorsal fin's position to regulate the amount of force generated and the angle at which it is generated. They utilize their fins similarly to how birds use their wings in this regard.

Molids are thought to be able to create sound by crushing their long, claw-like pharyngeal teeth. Their teeth are fused into a beak-like shape, making it difficult for them to seal their mouths, as is typical of Tetraodontiformes. Despite this, they prefer soft-bodied creatures like jellyfish and salps, however, they may also eat tiny fish and crabs. Other animals have been filmed interacting with molids. Cleaner fish are used by molids because they are sensitive to skin parasites. Halfmoon live in an area of floating algae or flotsam that a molid in need of cleaning will find.

Molid prepares for cleaning by swimming almost vertically with its head at the water's top and then waits for the smaller cleaner fish to eat on the parasite worms. Similarly, Molid's dorsal fin and mouth may breach the surface of the water to attract the attention of a gull or other seabird. The molid's ski will then be dug clean of worms and other parasites by Seabird. The genus Eomola, which includes the species E. bimaxillaria Tyler and Bannikov, 1992 from the Upper Eocene of the North Caucasus, has a known fossil history dating back to the Eocene. The Lower Miocene Ebelsberg Formation in Pucking, Austria, contains the fossil genus Austromola, which has one species, A. angerhoferi Gregorova, Schultz, Harzhauser & Kroh, 2009. 

Species of Mola

This genus presently has three known species:

• Mola mola (Linnaeus, 1758) (Ocean sunfish)

• Mola alexandrini (Giglioli, 1883) (Southern sunfish)

• Mola tecta Nyegaard et al., 2017 (Hoodwinker sunfish) 

Naming and Taxonomy

Many of the sunfish's many names refer to its flattened form. Mola is Latin for "millstone," which the fish resembles due to its grey hue, rough texture, and spherical body. The animal's popular English name, sunfish, relates to its habit of basking on the water's surface. Maanvis, peixe Lua, Poisson lune, pez luna, peix lluna, Pesce luna, ра-луна, o, mnefisk, and Mondfisch are its common names in Dutch, Portuguese, French, Spanish, Catalan, Italian, Russian, Greek, Norwegian, and German, and relate to its spherical form. The fish is also known as Schwimmender Kopf, or "swimming head" in German. Because it lacks a genuine tail, it is known as samogów in Polish, which means "head alone" or "just head." It is known as klumpfisk in Swedish, Danish, and Norwegian, klompvis in Dutch, and möhkäkala in Finnish, all of which mean "lumpfish." The Chinese translation of its scientific name is fān chē yú 翻車魚, which means "toppled wheel fish." The ocean sunfish has many outdated binomial synonyms and was previously classified as Tetraodon mola in the pufferfish genus. Mola is now its own genus, with two species: Mola mola and Mola alexandrini (previously known as Mola ramsayi). The ocean sunfish, Mola mola, is the genus's type species. The genus Mola belongs to the family Molidae. This family comprises three genera: Masturus, Mola, and Ranzania. The common name "sunfish" is used without qualification to designate both the marine family Molidae and the freshwater family Centrarchidae, which is unrelated to Molidae. The terms "ocean sunfish" and "mola," on the other hand, exclusively apply to the family Molidae. The Molidae family is part of the order Tetraodontiformes, which also contains pufferfish and filefish. Many characteristics are shared by members of this order, notably the four fused teeth that create the distinctive beak and give the order its name (tetra=four, odous=tooth, and forma=shape). Sunfish fry, in fact, resemble spiky pufferfish more than adult molas. 

Description

The ocean sunfish's caudal fin is replaced with a rounded clavus, giving the body its distinctive truncated form. When viewed from above, the body is flattened laterally, giving it a long oval appearance. The pectoral fins are tiny and fan-shaped, but the dorsal and anal fins are extended, resulting in a fish that is often as tall as it is long. Specimens up to 3.3 m tall have been discovered. The mature ocean sunfish is 1.8 m (5 ft 11 in) in length and 2.5 m from fin to fin (8 ft 2 in). Mature specimens can weigh between 247 and 1,000 kg (545 and 2,205 lb), though bigger individuals are not uncommon. The maximum length is 3.3 m (10 ft 10 in), the width of the fins is 4.2 m (13 ft 9 in), and the mass is up to 2,300 kg (5,070 lb). M. mola's spinal column has fewer vertebrae and is shorter in relation to the body than that of any other fish. Although the sunfish came from bony predecessors, its skeleton is mostly made up of cartilaginous tissues, which are lighter than bone and allow it to grow to proportions that other bony fishes cannot. Its teeth are fused into a beak-like structure, preventing them from fully closing their jaws, and it also has pharyngeal teeth in the throat. The sunfish does not have a swim bladder.

Some authors say that the internal organs, like the organs of other deadly tetraodontiformes, contain a concentrated neurotoxin called tetrodotoxin, but others disagree.

Fins

The sunfish's caudal fin (tail) vanished throughout evolution, to be replaced with a lumpy pseudo tail known as the clavus. This structure is produced by the convergence of the dorsal and anal fins and serves as a rudder for the fish. The smooth-denticled clavus has 12 fin rays and ends with a number of rounded ossicles. Ocean sunfish frequently swim near the surface, and their projecting dorsal fins are occasionally confused with shark fins. The motion of the fin, however, distinguishes the two. The sunfish, unlike other fish, swings its dorsal and anal fins in a sculling action.

Skin

Adult sunfish vary in colour from brown to silvery-grey to white, with a variety of mottled skin patterns that vary by area. As a kind of countershading camouflage, colouration is generally darker on the dorsal surface, diminishing to a lighter shade ventrally. M. mola may also change its skin colour from light to black, especially when under assault. The skin, which has a high concentration of reticulated collagen, maybe up to 7.3 cm thick on the ventral surface and is covered with denticles and a mucus layer rather than scales. The skin on the clavus is smoother than the skin on the rest of the body, which can be as rough as sandpaper. More than 40 parasite species can live on the fish's skin and inside, causing them to seek comfort in a variety of ways. The flatworm Accacoelium contortum is a common ocean sunfish parasite.

Drifting kelp fields in temperate climates are home to cleaning wrasses and other fish that remove parasites from the skin of visiting sunfish.

M. mola solicits cleaning assistance from reef fishes in the tropics. The sunfish allows seabirds to feed on parasites from their skin by sunbathing on its side at the surface. Sunfish have been observed breaching, clearing the surface by around 3 m (10 ft) in an apparent attempt to remove imbedded parasites.

Range and Behaviour

Ocean sunfish are found in all of the world's oceans, both temperate and tropical. Mola genotypes appear to differ significantly across the Atlantic and Pacific, although genetic variations between individuals in the Northern and Southern hemispheres appear to be minor. Despite early studies suggesting that sunfish traveled mostly by drifting with ocean currents, individuals have been recorded swimming 26 km (16 mi) in a day at a cruising speed of 3.2 km/h. While this is true most of the time, they can also move quickly while eating or escaping predators, to the point where they can vertically leap out of the water. Contrary to popular belief, adults of M. mola spend the majority of their time actively hunting at depths greater than 200 m (660 ft), inhabiting both the epipelagic and mesopelagic zones. Sunfish are most commonly found at water temperatures higher than 10 °C (50 °F); prolonged exposure to water temperatures of 12 °C (54 °F) or below can cause disorientation and death. Surface basking, in which a sunfish floats on its side, exposing its biggest profile to the sun, maybe a way of "thermally recharging" after dives into deeper, cooler water to eat. Sightings of the fish in colder waters outside of its usual habitat, such as that southwest of England, maybe evidence of rising sea temperatures, though, given England's southwestern coast's proximity to the Gulf Stream, many of these sightings could also be the result of the fish being carried to Europe by the current. Sunfish are generally found alone, although they can also be found in couples.

Feeding

Previously, it was assumed that the ocean sunfish's diet consisted largely of different jellyfish. However, genetic study shows that sunfish are generalist predators that mostly devour tiny fish, fish larvae, squid, and crustaceans, with jellyfish and salps accounting for just around 15% of the diet. They will occasionally consume eelgrass. This diversity of food items suggests that the sunfish eats on a variety of levels, from the surface to deep water and, in some cases, all the way down to the bottom.

Lifecycle

Ocean sunfish can survive in captivity for up to 10 years, but their natural lifetime has yet to be established. Their rate of growth is unknown. A baby specimen at the Monterey Bay Aquarium, on the other hand, grew in weight from 26 to 399 kg (57 to 880 lb) and in height from almost 1.8 m (5 ft 11 in) in 15 months. Many smaller predators are deterred by an adult's sheer size and thick skin, but juvenile fish are vulnerable to predation by bluefin tuna and mahi-mahi. Orcas, sharks, and sea lions devour adults. The ocean sunfish's mating habits are unknown, however spawning locations have been proposed in the North Atlantic, South Atlantic, North Pacific, South Pacific, and Indian seas. Females are thought to carry up to 300 million eggs, more than any other known vertebrate. Sunfish eggs are discharged into the water and are fertilized externally by sperm. Sunfish larvae are just 2.5 mm (3/32 in) long and weigh less than one gram when they hatch. They mature into fry, and those that survive can grow up to 60 million times their initial size before reaching adult size, perhaps the most dramatic size increase of any vertebrate species.

Sunfish fry resembles small pufferfish, their near cousins, with big pectoral fins, a tail fin, and body spines atypical of adult sunfish. Sunfish that are young will school for safety, but as they mature, they will forsake this habit.