Mola (fish)

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Mola
Temporal range: Late Miocene to Recent [1]
MolaMola Lisboa20051020 Modified.jpg
Mola mola
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Tetraodontiformes
Family: Molidae
Genus: Mola
Linck, 1790 [2]
Species

3, See text

A mola or sunfish, is any fish in the genus Mola (family Molidae). They include the heaviest of all bony fishes.

Contents

Description

Molas 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. [3] Mola in Latin means "millstone" and describes the ocean sunfish's somewhat circular shape. [4] [5] They are a silvery colour and have a rough skin texture. [6]

The mola is the heaviest of all the bony fishes: large specimens reach 4.3m (14ft) vertically and 3.0m (10ft) horizontally, and can weigh over 2,700kg (6,000 lb). [7]

Molas inhabit temperate and tropical oceans around the world. [4] 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. Due to their limited thermoregulatory ability and low behavioral responses, sunfish can sometimes overheat while basking at the surface and die as a result. [8] Their teeth are fused into a beak-like structure, and they are unable to fully close their relatively small mouths. [9]

Ocean sunfish can become infested with skin parasites, so they often invite small fish or even birds to feed on them. [10] Sunfish sometimes breach the surface up to 3m (10ft) in the air in an attempt to shake off parasites. [11]

Molas are relatively poor swimmers, waggling their large dorsal and anal fins to move, and steering with their clavus. [12] Their food of choice is jellyfish, though they will eat small fish and large amounts of zooplankton and algae as well. [4] They are harmless to people, but can be very curious and will often approach divers. [13]

Their population is considered vulnerable, [14] as they are frequently snagged in drift gill nets and can suffocate on plastic bags, which resemble jellyfish, their main food source. [15]

They breed by producing around 300 million eggs directly into the ocean, which are externally fertilized by sperm into the water column. [16]

Taxonomy

In 1766, Joseph Kölreuter published a fish name Mola but did not treat it as a Linnaean genus (i.e. not binomial), so the name is invalid under the rules of the ICZN. The first author who used the name Mola as a valid genus was Johann Heinrich Linck the Younger in 1790. Mola is therefore the oldest available name, with Tetraodon mola Linnaeus, 1758 as its type species. [17]

Species

There are currently 3 recognized extant species in this genus: [18] [19]

References

  1. Sepkoski, J. (2002). "A compendium of fossil marine animal genera". Bulletins of American Paleontology. 364: 560. Archived from the original on 2011-12-07.
  2. Welter-Schultes, F.W., V. Feuerstein (2008) Nomenclatural notes on Torpedo (Chondrichthyes: Torpedinidae) and some other early established fish taxa (Actinopterygii: Molidae, Eleginopidae and Citharinidae). Species, Phylogeny and Evolution 1(3):141-145.
  3. "Ocean Sunfish (Mola) | National Geographic". Animals. 2010-11-11. Retrieved 2025-09-11.
  4. 1 2 3 "Mola mola (Ocean sunfish)". FishBase. Retrieved 26 August 2025.
  5. Eschmeyer, William N. (2016). The Diversity of Fishes: Biology, Evolution, and Ecology (2nd ed.). Wiley-Blackwell.
  6. Yoshita, T. (2009). "Morphological studies on the ocean sunfish, Mola mola". Ichthyological Research. 56: 162–172. doi:10.1007/s10228-008-0071-5 (inactive 5 September 2025).{{cite journal}}: CS1 maint: DOI inactive as of September 2025 (link)
  7. Cartamil, D. (2011). "Ocean sunfish in the eastern Pacific: distribution, biology and ecology". Journal of Experimental Marine Biology and Ecology. 398 (1): 47–53. doi:10.1016/j.jembe.2010.12.017 (inactive 5 September 2025).{{cite journal}}: CS1 maint: DOI inactive as of September 2025 (link)
  8. "Ocean Sunfish (Mola mola)". Monterey Bay Aquarium. Retrieved 26 August 2025.
  9. Fraser-Brunner, A. (1951). "The ocean sunfishes (Family Molidae)". Bulletin of the British Museum (Natural History), Zoology. 1 (6): 87–121.
  10. Nakatsubo, T. (2007). "Cleaning symbiosis of the ocean sunfish Mola mola by the albatross Diomedea spp". Marine Biology. 150: 731–736. doi:10.1007/s00227-006-0384-4 (inactive 5 September 2025).{{cite journal}}: CS1 maint: DOI inactive as of September 2025 (link)
  11. "Sunfish Breaching". Natural History Museum (London). 2018-06-05. Retrieved 26 August 2025.
  12. Fish, F. E. (1998). "Biomechanics and energetics of swimming in the ocean sunfish, Mola mola". Journal of Zoology. 246 (3): 419–426. doi:10.1111/j.1469-7998.1998.tb00173.x.
  13. "Ocean Sunfish Fact Sheet". NOAA. Retrieved 26 August 2025.
  14. Liu, J.; Zapfe, G.; Shao, K.-T.; Leis, J.L.; Matsuura, K.; Hardy, G.; Liu, M.; Robertson, R.; Tyler, J. (2016) [errata version of 2015 assessment]. "Mola mola". IUCN Red List of Threatened Species . 2015 e.T190422A97667070. Retrieved 24 September 2025.
  15. Pope, E. C. (2010). "The biology and conservation of the ocean sunfish Mola mola: a review". Reviews in Fish Biology and Fisheries. 20: 471–487. doi:10.1007/s11160-009-9130-4 (inactive 5 September 2025).{{cite journal}}: CS1 maint: DOI inactive as of September 2025 (link)
  16. "Ocean Sunfish". Oceana. Retrieved 2025-09-11.
  17. Fraser-Brunner, A. (1951). "The ocean sunfishes (Family Molidae)". Bulletin of the British Museum (Natural History), Zoology. 1 (6): 87–121.
  18. Matsuura, K (2014). "Taxonomy and systematics of tetraodontiform fishes: a review focusing primarily on progress in the period from 1980 to 2014". Ichthyological Research. 62 (1): 72–113. doi: 10.1007/s10228-014-0444-5 .
  19. Nyegaard, Marianne; Sawai, Etsuro; Gemmell, Neil; Gillum, Joanne; Loneragan, Neil R.; Yamanoue, Yusuke; Stewart, Andrew L. (19 July 2017). "Hiding in broad daylight: molecular and morphological data reveal a new ocean sunfish species (Tetraodontiformes: Molidae) that has eluded recognition". Zoological Journal of the Linnean Society. 182 (3): 631–658. doi:10.1093/zoolinnean/zlx040.