Mirapinna is a genus of fish in the family Cetomimidae only known from the Atlantic Ocean near the Azores. It was formerly considered a member of the no-longer-recognized family Mirapinnidae, and the only known member of its genus is Mirapinna esau.
Mirapinna esau grows to a length of 5.5 centimetres (2.2in)total length (TL). Little is known of the fish beyond its appearance. Wheeler (1977) states that only one specimen was caught, near the sea surface, and that it was a copepod feeder.[2][3] The original specimen was captured north of the Azores at 47°20'North, 22°30'West.[4] The Mirapinna Esau is a mysterious fish to many. Known to the scientific community as the “hairy fish,” these epidermal growths are thought to produce toxins due to the large granular cells that aid in secretion. (Halstead et. al 2009). Mirapinnidae and its hair-like protrusions extend from the head of the organism to the caudal peduncle. Each hair is approximately 1.5 mm in length and is more abundant on the outer coverings of the pelvic fins as well as the pectoral fins. Members of the former Mirapinnidae lack both scales and a lateral line. They possess vertical jaws, and have a streamer that can extend from the body on the posterior side. The Mirapinnidae specimens accounted for in the study done ranged from 5 to 56 mm (Johnson et. al 2009). All species recorded were juveniles thus, the morphological differences between sexes were not specified in the study.
Etymology
The generic name is from the Latin mirus (wonderful) and pinna (thorn), for the unusual fins possessed by this fish.[5] The specific name, Mirapinna esau, is from the Biblical figure Esau, who is stated to be a hairy man (Genesis 27:11).[6]
Systematics
The taxonomy of the Mirapinna esau has long been debated. A recent study in 2009 on the systematics showed that the Mirapinna esau is not a single and separate species, but rather the larval form of the flabby whalefish species; Procetichthys kreffti a member of the family Cetomimdae (Johnson et. al 2009). A study done by A.E. Parr (1946) concluded that Barbourisia should be included witin the Cetomimdae family prior to the claims that the anatomical features, such as fully develoed pelvic fins, were taxonomically significant (Parr 1946). The Mirapinnidae belong to the family Cetomimdae, which is known for dwelling in bathypelagic waters and representing a basal lineage that carries ancestral traits such as a developed nasal organ and pseudobranch (Paxton 2000). Species within the Centomimdae family exhibit traits of sexual dimorphism and sex specified morphological characteristics that still have no known function; such as traits like cavernous tissue near the caudal end of the fish ( Kimura 2023). The family of Cetomimidae generally are small in size with large terminal mouths and small eyes and can be seen in a variation of brown or dark to black coloration (Vierira et. al 2012).
Distribution
Distribution of the Cetomimidae, including Mirapinna esau, can be found in the vast bathypelagic zone; which is located at the bottom of the ocean, and is both vast and dark. Only specially adapted organisms can thrive in this type of environment due to the hydrostatic pressure difference and its complete lack of light ( Eckley 2021). Adaptations due to the depth include the reduction of the eye-to-head ratio as well as an enlarged gape that is best fit for fecundity (Eckley 2021). Cetomimidae, as aloof as it is in research, is quite contrasted in actual nature. The mixture of biomes and other bodies of water pinpoint the Cetomimidae to be located in a variety of cosmopolitan distributions and can be mainly found in Brazilian waters (Eckley 2021).
Life History
New morphological studies reveal a new organ found in the pink flabby whalefish (Cetostoma regani). This organ is connected to the esophagus of the female whalefish on the post-dorsal side near the branchial arches (Kimura 2023). At first glance, this organ appears complex, presenting two openings into the esophagus of the female whalefish. Observations show thin epidermal tissue (Kimura 2023). It can be inferred that only females carry this specialized organ. Stromateiforms with similar esophageal specialized organs are known to have the function of shredding as well as grinding food (Kimura 2023). Organisms that belong to Cetomimidae are scaleless and smooth with an absence of pelvic fins (Parr 1946). Fishes that belong to this family have noticeably absent external scales and the loss of the pelvic fins is predominantly seen in females (Mincarone et. al 2014). This is significant as the taxonomy of Mirapinnidae has been the subject of debate for many years. The Mirapinna esau was proposed to have similarities to Kasidoridae due to the similarities in jaw structures however, it was reanalyzed as the larval form of Procetichthys Kreffti (Richard 1966). Cetomimidae start out as mirapinnid larvae and are small with elongated bodies that have pelvic fins similar in shape to those of wings, as well as jugular insertion with a long caudal streamer. Transitioning to adulthood, they become Cetomimidae (Herrera et. al 2016). The feeding habits of deep-sea fish depend on the vertical migrations of zooplankton. Many catch their prey in what is known as the benthic boundary layer, as the prey are not directly at the bottom (Herrera et. al 2016). Feeding patterns were very large during the early mornings with mainly meso-bathypelagic fish during that time frame, to then switch to shrimp in the afternoons (Herrera et. al 2016).
Conservation Status
There are currently no known conservation efforts present for Mirapinna esau or for the rest of the Cetomimdae family. The difficulty in sourcing and catching this species could be due to the benthic depths of the ocean as well as its high-pressure surroundings. This could be a contributing factor, making collecting specimens extremely difficult and dangerous.
Only 12 species total have been collected using an open net system of 8 meters with a 13 mm cod-end (Viera et. al 2012). Many popular research tools that hold documentation for thousands of fish species have a record of spotting 16 members of the Cetomimidae family from the Monterey Bay aquarium.
Due to the deep-sea environment in which they inhabit, it can be inferred that this population of fish is negatively impacted by deep-sea mining, as a study done in 2019 showed that mining removed important substrate as well as outwardly interfered with the organisms; causing impairment in growth and reproduction (Christiansen et. al 2019). Not only does deep sea mining continuously decimate habitats and the actual organisms themselves, but there have been causal effects on the overall populations of species heterozygosity that can cause a decline in beneficial alleles over deleterious alleles and shape the trajectory of the well-being of the population, and can lead to irreversible damage (Simon- lledo et. al 2019).
Roa-Varón, A.; Iwamoto, T. (2019). "Mirapinna esau". IUCN Red List of Threatened Species. 2019 e.T67965135A60786431. doi:10.2305/IUCN.UK.2019-2.RLTS.T67965135A60786431.en. Retrieved 5 March 2025. 2. "Hairyfish - Mirapinna esau - Details - Encyclopedia of Life". Encyclopedia of Life. Retrieved 5 May 2014. 3. Wheeler, A. (1977). Das Grosse Buch der Fische. Stuttgart: Eugen Ulmer. p. 356. 4. Froese, Rainer; Pauly, Daniel (eds.). "Mirapinna esau". FishBase. August 2012 version. Retrieved 5 May 2014. 5. "Mirapinna esau". Discover Life. Retrieved 5 May 2014. based on Romero, P. 2002, Madrid, unpublished. 6. Isaak, Mark. "Curiosities of Biological Nomenclature: Etymology: Names from Mythology". Retrieved 5 May 2014 7. Australian, media.australian.museum/media/Uploads/Journals/17707/141_complete.pdf. Accessed 16 Oct. 2025. 8. Christiansen, Bernd, et al. “Potential effects of deep seabed mining on pelagic and benthopelagic biota.” Marine Policy, vol. 114, Apr. 2020, p. 103442, https://doi.org/10.1016/j.marpol.2019.02.014. 9. Eckley, Rachael. “Journey Into Midnight: Population Dynamics, Vertical Distribution, Journey Into Midnight: Population Dynamics, Vertical Distribution, and Trophic Ecology of Whalefishes (Cetomimidae) in the and Trophic Ecology of Whalefishes (Cetomimidae) in the Bathypelagic Gulf of Mexico Bathypelagic Gulf of Mexico .” Nova Southeastern University , 21 Apr. 2021. 10. Halstead, Bruce W., et al. “On the morphology of the ‘hairs’ of the rare deep sea fish, mirapinna esau.” Annals and Magazine of Natural History, vol. 10, no. 118, Oct. 1957, pp. 767–768, https://doi.org/10.1080/00222935708656030. 11. Herrera, Guillermo A, et al. “Record of a larval whalefish (family Cetomimidae) from near the Juan Fernandez Seamounts, southeastern Pacific Ocean.” Revista de Biología Marina y Oceanografía, vol. 51, no. 1, Apr. 2016, pp. 171–174, https://doi.org/10.4067/s0718-19572016000100016. 12. Johnson, G. David, et al. “Deep-sea mystery solved: Astonishing larval transformations and extreme sexual dimorphism unite three fish families.” Biology Letters, vol. 5, no. 2, 20 Jan. 2009, pp. 235–239, https://doi.org/10.1098/rsbl.2008.0722. 13. Kimura, Katsuya. “An Enigmatic Internal Organ Discovered in Pink Flabby Whalefish, Cetostoma Regani (Teleostei: Cetomimidae) - Ichthyological Research.” SpringerLink, Springer Japan, 3 Nov. 2023, link.springer.com/article/10.1007/s10228-023-00932-2. 14. Modica, L., et al. “Food consumption of five deep‐sea fishes in the Balearic Basin (western Mediterranean Sea): Are there daily feeding rhythms in fishes living below 1000 m?” Journal of Fish Biology, vol. 85, no. 3, 22 July 2014, pp. 800–820, https://doi.org/10.1111/jfb.12459. 15. Parr, A. E. “On taxonomic questions related to the classification of Barbourisia, the Cetomimidae and the INIOMI.” Copeia, vol. 1946, no. 4, 30 Dec. 1946, p. 260, https://doi.org/10.2307/1438122. 16. Paxton, John R. “Synopsis of the whalefishes (family Cetomimidae) with descriptions of four new genera.” Records of the Australian Museum, vol. 41, no. 2, 22 Sept. 1989, pp. 135–206, https://doi.org/10.3853/j.0067-1975.41.1989.141. 17. 18. Robins, C. Richard. “Additional Comments on the Structure and Relationships of the Mirapinniform Fish Family Kasidoroidae.” Latest TOC RSS, University of Miami - Rosenstiel School of Marine, Atmospheric & Earth Science, 1 Dec. 1966, www.ingentaconnect.com/content/umrsmas/bullmar/1966/00000016/00000004/art00005#. 19. Simon-Lledó, Erik, et al. “Biological effects 26 years after simulated deep-sea mining.” Scientific Reports, vol. 9, no. 1, 29 May 2019, https://doi.org/10.1038/s41598-019-44492-w. 20. Vieira, R. P., et al. “First record of the deep‐water whalefish cetichthys indagator (Actinopterygii: Cetomimidae) in the North Atlantic Ocean.” Journal of Fish Biology, vol. 81, no. 3, 16 July 2012, pp. 1133–1137, https://doi.org/10.1111/j.1095-8649.2012.03378.x.
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