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Bichir

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For the Lebanese-Mexican family, see Bichir family.

Bichir
Temporal range: Late Cretaceous–Recent[1]
Nile bichir Polypterus bichir
Barred bichir Polypterus delhezi
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Subclass: Cladistia
Order: Polypteriformes
Bleeker, 1859
Family: Polypteridae
Bonaparte, 1835
Type species
Polypterus bichir
Genera

Erpetoichthys
Polypterus
See text for species.

Red: Polypterus extant , Light red: Polypterus possibly extant , Blue: Erpetoichthys extant

Bichirs /ˈbɪʃɪərz/ and the reedfish comprise Polypteridae /pɒlɪpˈtɛrɪdiː/, a family of archaic ray-finned fishes and the only family in the order Polypteriformes /pəˈlɪptərɪfɔːrmiːz/.[2]

All the species occur in freshwater habitats in tropical Africa and the Nile River system, mainly swampy, shallow floodplains and estuaries.

Cladistia, polypterids and their fossil relatives, are considered the sister group to all other extant ray-finned fishes (Actinopteri).[3][4] They likely diverged from Actinopteri at least 330 million years ago. A closely related group, the Scanilepiformes, are known from the later Permian to the Triassic, and are likely ancestral to polypterids. The oldest polypterids are around 100 million years old, from the early Late Cretaceous of South America and Africa.[5][6][7]

Anatomy

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Polypterids are elongated fish with a unique series of dorsal finlets which vary in number from seven to 18, instead of a single dorsal fin. Each of the dorsal finlets has bifid (double-edged) tips, and are the only fins with spines; the rest of the fins are composed of soft rays. The body is covered in thick, bonelike, and rhombic (ganoid) scales. Their jaw structure more closely resembles that of the tetrapods than that of the teleost fishes. Bichirs have a number of other primitive characteristics, including fleshy pectoral fins superficially similar to those of lobe-finned fishes.[1] They also have a pair of slit-like spiracles on the top of their heads that are used to breathe air,[8] two gular plates, and paired ventral lungs.[9] Both lungs are unchambered sacs. The larger right lung reaches the whole length of the body cavity, while the smaller left lung extends to the stomach. A slit-like opening called the glottis located on the ventral side of the oesophagus leads to the right lung, and a separate opening on the right lung leads to the left lung.[10] Four pairs of gill arches are present.[11]

Polypterids have a maximum body length ranging from 25 cm (9.8 in) to over 100 cm (39 in) depending on specific species and morphology.[12]

Diet and traits

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Polypterids are nocturnal and feed on small vertebrates, crustaceans, and insects.[1] Their common aquarium diet includes bloodworms (Chironomidae larvae). Polypterids are known to have extraordinary olfactory ability.[citation needed] Polypterid reproduction consists of the female laying anywhere from 100 to 300 eggs over the span of a few days, and subsequent fertilization by the male.[13]

Air breathing

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Polypterids possess paired lungs which connect to the esophagus via a glottis. They are facultative air-breathers, accessing surface air to breathe when the water they inhabit is poorly oxygenated.[14] Their lungs are highly vascularized to facilitate gas exchange. Deoxygenated arterial blood is brought to the lungs by paired pulmonary arteries, which branch from the fourth efferent branchial arteries (artery from the fourth gill arch), and oxygenated blood leaves the lungs in pulmonary veins. Unlike most lungfish and tetrapods, their lungs are smooth sacs instead of alveolated tissue. Polypterids are unique in that they breathe using recoil aspiration.[14] Polypterids appear to prefer breathing air via their spiracles when undisturbed or in extremely shallow waters where they are unable to incline their body enough to breathe air through their mouth.[8]

Polypterids as aquarium specimens

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Polypterids are popular subjects of public and large hobby aquaria. They are sometimes called dragon bichir or dragon fin in pet shops for a more appealing name due to their dragon-like appearance. Though predatory, they are otherwise peaceful, preferring to lie on the bottom (they tend to swim when there are lots of large plants present), and make good tankmates with other species large enough to not be prey but small enough to not eat them. Some aquarists note that pleco catfish eat the slime coat off of polypterids. Polypterids in captivity have life expectancies of 10–30+ years. They do well in heavily planted tanks as it mimics their natural habitat.

Classification

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In addition to the extinct genus Bawitius, the two living genera, Polypterus and Erpetoichthys, have 14 extant species:[12]

Phylogeny of Polypteridae.[3][4]
Polypteridae

Erpetoichthys calabaricus

Polypterus

P. retropinnis

P. congicus

P. ansorgii

P. endlicheri

P. bichir

P. mokelembembe

P. ornatipinnis

P. weeksii

P. teugelsi

P. palmas

P. senegalus

P. delhezi

P. polli

Restoration of †Bawitius
Polypterus endlicherii
Polypterus ornatipinnis
Polypterus delhezi

Order Polypteriformes

Suborder Polypterioidei

Clade Salamandrophysida

References

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  1. ^ a b c Wiley, Edward G. (1998). Paxton, J.R.; Eschmeyer, W.N. (eds.). Encyclopedia of Fishes. San Diego: Academic Press. pp. 75–76. ISBN 978-0-12-547665-2.
  2. ^ Helfman GS, Collette BB, Facey DE, Bowen BW. 2009. The Diversity of Fishes. West Sussex, UK: Blackwell Publishing. 720 p.
  3. ^ a b Suzuki, D.; Brandley, M. C.; Tokita, M. (2010). "The mitochondrial phylogeny of an ancient lineage of ray-finned fishes (Polypteridae) with implications for the evolution of body elongation, pelvic fin loss, and craniofacial morphology in Osteichthyes". BMC Evolutionary Biology. 10: 209. doi:10.1186/1471-2148-10-209. PMC 3055249. PMID 20624284.
  4. ^ a b Dai Suzuki, Matthew C. Brandley, Masayoshi Tokita: CORRECTION: The mitochondrial phylogeny of an ancient lineage of ray-finned fishes (Polypteridae) with implications for the evolution of body elongation, pelvic fin loss, and craniofacial morphology in Osteichthyes. BMC Evolutionary Biology. Bd. 10, Art.-Nr. 209, 2010, doi:10.1186/1471-2148-10-209
  5. ^ Near, Thomas J.; Dornburg, Alex; Tokita, Masayoshi; Suzuki, Dai; Brandley, Matthew C.; Friedman, Matt (April 2014). "Boom and Bust: Ancient and Recent Diversification in Bichirs (Polypteridae: Actinopterygii), A Relictual Lineage of Ray-Finned Fishes". Evolution. 68 (4): 1014–1026. doi:10.1111/evo.12323. PMID 24274466. S2CID 8026535.
  6. ^ Giles, Sam; Xu, Guang-Hui; Near, Thomas J.; Friedman, Matt (2017-09-14). "Early members of 'living fossil' lineage imply later origin of modern ray-finned fishes". Nature. 549 (7671): 265–268. Bibcode:2017Natur.549..265G. doi:10.1038/nature23654. ISSN 0028-0836. PMID 28854173. S2CID 205259531.
  7. ^ Bakaev, A. S.; Kogan, I. (2022). "Squamation of the Permian actinopterygian Toyemia Minich, 1990: evenkiid (Scanilepiformes) affinities and implications for the origin of polypteroid scales". www.geology.cz. Retrieved 2024-02-28.
  8. ^ a b Graham, Jeffrey (2014). "Spiracular air breathing in polypterid fishes and its implications for aerial respiration in stem tetrapods". Nature Communications. 5: 3022. Bibcode:2014NatCo...5.3022G. doi:10.1038/ncomms4022. PMID 24451680.
  9. ^ Berra, Tim M. (2001). Freshwater Fish Distribution. San Diego: Academic Press. ISBN 0-12-093156-7
  10. ^ Zaccone, Giacomo; Mauceri, Angela; Maisano, Maria; Fasulo, Salvatore (May 2009). "Innervation of lung and heart in the ray-finned fish, bichirs". Acta Histochemica. Nervous regulation of internal organs in fishes. 111 (3): 217–229. doi:10.1016/j.acthis.2008.11.013. PMID 19121535.
  11. ^ AccessScience | Encyclopedia Article | Polypteriformes
  12. ^ a b Froese, Rainer; Pauly, Daniel (eds.). "Family Polypteridae". FishBase. October 2023 version.
  13. ^ "Breeding Bichirs". www.aquaticcommunity.com. Retrieved 2021-08-27.
  14. ^ a b Graham, J.B. 1997. Air-breathing Fishes: Evolution, diversity, and adaptation. San Diego: Academic Press. 299 p.
  15. ^ Otero; Likius; Vignaud & Brunet (2006). "A new polypterid fish: Polypterus faraou sp. nov. (Cladistia, Polypteridae) from the Late Miocene, Toros-Menalla, Chad". Zoological Journal of the Linnean Society. 146 (2): 227. doi:10.1111/j.1096-3642.2006.00201.x.
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