| Bichir | |
|---|---|
 | |
| Nile bichirPolypterus bichir | |
 | |
| Barred bichirPolypterus delhezi | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Subclass: | Cladistia |
| Order: | Polypteriformes Bleeker, 1859 |
| Family: | Polypteridae Bonaparte, 1835 |
| Type species | |
| Polypterus bichir Lacépède,1803 | |
| Genera | |
Erpetoichthys | |
 | |
| Red:Polypterus extant, Light red:Polypterus possibly extant, Blue:Erpetoichthys extant | |
Bichirs/ˈbɪʃɪərz/ and thereedfish comprisePolypteridae/pɒləpˈtɛrədiː/, afamily of archaicray-finned fishes and the only family in theorderPolypteriformes/pəˈlɪptərəfɔːrmiːz/.[2]
All thespecies occur infreshwaterhabitats in tropicalAfrica and theNile River system, mainly swampy, shallowfloodplains andestuaries.
Cladistia, polypterids and their fossil relatives, are considered thesister 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, theScanilepiformes, are known from the laterPermian to theTriassic, and are likely ancestral to polypterids. The oldest polypterids are around 100 million years old, from the earlyLate Cretaceous of South America and Africa.[5][6][7]
Polypterids are elongatedfish with a unique series of dorsal finlets which vary in number from seven to 18, instead of a singledorsal 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. Theirjaw structure more closely resembles that of thetetrapods than that of theteleost fishes. Bichirs have a number of other primitive characteristics, including fleshy pectoral fins superficially similar to those oflobe-finned fishes.[1] They also have a pair of slit-likespiracles on the top of their heads that are used to breathe air,[8] two gular plates, and paired ventrallungs.[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 theoesophagus 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]
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]
Polypterids possess pairedlungs which connect to the esophagus via aglottis. 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 fourthgill arch), and oxygenated blood leaves the lungs in pulmonary veins. Unlike mostlungfish andtetrapods, 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 are popular subjects of public and large hobbyaquaria. 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). Polypterids make good tankmates with other species large enough to not be prey but small enough to not be predators. 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.
In addition to theextinctgenusBawitius, the two living genera,Polypterus andErpetoichthys, have 14 extant species:[12]
| Phylogeny of Polypteridae.[3][4] | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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OrderPolypteriformes
SuborderPolypterioidei
CladeSalamandrophysida
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