Bichirs and the

reedfish The reedfish, ropefish (more commonly used in the United States), or snakefish, ''Erpetoichthys calabaricus'', is a species of fish in the bichir family and order. It is the only member of the genus ''Erpetoichthys''. It is native to fresh and ...

comprise Polypteridae , a

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

of archaic

ray-finned fishes Actinopterygii (; ), members of which are known as ray-finned fishes, is a class of bony fish. They comprise over 50% of living vertebrate species. The ray-finned fishes are so called because their fins are webs of skin supported by bony or hor ...

and the only family in the order Polypteriformes .Helfman GS, Collette BB, Facey DE, Bowen BW. 2009. The Diversity of Fishes. West Sussex, UK: Blackwell Publishing. 720 p. All the

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

occur in

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ...

habitat In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...

s in tropical

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

and the

Nile The Nile, , Bohairic , lg, Kiira , Nobiin language, Nobiin: Áman Dawū is a major north-flowing river in northeastern Africa. It flows into the Mediterranean Sea. The Nile is the longest river in Africa and has historically been considered ...

River system, mainly swampy, shallow

floodplain A floodplain or flood plain or bottomlands is an area of land adjacent to a river which stretches from the banks of its channel to the base of the enclosing valley walls, and which experiences flooding during periods of high discharge.Goudi ...

s and

estuaries An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environment ...

Cladistia Cladistia is a clade of bony fishes whose only living members are the bichirs. Their major synapomorphies are a heterocercal tail in which the dorsal fin has independent rays, and a posteriorly elongated parasphenoid. Cladistia are the earliest ...

, polypterids and their fossil relatives, are considered the

sister group In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and t ...

to all other extant ray-finned fishes (

Actinopteri Actinopteri is the sister group of Cladistia in the class Actinopterygii (ray-finned fish). Dating back to the Permian period, the Actinopteri comprise the Chondrostei (sturgeons and paddlefish) and the Neopterygii (bowfin, gars, and teleos ...

).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, They likely diverged from Actinopteri at least 330 million years ago. A closely related group, the Scanilepiformes, are known from the

Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...

, and are likely ancestral to polypterids. The oldest polypterids are around 100 million years old, from the early

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the ...

of South America and Africa.

Anatomy

Polypterids are elongated

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...

with a unique series of dorsal finlets which vary in number from seven to 18, instead of a single

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

. 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 A fish scale is a small rigid plate that grows out of the skin of a fish. The skin of most jawed fishes is covered with these protective scales, which can also provide effective camouflage through the use of reflection and colouration, as w ...

) scales. Their

jaw The jaw is any opposable articulated structure at the entrance of the mouth, typically used for grasping and manipulating food. The term ''jaws'' is also broadly applied to the whole of the structures constituting the vault of the mouth and serv ...

structure more closely resembles that of the

tetrapod Tetrapods (; ) are four-limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant and extinct amphibians, sauropsids ( reptiles, including dinosaurs and therefore birds) and synapsids (pelycosaurs, extinct theraps ...

s than that of the

teleost Teleostei (; Greek ''teleios'' "complete" + ''osteon'' "bone"), members of which are known as teleosts ), is, by far, the largest infraclass in the class Actinopterygii, the ray-finned fishes, containing 96% of all extant species of fish. Tel ...

fishes. Bichirs have a number of other primitive characteristics, including fleshy pectoral fins superficially similar to those of

lobe-finned fishes Sarcopterygii (; ) — sometimes considered synonymous with Crossopterygii () — is a taxon (traditionally a class or subclass) of the bony fishes known as the lobe-finned fishes. The group Tetrapoda, a mostly terrestrial superclass includ ...

. They also have a pair of slit-like

spiracle Spiracle or spiraculum may refer to: * Spiracle (arthropods), opening in the exoskeletons of some arthropods * Spiracle (vertebrates), openings on the surface of some vertebrates * Spiraculum, a genus of land snails in family Cyclophoridae Cycl ...

s on the top of their heads that are used to breathe air, two gular plates, and paired ventral

lung The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of t ...

s (the left lung shorter than the right). Four pairs of gill arches are present. Polypterids have a maximum body length ranging from to over depending on specific species and morphology.

Diet and traits

Polypterids are nocturnal and feed on small vertebrates, crustaceans, and insects. Their common aquarium diet includes bloodworms (

Chironomidae The Chironomidae (informally known as chironomids, nonbiting midges, or lake flies) comprise a family of nematoceran flies with a global distribution. They are closely related to the Ceratopogonidae, Simuliidae, and Thaumaleidae. Many species ...

larvae). Polypterids are known to have extraordinary olfactory ability. 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.

Air breathing

Polypterids possess paired

lungs The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of th ...

which connect to the esophagus via a

glottis The glottis is the opening between the vocal folds (the rima glottidis). The glottis is crucial in producing vowels and voiced consonants. Etymology From Ancient Greek ''γλωττίς'' (glōttís), derived from ''γλῶττα'' (glôtta), va ...

. They are facultative air-breathers, accessing surface air to breathe when the water they inhabit is poorly oxygenated. 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 A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

arch), and oxygenated blood leaves the lungs in pulmonary veins. Unlike most

lungfish Lungfish are freshwater vertebrates belonging to the order Dipnoi. Lungfish are best known for retaining ancestral characteristics within the Osteichthyes, including the ability to breathe air, and ancestral structures within Sarcopterygii, i ...

and

tetrapods Tetrapods (; ) are four-limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant and extinct amphibians, sauropsids (reptiles, including dinosaurs and therefore birds) and synapsids ( pelycosaurs, extinct therapsi ...

, their lungs are smooth sacs instead of alveolated tissue. Polypterids are unique in that they breathe using recoil aspiration.Graham, J.B. 1997. Air-breathing Fishes: Evolution, diversity, and adaptation. San Diego: Academic Press. 299 p. 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.

Polypterids as aquarium specimens

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 greatly appreciate heavily planted tanks as it mimics their natural habitat.

Classification

In addition to the

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

''Bawitius'', the two living genera, ''

Polypterus ''Polypterus'' is a genus of freshwater fish in the bichir family (Polypteridae) of order Polypteriformes. The type species is the Nile bichir (''P. bichir''). Fish in this genus live in various areas in Africa. ''Polypterus'' is the only kno ...

'' and '' Erpetoichthys'', have 12 extant species: Bawitius_restoration

Order Polypteriformes Suborder Polypterioidei Clade Salamandrophysida * Family Polypteridae ** Genus †'' Bawitius'' Grandstaff et al. 2012 *** †'' Bawitius bartheli'' (Schaal 1984) Grandstaff et al. 2012 - Late

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

(

Cenomanian The Cenomanian is, in the ICS' geological timescale, the oldest or earliest age of the Late Cretaceous Epoch or the lowest stage of the Upper Cretaceous Series. An age is a unit of geochronology; it is a unit of time; the stage is a unit in the s ...

) of Egypt ** Genus †'' Serenoichthys'' Dutheil 1999a *** †'' Serenoichthys kemkemensis'' Dutheil 1999a ** Genus ''Erpetoichthys'' J. A. Smith, 1865 *** '' Erpetoichthys calabaricus'' J. A. Smith, 1865 (reedfish) ** Genus ''

'' Lacépède, 1803 *** †'' Polypterus dageti'' Gayet & Meunier 1996 *** †'' Polypterus faraou'' Otero et al., 2006 — late

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

*** †'' Polypterus sudanensis'' Werner & Gayet 1997 *** Retropinnis group **** '' Polypterus retropinnis'' Vaillant, 1899 (West African bichir) *** Bichir group **** '' Polypterus ansorgii'' Boulenger, 1910 (Guinean bichir) **** ''

Polypterus bichir ''Polypterus bichir'', the Nile bichir, is a fish which lives in the Nile and some of its tributaries in Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 millio ...

'' Lacépède, 1803 (Nile bichir) ***** ''P. b. bichir'' Lacepède, 1803 ***** ''P. b. lapradei'' Steindachner, 1869 ***** ''P. b. ornatus'' Arambourg 1948 **** '' Polypterus congicus'' Boulenger, 1898 (Congo bichir) **** ''

Polypterus endlicheri ''Polypterus endlicheri'' Heckel 1847, the saddled bichir, is one of the largest species of the ''Polypterus'' genus of freshwater fish. Named in honor of botanist Stephan Endlicher (1804-1849), who apparently discovered the species in the fis ...

'' Heckel, 1847 (saddled bichir) *** Weeksii group **** '' Polypterus mokelembembe'' Schliewen &

Schäfer Schaefer is an alternative spelling and cognate for the German language, German word Wikt:Schäfer, ''schäfer'', meaning Wikt:shepherd, 'shepherd', which itself descends from the Old High German ''Wikt:scāphare, scāphare''. Variants "Shaefer", " ...

, 2006 (Mokèlé-mbèmbé bichir) **** '' Polypterus ornatipinnis'' Boulenger, 1902 (ornate bichir) **** '' Polypterus weeksii'' Boulenger, 1898 (mottled bichir) *** Senegalus group **** ''

Polypterus delhezi The barred bichir, armoured bichir, bandback bichir, or banded bichir (''Polypterus delhezi'') is an elongated fish found in the Congo River, specifically in the upper and middle portions. This species is one of the more commonly available in comm ...

'' Boulenger, 1899 (barred bichir) **** '' Polypterus polli'' J. P. Gosse, 1988 **** ''

Polypterus palmas ''Polypterus palmas'', also called the shortfin or marbled bichir, is a fish in the family Polypteridae found in freshwater environments throughout West Africa. Distribution ''P. palmas'' has a wide range; it can be found in freshwater environm ...

'' Ayres, 1850 (shortfin bichir) ***** ''P. p. buettikoferi'' Steindachner, 1891 ***** ''P. p. palmas'' Ayres, 1850 **** ''

Polypterus senegalus ''Polypterus senegalus'', the Senegal bichir, gray bichir or Cuvier's bichir, and sometimes called the "dinosaur eel" (a misnomer, as the creature is neither an eel nor a dinosaur), "dinosaur bichir", or "dragon fish" is in the pet trade due to ...

'' Cuvier, 1829 (gray bichir) ***** ''P. s. meridionalis''

Poll Poll, polled, or polling may refer to: Figurative head counts * Poll, a formal election ** Election verification exit poll, a survey taken to verify election counts ** Polling, voting to make decisions or determine opinions ** Polling places o ...

, 1941 (most likely a variant of ''P. s. senegalus'') ***** ''P. s. senegalus'' Cuvier, 1829 **** ''

Polypterus teugelsi ''Polypterus teugelsi'' (Teugelsi bichir) is a species of carnivorous, nocturnal bichir (a group of ray-finned fishes) that lives in the Cross River drainage basin in the country of Cameroon. ''P. teugelsi'' was described in 2004 by Ralf Britz ...

Britz Britz () is a German locality (''Ortsteil'') within the Berlin borough (''Bezirk'') of Neukölln. History The village of ''Britzig'' was first mentioned in 1273. It was incorporated by the 1920 Greater Berlin Act. It is known for being the sit ...

, 2004 ( Teugelsi bichir)

References

External links

FishBase entry for Polypteridae
{{Authority control Fish of Africa Extant Cretaceous first appearances Taxa named by Charles Lucien Bonaparte