Bichirs
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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 family Polypteridae alongside the bichirs. It is the only member of the genus ''Erpetoichthys''. It is n ...
comprise Polypteridae , a
family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
of archaic
ray-finned fishes Actinopterygii (; ), members of which are known as ray-finned fish or actinopterygians, is a class (biology), class of Osteichthyes, bony fish that comprise over 50% of living vertebrate species. They are so called because of their lightly built ...
and the only family in the
order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...
Polypteriformes .Helfman GS, Collette BB, Facey DE, Bowen BW. 2009. The Diversity of Fishes. West Sussex, UK: Blackwell Publishing. 720 p. All the
species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
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. The term excludes seawater and brackish water, but it does include non-salty mi ...
habitat In ecology, habitat refers to the array of resources, 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 manifestation of its ...
s in tropical
Africa Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...
and the
Nile The Nile (also known as the Nile River or River Nile) is a major north-flowing river in northeastern Africa. It flows into the Mediterranean Sea. The Nile is the longest river in Africa. It has historically been considered the List of river sy ...
River system, mainly swampy, shallow
floodplain A floodplain or flood plain or bottomlands is an area of land adjacent to a river. Floodplains stretch from the banks of a river channel to the base of the enclosing valley, and experience flooding during periods of high Discharge (hydrolog ...
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 environm ...
.
Cladistia Cladistia is a subclass of bony fishes whose only living members are the bichirs of tropical Africa. Their major synapomorphies are a heterocercal tail in which the dorsal fin has independent rays, and a posteriorly elongated parasphenoid. ...
, 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 ...
to all other extant ray-finned fishes (
Actinopteri Actinopteri () is the sister group of Cladistia (bichirs) in the class Actinopterygii (ray-finned fish). Dating back to the Permian period, the Actinopteri comprise the Chondrostei (sturgeons and paddlefish), the Holostei ( bowfins and gars), ...
).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 Cladistia is a subclass of bony fishes whose only living members are the bichirs of tropical Africa. Their major synapomorphies are a heterocercal tail in which the dorsal fin has independent rays, and a posteriorly elongated parasphenoid. Cl ...
, are known from the later
Permian The Permian ( ) is a geologic period and System (stratigraphy), stratigraphic system which spans 47 million years, from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.902 Mya. It is the s ...
to the
Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...
, 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 more recent 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 ''cre ...
of South America and Africa.


Anatomy

Polypterids are elongated
fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...
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 on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...
. 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 jaws are a pair of opposable articulated structures 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 ...
structure more closely resembles that of the
tetrapod A tetrapod (; from Ancient Greek :wiktionary:τΔτρα-#Ancient Greek, τΔτρα- ''(tetra-)'' 'four' and :wiktionary:Ï€ÎżÏÏ‚#Ancient Greek, Ï€ÎżÏÏ‚ ''(poĂșs)'' 'foot') is any four-Limb (anatomy), limbed vertebrate animal of the clade Tetr ...
s than that of the
teleost Teleostei (; Ancient Greek, Greek ''teleios'' "complete" + ''osteon'' "bone"), members of which are known as teleosts (), is, by far, the largest group of ray-finned fishes (class Actinopterygii), with 96% of all neontology, extant species of f ...
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 clade (traditionally a class (biology), class or subclass) of vertebrate animals which includes a group of bony fish commonly referred to as lobe-finned fish. The ...
. They also have a pair of slit-like spiracles on the top of their heads that are used to breathe air, two gular plates, and paired ventral
lung The lungs are the primary Organ (biology), organs of the respiratory system in many animals, including humans. In mammals and most other tetrapods, two lungs are located near the Vertebral column, backbone on either side of the heart. Their ...
s. 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 The esophagus (American English), oesophagus (British English), or Ɠsophagus ( archaic spelling) ( see spelling difference) all ; : ((o)e)(Ɠ)sophagi or ((o)e)(Ɠ)sophaguses), colloquially known also as the food pipe, food tube, or gullet, ...
leads to the right lung, and a separate opening on the right lung leads to the left lung. 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 Chironomidae , commonly known as non-biting midges or chironomids , are a family of Nematoceran flies with a global distribution. They are closely related to the families Ceratopogonidae, Simuliidae, and Thaumaleidae. Although many chironomid ...
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 many animals, including humans. In mammals and most other tetrapods, two lungs are located near the backbone on either side of the heart. Their function in the respiratory syste ...
which connect to the esophagus via a
glottis The glottis (: glottises or glottides) is the opening between the vocal folds (the rima glottidis). The glottis is crucial in producing sound from the vocal folds. Etymology From Ancient Greek ''ÎłÎ»Ï‰Ï„Ï„ÎŻÏ‚'' (glƍttĂ­s), derived from ''Îł ...
. 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 respiration organ, respiratory organ that many aquatic ecosystem, 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 r ...
arch), and oxygenated blood leaves the lungs in pulmonary veins. Unlike most
lungfish Lungfish are freshwater vertebrates belonging to the class Dipnoi. Lungfish are best known for retaining ancestral characteristics within the Osteichthyes, including the ability to breathe air, and ancestral structures within Sarcopterygii, inc ...
and
tetrapods A tetrapod (; from Ancient Greek τΔτρα- ''(tetra-)'' 'four' and Ï€ÎżÏÏ‚ ''(poĂșs)'' 'foot') is any four- limbed vertebrate animal of the clade Tetrapoda (). Tetrapods include all extant and extinct amphibians and amniotes, with the lat ...
, 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). 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.


Classification

In addition to the
extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
''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 The reedfish, ropefish (more commonly used in the United States), or snakefish, ''Erpetoichthys calabaricus'', is a species of fish in the family Polypteridae alongside the bichirs. It is the only member of the genus ''Erpetoichthys''. It is na ...
'', have 14 extant species: Order Polypteriformes Suborder Polypterioidei Clade Salamandrophysida * Family Polypteridae ** Genus †'' Bawitius'' Grandstaff et al. 2012 *** †''
Bawitius bartheli ''Bawitius'' is an extinct genus of giant polypterid from the Upper Cretaceous (lower Cenomanian) Bahariya Formation of Egypt. The type species is ''B. bartheli'', named as a species of ''Polypterus'' in 1984, and the genus etymology comes from B ...
'' (Schaal 1984) Grandstaff et al. 2012 - Late
Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...
(
Cenomanian The Cenomanian is, in the International Commission on Stratigraphy's (ICS) geological timescale, the oldest or earliest age (geology), age of the Late Cretaceous epoch (geology), Epoch or the lowest stage (stratigraphy), stage of the Upper Cretace ...
) of Egypt ** Genus †'' Serenoichthys'' Dutheil 1999a *** †''
Serenoichthys kemkemensis ''Serenoichthys'' is an extinct genus of small bichir from the Late Cretaceous (Cenomanian) of southeastern Morocco. The genus is monotypic, the type and only species being ''Serenoichthys kemkemensis''. Only known at first from postcranial skele ...
'' Dutheil 1999a ** Genus ''Erpetoichthys'' J. A. Smith, 1865 *** '' Erpetoichthys calabaricus'' J. A. Smith, 1865 (reedfish) ** Genus ''
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 ...
'' LacĂ©pĂšde, 1803 *** †'' Polypterus dageti'' Gayet & Meunier 1996 *** †'' Polypterus faraou'' Otero et al., 2006 — late
Miocene The Miocene ( ) is the first epoch (geology), 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 mea ...
*** †'' Polypterus sudanensis'' Werner & Gayet 1997 *** Retropinnis group **** '' Polypterus retropinnis'' Vaillant, 1899 (West African bichir) *** Bichir group **** ''
Polypterus ansorgii The Guinean bichir (''Polypterus ansorgii'') is a ray-finned fish from rivers and other freshwater habitats in Western Africa, ranging from Guinea-Bissau to Nigeria. It reaches a maximum length of , is greenish-brown to black in color, and has la ...
'' Boulenger, 1910 (Guinean bichir) **** ''
Polypterus bichir ''Polypterus'' is a genus of freshwater fish in the bichir family (biology), family (Polypteridae) of order (biology), order Polypteriformes. The type species is the Polypterus bichir, Nile bichir (''P. bichir''). Fish in this genus live in vario ...
'' LacépÚde, 1803 (Nile bichir) ***** ''P. b. bichir'' LacepÚde, 1803 ***** ''P. b. lapradei''
Steindachner Franz Steindachner (11 November 1834 in Vienna – 10 December 1919 in Vienna) was an Austrian zoologist, ichthyologist, and herpetologist. He published over 200 papers on fishes and over 50 papers on reptiles and amphibians. Steindachner descri ...
, 1869
***** ''P. b. ornatus'' Arambourg 1948 **** ''
Polypterus congicus ''Polypterus congicus'', the Congo bichir, is a species of bichir with a maximum recorded size of . The colour also varies from yellowish brown to grey, darker in the top, paler in the ventral area. It has a pattern of around 8 irregular vertical ...
'' Boulenger, 1898 (Congo bichir) **** ''
Polypterus endlicherii ''Polypterus endlicherii'', 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 fish collecti ...
'' Heckel, 1847 (saddled bichir) *** Weeksii group **** '' Polypterus mokelembembe'' Schliewen & SchÀfer, 2006 (MokÚlé-mbÚmbé 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 a species of fish belonging to the class Actinopterygii, or the ray-finned fish, which constitute an order of the class of the bony fish. an elongate ...
'' Boulenger, 1899 (barred bichir) **** ''
Polypterus polli ''Polypterus polli'', Poll's bichir, is a species of bichir from the Malebo Pool and the lower and central basins of the Congo River. It was named in honor of Belgium, Belgian ichthyologist Max Poll. Description ''P. polli'' is an “upper-jaw” ...
'' J. P. Gosse, 1988 **** '' Polypterus palmas'' Ayres, 1850 (shortfin bichir) ***** ''P. p. buettikoferi''
Steindachner Franz Steindachner (11 November 1834 in Vienna – 10 December 1919 in Vienna) was an Austrian zoologist, ichthyologist, and herpetologist. He published over 200 papers on fishes and over 50 papers on reptiles and amphibians. Steindachner descri ...
, 1891
***** ''P. p. palmas'' Ayres, 1850 **** ''
Polypterus senegalus ''Polypterus senegalus'', commonly known as the Senegal bichir, gray bichir or Cuvier's bichir, is an African species of Actinopterygii, ray-finned fish in the bichir Family (biology), family, Bichir, Polypteridae. It is a typical example of poly ...
''
Cuvier Jean LĂ©opold Nicolas FrĂ©dĂ©ric, baron Cuvier (23 August 1769 – 13 May 1832), known as Georges Cuvier (; ), was a French natural history, naturalist and zoology, zoologist, sometimes referred to as the "founding father of paleontology". Cuv ...
, 1829
(gray bichir) ***** ''P. s. meridionalis''
Poll Poll, polled, or polling may refer to: Forms of voting and counting * Poll, a formal election ** Election verification exit poll, a survey taken to verify election counts ** Polling, voting to make decisions or determine opinions ** Polling pla ...
, 1941
(most likely a variant of ''P. s. senegalus'') ***** ''P. s. senegalus'' Cuvier, 1829 **** '' Polypterus teugelsi''
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