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) also called "dinosaur bichir" or "dragon fish" is in the pet trade due to its lungfish-like appearance which was described as more primitive and prehistoric than other modern fishes. It is a prototypical species of fish in the genus Polypterus, meaning most of its features are held across the genus. Commonly kept in captivity by hobbyists. They are native from Africa where they are the most widespread species of the genus.

Polypterus senegalus
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Polypteriformes
Family: Polypteridae
Genus: Polypterus
Species:
P. senegalus
Binomial name
Polypterus senegalus
Cuvier, 1829
Subspecies
  • P. s. meridionalis (Poll 1941)
  • P. s. senegalus Cuvier 1829
Synonyms[1][2]
  • Polypterus arnaudii Duméril 1870
  • Polypterus meridionalis Poll 1942

Appearance
Senegal bichir

An elongated fish, usually grey or beige in color, it sometimes has shades of white, pink or blue on some scales; most of the fish is covered in very subtle patterns with occasional darker blotches or dots. The face is smooth and rounded at the nose with larger scales than the rest of the fish, external nostrils protrude from the front; eyes are on each side of the head, they are usually pale yellow with a black pupil; the mouth is large and seems to grin when closed. The body is long and vaguely cylindrical; a serrated dorsal fin runs along most of the body until it meets the caudal fin which is pointed and flat. The pectoral fins attach just behind and below the gill openings, and are the primary means of locomotion, providing a slow, graceful appearance. P. senegalus is smaller than other bichirs, reaching about 35.5 cm (14 in).

The fish has a pair of primitive lungs instead of a swim bladder, allowing it to periodically gulp air from the surface of the water. In the aquarium, bichirs can be observed dashing to the surface for this purpose.

This bichir's skin serves as a particularly effective armor, and has been studied as a model for personal armor for better combinations of protection and mobility.[3][4]

Behavior

During active hours, Polypterus senegalus swim about their environment, performing activities such as exploring, feeding, hunting, investigating changes, and scavenging; social behavior is also observed as P. senegalus sometimes follow each other moving about; most individuals are inactive at night and rest low above the ground until sunrise.

Subspecies

Three subspecies of P. senegalus are recognized: P. s. senegalus, P. s. meridionalis, and a further unnamed subspecies.

  • P. s. senegalus grows to about 70 cm (28 in) in the wild, and 48 cm (19 in) in captivity. It is a uniform brownish-grey to olive color on the dorsal surface, and the ventral surface is whitish. No banding occurs on adults, but very young juveniles show three horizontal bands. The upper jaw is slightly longer than lower jaw. It has eight to 11 dorsal finlets.
  • P. s. meridionalis grows to about 110 cm (44 in) in the wild, and 81 cm (32 in) in captivity. It is a uniform olive-grey color on the dorsal surface. The upper and lower jaws are about the same length. It has 9 or 10 dorsal spines. P. s. meridionalis may be a regional variant of P. s. senegalus.

Distribution and habitat

This species of bichir is found in lakes, river margins, swamps, and floodplains of tropical Africa and the Nile river system, it occurs in at least twenty-six African countries which include Senegal, Egypt, Democratic Republic of Congo, Cameroon, Chad, Ethiopia, Kenya, Mali, Ivory Coast, Tanzania, Sudan, Nigeria, Gambia, Uganda, and others. Its distribution is widespread, detailed to include the Nile basin and West Africa (Senegal, Gambia, Niger, Volta, and Lake Chad basins, and Congo River Basin.

Captivity

Bichirs are predatory fish; in captivity they will take any live or dead animal that can be swallowed or broken apart and then swallowed. Only its lack of speed prevents a bichir from emptying an aquarium of smaller fish; the pectoral fins only allow for slow cruising, and while it can achieve amazing bursts of speed, it cannot catch fish of average speed. Given enough time, any fish that can fit in the bichir's mouth will be eaten; this fish should not be kept with any other fish smaller than three inches. It will also bite fins of other fishes if it can.

A juvenile bichir forages for food

Provided the skin remains moist, P. senegalus can remain out of the water indefinitely – it can even be raised on land, where it uses its large pectoral fins to walk.[5]

See also

References
  1. Froese, R.; Pauly, D. (2017). "Polypteridae". FishBase version (02/2017). Retrieved 18 May 2017.
  2. "Polypteridae" (PDF). Deeplyfish- fishes of the world. Retrieved 18 May 2017.
  3. Song J, Ortiz C, Boyce MC (July 2011). "Threat-protection mechanics of an armored fish". J Mech Behav Biomed Mater. 4 (5): 699–712. doi:10.1016/j.jmbbm.2010.11.011. PMID 21565718.
  4. Bruet BJ, Song J, Boyce MC, Ortiz C (September 2008). "Materials design principles of ancient fish armour". Nature Materials. 7 (9): 748–56. doi:10.1038/nmat2231. PMID 18660814. Lay summary – New Scientist (January 25, 2013).
  5. Standen EM, Du TY, Larsson HC (August 2014). "Developmental plasticity and the origin of tetrapods". Nature. 513 (7516): 54–8. doi:10.1038/nature13708. PMID 25162530. S2CID 1846308.
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