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Senegal (Cuvier's) Bichir
Polypterus senegalus Cuvier

by Joe Gallo
of Texas
Aquarticles

Scientific name: Polypterus senegalus Cuvier; Family - Polypteridae; Order - Polypteriformes
Synonyms: Polypterus arnaudii (not valid)
Common Names: Senegal Bichir, Cuvier's Bichir, Gray Bichir, Dinosaur Eel
Region: Nile River basin and western Africa
Maximum Size: about 50cm (19.5 inches). Aquarium specimens usually somewhat smaller.
pH Range and Hardness: very tolerant of a wide range of water conditions. Typically from pH 6.0 - 8.0 and dH between 5.0 - 19.0.
Temperature Range: decidedly tropical; temperature range between 77 - 82 degrees F.

Grouped with the Sturgeons and Paddlefish in the Subclass Chondrostei, the Senegal Bichir has characteristics that lead to it being described as a 'primitive' fish. The genus Polypterus was first described by Geoffroy Saint-Hilaire in 1802 while he accompanied Napoleon's invading army into Egypt. The name Polypterus means 'many fins' which is an apt description of all of these fish which have multiple dorsal finlets instead of a single dorsal fin.

There may be as many as three subspecies of Polypterus senegalus. Polypterus senegalus senegalus is widely accepted while P. senegalus meridionalis is somewhat questionable. There are old reports of a possible third, unnamed subspecies from the Nile River.

Habitat and Niche
The Senegal Bichir is generally found in slow-moving waters, often in swampy regions or along the banks of rivers. The water is frequently turbid (with a lot of suspended fine silt). Polypterus senegalus is primarily a nocturnal predator, feeding on smaller fish, amphibians and insect larvae.

Appearance
Polypterus senegalus has an elongated body and is generally olive-brown to gray dorsally and white ventrally. There is no pattern present in adult fish. The dorsal fin is divided into multiple 'finlets' which are continuous with the caudal fin (tail). The upper jaw of Polypterus senegalus usually protrudes a bit beyond the lower jaw (unlike that of Polypterus endlicheri in which the lower jaw is more prominent). The pectoral fins are 'lobe-shaped' and the fish frequently rests on the bottom supported by these fins.

A young albino Polypterus senegalus

Baby Polypterus senegalus

One of the above pictured baby Polypterus senegalus after one month. Notice the loss of the striped pattern.

The same Polypterus senegalus at the age of about 1 year and a length of 8 ½ inches

Special Characteristics
Scales - The scales of Polypterids are called 'ganoid' scales because they are covered with a coating of a material called ganoine. This material is very tough and helps to prevent water loss through the scales, enabling Polypterids to survive out of water for a day or two. They are generally diamond-shaped and often have fine, tooth-like projections at the rear of each scale.
Swim Bladder - The swim bladder of Polypterids is modified into a pair of functional lung-like structures which permit these fish to use atmospheric air. Also equipped with efficient gills, Polypterus species are able to use both means of respiration to survive. Polypterus will frequently come to the surface of the aquarium to gulp air.
Pectoral Fins - The pectoral fins of Polypterus are lobe-shaped, similar in appearance to those of the 'lobe-finned' fish like the Coelacanth (Latimeria). Bichirs have been known to propel themselves across land by using their pectoral fins as 'legs'.
External Gills - Very young Bichirs have prominent external gills very similar in appearance to those of some young salamanders. These feathery gills are lost as the individual matures.

Breeding Senegal Bichirs
Polypterus senegalus has been bred numerous times in captivity. Courting behavior, which can last a day or more, involves the male bumping the female with his snout and then chasing after her. If the female is receptive she will find a suitable location, generally in a clump of plants, to lay between 100 - 300 slightly adhesive eggs over a period of days. The eggs hatch in about 3 days. The parents should be removed after spawning to prevent them from eating the eggs.

Males can be distinguished from females by the appearance of their anal fin. This fin is much broader in males than in females.

Personal Experiences with Polypterus senegalus
I have successfully kept P. senegalus on a number of occasions over the years. Among my absolute favorite fish, Polypterids are remarkably tough, durable, and very long-lived (up to 34 years in one recorded instance). I have found them to be generally peaceful among fish that are too big to be eaten, though males will occasionally fight with each other and these fights may result in some damage, especially to snout and fins. They are relatively resistant (but not immune) to most common aquarium diseases, including 'Ich' (Ichthyophthirius multifilis). There is a freshwater fluke, Macrogyrodactylus polypteri, that is occasionally found on wild-caught specimens.

Though primarily a nocturnal fish, Polypterus senegalus can be quite active in the aquarium even when the lights are on. They will frequently prowl along the bottom looking for food during the daylight hours and often rise to the surface to get a breath of air. In my experience they like a tank with plenty of hiding places.

I have kept Polypterus senegalus in an aquarium with other fish that are found in their native habitat. Some tank-mates that I have successfully kept with the Senegal Bichir include Ctenopoma species, the African Butterfly Fish (Pantodon buchholzi), Congo Tetras (Phenacogrammus interruptus), the African Mud Fish (Phractolaemus ansorgii), 'Kribensis' cichlids (Pelvicachromis species), African Knife Fish (Xenomystus nigri) and the African Spotted Catfish (Parauchenoglanis macrostoma).

Because of its large adult size, I recommend a tank of at least 50 gallons for Polypterus senegalus. When young they can be housed in smaller aquariums but they will need a larger tank as they grow.

Feeding Polypterus senegalus is relatively easy. Though it isn't interested in flake food, the Senegal Bichir will greedily devour frozen bloodworms, frozen or fresh shrimp and frozen beef heart. They will also eat sinking pellets like shrimp pellets and cichlid pellets as well as the occasional suitably-sized feeder fish. If housed with other fish that are aggressive feeders, special care should be taken to ensure that the relatively slow-moving Polypterus is getting some of the food.

One special caution regarding all Polypterids needs to be mentioned here. They are all accomplished escape artists and their aquarium needs to be prepared in such a way as to block all of their possible escape routes. I once had a large (12 inch) Polypterus senegalus that managed to get out of its aquarium and decided to go for a stroll. I found it right after my cat did. Unfortunately for the cat, the Bichir wasn't in the least bit interested in being the feline's lunch and I watched as it lunged aggressively toward the cat with its mouth wide open! I returned it to its aquarium unharmed.

Summary
The Senegal Bichir, Polypterus senegalus, is an excellent choice for those who like 'primitive-looking' fish that are relatively active and have a lot of personality. They are very tough fish that will stand a lot of abuse before seeing fit to expire. As they grow they will require a fairly large aquarium and cannot be housed with fish that are small enough to be eaten.

References

Haruto Kodera, et al., 1994. Jurassic Fishes . T.F.H. Publications, New Jersey.

Herbert Axelrod, Warren Burgess, et al., 1985. Dr. Axelrod's Atlas of Freshwater Aquarium Fishes . T.F.H. Publications, New Jersey.

Article on Polypterus senegalus senegalus at Fishbase.org http://www.fishbase.org/Summary/SpeciesSummary.cfm?ID=5024&genusname=Polypterus&speciesname=senegalus%20senegalus

Article on DigiMorph of Polypterus senegalus from the University of Texas at Austin. http://www.digimorph.org/specimens/Polypterus_senegalus/whole/