Teugelsi Bichir

Teugelsi bichir（Polypterus teugelsi）。（圖片來源：Ooi Hong Liang ，採用 CC BY-NC 4.0 授權。）

The Teugelsi bichir (Polypterus teugelsi) is a member of the class Actinopterygii, order Polypteriformes, and family Polypteridae. It is a predatory fish commonly encountered in the aquarium trade. Because of its strongly primitive appearance and body structure that differs markedly from most other bony fishes, it is widely marketed as a “dinosaur fish.” In Chinese-speaking aquarium markets it is often called the Cameroon dinosaur bichir, while in English-speaking markets it is generally known as the Teugelsi bichir or the Cross River bichir.

Morphology

The Teugelsi bichir possesses the defining trait of the family Polypteridae: multiple separated dorsal finlets. These small, individual dorsal spines are one of the most important diagnostic features used to identify bichirs. This species typically has 7–9 dorsal finlets. The vertebral count ranges from 63 to 65, which is also an important taxonomic character for distinguishing the species.

Unlike most ray-finned fishes, bichirs retain several anatomical features that resemble those of early actinopterygian fishes. One example is their distinctive ganoid scales. These scales consist of several layers: an outer heavily mineralized ganoine layer, a cosmine-like dentine layer, a vascular layer containing canals with internal cavities, and an inner layer of lamellar bone known as isopedine.

Because their natural habitats are densely vegetated swamp environments, bichirs have evolved a cylindrical body and a flattened head that allow them to move effectively through structurally complex bottom habitats. In order to survive in swamps and lakes that experience pronounced wet and dry seasons, these fishes have also convergently evolved respiratory spiracles and a specialized swim bladder resembling the lungs of lobe-finned fishes. These structures allow them to supplement oxygen intake by breathing air, enabling them to temporarily leave drying pools during the dry season in search of more suitable water bodies.

In terms of coloration, adult Teugelsi bichirs have a light brown to yellowish-brown dorsum marked with black reticulated patterns, while the ventral surface is orange. Brown spots are scattered around the eyes, snout, upper lip, and lower lip. The pectoral, pelvic, and anal fins are light brown with irregular dark brown lines. The soft dorsal fin, caudal fin, anal fin, and pelvic fins display vertical black stripes. In size, the Teugelsi bichir is considered a medium-sized predatory fish and can reach a total length of about 41.5 cm.

In terms of development, members of the family Polypteridae differ from most other fishes in that their juveniles possess distinctive external gills, giving them an appearance similar to amphibian larvae. The evolutionary reason for this unusual trait remains unclear. However, these external gills gradually regress and disappear as the fish grows.

Native Range and Habitat

The Teugelsi bichir occurs in the Cross River basin of Africa and surrounding drainage systems. It inhabits streams, swamps, and slow-moving waters rich in vegetation. The species is primarily found in freshwater rivers and other low-current habitats.

As an ambush predator, bichirs prefer areas with slow flow, shallow zones, abundant vegetation, and muddy or sandy substrates. When dissolved oxygen levels decline, they are capable of supplementing oxygen uptake through aerial respiration.

Aquarium Conditions

The Teugelsi bichir is a medium-sized predatory fish. It is generally recommended to keep individuals singly rather than housing them with other fishes. Small fish may be preyed upon, while large aggressive predators may cause stress or injury. If mixed-species housing is desired, only large and relatively peaceful fish species should be considered.

Aquaria should be sized according to the adult dimensions of the fish. A single individual requires at least 300–500 liters of water volume, with a tank length of at least 120 cm to allow sufficient space for turning and movement. Larger aquaria are necessary when housing multiple individuals.

Bichirs are extremely powerful jumpers. Aquaria must therefore be fitted with tightly secured but well-ventilated lids to prevent escape, which may occur during stress or when the fish surfaces to breathe air.

In terms of habitat structure, bichirs are typical ambush predators that prefer dark or sheltered areas. The aquarium should include driftwood, caves, dense plants, or floating vegetation to provide cover. The substrate should consist of sand or fine sediment. Strong direct lighting should be avoided, as excessive illumination may cause stress.

Water conditions should be maintained at temperatures of 24–28°C with neutral to slightly alkaline water chemistry (approximately pH 6.5–7.8). Gentle water movement or moderate filtration flow is recommended, while strong currents should be avoided.

Because bichirs are benthic carnivores that produce considerable food waste and organic debris, frequent water changes are necessary. A weekly water change of about 20–30 percent is commonly recommended, although adjustments may be made depending on water quality. A high-quality filtration system combining both biological and mechanical filtration is strongly advised.

Feeding Conditions

Bichirs are bottom-dwelling carnivores. In the wild they feed primarily on small fish, crustaceans, earthworms, insects, and other aquatic invertebrates. In captivity they can be fed sinking carnivorous pellets as well as frozen foods such as bloodworms, shrimp, or fish flesh.

A varied diet is recommended to maintain balanced nutrition. Adult individuals are typically fed once per day or once every two days, depending on activity level and appetite. Juveniles require more frequent feeding, usually one to two times per day.

Feeding should ideally occur under dim lighting or during evening or nighttime periods, as bichirs are largely nocturnal and feed more actively in low-light conditions.

Breeding Conditions

The Teugelsi bichir is an egg-laying species that releases eggs freely into the environment. The eggs are slightly adhesive and attach to aquatic plants or other surfaces. A single spawning event may produce several dozen to several hundred eggs, although the exact number varies among species.

Fertilization occurs externally. During spawning the male typically wraps around the female and assists in releasing sperm to fertilize the eggs. Incubation generally lasts about 3–7 days depending on water temperature.

Newly hatched larvae initially feed on planktonic or extremely small benthic prey. During early development the larvae may possess external gills.

Successful captive breeding of the Teugelsi bichir has been recorded in the aquarium hobby, and in some regions the species is already produced through aquaculture. For breeding attempts, it is recommended to provide abundant plants or spawning mops, maintain stable water conditions, and simulate seasonal environmental changes such as temperature or water-level fluctuations, which may help stimulate spawning. During incubation, fungal growth should be prevented, for example by using treatments such as methylene blue. Newly hatched larvae should be supplied with microscopic live foods such as protozoans, micro-rotifers, or newly hatched brine shrimp.

Preventing Invasive Spread

The Teugelsi bichir is native to Africa and is a highly adaptable carnivorous fish. If released into non-native environments, it has the potential to become an invasive species that threatens local ecosystems. It may prey upon the eggs and juveniles of native fishes and compete for food resources, thereby disrupting local fish populations.

Aquarium keepers must therefore follow the principle of responsible ownership: never abandon or release aquarium animals into natural waterways. Under no circumstances should Teugelsi bichirs be released into the wild. If an owner is no longer able to keep the fish, it should instead be transferred to another aquarist or rehomed through an aquarium facility willing to accept it.

Author: Rodrigo

References:

1. Britz, R. (2004). Polypterus teugelsi, a new species of bichir from the Upper Cross River system in Cameroon (Actinopterygii: Cladistia: Polypteridae). Ichthyological Exploration of Freshwaters, 15(2), 179–186.

2. Froese, R., & Pauly, D. (Eds.). (2025). Polypterus teugelsi Britz, 2004. In FishBase. Retrieved September 13, 2025, from https://www.fishbase.se/summary/Polypterus-teugelsi.html

3. GBIF Secretariat. (2025). Polypterus teugelsi Britz, 2004. GBIF Backbone Taxonomy. Retrieved September 13, 2025, from https://www.gbif.org/species

4. Evans, S. (n.d.). Polypterus teugelsi (Teugelsi bichir). Polypterus.info. Retrieved September 13, 2025, from https://www.polypterus.info/p_teugelsi.htm

5. Moritz, T., & Britz, R. (2019). Revision of the extant Polypteridae (Actinopterygii: Cladistia). Verlag Dr. Friedrich Pfeil. (modern taxonomic treatment)