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Bichir

life science Maturity 7-9 Next article →

Bichirs are unique members of the family Polypteridae. This family includes the bichir and the reedfish. They are considered archaic ray-finned fishes. This means they are an ancient lineage of fish. They are the only family within the order Polypteriformes. These fish live in freshwater habitats across tropical Africa. You can also find them in the Nile River system. They prefer swampy areas, shallow floodplains, and estuaries.

Polypterus delhezi 3
Polypterus delhezi 3

The anatomy of a bichir is very distinct. They have elongated bodies covered in ganoid scales. These are thick, bony scales shaped like diamonds. Instead of one large dorsal fin, they have a series of dorsal finlets. There are between seven and 18 of these finlets. Each finlet has bifid tips, which means they are double-edged. These finlets are the only fins that possess spines. The rest of their fins consist of soft rays. Their fleshy pectoral fins look similar to those of lobe-finned fishes.

Bichirs have a fascinating way of breathing air. They are facultative air-breathers. This means they can breathe air when water oxygen is low. They possess two paired lungs that are unchambered sacs. The right lung is larger and spans the whole body cavity. The left lung is smaller and reaches the stomach. A slit-like opening called a glottis connects the esophagus to the right lung. A separate opening leads to the left lung. They use a process called recoil aspiration to breathe. They also have spiracles on their heads to breathe air.

Polypterus ornatipinnis
Polypterus ornatipinnis

Blood moves through the lungs in a specific way. Deoxygenated blood travels through paired pulmonary arteries. These branch from the fourth efferent branchial arteries. This means they come from the fourth gill arch. Once the blood is oxygenated, it leaves through pulmonary veins. The lungs are highly vascularized to help with gas exchange. This high level of blood vessels makes breathing efficient. This system allows them to survive in poorly oxygenated water.

Polypterus delhezi 3
Polypterus delhezi 3

The history of these fish stretches back millions of years. They likely diverged from other ray-finned fishes 330 million years ago. A related group called Scanilepiformes lived during the Permian and Triassic periods. These are likely the ancestors of the polypterids. The oldest known polypterid fossils are about 100 million years old. These fossils date to the early Late Cretaceous. They have been found in both South America and Africa. One extinct genus from this time is called Bawitius.

Bawitius restoration
Bawitius restoration

There are 14 living species of bichirs today. These belong to two main genera: Polypterus and Erpetoichthys. The genus Erpetoichthys includes the reedfish. The genus Polypterus includes many different groups. These include the Senegalus group and the Weeksii group. Some species are known as the Nile bichir or the mottled bichir. They are nocturnal predators that hunt at night. They use an extraordinary olfactory ability to find prey. They eat insects, crustaceans, and small vertebrates.

Polypterus ornatipinnis
Polypterus ornatipinnis

Bichirs are popular in the aquarium hobby. Some pet shops call them "dragon bichirs." This name comes from their dragon-like appearance. They are generally peaceful fish that stay near the bottom. They do well in tanks with many large plants. This mimics their natural swampy habitats. In captivity, they can live for 10 to over 30 years. They are good tankmates for fish that are large enough not to be eaten. However, some catfish may eat the slime coat off of them.

Polypterus delhezi 3
Polypterus delhezi 3
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File:Bawitius_restoration.png
Bawitius_restoration.png
File:Polypterus endlicheri endlicheri.jpg
Polypterus endlicheri endlicheri.jpg
File:Polypterus ornatipinnis.png
Polypterus ornatipinnis.png
File:Polypterus delhezi 3.jpg
Polypterus delhezi 3.jpg
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