Mokèlé-Mbèmbé Bichir
- Rodrigo
- Mar 16
- 5 min read
The Mokèlé-mbèmbé bichir (Polypterus mokelembembe) is a member of the order Polypteriformes within the class Actinopterygii. It belongs to the family Polypteridae and is a predatory fish commonly encountered in the aquarium trade. Because of its highly primitive appearance and body structure that differs markedly from most other bony fishes, it is widely referred to as a “dinosaur fish.” In Chinese aquarium markets it is commonly called “twist dinosaur bichir” or “spotted-back dinosaur fish,” while in English markets it is known as the Mokele-mbembe bichir or Moke bichir. Its name is derived from the legendary creature “Mokèlé-mbèmbé” from the Congo region.
Morphology
In appearance, the Mokèlé-mbèmbé bichir possesses the defining feature of the family Polypteridae: multiple separated dorsal finlets. These small dorsal spines are among the most important characteristics used to identify bichirs. This species typically has about six to eight dorsal finlets. A relatively high predorsal scale count and distinctive variations in the lateral line scales are also key diagnostic traits used to distinguish species within the group.
Unlike most ray-finned fishes, the Mokèlé-mbèmbé bichir retains many characteristics of early actinopterygians. One example is the presence of distinctive ganoid scales. These scales consist of several layers: a heavily mineralized ganoine layer on the surface, a cosmine-like dentine layer, a vascular layer containing medullary cavities, and an inner isopedine layer composed of parallel bony plates.
Because its natural habitat consists of vegetation-dense swamp environments, the Mokèlé-mbèmbé bichir has evolved a cylindrical body and a flattened head suited to navigating complex benthic habitats. In order to survive in swamps and lakes that experience pronounced wet and dry seasons, these fishes have also convergently evolved respiratory adaptations similar to those seen in lobe-finned fishes, including spiracles and a gas bladder capable of assisting aerial respiration. These features allow them to temporarily leave drying pools during drought periods and move in search of more suitable water bodies.
In terms of coloration, adult Mokèlé-mbèmbé bichirs generally display dark yellow to greenish-brown body coloration with blotches or banded patterns. The iris often carries a reddish tint. External differences between males and females are subtle, making sex determination by appearance difficult. In body size, this species is considered a medium-sized predatory fish, with a maximum standard length of approximately 23–36 cm, making it relatively small among members of the Polypteridae.
During development, bichirs differ from most other fishes in that their larvae possess external gills resembling those of amphibian larvae. The evolutionary reason for this unusual convergent feature remains unclear. What is known is that these external gills gradually regress and disappear as the fish grows.
Native Range and Habitat
The Mokèlé-mbèmbé bichir is native to the central Congo Basin of Central Africa. It inhabits streams, swamps, and slow-flowing waters rich in vegetation. The species primarily occupies freshwater rivers and gently flowing habitats. As an ambush predator, it prefers areas with slow currents, shallow zones, dense vegetation, and substrates composed largely of mud or sand. When dissolved oxygen levels decline, the fish can supplement its oxygen supply through aerial respiration using its lung-like swim bladder.
Aquarium Conditions
The Mokèlé-mbèmbé bichir is a medium-sized predatory fish and is generally recommended to be kept singly. It is not advisable to house it with small fish or large aggressive predators. If community housing is attempted, it should be done only with large, relatively peaceful species. Aquaria should ideally be designed according to the adult size of the fish. A single individual requires at least a 300–500 liter tank to provide sufficient turning space. If multiple individuals are to be kept together, a significantly larger aquarium is necessary.
Bichirs are powerful jumpers, so aquaria should be equipped with a well-fitted but ventilated lid to prevent individuals from escaping the tank during stress or while surfacing to breathe.
In terms of environmental layout, the Mokèlé-mbèmbé bichir is a typical ambush predator that prefers dark or sheltered spaces. Driftwood, caves, dense aquatic vegetation, or floating plants can be added to create shaded hiding areas. The substrate should ideally consist of fine sand or soft sediment. Strong direct lighting should be avoided, as it may cause stress.
For water conditions, a temperature of 24–28°C is recommended. The water should be neutral to slightly acidic, approximately pH 6.5–7.5. Gentle water movement or mild filtration is preferred, as strong currents are unsuitable for this species. Because it is a bottom-dwelling carnivore that produces significant leftover food and organic waste, frequent water changes are required. Replacing roughly 20–30 percent of the water each week, or adjusting according to water quality, is advisable. A high-quality filtration system combining biological and mechanical filtration is recommended.
Feeding Conditions
The Mokèlé-mbèmbé bichir is a bottom-dwelling carnivore that primarily feeds on small fish, crustaceans, earthworms, insects, and aquatic invertebrates. In captivity it can also accept sinking carnivorous pellets or frozen foods such as bloodworms, shrimp, and fish flesh. A varied diet is recommended to maintain balanced nutrition.
Adult individuals are usually fed once per day or once every other day, depending on their activity level and appetite. Juveniles require more frequent feeding, typically one to two times per day. Feeding is best carried out under dim lighting or during dusk and nighttime hours, as the species is largely nocturnal and feeds more actively under low-light conditions.
Breeding Conditions
The Mokèlé-mbèmbé bichir is an egg-laying species. It produces scattered eggs with slight adhesiveness that attach to plants or other structures. A single spawning event can produce anywhere from several dozen to several hundred eggs, depending on the species and conditions. Fertilization occurs externally: the male wraps around the female and releases sperm as the eggs are laid. Incubation typically lasts about three to seven days, depending on temperature.
Newly hatched larvae initially feed on planktonic or very small benthic prey, and the larvae may possess external gills during early development.
Within the aquarium hobby, this species is considered relatively uncommon and difficult to breed. Wild-caught individuals are common, while successful captive breeding has been reported only occasionally by aquarists. Those attempting to breed the species should provide abundant plants or spawning mops, maintain stable water conditions, and simulate seasonal changes such as temperature or water level fluctuations, which may help trigger spawning. During incubation, antifungal measures may be necessary, such as carefully controlled use of methylene blue, and the larvae should be provided with microscopic live foods such as protozoans, micro-rotifers, or newly hatched brine shrimp.
Preventing Invasive Spread
The Mokèlé-mbèmbé bichir originates from Africa and is a highly adaptable carnivorous fish. If released into non-native environments, abandoned individuals can easily become invasive species and threaten local ecosystems. They may prey on the eggs and larvae of native fishes and compete with indigenous species for food resources, ultimately affecting the survival of native fish populations.
For this reason, aquarists must follow the principle of never abandoning or releasing aquarium fish into the wild. Under no circumstances should bichirs be introduced into natural waterways. If an owner is unable to continue keeping the fish, it should be rehomed with another aquarist or transferred to an aquarium facility willing to care for it.
Author: Rodrigo
References:
Schliewen, U. K., & Schäfer, F. (2006). Polypterus mokelembembe, a new species of bichir from the central Congo River basin (Actinopterygii: Cladistia: Polypteridae). Zootaxa, 1129(1), 23–36. https://doi.org/10.11646/zootaxa.1129.1.2
Froese, R., & Pauly, D. (Eds.). (2025). Polypterus mokelembembe Schliewen & Schäfer, 2006. In FishBase. Retrieved September 13, 2025, from https://www.fishbase.se/summary/Polypterus-mokelembembe
Polypterus.info. (n.d.). Polypterus mokelembembe (Mokele Mbembe Bichir). Retrieved September 13, 2025, from https://www.polypterus.info/p_mokelembembe.htm
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