We received a species of mormyrid from Nigeria that we had not seen for years: Brienomyrus brachyistius. This comparatively small species, with a maximum length of 17.5 cm, but usually remaining significantly smaller at 10-12 cm, is a close relative of the comparatively frequently imported species B. niger (see https://www.aquariumglaser.de/en/03-bony-tongues/brienomyrus_niger_en-2/).
These playful, intelligent fish are very lively and are less noticeable for their coloration than for their unusual, amusing behavior. All mormyrids belong to the weakly electric fish species. They have an electric organ in their tail stalk; it is so weak that the electrical discharges cannot be felt. They use this to scan their surroundings, similar to bats using ultrasound, but also to communicate with other members of their species. In fact, mormyrids have developed a type of “language” that is almost unique in the animal kingdom (only New World knifefish do something similar). This language is species-specific. Using special electrodes that record electrical discharges and convert them into a graphic image (similar to an ECG), it is possible in Africa (mormyrids are an exclusively African family with currently (2025) 22 genera and 236 species) to identify the species present in a body of water without dipping a net into the water. New species have even been discovered in this way!
Among our animals, there are some larger, slimmer fish that we believe to be males, and some stockier-looking animals that are probably females. Nothing is known about the reproductive biology of these mormyrids. In the aquarium, the animals readily eat any type of live, frozen, or dry food that fits in their mouths. The chemical composition of the water is irrelevant for their care, and the water temperature can be between 22 and 28°C. The fish are peaceful towards other species and do not damage plants. They are mainly crepuscular, so you should provide plenty of hiding places and dense vegetation to give them cover during the day.
For our customers: the fish have code 103502 on our stock list. Please note that we only supply wholesale customers.
Text & photos: Frank Schäfer
