Knollenorgangen

Knollenorgane are specialized electroreceptor organs found in some freshwater electric fishes. They are one of the two main types of electroreceptors in these fishes, the other being ampullary organs. Knollenorgane occur most prominently in the African family Mormyridae (elephantfishes) and in several related lineages, with additional representatives in other electric fishes.

Anatomy and distribution: Each knollenorgan is a compact, bulbous structure embedded in the skin or just beneath it, often appearing as a small raised node. The organ contains a cluster of receptor cells and is innervated by a dedicated nerve fiber that connects to the fish’s electroreception pathway in the brain. Knollenorgane are typically arranged in rows or patches on the body surface, reflecting their role in sensing electric fields around the fish.

Physiology and function: Knollenorgans transduce local electric field changes into neural signals. They are particularly sensitive to rapid, near-field perturbations caused by the fish’s own electric organ discharges as well as by external sources. The sensory information is conveyed to the hindbrain and higher brain centers, where it contributes to electroreception, active electrolocation, prey detection, and social communication.

Ecology and significance: The knollenorgan system supports navigation in murky waters, obstacle avoidance, and the detection of prey or predators through electric cues. Differences in electric signals between species and individuals also play a role in mating and social interactions. In research, knollenorgans are important models in neuroethology and sensory biology, helping to illuminate how specialized receptors translate electric fields into behavior.