A new genus of electric fish, dubbed Procerusternarchus picxuna or the bluntnose knifefish, has been identified in branches of the upper Negro river, an Amazon tributary.
Electrogenic fish produce electric fields strong enough to be detected by other fish, usually from an organ situated in their tails. Strongly electric versions use their pulses to stun prey, while weakly electric species use the fields for communication, navigation and object detection. The most famous example, the electric eel, is not a true eel but a species of knifefish and therefore a relative, albeit a distant one, of P picxuna.
While the capacity to generate externally detectable electric fields is thought to have evolved independently several times, the principal exponents of that Gymnotiforms, also known as South American knifefish for their thin bodies and tapering tails.
New species are turning up frequently. University of Massachusetts Professor Cristina Cox Fernandes says that when she began studying electric fishes in the early 90s fewer than 100 species were known in the scientific literature. Since then the number has roughly doubled, in substantial part due to her own work.
However, while new species are common, a new genus does not come along every day. Fernandes hopes the new discovery, announced in the Proceedings of the Academy of Natural Sciences of Philadelphia will help trace the evolution of marine electric fish.
Although not widely fished or used for other commercial purposes Fernandes considers the knifefish important indicators of the health of river health. “As environmental changes affect rivers worldwide and in the Amazon region, freshwater fauna are under many different pressures. Fish populations are dwindling due to the pollution, climate change, the construction of hydroelectric plants and other factors that result in habitat loss and modification. As such the need to document the current fish fauna has become all the more pressing.”
Knifefish lack pelvic and dorsal fins, relying on their elongated anal fins, which allow them to move backwards as easily as forwards.