The Gymnotiformes are an order of teleost bony fishes commonly known as Neotropical knifefish or South American knifefish. They have long bodies and swim using undulations of their elongated anal fin. Found almost exclusively in fresh water, these mostly nocturnal fish are capable of producing electric fields to detect prey, for navigation, communication, and, in the case of the electric eel, attack and defense. A few species are familiar to the aquarium trade, such as the black ghost knifefish, the glass knifefish, and the banded knifefish.
The naked-back knifefishes are a family (Gymnotidae) of knifefishes found only in fresh waters of Central America and South America. All have organs adapted to electroreception. The family has about 43 valid species in two genera. These fish are nocturnal and mostly occur in quiet waters from deep rivers to swamps. In strongly flowing waters, they may bury themselves.
The electric rays are a group of rays, flattened cartilaginous fish with enlarged pectoral fins, composing the order Torpediniformes. They are known for being capable of producing an electric discharge, ranging from 8 to 220 volts, depending on species, used to stun prey and for defense. There are 69 species in four families.
An electric fish is any fish that can generate electric fields. Most electric fish are also electroreceptive, meaning that they can sense electric fields. The only exception is the stargazer family (Uranoscopidae). Electric fish, although a small minority of all fishes, include both oceanic and freshwater species, and both cartilaginous and bony fishes.
Electroreception and electrogenesis are the closely related biological abilities to perceive electrical stimuli and to generate electric fields. Both are used to locate prey; stronger electric discharges are used in a few groups of fishes to stun prey. The capabilities are found almost exclusively in aquatic or amphibious animals, since water is a much better conductor of electricity than air. In passive electrolocation, objects such as prey are detected by sensing the electric fields they create. In active electrolocation, fish generate a weak electric field and sense the different distortions of that field created by objects that conduct or resist electricity. Active electrolocation is practised by two groups of weakly electric fish, the Gymnotiformes (knifefishes) and the Mormyridae (elephantfishes), and by Gymnarchus niloticus, the African knifefish. An electric fish generates an electric field using an electric organ, modified from muscles in its tail. The field is called weak if it is only enough to detect prey, and strong if it is powerful enough to stun or kill. The field may be in brief pulses, as in the elephantfishes, or a continuous wave, as in the knifefishes. Some strongly electric fish, such as the electric eel, locate prey by generating a weak electric field, and then discharge their electric organs strongly to stun the prey; other strongly electric fish, such as the electric ray, electrolocate passively. The stargazers are unique in being strongly electric but not using electrolocation.
Malapterurus electricus is a thickset fish with six mouth barbels and a single fin on its back, just anterior to the rounded tail fin. It is brownish or grayish, irregularly spotted with black, and attains a length and weight of about 1.2 metres and 23 kilograms (51 lb) M. electricus is capable of generating and controlling the discharge of up to 450 volts of electricity. It uses its power to defend itself and to capture prey.
Gymnotus is a genus of Neotropical freshwater fish in the family Gymnotidae found widely in South America, Central America and southern Mexico. The greatest species richness is found in the Amazon basin. They are sometimes referred to by the English name banded knifefish, although this typically is reserved for the most widespread species, G. carapo. Overall Gymnotus is the most widespread genus in the order Gymnotiformes.
Carlos Chagas Filho was a Brazilian physician, biologist and scientist active in the field of neuroscience. He was internationally renowned for his investigations on the neural mechanisms underlying the phenomenon of electrogenesis by the electroplaques of electric fishes. He was also an important scientific leader, being one of the founders of the Biophysics Institute of the Federal University of Rio de Janeiro and was also a president for 16 years of the Vatican's Pontifical Academy of Sciences, and president of the Brazilian Academy of Sciences (1965–1967).
Amphibious fish are fish that are able to leave water for extended periods of time. About 11 distantly related genera of fish are considered amphibious. This suggests that many fish genera independently evolved amphibious traits, a process known as convergent evolution. These fish use a range of terrestrial locomotory modes, such as lateral undulation, tripod-like walking, and jumping. Many of these locomotory modes incorporate multiple combinations of pectoral-, pelvic-, and tail-fin movement.
In biology, the electric organ is an organ that an electric fish uses to create an electric field. Electric organs are derived from modified muscle or in some cases nerve tissue, called electrocytes, and have evolved at least six times among the elasmobranchs and teleosts. These fish use their electric discharges for navigation, communication, mating, defence, and in strongly electric fish also for the incapacitation of prey.
David Nachmansohn was a German-Jewish biochemist responsible for elucidating the role of phosphocreatine in energy production in the muscles, and the role of the neurotransmitter acetylcholine in nerve stimulation. He is also recognised for his basic research into the biochemistry and mechanism underlying bioelectric phenomena.
Malapterurus is a genus of catfishes of the electric catfish family (Malapteruridae). It includes 18 species.
The jamming avoidance response is a behavior of some species of weakly electric fish. It occurs when two electric fish with wave discharges meet – if their discharge frequencies are very similar, each fish shifts its discharge frequency to increase the difference between the two. By doing this, both fish prevent jamming of their sense of electroreception.
Rhamphichthys(Rhamphos = Greek for beak and Ichthys = Greek for fish) is a genus of fish that includes the South American sand knifefish. These fish are eel shaped with a distinct beak like snout which gave them their name. Like most other knifefish Rhamphichthys species have electrical organs that help them live in the murky waters of South America. Currently there are 10 recognized species of Rhamphichthys, although many changes have been made in their taxonomy since their original discovery.
The electric eels are a genus, Electrophorus, of neotropical freshwater fish from South America in the family Gymnotidae. They are known for their ability to stun their prey by generating electricity, delivering shocks at up to 860 volts. Their electrical capabilities were first studied in 1775, contributing to the invention in 1800 of the electric battery.
George Paul Hess was a research biochemist who specialized in studying acetylcholine receptors. Hess developed laser pulse photolysis and a quench flow technique.
Electrophorus varii, or Vari’s electric eel, is a species of electric eel found in South America.
Electrophorus voltai is a species of electric eel found in South America. It is the strongest known bioelectricity generator in nature.
Carl Sachs was a German zoologist, known for his discovery of what is now called Sachs' organ in the electric eel.
The history of bioelectricity dates back to ancient Egypt, where the shocks delivered by the electric catfish were used medicinally.
