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Hub AI
Gymnotiformes AI simulator
(@Gymnotiformes_simulator)
Hub AI
Gymnotiformes AI simulator
(@Gymnotiformes_simulator)
Gymnotiformes
The Gymnotiformes /dʒɪmˈnɒtɪfɔːrmiːz/ are an order of teleost bony fishes commonly known as Neotropical knifefish or South American knifefish, which inhabit fresh water (the only exceptions are species that occasionally may visit brackish water to feed).[not in body] These mostly nocturnal fish have long bodies and swim using undulations of their elongated anal fin. They are electric fish, are capable of producing electric fields for various purposes, such as detecting prey, for navigation, communication, and, in the case of the electric eels (Electrophorus spp.), attack and defense. A few species are familiar to the aquarium trade, such as the black ghost knifefish (Apteronotus albifrons), the glass knifefish (Eigenmannia virescens), and the banded knifefish (Gymnotus carapo).
Gymnotiformes are generally slender fish with narrow bodies and tapering tails, hence the common name of "knifefishes". They have neither pelvic fins nor dorsal fins, but do possess greatly elongated anal fins that stretch along almost the entire underside of their bodies. The fish swim by rippling this fin, keeping their bodies rigid. This means of propulsion allows them to move backwards as easily as they move forward.
The caudal fin is absent, or in the ghost knifefish (Apteronotidae), greatly reduced. The gill opening is restricted. The anal opening is under the head or the pectoral fins.
Most gymnotiforms are weakly electric, capable of active electrolocation but not of delivering shocks. The electric eels, genus Electrophorus, are strongly electric; despite the superficial resemblance, they are not closely related to the true eels of order Anguilliformes.
Ghost knifefish have approximately one hundred and fifty fin rays along its "ribbon-fin" (anal fin). These individual fin rays can be curved nearly twice the maximum recorded curvature for ray-finned fish fin rays during locomotion. These fin rays are curved into the direction of motion, indicating that the knifefish has active control of the fin ray curvature, and that this curvature is not the result of passive bending due to fluid loading.[verification needed] The forward movement is determined exclusively by the ribbon-fin and the contribution of the pectoral fins for forward movement was negligible. The body is kept relatively rigid and there is very little motion of the center of mass motion during locomotion compared to the body size of the fish.
Different wave patterns produced along the length of the elongated anal fin allow for various forms of thrust. The wave motion of the fin resembles traveling sinusoidal waves. A forward traveling wave can be associated with forward motion, while a wave in the reverse direction produces thrust in the opposite direction. This undulating motion of the fin produced a system of linked vortex-tubes that were produced along the bottom edge of the fin. A jet was produced at an angle to the fin that was directly related to the vortex tubes, and this jet provides propulsion that moves the fish forward. The wave motion of the fin is similar to that of other marine creatures, such as the undulation of the body of an eel, however the wake vortex produced by the knifefish was found to be a reverse Kármán vortex. This type of vortex is also produced by some fish, such as trout, through the oscillations of their caudal fins. The speed at which the fish moved through the water had no correlation to the amplitude of its undulations, however it was directly related to the frequency of the waves generated.
Studies have shown that the natural angle between the body of the knifefish and its fin is essential for efficient forward motion, for if the anal fin was located directly underneath, then an upwards force would be generated with forward thrust, which would require an additional downwards force in order to maintain neutral buoyancy. A combination of forward and reverse wave patterns, which meet towards the center of the anal fin, produce a heave force allowing for hovering, or upwards movement.
The ghost knifefish can vary the undulation of the waves, as well as the angle of attack of the fin to achieve various directional changes. The pectoral fins of these fishes can help to control roll and pitch control. By rolling they can generate a vertical thrust to quickly, and efficiently, ambush their prey.
Gymnotiformes
The Gymnotiformes /dʒɪmˈnɒtɪfɔːrmiːz/ are an order of teleost bony fishes commonly known as Neotropical knifefish or South American knifefish, which inhabit fresh water (the only exceptions are species that occasionally may visit brackish water to feed).[not in body] These mostly nocturnal fish have long bodies and swim using undulations of their elongated anal fin. They are electric fish, are capable of producing electric fields for various purposes, such as detecting prey, for navigation, communication, and, in the case of the electric eels (Electrophorus spp.), attack and defense. A few species are familiar to the aquarium trade, such as the black ghost knifefish (Apteronotus albifrons), the glass knifefish (Eigenmannia virescens), and the banded knifefish (Gymnotus carapo).
Gymnotiformes are generally slender fish with narrow bodies and tapering tails, hence the common name of "knifefishes". They have neither pelvic fins nor dorsal fins, but do possess greatly elongated anal fins that stretch along almost the entire underside of their bodies. The fish swim by rippling this fin, keeping their bodies rigid. This means of propulsion allows them to move backwards as easily as they move forward.
The caudal fin is absent, or in the ghost knifefish (Apteronotidae), greatly reduced. The gill opening is restricted. The anal opening is under the head or the pectoral fins.
Most gymnotiforms are weakly electric, capable of active electrolocation but not of delivering shocks. The electric eels, genus Electrophorus, are strongly electric; despite the superficial resemblance, they are not closely related to the true eels of order Anguilliformes.
Ghost knifefish have approximately one hundred and fifty fin rays along its "ribbon-fin" (anal fin). These individual fin rays can be curved nearly twice the maximum recorded curvature for ray-finned fish fin rays during locomotion. These fin rays are curved into the direction of motion, indicating that the knifefish has active control of the fin ray curvature, and that this curvature is not the result of passive bending due to fluid loading.[verification needed] The forward movement is determined exclusively by the ribbon-fin and the contribution of the pectoral fins for forward movement was negligible. The body is kept relatively rigid and there is very little motion of the center of mass motion during locomotion compared to the body size of the fish.
Different wave patterns produced along the length of the elongated anal fin allow for various forms of thrust. The wave motion of the fin resembles traveling sinusoidal waves. A forward traveling wave can be associated with forward motion, while a wave in the reverse direction produces thrust in the opposite direction. This undulating motion of the fin produced a system of linked vortex-tubes that were produced along the bottom edge of the fin. A jet was produced at an angle to the fin that was directly related to the vortex tubes, and this jet provides propulsion that moves the fish forward. The wave motion of the fin is similar to that of other marine creatures, such as the undulation of the body of an eel, however the wake vortex produced by the knifefish was found to be a reverse Kármán vortex. This type of vortex is also produced by some fish, such as trout, through the oscillations of their caudal fins. The speed at which the fish moved through the water had no correlation to the amplitude of its undulations, however it was directly related to the frequency of the waves generated.
Studies have shown that the natural angle between the body of the knifefish and its fin is essential for efficient forward motion, for if the anal fin was located directly underneath, then an upwards force would be generated with forward thrust, which would require an additional downwards force in order to maintain neutral buoyancy. A combination of forward and reverse wave patterns, which meet towards the center of the anal fin, produce a heave force allowing for hovering, or upwards movement.
The ghost knifefish can vary the undulation of the waves, as well as the angle of attack of the fin to achieve various directional changes. The pectoral fins of these fishes can help to control roll and pitch control. By rolling they can generate a vertical thrust to quickly, and efficiently, ambush their prey.
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