Appearance
''G. carapo'' reaches up to 76 cm in total length, but it rarely surpasses 42 cm and depending on exact population average is 15–26 cm. In a study where two breeding males were located one was 18 cm long and the other 33.5 cm.It is brown with an oblique banded pattern. The strength and details of this pattern varies, both individually and depending on region. There are also some morphometric variations depending on location. A review found that these were insufficient for recognizing the populations as separate species, but did recommend recognizing them as subspecies: ''G. c. carapo'' , ''G. c. australis'' , ''G. c. caatingaensis'' , ''G. c. madeirensis'' , ''G. c. occidentalis'' , ''G. c. orientalis'' and ''G. c. septentrionalis'' .
Naming
The English name "banded knifefish" is sometimes used for the entire genus ''Gymnotus'' instead of only the species ''G. carapo''.Behavior
This species, as with all Gymnotiformes, is an electric fish that has the capability to generate weak electric charges, and then measure the disturbance in the field of electricity created. This system is used for navigation, finding prey and communicating with other ''G. carapo''. They are highly territorial and will react aggressively if detecting the electric field of another individual of their species. However, they are not able to generate a strong electric field that can be used for incapacitating prey or enemies, like the related electric eel.Habitat
This South American fish is found in the Amazon, Orinoco and Río de la Plata basins, as well as rivers in the Guianas, northeastern Brazil and northern Argentina , and in Trinidad. This makes it the most widespread species of ''Gymnotus''.''G. carapo'' occurs in virtually any freshwater habitat in its range, such as rivers and streams , floodplains, estuaries, swamps and lakes. However, it is not known from deep river channels. It can survive in low-oxygen habitats , areas affected by pollution, and for a period on land if its aquatic habitat dries out.
Reproduction
The male takes care of the young by mouth brooding, and making and watching over a "nest", a depression in the bottom where the female lays the eggs.Food
''G. carapo'' are nocturnal and eat benthos, such a worms, insects, crustaceans, small fish and plant material.References:
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