The Fishes: Sternopygidae

GYMNOTIFORMES - electric fish

Family: Electrophoridae

All gymnotiform fish have the same characteristic elongate shape linked to the use of electricity for locating objects.

Sternopygidae
There are currently 23 sternopygid species which are grouped on the basis of dentition, skeletal structure and sensory pores. Genera include Distocyclus, Eigenmannia, Rhabdolichops, and Sternopygus. These are essentially nocturnal animals that remain undercover by day. At night they will enter open water in search of prey.

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Close-up of the head of Distocyclus conirostris	Close-up of the head of Eigenmannia cf. humboldtii	Close-up of the head of Eigenmannia virescens	Close-up of the head of Eigenmannia macrops	A recently caught specimen of Rhabdolichops caught in an eel trap in a white water river channel
Close-up of the head of an Eigenmannia sp	Close-up of the head of an Eigenmannia sp	Close-up of the head of an Eigenmannia sp	Close-up of the head of a Rhabdolichops species	Photograph of the anterior half of a Rhabdolichops species
	Photograph of the anterior half of a Rhabdolichops species		Photograph of the anterior half of a Rhabdolichops species

Rhamphichthidae
There are currently 13 described species in this family. These are divided between three genera, Rhamphichthys, Gymnorhamphichthys and Iracema.

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Close-up of the head of species of a Rhamphichthys species showing the characteristic trunk	Close-up of the head of species of a Rhamphichthys species showing the characteristic trunk	Close-up of the head of species of a Rhamphichthys species showing the characteristic trunk. This specimen was caught in Lake Tefe in an open water gill net	Living specimen of Gymnorhamphichthys rondoni	A large Rhamphichthys specimen caught in a gill net in Lake Tefe. This fish must have been swimming in open water when it was caught. This specimen was caught in Lake Tefe in a gill net set in open water.
		Head of a large Rhamphichthys specimen caught in a gill net in Lake Tefe. This fish must have been swimming in open water when it was caught. This specimen was caught in Lake Tefe in a gill net set in open water

Hypopomidae
Hypopomidae are electric or knife fish, and like other gymnotiform fish have the same characteristic elongate shape linked to the use of electricity for locating objects. This family possesses long tails, which can become very long in the males because the females assess the quality of their mates by the length of their tails! This happens because the electrical signals sent out by the male change with the length of the tail. Poor quality males loose their tails to piranha attack, but all is not lost, as they will re-grow. There are currently 16 species in the Hypopomidae and these are assigned to the genera Hypopomus, Brachyhypopomus, Microsternarchus, Steatogenys and Hypopygus. The members of this family tend to live within aquatic substrates such as leaf litter or floating meadow. They are often highly resistant to low oxygen levels. They have small mouths and feed on micro-crustaceans, small insects such as chironomids and other micro-invertebrates.

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Living specimen of Hypopygus lepturus	Close-up of the head of Brachyhypopomus beebei	Close-up of the head of Brachyhypopomus brevirostris	Close-up of the head of Brachyhypopomus pinnicaudatus	Close-up of the head of a member of the Hypopomidae
Close-up of the head of a member of the Hypopomidae	Close-up of the head of a member of the Hypopomidae	Close-up of the head of a member of the Hypopomidae	Close-up of the head of a member of the Hypopomidae	Close-up of the head of a member of the Hypopomidae
Lateral view of a preserved specimen of the electric fish Steatogenys elegans	Hypopomus species found in leaf litter	Hypopomus species found in leaf litter	Hypopomus species found in leaf litter

Apteronotidae
This family differs from other knife fish in the possession of a distinct tail fin and a long filamentous dorsal fin. At present there are 36 species in this family.

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Whole specimen of Apteronotus hasemani which was caught in an eel trap in a white water floodplain channel	Close-up of the head of a preserved specimen of Apteronotus bonapartii	Close up of the head of Apteronotus anas
Whole specimen of Apteronotus albifrons	Close up of the head of Sternarchella cf. terminalis	Close up of the head of Sternarchogiton porcinum	Close up of the head of Platyurosternarchus macrostomus

Gymnotidae
In this family, only the pectoral and anal fins are present. The family comprises a single genus, Gymnotus, which holds some of the most abundant and familiar knife fish from the Amazon. This genus is widely distributed in almost all forest and floodplain habitats. They possess large mouths for knife fish and are active nocturnal predators on insects, prawns and fish. Their bodies often have a black and white banded or even spotted pattern. Recent taxonomic revisions have placed the electric eel, Electrophorus within this family.

G. carapo
Identification: A deep-bodied knife fish reaching a length of more than 20 cm. It is the only species within the Taruma-Mirim with vertical banding along the full length of the body. It has a large mouth.
Colour: dark background with white bands.
Habitat: Leaf-litter banks, root mats and floating meadow
Abundance: Widely distributed within the Amazon and abundant in varzea. Seems not to be particularly common in the Taruma-Mirim.
Food: Active predator. Young feed on insects and crustaceans. Adults will also take fish.

Gymnotus sp1
A large mouthed robust knife fish much like Gymnotus carapo in form but thinner bodied. Only the rear 1/3 to 1/2 of the body is banded. It is similar to G. angularis in general form.

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Gymnotus carapo	Close-up of the head of a preserved specimen of Gymnotus anguillaris	Close-up of the head of an unidentified Gymnotus species
Close-up of the head of an unidentified Gymnotus species	Close-up of the head of an unidentified Gymnotus species	Close-up of the head of an unidentified Gymnotus species
A Gymnotid electric fish found in submerged leaf litter	Close-up of the head of a Gymnotid electric fish found in submerged leaf litter	A Gymnotid electric fish found in submerged leaf litter
	A Gymnotid electric fish found in submerged leaf litter

Electrophoridae
This family holds a single species, the famous electric eel, Electrophorus electricus. This is the only gymnotiform fish to generate powerful electric shocks and is by far the largest species of electric fish found in the Amazon. The electric discharge from this species is sufficient to knock a man from his feet and I have known biologists to be unable to walk properly for a day after being shocked. This is a widely distributed species found in both white and black waters in both flood plain lakes and small forest streams. It is a top predator of the system and is surprisingly abundant. It probably favours hunting along the margins of flooded forest and within forest streams. We found that eel traps placed within flooded forest close to the water margin caught a surprising number of specimens. When the water is rising, they lurk round the edge of islands ready to catch snakes, frogs and other animals as they are forced to enter the water. Electric eel often lie close to the surface and have the menacing presence of a nuclear hunter killer submarine; they are often quite indifferent to predatory threats. While working on leaf-litter banks in small streams, I have suddenly realized that a large specimen has silently moved close by, perhaps attracted by the disturbance. Thankfully, they do not discharge unless threatened or during capture of their prey.

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The head of the electric eel, Electrophorus electricus, near to the surface of the water	A living specimen of the electric eel, Electrophorus electricus	A living specimen of the electric eel, Electrophorus electricus	A living specimen of the electric eel, Electrophorus electricus