Page 185 - Encyclopedia of Aquarium and Pond Fish, 3rd Edition

OTHER AMERICAN SPECIES 183

Apteronotus albifrons
STING IN THE TAIL
Black Ghost Knifefish
The arrangement of fins in rays, such as this venom is pumped directly into the bloodstream.
ORIGINS South America, occurring in parts of Venezuela, Venezuelan stingray (Potamotrygon hystrix), is The effects of the venom on humans vary between
Ecuador, Peru, Brazil, and Guyana. very different from that seen in other freshwater the different stingray species, but they are always
SIZE 20 in (50 cm). fish. The unusual pectoral fins, which extend painful and in some people they can even be
DIET Live foods. all around the sides of the body, are responsible life-threatening.
WATER Temperature 73–82°F (23–28°C); soft for the distinctive swimming motion. Stingrays These ancient relatives of sharks rely on their
(50–100 mg/l) and acidic (pH 6.5). lack a dorsal fin and derive no propulsive power sting for protection against potential predators,
TEMPERAMENT Shy, sometimes aggressive. from the caudal fin. However, the caudal fin does including crocodilians and even jaguars, which
have a defensive function: it is equipped with a sometimes hunt them in the shallows. Stingrays
The dense black body of this fish is punctuated stinger in the form of a raised, venomous spine. are also well camouflaged to help them avoid
by two contrasting white areas—one on the head, The spine pierces an attacker’s flesh, triggering a detection and can modify their coloration to a
the other at the rear, often on the caudal peduncle. localized infection around the wound, while certain degree to blend in with the river bottom.
The Black Ghost Knifefish generates a weak
electrical current that helps it to find its prey in
murky water, acting rather like a form of radar. An
aquarium for these fish should be shaded, with a
dark substrate and a well-planted interior that
offers the
fish a range of
hiding places.

Eyes blend
in with
body color

Knifelike shape

Eigenmannia virescens Potamotrygon motoro
Glass Knifefish Ocellated Stingray aquarium. There is a very real danger associated
with keeping these fish—take great care to avoid
ORIGINS South America, from Colombia’s Rio Magdalena ORIGINS South America, where it is restricted to the contact with the stinger when servicing the tank.
south to the Plate River in Argentina. rivers of Paraguay. Always wear sturdy, unperforated gloves, and keep
SIZE 13 ⁄2 in (35 cm). SIZE 12 in (30 cm). disturbance to an absolute minimum. Whenever
1
DIET Live foods. DIET Meat-based diets. possible, use tongs rather than your hands to carry
WATER Temperature 73–82°F (23–28°C); soft WATER Temperature 73–82°F (23–28°C); soft out tank maintenance. In spite of their venomous
(50–100 mg/l) and acidic (pH 6.0). (50–100 mg/l) and acidic (pH 6.0). sting, these fish are not inherently aggressive, and
TEMPERAMENT Nervous yet social. TEMPERAMENT Fairly placid, but has a dangerous sting. groups can be kept together in a large aquarium.
The floor covering of the tank should be deep and
There is a significant difference in size between the The spots on the body of this ray consist of a sandy. This will enable the fish to burrow into the
sexes in this species, with females rarely growing light center surrounded by a dark outer circle. substrate, where they will lie with just their eyes
larger than 8 in (20 cm). Both sexes have a long, Patterning is highly variable, perhaps to match exposed. Mating is unknown in aquariums, but in
narrow body shape with neither a caudal fin nor a the different habitats in which these fish occur. the wild it occurs in September and October, with
dorsal fin. Glass Knifefish live in groups with a It is also affected by the level of lighting in the the young rays being born about five months later.
well-organized social structure, which helps to
reduce conflict. The dominant male is usually the
largest in the group. These Knifefish are most active
after dark, although spawning usually occurs early
in the morning, with up to 200 eggs being laid.
Semitransparent body

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