Piranhas are medium-sized,
carnivorous tropical fish native to
South
America. There is some considerable confusion over the definition of the
piranhas. The common name has been
hopelessly applied to any and all
voracious carnivorous fish, whether or not it is biologically a member of
the piranha
subfamily, the
Serrasalminae. Even further complicating
the definition of piranhas is the
aquarium trade, which often applies
upwards of five or six
common names for a single species, and often uses the
same common name for up to ten different species. The result is a horrible
mess of confusion, frustration and tears. What follows is a discussion of the
piranhas as best defined by
modern biological classification.
General Biology
The name Piranha, or more appropriately Piraña, is
etymologically from the Tupi-Guarani, and means toothed-fish
(pira=fish, ranha=tooth). They are also often called
Caribe, named
after the Carib natives who were known to the Spanish explorers (conquerors)
to be both fierce and cannibalistic.
They are deep-bodied laterally-compressed (imagine a dinner plate) fish with
very prominent jaws. They are best known for their highly developed and
very sharp teeth, which can grow to be 3/4 cm long. Their teeth are so sharp
that people who have been bitten claim not to have felt the contact at all,
and in fact until they saw the blood had no idea they were hurt. Piranhas
have well developed lateral lines, and a prodigious sense of smell. Their
vision, on the other hand, is quite poor. They are thus well adapted to living
in the murky waters of South American rivers.
Neonate piranhas feed on invertebrate prey (zooplankton, insects) but as they grow they
quickly shift to higher animals like fish, birds and rodents. They
school, and attack in packs. When piranhas attack a larger prey, they go
into a frenzy, causing the water around them to roil and turn red with
blood. In this feeding frenzy, they often bite one another, and are known to
be voraciously cannibalistic.
The above description of their feeding behaviour is generally valid for the
genera Pygocentris and Serrasalmus. It falls to pieces, however,
with the other members of the subfamily, the genera Pristobrycon and
Pygopristis, which are totally herbivorous. They feed on fruit and
seeds that fall from trees into the water, and can be kept in captivity on
commercial bird seed1.
The piranha is a preferred prey of many birds and larger predators in
South America. In particular, it is targeted by the caiman and crocodile
during the end of the rainy season (as the rivers and tributaries
dry up, the piranhas are easy prey).
Conservation status
Unlike many other species native to South America, the piranha is not
threatened by humans. In fact, the piranha presents the opposite problem for
the
conservation biologist: they are quite hardy
animals and have been transported all over the globe due to the
aquaculture
hobby. These animals are released into the wild relatively infrequently, but
have managed to survive in both North American and European waterways. Luckily
enough, they are normally
killed by the cold winter; they do not survive if
the water temperature drops below 23
0C. However, there is
considerable concern about a possible introduction leading to a permanent
population in the southern United States (
California,
Texas and
Florida), resulting in the banning of the species from some southern states.
Relationship to humans
The piranha,
despite horrible movies to the contrary, has never been a
confirmed
predator of human beings. However, humans are often injured by
piranhas, especially when fishing either for the species or for another fish
in the same waterway. In many areas in South American, the piranha is fished
locally for food. They apparently taste remarkably like the
crappie, and are
remarkably easy to catch (a line, a hook and any animal protein will do).
Taxonomy
There is a great deal of confusion as to what constitutes the piranha family,
subfamily or genus. What is presented below is the best classification
currently available based on both
classic morphlogical and
modern
genetic techniques.
Order: Characiformes 2
Family: Characidae
Subfamily: Serrasalminae
Genus Pygocentrus (the true piranhas)
P. piraya -- Red piranha
P. cariba -- Black-spot piranha
P. nattereri -- True piranha
Genus Pristobrycon
P. aureus
P. baratai
P. striolatus -- Striolated piranha
P. maculpinnus
P. careospinus
P. calmoni
Genus Serrasalmus
S. spilopleura -- Gold piranha
S. rhombeus -- Red-eyed piranha
S. maculatus
S. altispinnis
S. altuvei
S. brandti
S. compressus
S. eigenmanni
S. elongatus -- Slender piranha
S. irritans
S. gibbus
S. gouldingi
S. hastatus
S. hollandi
S. humeralis
S. manueli
S. marginatus
S. medinai
S. nalseni
S. neveriensis
S. nigricans
S. sanchezi
S. serrulatus
Genus Pygopristis
P. calmoni
P. denticulata -- Lobetoothed piranha
P. striolatus
1 Wonderful little facts, such as these, help to contribute to the
aforementioned weeping and frustration.
2 Formerly part of the Cypriniformes, the same family as the
goldfish, carp etc.
Information culled from ...
* http://www.fishbase.org
* http://www.wetwebmedia.com
* http://www.angelfire.com/biz/piranha038/