Pacu is a South American freshwater fish found in most rivers and
streams in the Amazon and Orinoco river basins of lowland Amazonia, but
they have also been reported as far as Papua New Guinea, where it was
artificially introduced to aid the local fishing industry. Pacu is
related to the meat-eating piranha, both sharing the same subfamily
Serrasalminae,
although they have different food habits. The piranha is a carnivorous
species while the pacu is omnivorous with vegetative tendencies. The
difference is evident in the structure of their teeth. Piranha have
pointed, razor-sharp teeth whereas pacu have squarer, straighter teeth,
that eerily resemble those of humans.
Pacu uses its teeth mainly to crush nuts and fruits, but sometimes
they also eat other fish and invertebrates. They usually eat floating
fruits and nuts that drop from trees in the Amazon, and on a few
occasions were reported to attack the testicles of male swimmers
mistaking them to be floating nuts. This has earned them the name of
"ball-cutter" after they castrated a couple of local fishermen in Papua
New Guinea. So when the fish was spotted in a few odd lakes in
Denmark and later in Washington, New Jersey and Illinois last year, a mild panic ensued.
While
they are not aggressive carnivores like the piranha, their crushing jaw
system can be hazardous. One toddler needed surgery after a pacu bit
her finger at Edinburgh Butterfly and Insect World in Scotland.
Commenting on the incident, Deep Sea World zoological manager Matthew
Kane warned, "Pacus will eat anything, even children's wiggling fingers.
Pacus
are legal to own in the United States, can be bought in aquarium stores
and are easy to raise. The trouble is many aquarium owners are unaware
that pacus can grow up to 4 feet long, which is way too large for a
typical home aquarium. When pet pacus outgrow their fish tank,
many owners end up dumping the fish in nearby lakes.
A fully-grown adult sheepshead has well-defined incisors sitting at the
front of the jaw, and molars set in three rows in the upper jaw and two
rows in the lower jaw. It has strong, heavy grinders set in the rear of
the jaw too, which are particularly important for crushing the shells of
its prey. As with humans, this unique combination of teeth helps the
sheepshead process a wide-ranging, omnivorous diet consisting of a
variety of vertebrates, invertebrates and some plant material.
Photo credit: Scientificamerican.com
