Facts about the Piranha Scientific(Remarkable Fish Piranhas)
Names:
Scientists used to lump all piranhas under the name Serrasalmus. Now scientists think there are at least four different groups of piranhas: Serrasalmus, Pygocentrus, Pygopristis, and Pristobrycon. Of these groups, scientists have identified some 30 different piranha species.
Description:
Size: From 8 inches (20 centimeters) to 2 feet (60 centimeters) long; most species a little over or under a foot (30 centimeters)
Physical Features:
All piranhas have a single row of sharp, triangular-shaped teeth in both jaws; plate-shaped body, adipose fin; lower jaw sticks out farther than upper jaw. Some have heavy bodies with blunt, bulldog snout; others have longer body and sharp snout. They can see and hear well.
Color
Wide range of colors and black markings. All young piranhas have a silvery body. Adult piranhas are usually more colorful, often with bright red or orange bellies and throats-sometimes with yellow markings.
Distinctive Habits
Piranhas are active mostly during the day. Large piranhas may also hunt into the evening and early night, or before dawn. They may hunt in groups or alone. Many piranhas are social fish but sometimes bite one another and may eat another wounded piranha. Also, different species may prey on one another.
Some piranhas have very organized hunting behavior. They are not likely to attack a large healthy animal or human. In aquariums, they are not very aggressive unless they are hungry or overcrowded.
Food
Varied. All piranhas eat whole fish or pieces of flesh, but a few piranhas prefer to eat seeds or fruits. Young piranhas and some adults frequently eat pieces of fish fins and tails. Many piranhas are scavengers and eat dead flesh. Piranhas will also eat insects, shrimp, and fish scales. They will occasionally eat birds, rodents, and reptiles. Sometimes they will bite the toes and tail tips of swimming animals.
Reproduction
Scientists know very little about the reproduction of piranhas in the wild. Most piranhas in the wild breed at the beginning of the rainy season; females probably attach eggs to floating water plants and may make nests. Piranhas in aquariums are known to guard their eggs and their newly hatched young. Young piranhas hide and hunt among the roots and leaves of water plants. Piranhas are sexually mature, or can reproduce, after about one year. Older adult piranhas change color during the breeding season.
Life Span
Several years; some may live as long as five years or more.
Range
Piranhas are freshwater tropical fish. They are only native to South America. Piranhas range from Venezuela south to the northern part of Argentina. They are found in all the major rivers that flow to the Atlantic Ocean, including the Amazon, Orinoco, Essequibo, La Plata, and Sao Francisco rivers.
Habitat
Piranhas are lowland fish that live in big rivers, small streams, and lagoons, as well as natural and manmade ponds, lakes, and reservoirs. They live in waters in both tropical forests and tropical savannas, or grasslands.
Different Fish, Different Habits
Most piranhas have a body shaped like a round dinner plate, with spines on the belly and many small scales. Many also have blunt noses and lower jaws that stick out farther than their upper jaws, making them look a little like bulldogs. The largest piranhas grow to be about 2 feet (about 60 centimeters) long. One of these lives in the S?o Francisco River in northeastern Brazil. You may think it lucky that this big hunter lives in only one river-but since that river is nearly 2,000 miles (3,200 kilometers) long, the piranha’s range still covers a great deal of territory. Most other piranhas are a little over or a little under 1 foot (about 30 centimeters) long. There are many species of smaller piranhas whose average size is between 8 and 12 inches (20 and 30 centimeters).
All piranhas have a single row of teeth in each jaw, and each tooth is shaped like a triangle. The upper and lower teeth slide against one another to shear off pieces of food-working like a powerful pair of scissors. If a piranha loses a tooth on one side of its jaw, it must grow an entirely new set on that side. Piranhas don’t chew-once they bite out a chunk of food, they swallow it whole.
Even though all piranhas have very similar types of teeth, different kinds of piranhas often use their teeth for different purposes. Not all piranhas prefer to eat whole fish or take bites out of fishes’ bodies. Young piranhas and adults of some species.
Frequently clip out pieces of other fishes’ fins and tails. Most piranhas will also bite off and swallow fish scales. Piranhas, especially young ones, will eat insects and small crustaceans. Adult piranhas will occasionally eat birds, rodents and other mammals, reptiles, and frogs. They will sometimes bite toes and tail tips of swimming animals also.
Only a few species of piranhas are able to seriously injure a large live animal or human. These include the red-bellied piranhas that most people think of when they hear the word piranha. They live in the Amazon Basin and in the Orinoco River, which flows through Venezuela and borders Colombia. Red-bellied piranhas grow to more than 14 inches (37 centimeters) long. Red-bellies live mostly in lagoons. One scientist said they were the most beautiful freshwater fish, with an olive green or brown face, a gold or silver back, a black tail, and red everywhere else. Black piranhas have powerful jaws, strong enough to bite through wood. Their eyes are red. Black piranhas are most Common in stream of Amazon and the Orinoco.
Piranha Relatives
Pacus look like piranhas but have two rows of teeth in the upper jaw. Some teeth are shaped like molars, the large, flat teeth you chew with. Pacus use their molarlike teeth to grind fruit, nuts, and leaves. Pacus also have sharp, incisor-like teeth and will eat insects, small shellfish, and fish. Some pacus grow very large, up to 3 feet (90 centimeters) long, and are important as food to people of the Amazon Basin. Some young pacus are colorful and make good aquarium fish. However, people who own pacus say that they will kill and eat other fish when they grow larger and start feeling cramped for space.
Surprising Diets
Until very recently, scientists thought that all piranhas ate only fish and meat. They called them carnivores-meat eaters. But scientists have discovered that some piranhas are more vegetarian than flesh. Eaters-they prefer to eat seeds and fruits that fall into the water. Piranha teeth work equally well in biting out a piece of hard seed as they do in clipping out a piece of flesh. Even the more carnivorous piranhas will eat fruits and seeds at certain times of the year when such foods are more plentiful than fish.
They’ll also bite at pieces of aquatic plants. Most piranhas are also scavengers-they eat the flesh of dead animals and people. It’s likely that this habit contributed to the piranha’s reputation for being a “man-eater”-when a skeleton is pulled out of the water, it’s hard to tell how the person died.
