英语时差:食人鱼
Piranha! For most people, the name sparks horror-movie images of vicious schools of fish that can reduce a human to a skeleton in minutes. But do they really deserve this fearsome reputation? Piranhas are freshwater fish that are found in rivers and floodplains of South America. The most well-known species is the red-bellied piranha, but there are nearly forty other different species of piranha.
They aren't very large, but do have a mouth full of razor-sharp teeth and a strong jaw. So it may surprise you to learn that piranhas are not the bloodthirsty killers portrayed in films. They aren't even strict carnivores!
Most piranha species are omnivores and scavengers. Their diet is mostly made of insects and other fish, but also plants. During the rainy season when food is plentiful, piranhas eat more plants and insects. But in the dry season when ponds and rivers dry up and food becomes more scarce, piranha turn to meat-eating, usually in the form of other fish. Piranhas occasionally bite humans or other mammals when very hungry or threatened, but serious attacks are extremely rare.
Another common belief is that piranha form large schools for hunting, allowing them to attack larger prey than a single fish could. However, researchers found that piranha most likely group together as a defense against such predators as river dolphins, caimans and bigger fish, and not to engage in feeding-frenzies.
Despite their sharp teeth and nasty reputation, these scavengers really spend their days grazing on different foods in their environment and huddle together for safety.
So while piranha may not win your hearts with cuddly good looks, they are probably more victim than vicious.
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