Few animals have as ferocious a reputation as piranhas (genus Serrasalmus), freshwater fish found in the tropics of South America. The name, inspired by the piranhas' razor-sharp triangular teeth, comes from the Portuguese piro for "fish," and sainha for "tooth." Piranhas are also known locally as caribe, derived from the Carib, an indigenous group for which the Caribbean Sea was named. Columbus also reported hearing the feared Carib tribe in Cuba called Canibaliterally, "strong men"and indeed believed this group to be cannibals.
Like their tribal namesakes, piranhas have long been thought to eat humans. However, reports of the man-eating fishnot to mention the man-eating menare greatly exaggerated.
Most of the more than 20 species of piranhas found in the Amazon are omnivorous, eating both seeds as well as the meat of other fishes or wounded animals who stray into the water. Even the most blood-thirsty piranhas, however, cannot eat an entire animal by themselves; instead they merely nip off scales or bits of flesh. And only when herded together by low waters during the dry season will most species of piranha congregate in large schools, the only time when healthy mammals (and humans) need fear treading in rivers and lagoons.
The one exception is the caju (Serrasalmus nattereri), which does frequently form large schools. The caju is the most publicized piranha species, helping to spread misconceptions about this widely varied fish.
The 44-plus species of harlequin frogs are easily the jesters of the Central and South American amphibian court. For one thing, these so-called frogs are actually toads. And they can be easily confused with poison dart frogs because they sport brightly colored smooth skin, and produce highly toxic skin secretions. But harlequin frogs intrigue herpetologists for other reasons: They have a Bidders organ, a rudimentary gland that enables males to develop functioning ovaries if their testicles are removed; and they exhibit "transsexual calling talents"meaning both sexes are able to call during breeding season. Furthermore, tadpoles hatch about 24 hours after the females lay their egg strands.