Distinguishing between the genders of many species of animals is a rather easy task, but not so much when it comes to red-bellied piranhas (Pygocentrus nattereri). Both sexes of the tropical freshwater fish are extremely alike on the outside, which is why they require close attention to their vivid belly regions.
Red-bellied piranhas are a mid-sized species from South America, specifically countries including Guyana, Argentina, Venezuela, Uruguay, Paraguay, Brazil and others. These omnivorous piranhas typically achieve lengths of anywhere from 10 to 14 inches long. They tend to set up residence in rivers, particularly those with swift movement, and are prevalent in whitewater rather than blackwater settings. Lakes are also common living habitats for red bellies. As food goes, they dine on a lot of tiny fishes, bugs, worms, amphibians, birds, snails, crustaceans and even little mammals. They are opportunistic about eating and do not turn away from many foods. They do not feed solely on meat, however, routinely eating aquatic plants and algae. Red-bellied piranhas are often considered to be tough and truculent fish, with teeny knife-like chompers that are shaped like triangles.
Male and Female Differences
As their names show, red-bellied piranhas boast trademark crimson stomachs. This red tummy coloration, however, is markedly more pronounced in the males of the species, notes the website for the Bristol Zoo in the United Kingdom. This is a telling difference between the sexes, and it's particularly heightened during times of reproduction. But, although the boys have redder bellies, the girls often have strong yellowish tinges to theirs.
Other Coloration Facts
Although red-bellied piranhas have brightly colored stomachs, the rest of their physiques are gray with blots of either gold or silver. Their fins are dark. Coloration of the species often varies subtly based not only on gender, but also on factors such as geography, notes the Mystic Aquarium website. Red-bellied piranhas also have red eyes.
Youngsters and Aging Individuals
You might be able to tell male and female red-bellied piranhas apart just by gazing at their bellies, and this also applies to the youngsters of the species. Young red-bellied piranhas are uniformly silver but also feature darker-colored markings throughout their forms. Notably, however, they do not yet possess the characteristic yellowish-red or pure red stomach coloration of the male and female adults. At the other end of the spectrum, the red also tends to fade away on aging individuals, indicates the website for the Houston Zoo.