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Today on Animal Fact Files we’re talking about platies and swordtails. Platies and swordtails are both fish that belong to the same genus, though they can look a little different from one another. The common name “swordtail” gives a bit of a clue. Male swordtails usually have an elongated lower tail fin, and swordfish in general tend to have a more narrow body structure. Platies, on the other hand, don’t usually come with a swordtail and they are a little more chonky. Then again, some fish that have an elongated tail are called platies and some swordfish don’t have the sword, so we’ll just talk about both.

Like the colorful feathers in some male birds, or the hulking antlers in male deer, swordtails have an elongated tail to attract females. Platies, obviously get by without this trait. In some species there are hierarchies of males in which the males fight over females and the dominant males have breeding rights. In other species the males may put on mating displays that are specific to their species - an important factor we’ll touch on later in this video.

With swordtails, it’s relatively easy to tell a female from a male - the ladies don’t have swords. In platies, it’s still pretty easy because females have rounded anal fins while males have modified, pointy anal fins which are used in mating. Instead of releasing their eggs into the water column to be fertilized externally, female swordtails and platies retain their eggs which are fertilized internally by the males. The females will gestate for one to three months - temperature as well as species can play a role in this - and then give birth to approximately 50 live babies. Not eggs, free-swimming, baby fish. And the female platies and swordtails may produce multiple broods of babies in a single year!

The young fish reach maturity quickly, and warmer water temperatures can speed up this process. The young fish are ready to begin breeding after about eight to ten weeks, or once they reach about 20 millimeters (0.79 inches) in length. As adults, the largest of these fish are green swordtails who can reach more than six inches (15.24 centimeters) in length, though the other nearly thirty species are less than half this long at full size. The females are usually longer than the males, and the swords in swordtails don’t really give them an edge over platies in length.

Platies and swordtails are natively found in Central America. These are hardy fish that can handle a variety of habitats. Some species may be found in stagnant water systems, others live in forest streams, and there are some who enjoy the fast flowing rivers in mountainous regions. The species are typically separated by the land’s geography, but in areas where species overlap, they’re typically separated by mating styles. This is why the species specific mating dances can be important - the dances likely inhibit hybridization among different species in the wild. This is not the case with captive platies and swordtails!

These fish are popular in the pet trade. Their distribution around the world as pets has likely lead to their invasive introduction to water systems around the world - including India, Australia, and the United States. Most pet platys and swordtails are actually hybridized species and this is why they come in all kinds of colors in the pet trade. In the wild, they take on more neutral hues - similar to the betta fish we’ve talked about previously.

Platies and swordtails eat plant materials, detritus, copepods, and fish larvae. They, in turn are likely taken by larger fish, mammals, and birds, and it’s thought the sword in swordtails may be a detriment to their survival because it’s an easy place for a predator to grab!

For more facts on platies and swordtails, check out the links in the description. Thank you to shelly la tortuga for today’s request. Give a thumbs up if you learned something new today, and thank you for watching Animal Fact Files!