Poeciliinae

Content sourced from Wikipedia, licensed under CC BY-SA 3.0.

Poeciliinae is a subfamily of livebearing fish in the Poeciliidae family. They come from the Americas and are called livebearers because most species give birth to live young after internal fertilization. In males, the anal fin is elongated into a gonopodium used for mating.

They are mostly freshwater fish, but some live in brackish water or can even tolerate seawater. Their range extends from southern Canada through Central and South America to Patagonia.

Many well-known aquarium fish—such as guppies, swordtails, and mollies—belong to this group. They have been introduced around the world, sometimes on purpose to control mosquitoes, but they can become invasive and threaten local small fishes. A notable example is the eastern mosquitofish (Gambusia holbrooki), listed among the world’s worst invasive species.