Poecilia Species

Poecilia is a genus of fishes in the family Poeciliidae of the order Cyprinodontiformes.^[1] These livebearers are native to fresh, brackish and salt water in the Americas, and some species in the genus are euryhaline. A few have adapted to living in waters that contain high levels of toxic hydrogen sulfide (H
2S)^[2] and a population of P. mexicana lives in caves (other populations of this species are surface-living).^[3]

Some common and widespread species are often kept as aquarium fish, while other have very small ranges and are seriously threatened.^[2] All species in Poecilia are called mollies except for the Endler's livebearer (P. wingei) and the well-known guppy (P. reticulata). Without a modifying adjective, molly usually refers to the species Poecilia sphenops.