Molly: Poecilia gillii

Poecilia is a genus of fishes in the family Poeciliidae of the order Cyprinodontiformes. These livebearers are native to fresh, brackish and salt water in the Americas, and some species in the genus are euryhaline.

Poecilia is a genus of fishes in the family Poeciliidae of the order Cyprinodontiformes. 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) and a population of P. mexicana lives in caves (other populations of this species are surface-living).

Some common and widespread species are often kept as aquarium fish, while other have very small ranges and are seriously threatened.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.

Micropoecilia has been proposed to be included as a subgenus of Poecilia.

Etymology, taxonomy, and history

Franz Steindachner first described the species in 1863. Poecilia refers to the Greek word poikilos, which means “with a lot of colours”. Common names include “shortfin molly” and “Atlantic molly.” The type specimen was found in Orizaba, Mexico.


Along with their swordtail and platy relatives, the mollies are part of a pivotal aquaculture group of livebearers, which can live in water from fresh to fully marine, and a wide range of other conditions. They feed on smaller insects, animals, and vegetation.

IUCN lists two of the species, the sulphur molly, P. sulphuraria, and the broadspotted molly, P. latipunctata, as Critically Endangered.

The generic name Poecilia derives from the Greek ποικίλος (variegated), in reference to the fishes’ coloration.

The common mollies (P. sphenops) occur in several different colors and spot patterns, such as black, white, black and white spots, orange, and orange and white spots. These have been kept successfully in freshwater, brackish, and saltwater conditions, although the last is not recommended for the novice aquarist.


The 40 currently recognized species in this genus are: