Livebearers Family – Poeciliidae

There are currently SEVENTEEN members of the Livebearers or Poeciliidae Family, nine from the freshwater systems that drain into the Atlantic Ocean, two form the freshwater systems that drain into the Pacific Ocean, and six from the freshwater systems that drain into both the Atlantic and Pacific Oceans, presented in this website:

FROM THE ATLANTIC (9):

FROM THE PACIFIC (2):

FROM THE ATLANTIC & THE PACIFIC (6):

The fish of the Livebearers or Poecilidae Family are a group of at least three hundred species that have been placed into forty-four genera. Of these ten fish from four genera are found in Mexican waters of the Atlantic Ocean. They are collectively known as topotes and espadas in Mexico.

The Livebearers are all small fish that do not exceed 20 cm (7.9 inches) in length that have elongated to moderately deep bodies. Many are dimorphic with the females being larger than the males and the males and females are differently colored. They have fins without spines, one dorsal fin found at the rear of the body with its origin over the anal fin in males and behind the anal fin in females, pectoral fins that are high on the sides of the body, pelvic fins that originate behind the pectoral fin base and the majority of males have a gonopodium, an elongated structure within the anal fin that facilitates internal fertilization that transfer sperm in bundles to female fish. They do not have lateral lines and the head and body are covered with smooth large scales.

The Poeciliidae are found in the fresh water systems of North and South America within low altitude coastal regions but have now been introduced on a global basis by aquarium releases and for mosquito control and today can be found in all tropical and subtropical regions of the world. They are considered to be high on the evolutionary scale with their reproduction cycles being viviparous involved internal fertilization and ending in live birth that gives their young and advantage over egg-laying species.

They are utilized extensively by the aquarium trade as they are accessible and easy to maintain, many are colorful and can be crossbreed in captivity as they are prolific breeders able to deliver several batches of young from a single fertilization from a male. They are generally peaceful fish but do practice a high level of cannibalism on their young. Popular aquarium fish include the guppy, mollies, mosquito fishes, platy, and swordtails.  Several of the individual family members have been evaluated from a conservation perspective and they are all listed to be of Least Concern being abundant with wide ranging populations. The Poeciliines have been used extensively for scientific research by anatomists, embryologists and ecologists.