A freshwater fish of the pecilian family. Small fish, males up to 4 cm long, females up to 6 cm. 

In males, the anterior rays of the anal fin are transformed into a copulatory organ (gonopodium). 

The common Gambusia is grey to brown in colour, with a bluish tinge to the sides. Sometimes there are a few black spots on the body, otherwise there is no body pattern. The fish changes its colour by increasing or decreasing the concentration of melanin in the chromatophores. 

Widespread in the waters of southern North America. Known from the Caucasus, Ukraine, Central Asia and Russia. 

The fish are viviparous, precocious: fry become sexually mature only 1.5-2 months after birth. Mating takes place in late April - early May. During the summer, Gambusia gives birth to 3 litters of 50-70 fry each. Life expectancy - about 3 years. 

Feeds on planktonic crustaceans and insect larvae. An undesirable object in ponds, it destroys eggs and larvae of bred fish and is a food competitor for their young.

These fish are known to feed on mosquito larvae, so they have been artificially introduced into many new habitats where they have become established due to their resilience. At the same time, the introduction of Gambusia is thought to have negative effects on other invertebrates, as well as fish and amphibians.