The guppy (Poecilia reticulata), also known as millionfish or the rainbow fish, is one of the world’s most widely distributed tropical fish and one of the most popular freshwater aquarium fish species. It is a member of the family Poeciliidae and, like almost all American members of the family, is live-bearing. Guppies originate from northeast South America, but have been introduced to many environments and are now found all over the world. They are highly adaptable and thrive in many different environmental and ecological conditions. Male guppies, which are smaller than females, have ornamental caudal and dorsal fins. Wild guppies generally feed on a variety of food sources, including benthic algae and aquatic insect larvae.Guppies are used as a model organism in the fields of ecology, evolution, and behavioural.

Guppies exhibit sexual dimorphism. While wild-type females are grey in body colour, males have splashes, spots, or stripes that can be any of a wide variety of colors.The development and exhibiting of color patterns in male guppies is usually due to the amount of thyroid hormone that they contain. The thyroid hormones not only influence color pattern, but control endocrine function in response to their environment. The size of guppies vary, but males are typically 1.5–4 cm (0.6–1.6 in) long, while females are 3–7 cm (1.2–2.8 in) long.

A variety of fancy guppy strains are produced by breeders through selective breeding, characterized by different colours, patterns, shapes, and sizes of fins, such as snakeskin and grass varieties. Many domestic strains have morphological traits that are very distinct from the wild-type antecedents. Males and females of many domestic strains usually have larger body size and are much more lavishly ornamented than their wild-type antecedents.

Guppies have 23 pairs of chromosomes, including one pair of sex chromosomes, the same number as humans. The genes responsible for male guppies’ ornamentations are Y-chromosome linked and are heritable.

size (1″-1.25″)