Courtship in Guppies
Introduction
Guppies (Poecilia reticulata) are freshwater fish native to streams in northeastern South America and Trinidad. They can also be found in many other areas due to unintentional introduction from the aquarium trade or intentional introduction for mosquito control. They are very popular with aquarium hobbyists due to the males’ bright colors. Where they live in small streams in tropical countries, guppy populations are frequently dense. Males compete for access to females and larger females produce more offspring per brood than do smaller ones.
Guppies are live-bearing fishes, having broods of 1-25 babies depending on female size. In order for a fish to be live bearing, internal fertilization must occur. This is accomplished using an elongated and specialized anal fin, called a gonopodium. Baby guppies are born 4-6 weeks after mating occurs. Several broods may occur after just one mating.
Sexual dimorphism occurs in guppies, meaning that males and females look very different from each other. Female guppies are a drab silvery in coloration – better for avoiding notice from predators. The males, on the other hand, are very colorful. Males increase their chances of mating by increasing the rate at which they court females. More attempted matings usually means more actual matings. Females appear to prefer to mate with males having higher courtship rates. Males that court at a high rate or with elaborate, colorful tails pay a price. Predators selectively eat the brightly-colored, flashy, courting males. In areas where there are many predators, there must be a balance between being very colorful (attractive to females) and less colorful (better for hiding from predators).
