by Ruby Bayan
The term "livebearers" means that these fish do not lay eggs. Instead, they give birth to live, fully formed young which are capable of swimming and feeding as soon as they are born. The eggs are fertilized and develop inside the body of the female. Since these young fish are born live and swimming, the broods are usually small in number. Each group usually averages 20 to 50 fish.
The male members of this livebearing species have a gonopodium, a sex organ formed by the fusion of several rays of the anal fin. During mating, this gonopodium is directed forward, toward the female. With the help of tiny hooks at its tip, this specialized fin gets briefly attached to the cloaca of the female while sperm is channeled into her.
The unique thing about livebearing females is that they are capable of storing sperm. This gives them the capability to develop several successive broods from just one mating session.
The guppy is a native of South America, Barbados, and Trinidad. But because of its hardiness and ease of proliferation, the guppy is now commercially bred and available in many fish farms in America, Asia, and Europe.
At one time, the guppy, which prefers a diet of mosquito larvae, was deployed" to different areas as a countermeasure to fight malaria. Recently, exotic breeding has given rise to rainbow-colored, large-finned varieties that are a delight to own.
Guppies do well in aquariums filled with either fresh or brackish-water. They prefer well-planted setups and love to explore them. They will be happy in a community tank as long as there are no aggressive fish that will nip at their fins and tails. Populate your tank with males and females since the males will tend to pick on each other's tails if there are no females to catch their attention.
Also native to the South America region, the sailfin and the hybridized gold, black, albino, and lyretail mollies prefer hard, alkaline water that can get as cold as 68 degrees Fahrenheit. Known to thrive best in brackish to marine waters, mollies have been used to help "mature" start-up marine aquariums. They are relatively easy to care for, as long as the waterconditions are kept to their liking. If the water quality is deteriorating or too cold, they will clamp their fins, sit still on the substrate, or move about listlessly.
Like all livebearers, molly males are distinguishable by their gonopodium. The male sailfin molly has a well-developed dorsal fin that he uses to catch the attention of the female.
Platies and swordtails are just as fertile and prolific as the guppies. They are also popular among tropical fish aquarists. Cross-bred and hybridized extensively, platies and swordtails are now available in various color combinations and fin types. Originally greenish, with the male having a single orange caudal fin extension (or sword), the swordtail has now been cross-bred with the platy. This has led to the creation of the Xiphphorus variatus that can be of marigold, sunset, tuxedo, or tiger colors There are also elaborate double swords (lyre-tails) and high-fins (topsails) in black, albino, red, and tuxedo.
Among the livebearers, the swordtails are regarded as the most active. They are the first to jump out of the aquarium when stressed or involved in a frantic courtship. Therefore, be sure to provide enough plants as hiding places and as deterrents to their impulse to jump. Itís also a good idea to purchase an aquarium cover that fits well.
See also: Feeding and Breeding Livebearers