Are guppies viviparous or oviparous? A detailed explanation of guppy reproduction

Guppies are neither viviparous nor oviparous, but ovoviviparous. Ovoviviparity refers to a reproductive mode in which the animal's eggs develop into new individuals inside the mother's body before being released from the mother. Although the fertilized eggs develop into new individuals inside the mother's body, their nutrients still come from the yolk contained in the eggs themselves, with no or very little nutritional connection to the mother.

Guppies are easy to sex. The female has a relatively large belly, with a transparent gravid spot in front of the vent; when she is about to give birth, the gravid spot turns black. The male has a smaller, slender belly, and the most important feature is that its anal fin has evolved into a gonopodium, used to transfer sperm during reproduction.

Guppies breed regardless of season, and can even reproduce normally in winter. When breeding guppies, choose a larger aquarium; the breeding temperature should be kept at 26-28°C, pH 6.8-7.4, and plenty of aquatic plants should be provided to ensure the survival of the fry, then add broodstock at a ratio of 1 male to 4 females.

After guppies come into heat, the female's belly gradually swells and a black gravid spot appears, while the male constantly chases the female; when the male's gonopodium inserts into the female's vent, it releases sperm for internal fertilization. After a gestation period of four to six weeks, the female guppy gives birth to 20-40 fry. Immediately after birth, the mother fish must be removed, otherwise she may eat the fry.