1. Male Guppy Mating Organ: Male guppies possess a specialized reproductive organ called the gonopodium. The gonopodium is a modified anal fin that serves as the primary organ for delivering sperm during mating.
2. Courtship Behavior: When a male guppy is ready to mate, he engages in courtship behavior. This behavior involves displaying his colorful body and fins, approaching the female, and swimming around her.
3. Positioning for Mating: The male guppy positions himself alongside the female, often facing her head. He swims close to her and attempts to align his gonopodium with the female's reproductive opening, which is located near the anal fin.
4. Intromission and Sperm Transfer: When the male guppy successfully aligns his gonopodium, he quickly inserts it into the female's reproductive opening. This process is known as intromission. During intromission, the male transfers a small packet of sperm, called a spermatophore, into the female.
5. Internal Fertilization: The spermatophore contains numerous sperm cells. Once inside the female, the sperm cells are released and swim towards the female's eggs, which are located in her ovaries. If fertilization occurs, the egg is fertilized by the sperm, resulting in the formation of a zygote.
6. Gestation Period: Unlike some other species of fish, guppies do not lay their fertilized eggs externally. Instead, they retain the fertilized eggs within their bodies and go through a gestation period. The gestation period in guppies varies depending on factors such as water temperature and the female's health but typically lasts around 21 to 30 days.
7. Live Birth: After the gestation period, the guppy female gives birth to live young. She releases small, fully formed guppies, each enclosed in a thin membrane. These baby guppies are referred to as fry. The number of fry produced in a single birth can range from a few to several dozen, depending on the size and age of the female guppy.
8. Parental Care: Guppy parents typically do not exhibit any form of parental care. The fry are born independent and fend for themselves from the moment they are released from the mother. They swim freely and begin to search for food and shelter.
This reproductive strategy, involving internal fertilization and live birth, is common among many species of fish belonging to the family Poeciliidae, which includes guppies, mollies, and swordtails.