The differences between male and female guppies are mainly reflected in body shape, color, fin structure, and reproductive characteristics. Here are the specific ways to distinguish them:
1. Core Distinguishing Features
Body Shape Differences
Female guppies are significantly larger (5–7 cm) with a rounded, swollen abdomen, which becomes more prominent when pregnant.
Male guppies are slimmer (3–4 cm), only about half the size of females.
Color Performance
Males have vivid, bright colors, with their tail fins accounting for over two-thirds of their body length. Common elaborate tail shapes include fan tails and sword tails.
Females have plain body colors, with short tail fins and monotonous coloring (though some artificially bred varieties may be exceptions).
2. Key Reproductive Characteristics
Anal Fin (Genital) Shape
Males: The anal fin is specialized into a slender copulatory organ, shaped like a sharp needle.
Females: The anal fin is fan-shaped or triangular, with a round cloaca.
Gravid Spot Identification
Females have a black or red gravid spot near the rear of their abdomen (more noticeable when pregnant); males lack this feature.
3. Tips for Distinguishing Juveniles
For 1–2 month old juveniles, a preliminary can be made by noting that those which develop color earlier are likely males.
Microscopic observation: Male juveniles show a tubular protrusion in their anal fin at an early stage.
4. Behavioral Differences
Males frequently chase females to court them, while females swim more slowly—especially during pregnancy, when they may avoid males.
Note: Artificially bred varieties may produce females with bright colors. In such cases, comprehensive should be made based on the anal fin shape and gravid spot.