1. Size and Shape: Male guppies are typically smaller and slimmer than females. Females tend to be larger, rounder, and have a more robust belly, especially when pregnant.
2. Coloration: Male guppies are known for their vibrant and flashy colors, often with bright patterns and spots. Females, on the other hand, tend to have duller and less intense coloration.
3. Fins: Male guppies have larger, more elaborate, and colorful fins, particularly the dorsal (top) fin and caudal (tail) fin. Female guppies have smaller, less ornate fins.
4. Anal Fin: The anal fin of a male guppy is modified into a structure known as the gonopodium, which is used for reproduction. In females, the anal fin is normal and not modified.
5. Gravid Spot: Female guppies develop a dark spot near the anal fin when they are pregnant. This gravid spot indicates the presence of developing fry (baby guppies) inside the female.
It's important to note that these physical characteristics can vary depending on the specific guppy species and strains, so it's always best to consult additional resources or compare multiple guppies for accurate identification of their gender.