Guppy Gravid Spot. Male guppies are covered in bright colored patterns and their tails are usually brightly colored as well. The other obvious sign is that the guppies belly is growing larger.
A female guppy’s gravid spot can be a good indicator of her pregnancy. Located at the base of the tail, the gravid spot signals the location where the fry will grow when the female guppy becomes pregnant. The gravid spot is a unique physical feature that’s exclusive to livebearing females.