David Walsh, age 8, of Staten Island, N.Y., for his question:

HOW MANY BABIES DOES A MOTHER GUPPY HAVE?

A guppy is a popular Trinidad and South American fish found in lots of home aquariums. The male is about an inch and a quarter long, while the female is about twice the length.

A female bears living young that are able to swim and feed at birth. Eggs that form in the female's body are fertilized by the male. The male has a specially formed anal fin called the gonopodium which carries the fertilizing sperm. About 50 young guppies are born every four to six weeks.

Once the female has produced a brood, it may be separated from the male but continue to give birth to young. This is possible because the mother can store the sperm in her body for several months. No two males are exactly alike. Bright rainbow hues help him to pay ardent court to the female as he shows off by "dancing."