Sea-Monkeys, made popular as pets for decades by comic-book advertisements touting them as space-creature-like colonies of Atlantis, are simply branded, proprietary hybrid brine shrimp. In 1957, Harold van Braunhut trademarked them and started selling kits that allowing consumers to raise the little creatures at home. Any Sea-Monkey population will include a blend of male and female brine shrimp, and a few ways exist to tell them apart.
Generally there are more female Sea-Monkeys than males, but a male Sea-Monkey will be a little shorter than a female. He will have two sets of antennae -- the first set will be thin, the second will be long and thick. The second set of antennae will look like claws.They are known as claspers; he uses them to grasp a female during spawning.
A female Sea-Monkey will always have a circular egg sack around the middle of her body. If she is carrying eggs, the sack will be brown; if she is not, it will be white. A female Sea-Monkey will have two sets of antennae, but unlike the male's: The first will be short and thick and the second will be small.