Often they are only 0.08 mm wide or barely visible with the human eye. These legs are used to move water over their mouths to help them feed as they slowly swim along. Except for the pointed heads, the bodies of most daphnia are covered with a transparent shell or carapace. In most daphnia, the inside organs can easily be seen through the shell under a microscope. Under a microscope, the workings of the heart, digestive system and brood pouch can be seen in the living animal.
Daphnia feed by filtering plankton and microscopic debris from the water.
They have two large secondary antennae. They use their antennae to move through the water. They move in a jerky path through the water. Their main way of surviving against their many enemies is their fast reproduction. With the resulting large numbers there are always a few that survive.