Content on this page requires a newer version of Adobe Flash Player.

Get Adobe Flash player


Search in the Encyclopedia

Dieren en planten

Crustaceans   Water fleas   Copepods   

Water en land

Water fleas


up to 5 millimeters




several months, never longer than a year


phytoplankton, organic waste, bacteria


small freshwater fish


sexual and vegetative

  • Dut: Watervlooien
  • Lat: Cladocera
  • Eng: Waterfleas
  • Ger: Wasserflöhe
  • Fre: Puces d'eau

Water fleas

Water fleas live in stationary freshwater regions. They have a strong sense of smell via their special antennae. For example, they can even smell where their enemies are hiding. They are born with two eyes which later fuse together into one eye. Water fleas are eaten by many animals, such as fish and aquatic insects. Because there are so many of them, they form an important source of food. Water fleas are not found in the sea. Other small crustaceans serve as an important source of food there, such as the copepod.

  • Jumping fleas

    Water fleas move just like fleas, in a jerky motion. They thrust their branched antennae sidewards, shooting them diagonally upwards. In between swimming strokes, they sink downwards again in a zigzagging motion.
    The abdomen legs serve for gathering food, particularly phytoplankton. By moving these legs, a water current is created which the water fleas use to filter out the food. There are also appendages on these legs which serve as breathing gills.

  • Distribution and habitat

    Water fleas are extremely common in the Netherlands. They can reproduce in a short period of time so sometimes there are large amounts available. They live in all kinds of freshwater regions, including ditches, lakes, rivers, canals and drinking pools.

  • Unusual manner of reproduction

    All species of water fleas produce two kinds of eggs. In the summer, the females produce eggs when there is lots to eat, without needing a male. These unfertilized eggs hatch into young females within two days. As long as the conditions are okay, the females can produce new female larvae for months, without needing a male. If the conditions worsen, such as in the winter, then the females produce larger eggs, which need to be fertilized by a male. Males and females hatch from the winter eggs. In this way, there is an alternation between dioeciously (unisexual) and homogamically (bisexual) reproduction. Male water fleas are usually in the minority in a population.