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Latreille 1829


Phylum Arthropoda
Subphylum Crustacea
Class Branchiopoda
Order Cladocera


  • Approximately 1 mm long.


  • Commonly called water fleas.

Distinguishing characteristics

  • The thoracic appendages (pereiopods) are typically leaf-like, lobed and densely setose.
  • These appendages also bear gills and explain the derivation of the name Branchiopoda (gill-feet).
  • The carapace of cladocerans is folded along the back, giving a bivalve appearance, but there is neither a dorsal hinge nor an adductor as seen in scallops, mussels and ostracods.
  • The carapace terminates posteriorly with an apical spine.
  • The first antenna is uniramous and short.
  • The second antenna is biramous and used for swimming.
  • Cladocerans are generally transparent with little pigmentation except for the single black compound eye.


  • Widely distributed throughout the world.
  • Common in coastal waters and can also be found in open ocean systems.


  • Marine cladocerans are usually herbivorous filter feeders that sieve phytoplankton from the water using setae on the pereiopods. However, they also graze on bacteria and microzooplankton including protozoans.
  • Quite selective in their feeding, preferring certain species of phytoplankton to others.
  • Asexual reproductive strategies allow cladocerans to exploit favourable food conditions.
  • Environmental stress may induce females to produce male offspring, thus leading to bisexual reproduction.
  • After copulation and internal fertilization, the eggs are brooded in a pouch within the carapace of the female until they are ready to hatch as miniature adults.
  • Cladocerans can also reproduce asexually through a process called parthenogenesis, which results in females dominating the population before reverting to sexual reproduction.
  • In some cases, paedomorphosis has been observed where developing embryos in the mother's brood pouch become sexually mature and can themselves carry eggs.