suborder of Branchiopoda

Cladocera is an order of small crustaceans commonly called water fleas. Around 620 species have been recognised so far, with many more undescribed.[1]

Daphnia pulex.png
Daphnia pulex
Scientific classification

Latreille, 1829

They are everywhere in inland aquatic habitats, but rare in the oceans.[2] Most are 0.2–6.0 mm (0.01–0.24 in) long, with a down-turned head, and a carapace covering the thorax and abdomen.[3] There is a single median compound eye.[2] They swim with jerking flea-like movements.

Most species show cyclical parthenogenesis, where asexual reproduction is occasionally supplemented by sexual reproduction. The sexual reproduction produces resting eggs that allow the species to survive harsh conditions and disperse to distant habitats.[4]


  1. L. Forró N.M. Korovchinsky, A.A. Kotov & A. Petrusek (2008). Estelle V. Balian, Christian Lévêque, Hendrik Segers & Koen Martens (ed.). "Freshwater animal diversity assessment" (PDF). Hydrobiologia. Developments in Hydrobiology 198. 595 (1): 177–184. doi:10.1007/s10750-007-9013-5. ISBN 978-1-4020-8259-7. |chapter= ignored (help)CS1 maint: multiple names: editors list (link) doi:10.1007/978-1-4020-8259-7_19
  2. 2.0 2.1 Denton Belk (2007). "Branchiopoda". In Sol Felty Light & James T. Carlton (ed.). The Light and Smith Manual: intertidal invertebrates from Central California to Oregon (4th ed.). University of California Press. pp. 414–417. ISBN 9780520239395.
  3. Douglas Grant Smith & Kirstern Work (2001). "Cladoceran Branchiopoda (water fleas)". In Douglas Grant Smith (ed.). Pennak's freshwater invertebrates of the United States: Porifera to Crustacea (4th ed.). Wiley. pp. 453 488. ISBN 9780471358374.
  4. Ellen Decaestecker, Luc De Meester & Joachim Mergaey (2009). "Cyclical parthenogeness in Daphnia: sexual versus asexual reproduction". In Isa Schön, Koen Martens & Peter van Dijk (ed.). Lost sex: the evolutionary biology of parthenogenesis. Springer. pp. 295–316. doi:10.1007/978-90-481-2770-2_15. ISBN 9789048127696.