Daphnia (water flea)
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
Preferred Common Name
- water flea
International Common Names
- English: common water flea
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Metazoa
- Phylum: Arthropoda
- Subphylum: Crustacea
- Class: Branchiopoda
- Order: Cladocera
- Family: Daphniidae
- Genus: Daphnia
DescriptionTop of page
Daphnia can be found in almost any permanent body of water. They are mainly freshwater and densely populate most lakes and ponds. They live as plankton in the open water of lakes, or live either attached to vegetation or near the bottom of the body of water (Miller, 2000).
Four distinct periods may be recognized in the life history of Daphnia:
The mode of reproduction of Daphnia is alternating asexual (parthenogenic) and sexual (Curtis and Barnes, 1989). Daphnia multiply by parthenogenesis when their food is abundant, following which, in response to an environmental cue, both males and females are produced (Curtis and Barnes, 1989). The asexual phase occurs when rapid growth of the Daphnia population is required. The sexual phase results in the creation of ephippial eggs, which are often blown inshore, where they then overwinter. The eggs hatch in the littoral regions the following spring (Hutchinson, 1967; Balcer et al., 1984).
Daphnia have a very high degree of genetic variation even within a single population or species. They are able to change their size and shape in response to their environment and this ability makes it harder to classify these organisms into specific groups (Miller, 2000). Often there seems to be more variation within a species than between species.
DistributionTop of page
Daphnia are extremely widespread and common throughout the world. Daphnia pulex is the most common species of the water flea, an organism which can be found in almost every permanent, eutrophic (nutrient-rich) water body. A few species are marine, but generally Daphnia, including Daphnia pulex, are freshwater organisms (Miller, 2000).
ClimateTop of page
|A - Tropical/Megathermal climate||Preferred||Average temp. of coolest month > 18°C, > 1500mm precipitation annually|
|C - Temperate/Mesothermal climate||Preferred||Average temp. of coldest month > 0°C and < 18°C, mean warmest month > 10°C|
Natural enemiesTop of page
Impact SummaryTop of page
|Fisheries / aquaculture||Positive|
Impact: BiodiversityTop of page
Daphnia may have an indirect impact on the biodiversity. They are often used as a food source for aquarium fish and although some of these are raised specifically for this purpose, many are harvested from lakes or ponds. Although this practice is unlikely to erradicate all Daphnia species, it could damage some rare populations with a limited range (Miller, 2000).
ReferencesTop of page
Balcer MD; Korda NL; Dodson SI, 1984. Zooplankton of the Great Lakes. USA: University of Wisconsin Press.
Clare J, 2002. Daphnia: An aquarist’s guide. Caudata Online at www.caudata.org/daphnia/. Accessed 30 January 2005.
Curtis H; Barnes NS, 1989. Biology: Fifth Edition. New York: Worth Publishers, Inc. New York.
Davison J, 1969. Activation of the ephippial egg of Daphnia magna for insecticide bioassay. J. Econ. Entom., 57: 821-825.
FAO, 1996. Cladocerans, nematodes and trochophora larvae. In: Lavens P, Sorgeloos P, eds. Manual on the Production and Use of Live Food for Aquaculture. Rome, Italy: FAO, FAO Fisheries Technical Paper 361.
Hutchinson GE, 1967. A treatise on limnology Vol. II. New York: John Wiley and Sons.
Miller C, 2000. Daphnia pulex. Animal Diversity Online. Online at http://animaldiversity.ummz.umich.edu/site/accounts/information/Daphnia_pulex.html . Accessed January 28 2005.
ContributorsTop of page
06/03/2008 Updated by:
James Stoeckel, Auburn University, Dept. of Fisheries & Allied Aquacultures, 203 Swingle Hall, Auburn, Alabama 36849, USA
Institute of Aquaculture, University of Stirling, Stirling, FK9 4LA, UK