Daphnia magna

Geographic Range

This species of water flea can be found in rocky pools along the Atlantic coastline of the northeastern United States. It is not considered to be widespread in this area, but is regularly found in certain pools in Maine. This species is also found in Western Europe, including England, Belgium, the Netherlands, Finland, areas of the Black Sea bordering Ukraine, and some Baltic Islands. ("Daphnia magna Straus, 1820", 2012; Ebert, 2005; Haney, 2010; Hanski and Ranta, 1983)


This species is found in freshwater and brackish (up to 8 ppt salinity) habitats including lakes, rivers, and temporary pools. Although they prefer temperatures between 18-22°C, they can tolerate a much broader range. (Ebert, 2005; Haney, 2010; Vanoverbeke, et al., 2007)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams
  • temporary pools
  • brackish water

Physical Description

These water fleas are very small, usually 2-5 mm long, with an overall shape similar to a kidney bean. The body is enclosed by a transparent shell-like structure, called a carapace, that is mostly made of chitin. Due to its transparent carapace, this species tends to be the color of what it is currently eating. The carapace extends into the head shields, an important diagnostic characteristic for this species. They have two sets of long, doubly branched antennae and six thoracic appendages that are held inside of the carapace and help to produce a current of water, carrying food and oxygen to their mouths and gills. They also have two large claws, used mainly for cleaning the carapace. They have one compound eye, which appears as an anterior dark spot, and one simple eye (ocellus). Males are smaller than females (typically only 2 mm long while females are 3-5 mm long) but have longer antennules and modified, hook-like first appendages used for clasping females during mating. (Clare, 2002; Ebert, 2005; Haney, 2010; "Daphnids", 2005)

  • Sexual Dimorphism
  • female larger
  • sexes shaped differently
  • Range length
    2 to 5 mm
    0.08 to 0.20 in


The life cycle begins when a female produces a clutch of eggs (usually 6-10) that are released into her brood chamber, located under her carapace. Eggs hatch into juveniles within this brood chamber and are released when their mother molts, typically within 2-3 days. Juveniles, which already resemble adults, go through a series of molts and instars. Females are considered sexually mature after developing brood pouches, usually after 4-6 instars, usually 6-10 days. If conditions are not favorable, or if they have been produced sexually, eggs will be released into an ephippium, a hard, protective casing, where eggs enter diapause before hatching when conditions are more favorable. (Clare, 2002; Ebert, 2005; Haney, 2010)


These water fleas reproduce both asexually and sexually and have a cyclic parthenogenetic life cycle, exhibiting heterogonic reproduction. In asexual reproduction, females produce diploid eggs that develop into exact clones; only females are produced during asexual reproduction cycles. However, during adverse conditions (low food availability, temperature extremes, high population density), this species amy reproduce sexually. During sexual reproduction, males grab onto females using their specialized second antennae. Females produce haploid eggs which are fertilized by males and encased in ephippia. These cases are carried on the female's back and fall off during her next molt. Eggs enter diapause and stay in ephippia until conditions are favorable. Sexual reproduction tends to take place in late fall months, with the ephippia-protected eggs providing a population burst when spring comes. ("Daphnia spp., water flea", 2011; Alekseev and Lampert, 2001; Ebert, 2005)

Peak egg production is during spring months (April and May), but eggs can be produced during summer and fall as well. During spring months, a female can produce eggs every four days; eggs/juveniles remain in brood pouches for 2-3 days. Number of eggs produced at one time can be anywhere from 1-100, with an average of 6-10 eggs per brood. A female can reproduce up to 25 times throughout her lifetime, although the average is only 6 times. (Clare, 2002; Enserink, et al., 1995; Ignace, et al., 2011; Tessier, et al., 1983)

  • Breeding interval
    Females produce eggs as often as every four days during their breeding season.
  • Breeding season
    These water fleas reproduce most frequently during April and May, though they are known to reproduce during summer and fall as well.
  • Range number of offspring
    1 to 100
  • Average number of offspring
  • Range gestation period
    1 to 4 days
  • Average gestation period
    3 days
  • Average time to independence
    3 days
  • Range age at sexual or reproductive maturity (female)
    6 to 10 days
  • Range age at sexual or reproductive maturity (male)
    6 to 10 days

Females keep their eggs and recently hatched young in their brood chambers for several days, providing nutrients during development. Once juveniles are released there is no additional parental care. (Ebert, 2005)

  • Parental Investment
  • female parental care
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • protecting
      • female
  • pre-independence
    • provisioning
      • female


Lifespan of these water fleas depends heavily on environmental conditions such as oxygen levels, food availability, and temperature. In general, as temperature decreases, lifespan increases, with averages of 40 days at 25°C and 56 days at 20°C. Unstable environmental conditions tend to lead to shorter lifespans. While it has been suggested that males of this species have shorter lifespans than females, recent research shows evidence that this is likely not the case. (Clare, 2002; Grzesiuk, et al., 2010; Pietrazak, et al., 2010)

  • Range lifespan
    Status: wild
    1 to 56 days
  • Average lifespan
    Status: captivity
    40-56 days


This species lives in groups and is very abundant when present in a habitat. There is no social hierarchy, though there is competition for resources between individuals of this and other Daphnia species when present. They use their antennae to propel themselves with quick, upward, jumping-like movements in the water and exhibit diel vertical migration, moving to upper levels of water at night to feed and back down during the day to avoid predators. Their larger size excludes them from predation by species who feed on smaller g. Daphnia, but can cause problems when space and resources are limited. Even though these water fleas are one of the larger species in their genus, they can go extinct in habitats including Daphnia pulex and Daphnia longispina. This species goes through population density cycles, with numbers decreasing during cold or dry seasons. (Coors, et al., 2009; Ebert, 2005; Haney, 2010; Hanski and Ranta, 1983)

Home Range

Individuals of this species do not have distinct home ranges.

Communication and Perception

These water fleas have a compound eye that responds to light stimulus, can perceive different color wavelengths, and can also track movements. They also use olfactory and chemical cues in order to help them locate and evaluate potential food sources, conspecifics, and potential predators. ("Daphnia spp., water flea", 2011; Consi, et al., 1990; Roozen and Lürling, 2001; Young, 1974)

Food Habits

These water fleas are filter feeders; filtration rates depend on temperature, body size, food density and quality, oxygen concentration, and water pH. These animals use leaf-like appendages called phylopods, located under their carapaces, to help produce a water current. Setae on their thoracic legs filter food particulates (generally smaller than 50 micrometers in diameter), which are then moved along a body groove to their mouths. Their primary diet consists of zooplankton and phytoplankton; they are also known to consume bacteria, detritus, and fungal spores. ("Daphnia spp., water flea", 2011; Buck, et al., 2011; Ebert, 2005; Haney, 2010; Hanski and Ranta, 1983; Roozen and Lürling, 2001)


Predators of this species include many species of fishes, insects and other invertebrates. They are larger than many other zooplankton species, which protects them from some invertebrate predators, and they migrate to upper water levels at night to avoid predators that feed during the day. Individuals can also alter their size and age at maturity, egg production levels, and perform swarming behavior and escape reactions to avoid predation. ("Daphnia spp., water flea", 2011; Roozen and Lürling, 2001; "Daphnia spp., water flea", 2011; Boersma, et al., 1998; Ebert, 2005; Haney, 2010; Lauridsen and Lodge, 1996; Roozen and Lürling, 2001)

Ecosystem Roles

These water fleas consume algae, bacteria and detritus in the water. They play a key part in aquatic food webs as prey to fishes and invertebrates. (Ebert, 2005; Hooper, et al., 2008)

This species is host to a number of bacteria (including one causing White Fat Cell Disease) and fungi, as well as some species of nematodes, amoebas and tapeworms. (Ebert, 2005)

Commensal/Parasitic Species
  • Pasteuri ramosa (Kingdom Bacteria)
  • Spirobacillus cienkowskii (Kingdom Bacteria)
  • Flabelliforma magnivora (Phylum Microsporidia, Kingdom Fungi)
  • Glugoides intestinalis (Phylum Microsporidia, Kingdom Fungi)
  • Larssonia obtusa (Phylum Microsporidia, Kingdom Fungi)
  • Octosporea bayeri (Phylum Microsporidia, Kingdom Fungi)
  • Ordospora colligata (Phylum Microsporidia, Kingdom Fungi)
  • Metschnikowia bicuspidata (Order Saccharomycetales, Kingdom Fungi)
  • Echinuria uncinata (Family Acuariidae, Phylum Nematoda)
  • Pansporella perplexa (Order Amoebida, Phylum Protozoa)
  • Cysticercus mirabilis (Class Cestoda, Phylum Platyhelminthes)

Economic Importance for Humans: Positive

This species can provide cleaner water in ponds and lakes, by eating algae and other detritus that may build up in the water. It is also an indicator organism for water quality and is used in tests of water toxicity and detecting various pollutants. This species is easily cultivated, and is commonly fed to fish reared in aquaria. (Clare, 2002; Coors, et al., 2009)

  • Positive Impacts
  • pet trade
  • research and education

Economic Importance for Humans: Negative

There are no known adverse effects of this species on humans.

Conservation Status

This species has not been evaluated by the International Union for Conservation of Nature and Natural Resources and is not considered endangered or threatened. (IUCN, 2012)


Molly Elenbaas (author), University of Michigan-Ann Arbor, Alison Gould (editor), University of Michigan-Ann Arbor, Jeremy Wright (editor), University of Michigan-Ann Arbor.



living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map


living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map


reproduction that is not sexual; that is, reproduction that does not include recombining the genotypes of two parents

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

brackish water

areas with salty water, usually in coastal marshes and estuaries.


uses smells or other chemicals to communicate


an animal that mainly eats decomposed plants and/or animals


particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).


a period of time when growth or development is suspended in insects and other invertebrates, it can usually only be ended the appropriate environmental stimulus.


animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

female parental care

parental care is carried out by females


union of egg and spermatozoan


a method of feeding where small food particles are filtered from the surrounding water by various mechanisms. Used mainly by aquatic invertebrates, especially plankton, but also by baleen whales.


mainly lives in water that is not salty.


An animal that eats mainly plants or parts of plants.

internal fertilization

fertilization takes place within the female's body


offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).


having the capacity to move from one place to another.


an animal that mainly eats fungus


specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.


active during the night


reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.


reproduction in which eggs develop within the maternal body without additional nourishment from the parent and hatch within the parent or immediately after laying.


development takes place in an unfertilized egg

pet trade

the business of buying and selling animals for people to keep in their homes as pets.


photosynthetic or plant constituent of plankton; mainly unicellular algae. (Compare to zooplankton.)


an animal that mainly eats plankton


the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

seasonal breeding

breeding is confined to a particular season


reproduction that includes combining the genetic contribution of two individuals, a male and a female


associates with others of its species; forms social groups.


uses touch to communicate


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


uses sight to communicate

year-round breeding

breeding takes place throughout the year


animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)


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Marinco Bioassay Laboratory, Inc. 2005. "Daphnids" (On-line). Marinco Bioazzay Laboratory Aquaculture. Accessed January 30, 2012 at http://mblaquaculture.com/content/organisms/daphnids.php#daphnia.

Alekseev, V., W. Lampert. 2001. Maternal control of resting-egg production in Daphnia. Nature, 414/6866: 899-901.

Boersma, M., P. Spaak, L. De Meester. 1998. Predator-mediated plasticity in morphology, life history, and behavior of Daphnia: the uncoupling of responses. American Naturalist, 152/2: 237-248.

Buck, J., L. Truong, A. Blaustein. 2011. Predation by zooplankton on Batrachochytrium dendrobatidis: biological control of the deadly amphibian chytrid fungus?. Biodiversity and Conservation, 20/14: 3549-3553. Accessed February 08, 2013 at http://link.springer.com/article/10.1007%2Fs10531-011-0147-4.

Clare, J. 2002. "Daphnia: An aquarist's guide" (On-line). Accessed December 05, 2012 at http://www.caudata.org/daphnia/#anatomy.

Consi, T., M. Passani, E. Macagno. 1990. Eye movements in Daphnia magna. Regions of the eye are specialized for different behaviors. Journal of Comparative Physiology A, 166/3: 411-420. Accessed February 08, 2013 at http://www.ncbi.nlm.nih.gov/pubmed/2324997.

Coors, A., J. Vanoverbeke, T. De Bie, L. De Meester. 2009. Land use, genetic diversity and toxicant tolerance in natural populations of Daphnia magna. Aquatic Toxicology, 95/1: 71-79.

Ebert, D. 2005. Ecology, Epidemiology, and Evolution of Parasitism in Daphnia. Bethesda, Maryland: National Center for Biotechnology Information (US).

Enserink, E., M. Kerkhofs, C. Baltus, J. Koeman. 1995. Influence of food quality and lead exposure on maturation in Daphnia magna: evidence for a trade-off mechanism. Functional Ecology, 9/2: 175-185.

Grzesiuk, M., B. Pietrzak, A. Bednarska. 2010. Longevity of Daphnia magna males and females. Hydrobiologia, 643: 71-75.

Haney, J. 2010. "Daphnia magna" (On-line). An Image-Based Key To The Zooplankton of the Northeast (USA). Accessed February 01, 2012 at http://cfb.unh.edu/CFBKey/html/Organisms/CCladocera/FDaphnidae/GDaphnia/Daphnia_magna/daphniamagna.html.

Hanski, I., E. Ranta. 1983. Coexistence in patchy environment: three species of Daphnia in rock pools. Journal of Animal Ecology, 52/1: 263-279.

Hooper, H., R. Connon, A. Callaghan, G. Fryer, S. Yarwood-Buchanan, J. Biggs, S. Maund, T. Hutchinson, R. Sibly. 2008. The ecological niche of Daphnia magna characterized using population growth rate. Ecology, 89/4: 1015-1022.

IUCN, 2012. "The IUCN Red List of Threatened Species" (On-line). Accessed February 08, 2013 at http://www.iucnredlist.org/search.

Ignace, D., S. Dodson, D. Kashian. 2011. Identification of the critical timing of sex determination in Daphnia magna (Crustacea, Branchiopoda) for use in toxicological studies. Hydrobiologia, 668/1: 117-123.

Lauridsen, T., D. Lodge. 1996. Avoidance by Daphnia magna of fish and macrophytes: chemical cues and predator-mediated use of macrophyte habitat. Limnology and Oceanography, Vol. 41/ No. 4: 794-798.

Pietrazak, B., A. Bednarska, M. Grzesiuk. 2010. Longevity of Daphnia magna males and females. Hydrobiologia, 643/1: 71-75. Accessed February 08, 2013 at http://rd.springer.com/article/10.1007/s10750-010-0138-6.

Roozen, F., M. Lürling. 2001. Behavioural response of Daphnia to olfactory cues from food, competitors and predators. Journal of Plankton Research, 23/8: 797-808. Accessed February 08, 2013 at http://plankt.oxfordjournals.org/content/23/8/797.full.

Tessier, A., L. Henry, C. Goulden. 1983. Starvation in Daphnia: energy reserves and reproductive allocation. Limnology and Oceanography, 28/4: 667-676.

Vanoverbeke, J., K. De Gelas, L. De Meester. 2007. Habitat size and the genetic structure of a cyclical parthenogen, Daphnia manga. Heredity, 98: 419-426. Accessed January 24, 2012 at http://www.nature.com/hdy/journal/v98/n6/full/6800958a.html.

Young, S. 1974. Directional differences in the colour sensitivity of Daphnia magna. Journal of Experimental Biology, 61: 261-267. Accessed February 08, 2013 at http://jeb.biologists.org/content/61/1/261.full.pdf.