page_title: Daphnia magna
section_title: Reproduction
hierarchical_section_title: Daphnia magna / Reproduction
caption_attribution_description: English: Female Daphnia magna carrying a resting egg ("ephippium"). The black ephippium is part of the carapace and contains usually two sexual eggs.
context_page_description: Daphnia magna is a small planktonic crustacean that belongs to the subclass Phyllopoda. It inhabits a variety of freshwater environments, ranging from acidic swamps to rivers made of snow runoff, and is broadly distributed throughout the Northern Hemisphere and South Africa.
  The species has been subject of biological research since the 18th century. It is widely used in ecological and evolutionary studies, and in ecotoxicology. It is a popular fish food in aquaculture and aquaria.
context_section_description: As most of the other species of the genus Daphnia, D. magna reproduces by cyclical parthenogenesis. This form of reproduction is characterised by the alternating production of asexual offspring (clonal reproduction) and at certain time sexual reproduction through haploid eggs that need to be fertilised.
  The asexual eggs (up to few dozens per clutch) are diploid and usually develop into females, or in response to adverse environmental stimuli, into males.
  Asexual eggs hatch in the female brood pouch 1 day after being laid and are released after 3 days. Juveniles go through four to about six moults before becoming mature over a period of 5–10 days. An adult female produces one clutch with up to 100 eggs every 3–4 days until her death. It can live over 3 months in the laboratory at 20 °C.
  In response to unfavourable environmental conditions (which could lead to the freezing or the drying up of the pond), the same female can produce haploid resting eggs (usually two at a time), which when fertilised by males, are wrapped within a protective shell called an ephippium. These resting eggs enter a phase of diapause and are able to resist long periods of adverse environmental conditions over a long period of time. Hatching is triggered in response to specific stimuli such as increasing photoperiod and temperatures. The hatchlings from resting eggs develop exclusively into females.
  Some clones of D. magna that do not produce males reproduce by automictic parthenogenesis, in which two haploid cells produced by meiosis fuse to produce a female zygote without fertilisation. This tends to make the resulting daughters homozygous, which may be deleterious.
caption: Female carrying an ephippium
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