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Daphnia is a genus of small planktonic crustaceans, 0.2–6.0 mm (0.01–0.24 in) in length. Daphnia are members of the order Anomopoda, and are one of the several small aquatic crustaceans commonly called water fleas because their saltatory swimming style resembles the movements of fleas.
In this reproductive system, individuals can alternate between sexual and parthenogenetic reproduction. When reproducing parthenogenetically, diploid asexual embryos fully develop in the brood chamber of mature female daphnias, and are then directly released in the environment.
Daphnia magna is a typical water flea of the genus Daphnia. The females reach up to 5 mm in size, the males about 2 mm, thus they are among the largest species in the genus. [ 2 ] The body is protected by a translucent carapace made of chitin , a transparent polysaccharide. [ 3 ]
Cyclic parthenogenesis is the primary mode of reproduction in D. pulicaria and other species within the genus Daphnia. [2] Therefore, D. pulicaria are capable of switching between sexual and asexual reproduction based on environmental conditions. [9]
The switch between sexuality and parthenogenesis in such species may be triggered by the season (aphid, some gall wasps), or by a lack of males or by conditions that favour rapid population growth (rotifers and cladocerans like Daphnia). In these species asexual reproduction occurs either in summer (aphids) or as long as conditions are favourable.
Like all Daphnia species, D. longispina is a filter feeder, collecting particles of about 2 to 40 μm suspended in the water. [5] The main food are green algae. At 20 °C maturity is reached within about 6 to 12 days, followed by a period of regular reproduction in about 3-4 day intervals.
Daphnia lumholtzi is typically found in the warm, shallow regions [6] of bodies of water with larger surface areas. [7] While most species of Daphnia see high mortality at temperatures greater than 25 °C, [8] D. lumholtzi individuals can survive and reproduce at temperatures up to 30 °C, [8] [9] [10] with a thermal optimum occurring at 29 °C. [9]
Ephippia (singular: ephippium) are winter or dry-season eggs of the various species of small crustacean in the order Cladocera (within the Branchiopoda); they are provided with an extra shell layer, [1] which preserves and protects the resting stages inside from harsh environmental conditions until the more favorable times, such as spring, when ...