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Daphnia species are normally r-selected, meaning that they invest in early reproduction, so have short lifespans. An individual Daphnia lifespan depends on factors such as temperature and the abundance of predators, but can be 13–14 months in some cold, oligotrophic, fish-free lakes. [11]
Daphnia pulicaria is a species of freshwater crustaceans found within the genus of Daphnia, which are often called "water fleas," and they are commonly used as model organisms for scientific research. [1] Like other species of Daphnia, they reproduce via cyclic parthenogenesis. [2]
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 ]
Crustacean reproduction varies both across and within species. The water flea Daphnia pulex alternates between sexual and parthenogenetic reproduction. [17] Among the better-known large decapod crustaceans, some crayfish reproduce by parthenogenesis. "Marmorkrebs" are parthenogenetic crayfish that were discovered in the pet trade in the 1990s. [18]
Daphnia pulex. The genus Daphnia (Crustacea: Cladocera: Daphniidae) contains over 200 species of water fleas, many of which are in need of further taxonomic investigation (species inquirendae; marked with asterisks). [1]
Daphnia lumholtzi is a species of small, invasive water fleas that originates in the tropical and subtropical lakes of Africa, Asia, and Australia. [ 1 ] [ 2 ] [ 3 ] As an invasive species , Daphnia lumholtzi disrupts aquatic habitats by spreading throughout the warmer waters of lakes and reservoirs.
Daphnia studeri is a species of microcrustacean in the genus Daphnia. D. studeri lives in oligotrophic freshwater and slightly brackish lakes in Antarctica and sub-Antarctic islands. Adult Daphnia studeri are typically 1.5 to 2.5 mm (0.059 to 0.098 in) [ 1 ] and colorless or slightly pink.
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.