| Daphnia magna | |
|---|---|
| Daphnia magna - female adult | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Subphylum: | Crustacea |
| Class: | Branchiopoda |
| Order: | Cladocera |
| Family: | Daphniidae |
| Genus: | Daphnia |
| Species: | D. magna |
| Binomial name | |
| Daphnia magna Straus, 1820 [1] |
|
Daphnia magna is a species of Daphnia (a cladoceran freshwater water flea) which is native to northern and western North America. It is also widely distributed in Eurasia and in some regions of Africa.
Domesticated, it is widely used as a laboratory animal for testing ecotoxicity starting with Einar Naumann in 1934.[2] As Anderson stated in 1944:[3]
The use of Daphnia magna as an experimental animal for such purposes is advantageous in many respects. Daphnids are small, reaching a size of five mm, so that a great many can be reared in a small space. They have a relatively short life span, which reaches a maximum of about two months when they are reared at 25°C. Daphnids are easy to culture, requiring only water containing bacteria or their equivalent for food. They can be grown individually in small bottles or in mass culture in large aquaria. They mature early, giving birth to young within their first week of life. After their first brood, they give rise to new broods every two or three days throughout the remainder of their lives. An average of twenty or more young may be produced in each brood. Each female who lives to a ripe old age can bear four hundred or more offspring. Again, all the young from one female are genetically like the mother if produced parthenogenically, and reproduction can be limited to parthenogenesis if the proper conditions are maintained. Further, daphnids are representatives of a class of animals that serve as food for many fish, especially while the fish are young. Fishes do not remain long in waters where their food supply has been destroyed, even though the fishes may not be affected directly. For these reasons daphnids should prove satisfactory for testing waters for toxic materials.
D. magna is specified to be used in the OECD Guidelines for the Testing of Chemicals, Tests No. 202 "Daphnia sp., Acute Immobilisation Test and Reproduction Test",[4] and Test No. 211 "Daphnia magna Reproduction Test".[5] Test No. 202 is a 48 hour acute toxicity study, where young Daphnia are exposed to varying concentrations of the substance under test and the EC50 determined. Other Daphnia species than D. magna may occasionally be used, but labs mostly use D. magna as standard.
Test No. 211 is a 21 day chronic toxicity test, at the end of which, the total number of living offspring produced per parent animal alive at the end of the test is assessed, in order to determine the lowest observed effect concentration of the test substance.
As it is easy to culture, D. magna is widely grown as fish food.
A recent study has postulated that Daphnia magna eats the spores of the devastating chytrid fungus Batrachochytrium dendrobatidis [6]