Daphnia test
As daphnia various investigations are pollutants in water or aqueous media referred. The small crustaceans are on the one hand quite sensitive to pollutants because they permanently filter large amounts of water, on the other hand they are very important in the food web . The quick reaction, easy maintenance and short generation time have made daphnia a popular model organism for toxicity tests.
Inability to move
Determining the death of the Daphnia is complex and time consuming. It is therefore assumed that immobile laboratory animals are dead. The immobilization of the daphnia is therefore not a temporary problem for the animals, but mostly the evidence of their death. Daphnia are considered immobile if they do not start swimming within 15 seconds after a slight jolt of the test container.
Determination of toxicological endpoints
Daphnia are used in a variety of tests that can identify various toxicological endpoints . An example is the EC 50 as an evaluation standard for the toxicity of substances. The EC 50 always relates to a test organism and indicates the concentration ( E ffect C oncentration) of the poison in which the biological capabilities of the organism are reduced by half (growth, size, etc.).
The exact steps for determining these values are prescribed in Europe by standards ( EN ). The DIN EN ISO 6341-L40 from 1996 describes the determination of the 24h-EC 50 . (L40 Determination of the inhibition of the mobility of Daphnia magna Straus (Cladocera, Crustacea) acute toxicity test)
Dynamic daphnia test
This is a biological early warning system which was developed by J. Knie in 1978, which is why it is also called the knee daphnia test . This test is used for water monitoring and shows the direct effect of substances and mixtures of substances and has been in use since 1982. Daphnia are automatically examined for their movement activity in a vessel with the water to be examined by photocells . If the movement activity of the daphnia falls below a threshold value, an alarm is triggered. This is followed by sampling and, if necessary, further investigation and analysis steps. Since it is extremely difficult to determine the biological effect of a substance by means of a chemical analysis and the effort to monitor all possible pollutants is impossible, biological test procedures are indispensable in water monitoring.
The "predecessor" of the dynamic daphnia test was the Kerren current fish test (1971), in which gold orfe must swim against a current generated at periodic intervals. This is no longer permitted in Germany for reasons of animal welfare .
See also
Web links
- Use of continuous biotest procedures for water monitoring (PDF file; 248 kB)
- Test No. 202: Daphnia sp. Acute Immobilization Test . In: Organization for Economic Co-operation and Development (Ed.): OECD Guidelines for the Testing of Chemicals . 2004. doi : 10.1787 / 9789264069947-en .
- Test No. 211: Daphnia magna Reproduction Test . In: Organization for Economic Co-operation and Development (Ed.): OECD Guidelines for the Testing of Chemicals . 2012. doi : 10.1787 / 9789264185203-en .