THE IMPORTANCE OF MAINTENANCE CONDITIONS OF DAPHNIA MAGNA STRAUS AS A TEST ORGANISM FOR ECOTOXICOLOGICAL ANALYSIS

Abstract

Insufficient attention to the standardization of conditions for test organisms can lead to a distortion of bioassay results by changing the characteristics of the culture. The article deals with the influence of abiotic factors (temperature of cultivated water, its chemical composition, season of the year) and biotic factors (seeding density) on the culture of Daphnia magna Straus. It is shown that the natural mortality of D. magna is described by the Gompertz equation. One of the parameters of equation related to daily increase of mortality is very stable and we suggest to monitor its constancy as a sign of the "health" of D. magna culture. Seeding density of crustaceans affects both the fertility of species and their mortality. It was shown a high degree of compensation for the natural death of adults with increasing fertility for groups of 10 and 25 species living in 1 L of water: the current population density of D. magna regulates the birth rate of juveniles. If the density is 50 ind./L the compensatory effect is reduced. Keeping Daphnia in small groups (for example, 10 individuals) and an increase in temperature from 20 °C to 25 °C reduce the average life expectancy. Therefore, when choosing a test protocol to determine chronic toxicity it is important to pay attention to the seeding density of daphnia, the optimal value is approximately 25 ind./L. Sensitivity of D. magna depends on the season: it is maximum in winter and minimal in spring and summer. Also, crustaceans sensitivity increases when they are kept in water with low content of natural salts. This article is protected by copyright. All rights reserved

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