Vyatka State University, Kirov, Russia.
Institute of Biology of Komi Scientific Centre of the Ural Branch of the Russian Academy of Sciences, Syktyvkar, Russia.
Environ Toxicol Chem. 2018 Feb;37(2):376-384. doi: 10.1002/etc.3956. Epub 2017 Dec 18.
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 present study 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. The natural mortality of D. magna is described by the Gompertz equation. One of the parameters of the equation related to daily increase of mortality is very stable, and we suggest monitoring 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. We observed 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 individuals/L, the compensatory effect is reduced. Keeping Daphnia in small groups (for example, 10 individuals) and an increase in temperature from 20 to 25 °C reduces 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 being approximately 25 individuals/L. Sensitivity of D. magna depends on the season: it is maximal in winter and minimal in spring and summer. In addition, crustaceans' sensitivity increases when they are kept in water with low content of natural salts. Environ Toxicol Chem 2018;37:376-384. © 2017 SETAC.
对试验生物条件的标准化重视不足，可能会通过改变培养物的特性导致生物测定结果发生扭曲。本研究探讨了非生物因素（培养水的温度、化学成分、年份季节）和生物因素（接种密度）对大型溞（Daphnia magna Straus）培养的影响。大型溞的自然死亡率由 Gompertz 方程描述。该方程中与死亡率日增长率相关的一个参数非常稳定，我们建议监测其稳定性，作为大型溞培养物健康状况的标志。甲壳类动物的接种密度会影响物种的繁殖力和死亡率。我们观察到，在 1 L 水中生活的 10 只和 25 只种群中，随着繁殖力的增加，成虫的自然死亡得到了高度补偿；大型溞的当前种群密度调节着幼体的出生率。如果密度为 50 个/升，则补偿效应会降低。将大型溞保持在小群体中（例如 10 个个体），并将温度从 20°C 升高到 25°C，会降低平均预期寿命。因此，在选择确定慢性毒性的试验方案时，重要的是要注意大型溞的接种密度，最佳值约为 25 个/升。大型溞的敏感性取决于季节：冬季最大，春季和夏季最小。此外，当甲壳类动物在低盐含量的水中饲养时，其敏感性会增加。Environ Toxicol Chem 2018;37:376-384. © 2017 SETAC.
