Hydra Attenuata, a Model System for Determining the Acute Lethal and Chronic Toxicity of Drinking and Natural Waters and Aqueous Solutions of Chemicals

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Environmental assessment using living test organisms contribute to the timely detection of negative for human health pollutants. Hydra is a small freshwater organism that has been widely used in different types of bioassays to study the toxic potential of numerous chemical substances and is recently growing in popularity for assessing the impacts of water pollutants. Under normal conditions, adult hydra has a radially symmetric body of about 5 mm long with 6–8 straightened tentacles. Hydra is an appropriate bioindicator species because of their simple anatomy, clear morphological reactions in response to alterations in the aquatic environment, high reproduction rate and simplicity of laboratory-scale cultivation. Moreover, in the optimal cultivation environment, hydra reproduces by budding that enables in a short time obtaining a large number of genetically and morphologically identical animals for a bioassay. Here we propose a rapid bioassay for the assessment of the quality of aquatic environment including drinking water, water from natural environments sources and aqueous solutions of chemicals. This bioassay is based on the registration of survival and morphological reactions in hydra (Hydra attenuata), and allows us to determine the acute and chronic toxic effect of water pollutants. We also describe the optimal laboratory-scale cultivation conditions of hydra. Hydra attenuata bioassay of an aqueous medium can be recommended as a State Standard of Ukraine for assessing the quality of natural and drinking waters.