THE ROLE OF HYDRA VULGARIS (PALLAS) IN ASSESSING THE TOXICITY OF FRESHWATER POLLUTANTS

The freshwater coelenterate Hydra vulgaris is an important component of freshwater ecosystems, and this study aimed to establish its value as an indicator of pollutants entering freshwater. The toxicity of the heavy metals copper, cadmium and zinc was assessed using both acute lethal and sub-lethal responses. Techniques involving the identification and large-scale culture of Hydra were also examined. The acute lethal toxicity of copper, cadmium and zinc was measured by determining 24-h, 48-h, 72-h and 96-h LC50 values and the sub-lethal effects assessed using a feeding test. The feeding test examined toxic effects on the normal responses of Hydra to the presence of the prey provided, neonate Daphnia magna (Strauss). Results of this study demonstrated that H. vulgaris (Pallas) is a suitable species for evaluating the toxicity of freshwater pollutants and can be used successfully to rank toxicants in order of potential hazard. It can be cultured easily in the laboratory to provide large numbers of test animals and can be used in simple, cost-effective bioassays of both acute and sub-acute toxicity. © 1998 Elsevier Science Ltd. All rights reserved