THE ROLE OF HYDRA-VULGARIS (PALLAS) IN ASSESSING THE TOXICITY OF FRESH-WATER POLLUTANTS

The freshwater coelenterate Hydra vulgaris is an important component o f freshwater ecosystems, and this study aimed to establish its value a s an indicator of pollutants entering freshwater. The toxicity of the heavy metals copper, cadmium and zinc was assessed using both acute le thal 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 n ormal responses of Hydra to the presence of the prey provided, neonate Daphnia magna (Strauss). Results of this study demonstrated that H. v ulgaris (Pallas) is a suitable species for evaluating the toxicity of freshwater pollutants and can be used successfully to rank toxicants i n order of potential hazard. It can be cultured easily in the laborato ry to provide large numbers of test animals and can be used in simple, cost-effective bioassays of both acute and sub-acute toxicity. (C) 19 98 Elsevier Science Ltd. All rights reserved.