HYDRA VULGARIS PALLAS, 1766 (HYDROZOA: HYDRIDAE) AS BIOINDICATOR OF THE WATER QUALITY OF THE RIVER CHILI, AREQUIPA, PERU

The aim of this study was to use Hydra vulgaris Pallas, 1766 (Hydrozoa: Hydridae) as a bioindicator of water quality of the Chili River, Arequipa, Peru. The freshwater hydra were collected in the spring "Ojo del Milagro", Characato District, Arequipa, Peru. H. vulgaris was cultivated under standardized conditions and were fed Artemia sp. K2Cr2O7 was used as a positive control and as a reference toxin. Acute toxicity and morphological changes of H. vulgaris were evaluated on Tiabaya and Tingo, sampling points of the Chili River. The LC50 (median lethal concentration) showed: Tingo (LC50-96h = 135.95% classifying it as non-toxic) and Tiabaya (LC50 -24h = 61.83%, classifying it as moderately toxic; LC50-48h = 44.19% and LC50 -72h = 38.28% classifying them as toxic; LC50 -96h = 21.44% rating it as very toxic). Significant differences in the morphological changes of H. vulgaris were observed with regard to different concentrations and exposure time in waters sampled from Tingo from 48 h to 96 h and in Tiabaya, significant differences in morphological changes from 24 h to 96 h exposure. The results of the physicochemical parameters of the Chili River were compared with the Peruvian National Standards for Environmental Quality (ECA) for water (categories 3 and 4) and recorded high values of biochemical oxygen demand BOD5, NH4 and PO4, and low dissolved oxigen OD values for Tiabaya. In Tingo, NH4 and phosphate were high. In Tiabaya, water was considered more toxic than at Tingo.