title: The acute and chronic toxicity of cadmium and zinc to two hydra species.
abstract: The potential of two hydra species, Hydra vulgaris (pink) and Hydra viridissima (green), for use as invertebrate models for toxicity testing of waterborne metals was investigated. The acute and subchronic toxicities of cadmium (a nonessential metal) and zinc (an essential metal) were determined. Results showed that both the hydra species were more sensitive to cadmium than to zinc, and that green hydra were more sensitive than pink hydra. The mean (SE) 96 h LC50 values of cadmium and zinc for pink hydra were 83 (8.5) and 2300 (150) micrograms/L, respectively. For green hydra, the respective 96 h LC50 values for cadmium and zinc were 3.0 (0.0) and 935 (46.5) micrograms/L. The respective 7-day no-observed-effect-concentrations (NOEC) and lowest-observed-effect-concentrations (LOEC) for pink hydra were < 13 and 13 micrograms/L for cadmium, and < 250 and 250 micrograms/L for zinc. The respective 7-day NOEC and LOEC values for green hydra were 0.4 and 0.8, microgram/L for cadmium, and 38 and 75 micrograms/L for zinc. Neither 1, 2, or 3 x 90-min pulse-exposures to 0.4, 0.8, or 1.5 micrograms/L of cadmium had any significant deleterious effect on total green hydra numbers after seven days in clean water. Green hydra appeared to be excellent freshwater invertebrate models for testing dissolved metals based on their sensitivity and the ability to rapidly assess population reproduction in the laboratory.
authors.affiliation: Department of Biotechnology and Environmental Biology, RMIT-University, Bundoora West Campus, GPO Box 71, Bundoora, Melbourne, Vic. 3083, Australia. d.holdway@rmit.edu.au
authors.forename: D A
authors.initials: DA
authors.lastname: Holdway
authors.forename: K
authors.initials: K
authors.lastname: Lok
authors.forename: M
authors.initials: M
authors.lastname: Semaan
mesh_terms: D000818:Animals; D002104:Cadmium / Q000633:toxicity*; D004781:Environmental Exposure / Q000032:analysis; D006829:Hydra / Q000187:drug effects* / Q000254:growth & development; D007928:Lethal Dose 50; D019055:No-Observed-Adverse-Effect Level; D013045:Species Specificity; D018675:Toxicity Tests / Q000379:methods; D023382:Toxicity Tests, Acute; D014874:Water Pollutants, Chemical / Q000633:toxicity*; D015032:Zinc / Q000633:toxicity*
chemical_list: D014874:Water Pollutants, Chemical; D002104:Cadmium; D015032:Zinc