MP13 Aquatic Ecotoxicology
Monday, 14 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(HAR-1117-810450) Sensitivity differences among various strains of Hyalella azteca.

Haring, H¹, Markert, J², Lazorchak, J³, Smith, M¹, ¹ SoBran Inc c/o US EPA, Cincinnati, OH, USA² ORISE/EERD/MERB c/o US EPA, Cincinnati, OH, USA³ US EPA/NERL/MIRB, Cincinnati, OH, USA

ABSTRACT- The North American amphipod Hyalella azteca is widely used in toxicity testing. H. azteca has a broad geographic distribution, and genetic evidence suggests that populations diverged from each other long ago. The importance of this genetic divergence to toxicity testing is unclear. Here we report the LC50 results for two different toxicants, Cu²⁺ and NH₃, from tests with geographically isolated strains of H. azteca from 7 academic and government laboratories and one wild strain. The strains were reared and tested under identical conditions. These tests were 96 h renewed acute toxicity tests conducted in triplicate using serial dilutions up to 500 ug/l CuSO₄ and 500 mg/l (NH₄)₂HPO₄. The Cu²⁺ LC50s ranged from 105.76 ug/l to126.14 ug/l. The NH₃ LC50s ranged from 3.88 mg/l to 5.18 mg/l. Of the eight strains tested with each toxicant, none were found to differ statistically based on the LC50 data generated. Therefore, it appears no sensitivity differences exist among different strains of H. azteca tested thus far using Cu²⁺ and NH₃ as toxicants. Although this work was reviewed by EPA and approved for publication it may not necessarily reflect official agency policy.

Key words: Hyalella azteca, Toxicity, Sensitivity, Strains