Development and Evaluation of a Novel Toxicity Test Method with Hyalella azteca to Optimize Reproduction Endpoints

Hyalella azteca is a freshwater invertebrate used extensively in ecotoxicology. However, there are challenges associated with using reproduction as an endpoint in current standard methods, including: confounding effects of growth on reproduction, high biological variability associated with reproduction, and difficult recovery of juveniles from sediment. A novel, 28-d toxicity test method was created to optimize the reproduction endpoints by initiating tests with sexually mature amphipods to eliminate the confounding effects of growth, using a sex ratio of 2.3 females per male to reduce reproductive variability, and conducting tests in water-only conditions to improve juvenile recovery. The novel method was evaluated by comparing the sensitivity and reliability of reproduction data to standard methods. Reproduction endpoints produced similar results between methods, but the data were less variable in novel tests. The novel method shows promise to improve the use of reproduction as an endpoint in water-only toxicity tests with H. azteca.