Utilization of a Gender-Based Sorting Machine for Crustacean Selection in Bioconcentration Studies with the Freshwater Amphipod Hyalella Azteca.

Bioconcentration factors are determined by fish flow-through tests performed according to the OECD 305 TG (OECD, 2012). These are time consuming, expensive, and use a large number of animals. Alternative test design using the freshwater amphipod Hyalella azteca for bioconcentration studies has been recently developed and highlighted a high potential. For bioconcentration studies using H. azteca, male amphipods are preferred compared to female organisms. Manual sexing of male adults amphipods is however time consuming and requires care and skills. A new fully automatic sorting and dispensing machine for H. azteca based on image analysis has recently been developed by the company Life Science Methods (LSM). Nevertheless, an anesthesia step is necessary prior to the automatic selection. In this study, we showed that a single-pulse of 90 minutes of tricaine at the concentration of 1 g/L can be used and recommended to select H. azteca males manually or automatically using the sorting machine. In a second part, we demonstrate that the machine has the ability to select, sort and disperse the males of a culture batch of H. azteca as efficiently as manually. In a last part of the study, bioconcentration factor of two organic substances was evaluated using the HYBIT (H. azteca bioconcentration test) protocol, with an anesthetizing step and robotic selection compared to manual selection without an anesthetizing step. The different BCFs values obtained were in accordance with those indicated in the literature and showed that an anesthetizing step had no effect on the BCFs values. Therefore, these data validated the interest for this sorting machine for selecting males in order to perform bioconcentrations studies with H. azteca. This article is protected by copyright. All rights reserved. Environ Toxicol Chem 2023;00:0-0. © 2023 SETAC.