High-Throughput Phototactic Ecotoxicity Biotests with Nauplii of Artemia franciscana

Analysis of sensorimotor behavioral responses to stimuli such as light can provide an enhanced relevance during rapid prioritisation of chemical risk. Due to technical limitations, there have been, however, only minimal studies on using invertebrate phototactic behaviors in aquatic ecotoxicity testing. In this work, we demonstrate an innovative, purpose-built analytical system for a high-throughput phototactic biotest with nauplii of euryhaline brine shrimp Artemia franciscana. We also, for the first time, present a novel and dedicated bioinformatic approach that facilitates high-throughput analysis of phototactic behaviors at scale with great fidelity. The nauplii exhibited consistent light-seeking behaviors upon extinguishing a brief programmable light stimulus (5500K, 400 lux) without habituation. A proof-of-concept validation involving the short-term exposure of eggs (24 h) and instar I larval stages (6 h) to sub-lethal concentrations of insecticides organophosphate chlorpyrifos (10 mu g/L) and neonicotinoid imidacloprid (50 mu g/L) showed perturbation in light seeking behaviors in the absence of or minimal alteration in general mobility. Our preliminary data further support the notion that phototactic bioassays can represent an attractive new avenue in behavioral ecotoxicology because of their potential sensitivity, responsiveness, and low cost.

Automated summary

Analysis of sensorimotor behavioral responses to stimuli such as light can provide enhanced relevance in prioritizing chemical risks. However, there have been minimal studies on using invertebrate phototactic behaviors in aquatic ecotoxicity testing due to technical limitations. In this research, a high-throughput phototactic biotest system for brine shrimp nauplii was demonstrated, along with a novel bioinformatic approach for analyzing phototactic behaviors at scale. The preliminary data showed consistent light-seeking behaviors in nauplii without habituation, and exposure to sub-lethal concentrations of insecticides resulted in perturbed light seeking behaviors. These findings suggest that phototactic bioassays have the potential to be a sensitive, responsive, and cost-effective method in behavioral ecotoxicology.