Behavioral Responses\nof Chironomus\naprilinus Larvae as Proxies for Cyanobacterial Metabolite\nInteractions: Insights from Ternary Combinations

This study aimed to assess the behavioral responses (immobilization,\nhorizontal and vertical motility, and response to light) of Chironomus aprilinus larvae exposed to individual\ncyanobacterial metabolites aeruginosin 98B (AER-B), anabaenopeptin-B\n(ANA-B), and cylindrospermopsin (CYL), and their binary and ternary\nmixtures. The investigation revealed that single metabolites ANA-B\nand CYL exhibited the highest potency in immobilizing the larvae.\nNotably, the binary mixture AER-B+CYL induced a remarkably strong\nsynergistic interaction, while other tested binary and ternary mixtures\ndemonstrated antagonistic effects. Both individual metabolites and\ntheir mixtures led to a decrease in larval movement speed, with the\nAER-B+CYL combination showing a very synergistic effect, and strong\nantagonistic interactions between the oligopeptides in the ternary\nmixture. Conversely, while AER-B and the binary mixture ANA-B+CYL\nstimulated vertical movement, other single metabolites and binary\nand ternary mixtures decreased this parameter. Antagonistic interactions\nwere observed in all mixtures. ANA-B emerged as the most potent inhibitor,\nyet all tested metabolites and their mixtures decreased larval response\nto light, displaying synergistic interactions, except for the AER-B+ANA-B\nmixture at 250 μg L<sup>–1</sup> + 250 μg L<sup>–1</sup>. These findings underscore the sensitivity of <i>Chironomus</i> larvae behavioral parameters as indicators of\nenvironmental stressors and mixtures. Consequently, they are recommended\nfor assessing toxic effects induced by cyanobacterial products and\nother bioactive chemicals.