Assessing Toxicant Effects: Comparison Between Individual-Based Behaviour and Reproduction Analysis

Behaviour is a crucial variable for assessing the fitness of animals, providing indication of their interactions with environmental stressors, particularly toxicant exposure. However, incorporating behavioural variables into bioassays requires a better understanding of individual behaviour. Most bioassays focus on the toxicant effects on the average behaviour of the studied population, assuming that all individuals in the population respond similarly to toxicant exposure. Consequently, this oversight may reduce the predictive accuracy and environmental relevance of toxicity bioassays. This study investigates the effects of unionized ammonia and fluoride ion exposure (28 days) on individual behaviour and reproduction of the aquatic snail Potamopyrgus antipodarum. Each bioassay included one control and three toxicant concentrations, with 20 animals per treatment group. Behaviour and reproduction of each animals were monitored individually over 28-day period. Results showed that the two highest concentrations of both toxicants caused significant changes in individual snail behaviour. Both individual behaviour and reproduction exhibited a similar level of sensitivity to these toxicants. This study shows that individual behaviour can be as effective as reproductive metrics in detecting toxicant exposure. Therefore, to maintain the sensitivity of behavioural bioassays, it is essential to carefully analyse individual behavioural responses in aquatic snails.