Impact of Polystyrene Micro- and Nanoplastics on the Biological Traits of the Japanese Carpenter Ant, Camponotus japonicus Mayr (Hymenoptera: Formicidae)

Insects, being among the most diverse and abundant organisms in terrestrial ecosystems, are inevitably exposed to ubiquitous micro- and nanoplastic contaminants. Although studies on the impact of these contaminants on terrestrial insects are gradually emerging, they remain limited in scope. In this study, we investigated the biological traits (including foraging behavior, food assumption, digging ability, body weight and survival) of the Japanese carpenter ant, <i>Camponotus japonicus</i>, in response to exposure to polystyrene micro- and nanoplastic (PS-M/NP) solutions containing three particle sizes (0.05, 1 and 50 μm) and four concentrations (0.1, 1, 10 and 50 mg/mL). The results showed that worker ants exhibited significant foraging preference and food consumption for non-contaminated solutions in multiple-choice experiments, indicating that worker ants <i>C. japonicus</i> can differentiate and avoid feeding on PS-M/NP-contaminated solutions. Meanwhile, PS-M/NPs significantly reduced the foraging ability of worker ants in multiple-choice and no-choice experiments, with the smallest particle size (0.05 μm) and highest concentration (50 mg/mL) of PS-M/NPs resulting in the longest pre-foraging period, the lowest percentage of licking and the amount of food consumption. In addition, the weight of sand removed by worker ants, the body weight and survival of worker ants showed a dramatic decline with a decrease in particle size, increase in concentration and prolonged in exposure time of PS-M/NP-contaminated solutions. The results of this study confirm that PS-M/NPs have an adverse effect on these worker ants in a particle size, concentration and exposure time-dependent manner, with small particle size, high concentration and longer exposure time being the key factors in decreasing the foraging behavior and biological traits of this insect.