Overlooked role of peristalsis-driven gut fragmentation of microplastics by plastivore Tenebrio molitor larvae

Microplastic (MP) degradation by plastivore insects and their plastic-degrading gut microbiota has attracted significant attention. However, the contribution of intestinal fragmentation capacity to in vivo MP degradation processes in plastivores remains poorly understood. Here, we investigate, for the first time, the role of peristalsis-driven gut fragmentation in the digestive removal, biodegradation, and size reduction of MPs by the model plastivore Tenebrio molitor larvae. Our findings demonstrate that peristalsis-driven fragmentation is essential for both degrading and propelling MPs within the plastivore T. molitor larvae. When intestinal fragmentation was either severely or moderately inhibited with 5 % and 2 % (wt/wt) concentrations of gut peristalsis inhibitors, MP removal efficiency significantly decreased from 59.81 % under normal conditions to 39.58 % and 51.06 %, respectively, accompanied by prolonged retention of MPs in the gut. Importantly, impaired fragmentation directly limited depolymerization efficiency, as evidenced by higher molecular weights of residual polymers post-biodegradation. Ultrasensitive particle analysis further demonstrated that the inhibition of peristalsis-driven fragmentation resulted in the excretion of undigested plastic particles of larger sizes. Additionally, under inhibitory conditions, the smallest undigested particles were even smaller, likely due to reduced surface abrasion. These findings highlight the previously underappreciated role of peristalsis-driven fragmentation function in facilitating MP biodegradation in plastivore invertebrates.