Stage‐specific phototactic behavior and opsin‐mediated light perception in the concealed‐feeding palm pest
Octodonta nipae
Jia‐Wei Li, Pei Chen, You‐Dan Zhang, Cheng‐Cheng Wang, Huan‐Ran Jing, Zhi‐Ming Chen, You‐Ming Hou, Bao‐Zhen Tang Abstract
BACKGROUND
Negative phototaxis is a widespread but underexplored behavior in concealed‐feeding insects, and its adaptive value and sensory mechanisms remain poorly understood compared with light attraction. The invasive palm pest Octodonta nipae inhabits folded leaflets and shaded microhabitats, providing a suitable system to examine how light avoidance contributes to habitat adaptation and whether opsin‐mediated perception regulates stage‐specific phototaxis.
RESULTS
Larvae of O. nipae exhibited strong negative phototaxis (>70% selected dark chambers), whereas adults displayed positive phototaxis (~70% selected illuminated chambers). Complete darkness promoted larval body‐length growth, with larvae reaching 7.75 mm at 15 days, and shortened development by ~1.7 days under leaf‐bound conditions compared with the standard 12 h light:12 dark cycle, while survival remained comparable. Five opsin genes were identified, including the UV‐sensitive OnRh3 and long‐wavelength‐sensitive OnRh6 , which showed pronounced adult‐biased expression and strong transcriptional responses to light regimes. RNAi‐mediated silencing of either gene reversed adult positive phototaxis, with approximately 80% of silenced adults selecting dark chambers, whereas ectopic overexpression in Drosophila melanogaster larvae shifted behavior from innate light avoidance (~70% selecting dark sectors) to increased light selection (>60% selecting illuminated sectors).
CONCLUSION
These findings link larval negative phototaxis to developmental advantages in concealed habitats and identify OnRh3 and OnRh6 as key mediators of opsin‐dependent phototactic behavior. They further indicate that opsin‐mediated light perception contributes to stage‐specific behavior in this invasive pest, providing insights for future light‐based monitoring studies. © 2026 Society of Chemical Industry.