Ontogenetic regulation of cuticular hydrocarbon profiles and oviposition geometry in the spiralling whitefly, Aleurodicus dispersus

Abstract

The insect cuticle is a dynamic physiological interface that integrates structural and chemical traits to mediate interactions with the environment. In the polyphagous whitefly Aleurodicus dispersus, reproduction involves the deposition of eggs in wax-embedded spirals, yet the physiological coordination of these surface traits across life-history transitions remains poorly understood. This study integrates developmental morphometrics, host-resolved behavioural assays and gas-chromatographic profiling of cuticular hydrocarbons (CHCs) to examine the functional organisation of the A. dispersus surface. Morphometric analysis revealed pronounced sexual dimorphism and directional asymmetry in sensory and flight structures, with large effect sizes supporting these differences, reflecting sex-specific physiological investment in dispersal versus fecundity. Oviposition geometry exhibited significant behavioural plasticity, with regular spiral formation declining sharply as a function of infestation age and host-plant identity, including the occurrence of fragmented and overlapping spiral patterns at later infestation stages. CHC profiles, identified primarily based on retention time comparison with n-alkane standards (C₈–C₃₀) and extrapolated retention patterns for longer chains (e.g., C₃₂–C₃₆), demonstrated clear developmental structuring, with compound assignments considered putative in the absence of GC–MS confirmation. Mobile feeding stages and adults were dominated by short-chain hydrocarbons (C₈–C₁₀), while immobile eggs and pupae selectively accumulated long-chain compounds (C₂₇–C₃₆). Multivariate analyses confirmed a clear chemical separation between life stages based on mobility, indicating systematic developmental reorganisation of surface chemistry. The observed association between hydrocarbon chain length and inferred barrier properties is consistent with established physicochemical principles rather than directly measured functional outcomes, and functional implications should be interpreted cautiously in the absence of direct permeability or water-loss measurements. These findings provide a physiological framework for understanding how invasive generalist insects may modulate their external interface to support shifting reproductive and survival requirements across the life cycle.