Invasive ambrosia beetles have zinc-enriched mandibles: support for the metal-prioritization hypothesis and insights into the mechanisms of metal deposition

Authors: MYERS, KENDALL - Kent State University; RAUBENOLT, JESSI - The Ohio State University; PERKOVICH, CYNTHIA - Ashland University; Ranger, Christopher; LEHNERT, MATTHEW - Kent State University

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/12/2026
Publication Date: 5/15/2026
Citation: Myers, K.O., Raubenolt, J., Perkovich, C., Ranger, C.M., Lehnert, M. 2026. Invasive ambrosia beetles have zinc-enriched mandibles: support for the metal-prioritization hypothesis and insights into the mechanisms of metal deposition . Scientific Reports. https://doi.org/10.1038/s41598-026-53349-y.
DOI: https://doi.org/10.1038/s41598-026-53349-y

Interpretive Summary: The hardness of the structural tools of insects can be increased through the integration of transition metals into the cuticle. It is unknown whether there are metal preferences for insect cuticle, and whether metals accumulate in cuticle through different life stages. To address these questions, we characterized metal deposition in the mandibles of ambrosia beetles, as well as their fungal diet, and the wood the fungus digests. Microscopy analysis revealed low metal concentrations in the wood and fungus, but high concentrations of zinc in the the mandibles of larvae and adult ambrosia beetles. The mandibles showed patterns in hardness (i.e., sclerotization) that coincided with zinc distributions. Zinc was absent from the mandible or young larvae, which indicates that metals are not inherited. Furthermore, the similar concentrations between mature larvae and adult males indicate that metals do not accumulate through life stages. Instead, zinc is believed to accumulate in larvae and adults from the fungal diet within each instar. These results will help researchers identify biological weakness in ambrosia beetles for developing targeted management tactics.

Technical Abstract: The hardness of the structural tools of insects can be increased through the integration of transition metals into the cuticle. However, questions remain regarding how metal concentrations change as they flow through ecological systems, whetherif there are metal preferences for insect cuticle, and whetherif metals accumulate in cuticle through different life stages. To address these questions, we characterized structures in an insect-fungal symbiont system, including mandibles of ambrosia beetles, their fungal diet, and the wood the fungus digests. SEM-EDX revealed low metal concentrations in the wood and fungus, but high concentrations of zinc in distal regions of the distal regions of the mandibles of 3rd-instar larvae and adults. CLSM of mandibles showed sclerotization patterns that coincided with zinc distributions, and nanoindentation confirmed increased hardness. Zinc was absent from neonate mandibles, indicating a lack of maternal inheritance, and the similar concentrations between 3rd-instar larvae and adult males indicates indicate that metals do not accumulate through life stages. These patterns suggest a mechanism for zinc to accumulate from the fungal diet within each instar and for the post-ecdysial deposition of these metals to replace the metals lost in the exuvium.