Mechanical properties of larval mouthparts of the antlion Euroleon nostras (Neuroptera: Myrmeleontidae) and their correlation with cuticular material composition

Abstract

The diversity of insects can be explained by their ability to fill various ecological niches, which includes the foraging from diverse sources. The cuticle-based feeding structures interact with the food and show adaptations in shape, material composition and mechanical properties to it. In this study, we focus on the mouthparts of a very prominent ambush predator, the antlion larvae of Euroleon nostras. By nanoindentation, we tested the hardness and the Young’s modulus of the mouthparts, which are significantly harder and stiffer than other insect cuticle structures. To gain insight into the origins of the high values, we studied the degree of tanning using confocal laser scanning microscopy. Additionally, we determined the content of transition and alkaline earth metals by energy dispersive X-ray spectroscopy. We found that the proportions of Zn, Mn, Fe, Cu, Ca, Mg, and Si correlate with the mechanical property values. We also conducted experiments on the breaking stress, the puncturing and biomechanical behaviour of the jaws, which highlighted their extraordinary strength. These findings are not only valuable for biologists, but also for material scientists, as they contribute to our understanding of the origins of mechanical property heterogeneities in insect cuticle.

Elemental composition and material properties of radular teeth in the heterobranch snail Gastropteron rubrum (Mollusca, Gastropoda, Cephalaspidea) foraging on hard organisms

“…When proteins were abundant, those structures appeared brown, yellow, or pink in overlay. This protocol (Michels & Gorb, 2012) was applied in many studies on arthropod cuticles (e.g., Beutel et al, 2020; Friedrich & Kubiak, 2018; Lehnert et al, 2021; Matsumura et al, 2021; Peisker et al, 2013) and cross‐validated by employing nanoindentation in lady beetles and antlions (Krings & Gorb, 2023b; Peisker et al, 2013).…”

Mechanical and elemental characterization of ant mandibles: consequences for bite mechanics

“…A higher degree of cuticular H and E along the mandible masticatory margin is commonly observed in ants (Brito et al 2017;Schofield et al 2002;2021), although only a few species were measured so far, mainly leaf-cutter ants. Such higher levels of material properties along the masticatory margin usually follow the concentration of transition metals like Zn (Schofield et al 2021), which tend to concentrate along the cutting edge or other cutting and piercing tools of arthropods (Polidori et al 2020;Schofield et al 2021;Krings & Gorb 2023;Reiter et al 2023;Krings & Gorb 2023). In leaf cutter ants, the mandible cutting edge is usually stiffer and harder (Schofield et al 2002;2021), which could be a mechanism to deal with the abrasion associated with the behavior of cutting leaves, as well as to improve the selfsharpening mechanism of such a structure (Martínez et al 2020).…”

“…Such behaviors usually generate friction between body parts and the environment and even among body parts that can lead to cuticular wear, which could also happen with the frequent use of a structure like the mandibles to process hard materials (Schofield et al 2011;2022;Püffel et al 2023b). Therefore, it is not surprising that substantial variation in cuticle material sclerotization levels is observed along the body of an insect (Michels & Gorb 2012;Büsse & Gorb 2018;Eshghi et al 2018;Josten et al 2022;Krings & Gorb, 2023), besides the differences among the cuticular layers or the abundance of transition or alkaline earth metals. This intraindividual variation in the cuticle can have significant functional relevance due to its effects on the cuticle material properties (Das et al 2018;Jafarpour et al 2020;Matsumura et al, 2020;Toofani et al 2020;Xing & Yang 2020;Casey et al 2022).…”

“…Transition and alkaline earth metals in the cuticle are observed in several arthropod lineages, especially on appendages associated with biting or puncture, like spider fangs (Politi et al 2021;Schofield et al 2021), scorpion claws, pedipalps, and chelicerae (Schofield et al 2003;Schofield et al 2021), mandibles of termites (Cribb et al 2007), cicadas (Reiter et al 2023), ant lions (Krings & Gorb 2023), and ants (Schofield et al 2002;2021;Polidori et al 2020). Along with these cross-links, it is known that ant species can incorporate minerals into their cuticle , similar to the cuticles of crustaceans.…”

Mandible elemental composition and mechanical properties from distinct castes of the leafcutter ant Atta laevigata (Attini; Formicidae)

“…Cu, Fe, Mn and/or Zn ions probably serve as cross-links [41,61,80,[84][85][86][87], whereas Ca and Mg could be present in crystalline form [34,[43][44][45]. Most of the elements, especially Zn, Mn, Ca and Mg, directly relate to an increase in hardness and wear resistance in insects [23,28,29,33,34,61,63,74,88,89].…”