1. Comparative Material and Mechanical Properties among Cicada Mouthparts: Cuticle Enhanced with Inorganic Elements Facilitates Piercing through Woody Stems for Feeding.
- Author
-
Reiter, Kristen E., Perkovich, Cynthia, Smith, Katelynne N., Feng, Jiansheng, Kritsky, Gene, and Lehnert, Matthew S.
- Subjects
MECHANICAL behavior of materials ,CICADAS ,ENERGY dispersive X-ray spectroscopy ,WOOD density ,CUTICLE ,HARDWOODS - Abstract
Simple Summary: Cicadas are one of the most popular insects. Their loud mating songs, newsworthy mass emergences and prolonged lifespan underground (17 years in some species) make cicadas a model organism for building bridges between scientific studies and the public. A key aspect of cicada biology is that the adults use their tube-like mouthparts to pierce through the hard wood of trees to feed on fluids, an ability that suggests that their mouthparts might have adaptations for piercing wood, such as increased hardness and stiffness. Here, we aimed to determine if the cuticle that comprises cicada mouthparts is enhanced with metals and other inorganic elements that could increase cuticular hardness and stiffness. We used scanning electron microscopy and energy dispersive X-ray spectroscopy to study mouthpart morphology and to determine which elements are found in the mouthpart cuticle. We found metals and other inorganic elements in the cicada mouthparts. Additionally, nanoindentation was also used to determine mouthpart mechanical properties. Metals were mostly located at the tip of the mouthparts (the part that pierces wood) and were harder than other regions. These findings are not only valuable to the fields of material sciences, coevolution, and ecology, but provide another interesting aspect of cicada biology. Adult cicadas pierce woody stems with their mouthparts to feed on xylem, suggesting the presence of cuticular adaptations that could increase hardness and elastic modulus. We tested the following hypotheses: (a) the mouthpart cuticle includes inorganic elements, which augment the mechanical properties; (b) these elements are abundant in specific mouthpart structures and regions responsible for piercing wood; (c) there are correlations among elements, which could provide insights into patterns of element colocalization. We used scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) to investigate mouthpart morphology and quantify the elemental composition of the cuticle among four cicada species, including periodical cicadas (Magicicada sp.). Nanoindentation was used to quantify hardness and elastic modulus of the mandibles. We found 12 inorganic elements, including colocalized manganese and zinc in the distal regions of the mandible, the structure most responsible for piercing through wood; nanoindentation determined that these regions were also significantly harder and had higher elastic modulus than other regions. Manganese and zinc abundance relates to increased hardness and stiffness as in the cuticle of other invertebrates; however, this is one of the first reports of cuticular metals among insects with piercing-sucking mouthparts (>100,000 described species). The present investigation provides insight into the feeding mechanism of cicadas, an important but understudied component of their life traits. [ABSTRACT FROM AUTHOR] more...
- Published
- 2023
- Full Text
- View/download PDF