Mechanical properties of the cuticles of three cockroach species that differ in their wind-evoked escape behavior

Abstract

The structural and material properties of insect cuticle remain largely unexplored, even though they comprise the majority (approximately 80%) of animals. Insect cuticle serves many functions, including protection against predatory attacks, which is especially beneficial to species failing to employ effective running escape responses. Despite recent advances in our understanding of insect escape behaviors and the biomechanics of insect cuticle, there are limited studies on the protective qualities of cuticle to extreme mechanical stresses and strains imposed by predatory attacks, and how these qualities vary between species employing different escape responses. Blattarians (cockroaches) provide an appropriate model system for such studies. Wind-evoked running escape responses are strong in Periplaneta americana, weak in Blaberus craniifer and absent in Gromphodorhina portentosa, putting the latter two species at greater risk of being struck by a predator. We hypothesized that the exoskeletons in these two larger species could provide more protection from predatory strikes relative to the exoskeleton of P. americana. We quantified the protective qualities of the exoskeletons by measuring the puncture resistance, tensile strength, strain energy storage, and peak strain in fresh samples of thoracic and abdominal cuticles from these three species. We found a continuum in puncture resistance, tensile strength, and strain energy storage between the three species, which were greatest in G. portentosa, moderate in B. craniifer, and smallest in P. americana. Histological measurements of total cuticle thickness followed this same pattern. However, peak strain followed a different trend between species. The comparisons in the material properties drawn between the cuticles of G. portentosa, B. craniifer, and P. americana demonstrate parallels between cuticular biomechanics and predator running escape responses.

Cockroaches traverse crevices, crawl rapidly in confined spaces, and inspire a soft, legged robot

“…After the tests, cockroaches were able to fly normally and showed no significant changes in unconstrained running velocity (76.67 ± 7.34 cm·s −1 ) compared with controls [P = 0.49, F (1,35) = 6.21]. The relatively lower strain and higher buckling stiffness (3.36 GPa) measured in fresh sclerotized locust tibia (61) suggest the cockroach's compressibility derives from their soft arthrodial membranes rather than compression or bending of stiff exoskeletal plates (41) or tubes (36).…”

“…As a first step toward quantifying the exoskeletal material properties (41) and shape changes that enable cockroaches to traverse crevices and crawl in confined spaces, we measured the compression of selected head and body segments by adding loads to anesthetized animals and performed a series of dynamic compressive cycle tests on living animals.…”

“…We selected the American cockroach, Periplaneta americana, because of its high speed (31), maneuverability (34,40), robustness (41), and tenacity to enter and leave spaces. To determine the smallest horizontal crevice that a cockroach could traverse, we challenged animals with a series of decreasing crevice heights.…”

Stag Beetle Elytra: Localized Shape-Retaining, Puncture and Wear-Resistant

“…Elytra were shown to play an important function as a protective cuticle for the delicate wings and the abdomen of the Japanese rhinoceros (Allomyrina dichotoma) beetle [18]. There are a few studies aimed at studying puncture resistant mechanisms in fish scales and cockroach abdomen cuticle [19,20].…”

Cutting food in terrestrial carnivores and herbivores

“…While different insect groups vary in their overall hardness, e.g. moths are softbodied and beetles often hard-bodied [39], and larvae are rsfs.royalsocietypublishing.org Interface Focus 6: 20150109 usually softer than adults, variation of the biomechanical properties across insect groups is poorly known [40].…”