Functional Morphology of the Thorax of the Click Beetle Campsosternus auratus (Coleoptera, Elateridae), with an Emphasis on Its Jumping Mechanism

Hybrid Compliant Musculoskeletal System for Fast Actuation in Robots

A nature-inspired musculoskeletal system is designed and developed to examine the principle of nonlinear elastic energy storage-release for robotic applications. The musculoskeletal system architecture consists of elastically rigid segments and hyperelastic soft materials to emulate rigid-soft interactions in limbless vertebrates. The objectives are to (i) improve the energy efficiency of actuation beyond that of current pure soft actuators while (ii) producing a high range of motion similar to that of soft robots but with structural stability. This paper proposes a musculoskeletal design that takes advantage of structural segmentation to increase the system's degrees of freedom, which enhances the range of motion. Our findings show that rigid-soft interactions provide a remarkable increase in energy storage and release and, thus, an increase in the undulation speed. The energy efficiency achieved is approximately 68% for bending the musculoskeletal system from the straight configuration, compared to 2.5-30% efficiency in purely soft actuators. The hybrid compliance of the musculoskeletal system under investigation shows promise for alleviating the need for actuators at each joint in a robot.

Complete mitochondrial genome of Pectocera sp. (Elateridae: Dendrometrinae: Oxynopterini) and its phylogenetic implications

The Elateridae family (click beetles) represents a highly diverse lineage that possesses a specialized clicking mechanism to startle predators. At present, however, phylogenetic relationships, especially among recognized subfamilies, remain contentious. Mitochondrial genomes (mitogenomes) can help resolve previously intractable phylogenetic relationships using morphological or limited molecular data. Here, we report the complete mitogenome of Pectocera sp. (Elateridae: Dendrometrinae: Oxynopterini), which was 15,962 bp in length and showed a typical gene number and order as most beetle mitogenomes, including 13 protein-coding genes (PCGs), 22 transfer RNA genes, 2 ribosomal RNA genes, and 1 noncoding control region (AT-rich region). Comparative genomic analyses showed a high degree of feature similarity among Pectocera sp. and other click beetles. Evolutionary analysis of all PCGs based on the nonsynonymous/synonymous substitution rate ratio (ω) indicated that cox1 and atp8 exhibited the lowest and highest evolutionary rates, respectively, and that the evolutionary rates of all PCGs, except for cox3, nad2, and nad3, were lower than the average ω of click beetles. Phylogenetic analyses based on concatenated and coalescent approaches indicated that Pectocera sp. was sister to Campsosternus auratus in the same tribe (Oxynopterini) with high support. This study offers insight into the mitogenomic basis of Pectocera sp. and provides an important data resource for exploring the taxonomy, phylogeny, and evolution of click beetles.