Lubrication in the joints of insects (Arthropoda: Insecta)

Abstract

Femoro-tibial leg joint, head-prothorax joint (gular area) and occipital region of the head were examined using scanning electron microscopy in insects from the orders Blattodea and Coleoptera. Lubricating substances and corresponding pore openings were found in Argentinean Wood Roach Blaptica dubia and in the beetles from families Carabidae, Hydrophilidae, Silphidae, Scarabaeidae, Elateridae, Tenebrionidae and Curculionidae. Lubricant on the contacting surfaces were found on femoral and tibial counterparts of leg joints of different beetle species and cockroaches, in the gular region of the head in beetles, and in the occipital region of the head of the cockroach. Typical pore opening was on an average 1 µm in diameter (ranging from 0.5 µm to 10.0 µm). The amount of pore openings in a joint varies from a few pores to hundreds. The lubricant is found to be strongly variable in its appearance usually in the form of a single elongated filiform flow, as well as long or short drops, often forming accumulations or spreading over the surface. The supposed function of the lubricant in studied joints is discussed and assumed as friction and wear minimization. The presence of a high amount of the lubricant in leg joints of insects with intense leg locomotion is presumed.

Smart joints: auto-cleaning mechanism in the legs of beetles

“…For the comparison, the experiments with contamination were performed for darkling beetle Zophobas morio having simple walking leg without evident structures that can be attributed to cleaning mechanism 21 , 22 . As follows from the experimental results the leg joint of Zophobas morio can easily be contaminated by metallic particles of 2–5 μm (Supplementary Fig.…”

“…SEM images of the outflow canal show the presence of microparticles trapped in the lubricant. This could presumably be evidence of one more function of the lubricant being involved in the entrapment of contaminants particles that facilitates their removal 21 , 22 .…”

“…It may be supposed that leg joint structures involved in the cleaning mechanism in Pachnoda marginata are the result of specialized adaptation for digging. Thus, the legs of beetles not adapted to burrowing may not have such adaptive structures, as seen by the example of the simple walking legs of darkling beetle Zophobas morio 21 , 22 whose joints can easily be contaminated (Supplementary Fig. S 9 ).…”

Jumping mechanism in the marsh beetles (Coleoptera: Scirtidae)

“…8 The femoro-tibial joint of the hind jumping legs of the marsh beetles morphologically strongly differs from that of other jumping beetles. Despite of some lack of broad comparative morphological studies on this topic, one may discuss the generalized structure of the femoro-tibial joint 47,48 as that having such specific elements as a pair of symmetric femoral condyles (convex, circular structure of the toroid shape) and a pair of tibial concavities with the corresponding complementary shape. The femoral condyle inserts into the tibial concavity and is bent Table 2.…”

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

“…Several insect behaviors impose relevant mechanical demands on their exoskeleton, like flying, jumping, running, walking, biting, and the associated muscle contractions. 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; Nadein and Gorb, 2021; 2022; Nadein et al, 2021; 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; Li et al 2020; Josten et al 2022; Krings & Gorb, 2023), besides the differences among the cuticular layers or the abundance of transition or alkaline earth metals.…”