To attach or not to attach? The effect of carrier surface morphology and topography on attachment of phoretic deutonymphs of Uropoda orbicularis (Acari)

Patterns of Distribution of Phoretic Deutonymphs of Uropodina on Longhorn Beetles in Białowieża Primeval Forest, Central Europe

We studied the distributional patterns of phoretic deutonymphs of the genera Oodinychus and Trichouropoda (Uropodina) on the longhorn beetles Monochamus sartor urussovii, Plagionotus detritus, Tetropium castaneum, and Te. fuscum, based on large samples of specimens (992 beetles and 25,587 mites) collected in the Białowieża Primeval Forest in Central Europe in the years 2008 and 2012–2016. All the studied phoretic phoront-host associations are characterized by different patterns of the attachment sites of mites on beetle’s body. In the case of O. ovalis and M. sartor urussovii association, the deutonymphs were found mostly on the pronotum and dorsal surface of the elytra. This is the only instance in which phoronts were absent on the legs. Deutonymphs of T. sociata on P. detritus preferred the abdomnen (both tergites and ventrites) and the hindlegs. Only in this case the phoronts were attached inside the subelytral space. The highest number of deutonymphs of T. shcherbakae on both Tetropium species occured on the legs. In the case of Te. castaneum, similar proportions of mites were recorded on all pairs of legs, while the preferred location of mites phoretic on Te. fuscum were the forelegs. Both the preferences of phoretic deutonymphs for specific parts of the host’s body and the participation of carriers transporting deutonymphs on particular parts of their bodies were very consistent.

Dynamic biological adhesion: mechanisms for controlling attachment during locomotion

The rapid control of surface attachment is a key feature of natural adhesive systems used for locomotion, and a property highly desirable for man-made adhesives. Here, we describe the challenges of adhesion control and the timescales involved across diverse biological attachment systems and different adhesive mechanisms. The most widespread control principle for dynamic surface attachment in climbing animals is that adhesion is 'shear-sensitive' (directional): pulling adhesive pads towards the body results in strong attachment, whereas pushing them away from it leads to easy detachment, providing a rapid mechanical 'switch'. Shear-sensitivity is based on changes of contact area and adhesive strength, which in turn arise from non-adhesive default positions, the mechanics of peeling, pad sliding, and the targeted storage and controlled release of elastic strain energy. The control of adhesion via shear forces is deeply integrated with the climbing animals' anatomy and locomotion, and involves both active neuromuscular control, and rapid passive responses of sophisticated mechanical systems. The resulting dynamic adhesive systems are robust, reliable, versatile and nevertheless remarkably simple. This article is part of the theme issue 'Transdisciplinary approaches to the study of adhesion and adhesives in biological systems'.

The influence of the topography and physico-chemical properties of the cuticle surface on the wettability and adhesive properties of the elytra of the dung beetle Geotrupes stercorarius (Coleoptera, Scarabaeidae)

The elytral surface of dung beetles is generally accepted to be self-cleaning due to its anti-adhesive properties. In this article, the wettability and adhesive properties of elytral surface (intact and treated with Acetone and Ethanol) of the beetle Geotrupes stercorarius were characterized. Since these properties are influenced by the surface structure and chemistry, the micro- and nanostructure of the elytra were observed using scanning electron microscopy and the surface roughness were estimated with white light interferometery, whereas the water contact angle and adhesion force of the elytra were evaluated using contact angle measurement device and force transducer, respectively. The results show that the microstructure of the elytra changed greatly after different chemical treatments and the changes in wettability were mainly related to the changes of elytra roughness after treatments. The differences in adhesion force between differently treated elytra and wet sand indicate that the molecular polarity of the elytral surface is decisive for its anti-adhesive (self-cleaning) property.