Oliver Betz

On the possibilities of hard X-ray imaging with high spatio-temporal resolution using polychromatic synchrotron radiation.

Time-resolved imaging with penetrating radiation has an outstanding scientific value but its realisation requires a high density of photons as well as corresponding fast X-ray image detection schemes. Bending magnets and insertion devices of third generation synchrotron light sources offer a polychromatic photon flux density which is high enough to perform hard X-ray imaging with a spatio-temporal resolution up to the μm-μs range. Existing indirect X-ray image detectors commonly used at synchrotron light sources can be adapted for fast image acquisition by employing CMOS-based digital high speed cameras already available on the market. Selected applications from life sciences and materials research underline the high potential of this high-speed hard X-ray microimaging approach.

Adhesive Exocrine Glands in Insects: Morphology, Ultrastructure, and Adhesive Secretion

A literature survey is provided summarizing the available information on exocrine epidermal glands that produce adhesive secretions in insects. The focus is on both the ultrastructure of the gland cells and the identity and function of the chemical secretion produced by them. Insects employ adhesives for various functions such as tarsal attachment during locomotion, resisting external detachment forces, mating, phoresy and parasitism, egg anchorage, retreat building, self-grooming, prey capture, and active and passive defence. The available studies on the ultrastructure and the secretion of adhesive insect glands cover a broad spectrum of developmental stages and higher taxa, i.e., the Elliplura, the Ephemeroptera, the Polyneoptera, the Acercaria, the Coleoptera, the Amphiesmenoptera, the Hymenoptera, and the Diptera (Table 8.1). Based on this diversity of biological contexts and systematic groups, adhesive structures are found at various tagmata of the body, mainly at the head, the abdomen, and the legs, but also within the thorax in the form of the metapleural glands of ants. Class 1 epidermal cells are the predominant glandular cell type among the adhesive gland systems in insects. With respect to their ultrastructure, the adhesive class 1 cells show features (in terms of their provision with endoplasmic reticulum, Golgi system, free ribosomes, and secretion vesicles and granules) that are either indicative of predominant non-proteinaceous (lipid) or protein secretion. In class 1 cells that are employed in locomotion (i.e., reversible tarsal adhesion to natural substrates such as plant surfaces), lipoidal secretion seems to prevail (although these secretions often appear to be complex mixtures of lipids with proteins and carbohydrates), whereas in the contexts of more permanent body or egg anchorage and of retreat building, protein-based secretion dominates. Oenocyte-like class 2 adhesive gland cells have hitherto only been found in the defence systems of Aphidoidea and Tingidae (both Hemiptera). Adhesive class 3 glands are almost always bicellular, consisting of a terminal secretorily active cell and an adjacent canal cell that surrounds the cuticular conducting duct.

Turning snails into slugs: induced body plan changes and formation of an internal shell

SUMMARY The archetypal body plan of conchiferan molluscs is characterized by an external calcareous shell, though internalization of shells has evolved independently in a number of molluscan clades, including gastropod families. In gastropods, the developmental process of torsion is regarded as a hallmark that is associated with a new anatomical configuration. This configuration is present in extant prosobranch gastropod species, which predominantly bear external shells. Here, we show that short‐term exposure to platinum during development uncouples at least two of the processes associated with torsion of the freshwater snail Marisa cornuarietis. That is, the anus of the treated snails is located anteriorly, but the gill and the designated mantle tissue remains in a posterior location, thus preventing the formation of an external shell. In contrast to the prosobranchian archetype, platinum treatment results in the formation of a posterior gill and a cone‐shaped internal shell, which persists across the lifetime. This first finding of artificially induced snail‐slug conversion was also seen in the pulmonate snail Planorbarius corneus and demonstrates that selective alteration of embryonic key processes can result in fundamental changes of an existing body plan and—if altered regulation is inherited—may give rise to a new one.

Jumping mechanisms and performance in beetles. I. Flea beetles (Coleoptera: Chrysomelidae: Alticini)

ABSTRACT The present study analyses the anatomy, mechanics and functional morphology of the jumping apparatus, the performance and the kinematics of the natural jump of flea beetles (Coleoptera: Chrysomelidae: Galerucinae: Alticini). The kinematic parameters of the initial phase of the jump were calculated for five species from five genera (average values from minimum to maximum): acceleration 0.91–2.25 (×103) m s−2, velocity 1.48–2.80 m s−1, time to take-off 1.35–2.25 ms, kinetic energy 2.43–16.5 µJ, g-force 93–230. The jumping apparatus is localized in the hind legs and formed by the femur, tibia, femoro-tibial joint, modified metafemoral extensor tendon, extensor ligament, tibial flexor sclerite, and extensor and flexor muscles. The primary role of the metafemoral extensor tendon is seen in the formation of an increased attachment site for the extensor muscles. The rubber-like protein resilin was detected in the extensor ligament, i.e. a short, elastic element connecting the extensor tendon with the tibial base. The calculated specific joint power (max. 0.714 W g−1) of the femoro-tibial joint during the jumping movement and the fast full extension of the hind tibia (1–3 ms) suggest that jumping is performed via a catapult mechanism releasing energy that has beforehand been stored in the extensor ligament during its stretching by the extensor muscles. In addition, the morphology of the femoro-tibial joint suggests that the co-contraction of the flexor and the extensor muscles in the femur of the jumping leg is involved in this process. Highlighted Article: Flea beetles use a resilin-based structure as an elastic energy store for the catapult jumping mechanism.

High-Speed X-ray Cineradiography for Analyzing Complex Kinematics in Living Insects

More than one hundred years ago, Lucien Bull showed, by means of his famous high-speed cinematographic movies of living species, the outstanding scientific value of time-resolved imaging, e.g. to understand the mechanisms behind insect flight [1]. For X-ray imaging, synchrotron light sources offer a photon beam that (i) propagates quasi-parallel, (ii) has fluxes that are higher by orders of magnitude than laboratory sources, and (iii) allows one to exploit more sophisticated contrast modalities. The use of synchrotron light is thus the next step in fast-imaging development: high-speed hard X-ray cineradiography employing phase contrast mechanisms [2,3]. Imaging with X-rays offers the chance to investigate complex kinematics of, for example, feeding and locomotion devices of animals, as the penetrating nature of the radiation reveals internal information.

Analysis of chemical profiles of insect adhesion secretions by gas chromatography–mass spectrometry

This article reports on the chemical analysis of molecular profiles of tarsal secretions of the desert locust Schistocerca gregaria (Forsskål, 1775) by gas chromatography hyphenated with quadrupol mass spectrometry (GC-MS) as well as (1)H-nuclear magnetic resonance ((1)H NMR) spectroscopy. Special focus of this study was to elaborate on sampling methods which enable selective microscale extraction of insect secretions in a spatially controlled manner, in particular tarsal adhesive secretions and secretions located on cuticle surfaces at the tibia. Various solvent sampling procedures and contact solid-phase microextraction (SPME) methods were compared in terms of comprehensiveness and extraction efficiencies as measured by signal intensities in GC-MS. Solvent sampling with water as extraction solvent gave access to the elucidation of chemical profiles of polar compound classes such as amino acids and carbohydrates, but is extremely tedious. Contact SPME on the other hand can be regarded as a simplified and more elegant alternative, in particular for the lipophilic compound fraction. Many proteinogenic amino acids and ornithine as well as carbohydrate monomers arabinose, xylose, glucose, and galactose were detected in tarsal secretions after acid hydrolysis of aqueous extracts. Qualitatively similar but quantitatively significantly different molecular profiles were found for the lipid fraction which contained mainly n-alkanes and internally branched monomethyl-, dimethyl-, and trimethyl-alkanes in the C23-C49 range as well as long chain fatty acids and aldehydes. Especially, hydrocarbons with >C40 carbon numbers have previously been rarely reported for insect secretions. The results suggest that the investigated insect secretions are complex emulsions which allow the attachment of tarsi on various otherwise incompatible materials of smooth and rough surfaces. The solid consistence of the established alkanes at ambient temperatures might contribute to a semi-solid consistence of the adhesive, amalgamating partly opposing functions such as slip resistance, tarsal release, desiccation resistance, and mechanical compliance. The methods developed can be extended to other similar applications of studying compositions of insect secretions of other species.

Functional morphology and adhesive performance of the stick-capture apparatus of the rove beetles Stenus spp. (Coleoptera, Staphylinidae)

The adhesive prey-capture apparatus of the representatives of the rove beetle genus Stenus (Coleoptera, Staphylinidae) is an outstanding example of biological adhesive systems. This unique prey-capture device is used for catching elusive prey by combining (i) hierarchically structured adhesive outgrowths, (ii) an adhesive secretion, and (iii) a network of cuticular fibres within the pad. The outgrowths arise from a pad-like cuticle and are completely immersed within the secretion. To date, the forces generated during the predatory strike of these beetles have only been estimated theoretically. In the present study, we used force transducers to measure both the compressive and adhesive forces during the predatory strike of two Stenus species. The experiments revealed that the compressive forces are low, ranging from 0.10 mN (Stenus bimaculatus) to 0.18 mN (Stenus juno), whereas the corresponding adhesive forces attain up to 1.0 mN in S. juno and 1.08 mN in S. bimaculatus. The tenacity or adhesive strength (adhesive force per apparent unit area) amounts to 51.9 kPa (S. bimaculatus) and 69.7 kPa (S. juno). S. juno beetles possess significantly smaller pad surface areas than S. bimaculatus but seem to compensate for this disadvantage by generating higher compressive forces. Consequently, S. juno beetles reach almost identical adhesive properties and an equal prey-capture success in attacks on larger prey. The possible functions of the various parts of the adhesive system during the adhesive prey-capture process are discussed in detail.

Adhesive performance of the stick-capture apparatus of rove beetles of the genus Stenus (Coleoptera, Staphylinidae) toward various surfaces

Rove beetles of the genus Stenus possess a unique adhesive prey-capture apparatus that enables them to catch elusive prey such as springtails over a distance of several millimeters. The prey-capture device combines the hierarchically organized morphology of dry adhesive systems with the properties of wet ones, since an adhesive secretion is released into the contact zone. We hypothesize that this combination enables Stenus species successfully to capture prey possessing a wide range of surface structures and chemistries. We have investigated the influence of both surface energy and roughness of the substrate on the adhesive performance of the prey-capture apparatus in two Stenus species. Force transducers have been used to measure both the compressive and adhesive forces generated during the predatory strike of the beetles on (1) epoxy resin surfaces with defined roughness values (smooth versus rough with asperity diameters ranging from 0.3 to 12 μm) and (2) hydrophobic versus hydrophilic glass surfaces. Our experiments show that neither the surface roughness nor the surface energy significantly influences the attachment ability of the prey-capture apparatus. Thus, in contrast to the performance of locomotory adhesive systems in geckos, beetles, and flies, no critical surface roughness exists that might impede adhesion of the prey-capture apparatus of Stenus beetles. The prey-capture apparatus of Stenus beetles is therefore well adapted to adhere to the various unpredictable surfaces with diverse roughness and surface energy occurring in a wide range of potential prey.

Head morphology of selected Staphylinoidea (Coleoptera: Staphyliniformia) with an evaluation of possible groundplan features in Staphylinidae

In insects, anatomical features of the head have been found to provide important information for phylogenetic and comparative evolutionary studies. We analyzed the internal head morphology of three (omaliine, tachyporine, oxyteline group) out of the four subfamily groups of the beetle family Staphylinidae plus two non‐staphylinid outgroups (i.e., Agyrtidae and Leiodidae). Synchrotron X‐ray micro‐tomography was used to obtain comparative head anatomical datasets of eight species to describe (i) the presence/absence of muscles inside the head capsule and (ii) the variability in their points of origin. Nineteen of these muscles were phylogenetically informative (nine with respect to presence/absence and eleven with respect to the origin; one muscle had an influence on both analyses) and were used in character mapping analyses to reconstruct groundplan patterns of the head musculature in Staphylinidae and their subgroups. Three muscles (Mm. 7, 9, 50) were identified as possibly autapomorphic for Staphyliniformia. The taxon (Agyrtidae + Leiodidae) is supported by the absence of M. 9. The monophyly of the tachyporine group is supported by a common origin of M. 4. Aleocharinae, a subfamily within the tachyporine group, is supported by the absence of M. 42 and possibly by numerous points of origin of various muscles (Mm. 1, 17, 28, 29, 30). Our analysis of the general organization of the hypopharynx‐prementum‐complex has revealed that this complex is organized in a similar way in the investigated staphylinoids, i.e., with the prementum lying anteriorly to and being in line with the hypopharynx and the mentum. We have found deviating conditions in the investigated species of the Aleocharinae, in which the prementum can be largely retracted posteriorly. Consequently, it is sandwiched between the ventral mentum and the dorsal hypopharyngeal region. The hypopharyngeal region is thus lifted dorsad to a large extent, approaching the cibarial roof. This situation is paralleled by a loss of the hypopharyngeal retractor (M. 42) and a shift of origin of premental retractors (Mm. 28–30) posteriorly toward the gula. J. Morphol. 270:1503–1523, 2009.

Hunting Ants in Mediterranean clay soils: life history of Siagona europaea (Coleoptera, Carabidae)

Abstract In southern Italy, Siagona europaea is common on clay soils and occurs up to the 38th parallel. Activity recordings have revealed that the beetles are strictly nocturnal. They are resistant to desiccation and prefer temperatures above 30 °C. Their flat body indicates adaptation to life in clay soils, which, in southern Italy, are deeply fissured from April to September. The behaviour of the beetles was observed in a transparent system of cavities consisting of plastic boxes connected by tubes. The beetles feed exclusively on ants that are caught by surprise attack outside their nests. Ants perceive the beetles as being hostile via chemical cues. Single ants then normally retreat, whereas groups of ants attack immediately. The beetles behave unaggressively against cospecifics and rest in groups of various numbers in flat soil crevices. Copulation takes place from the end of April onwards, whereas egg laying occurs from the end of May onwards. The females produce only a few eggs, which are unusually large, and shift them singly in narrow soil cracks. The larvae develop during the summer deep in the soil; they are blind and can be characterized as cave‐life forms by their extremely long cerci and antennae that have a whip‐like unsclerotized sticky distal part.