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Intensive land use has been shown to alter the composition and functioning of soil communities. Due to their low dispersal ability, oribatid mites are particularly vulnerable to land-use intensification and species which are not adjusted to management-related disturbances become less abundant. We investigated how different land-use parameters in forests and grasslands affect oribatid mite diversity and abundance, with a focus on: (1) species-level impacts, by classifying species as increasing (‘winners’) or decreasing (‘losers’) in abundance with higher land-use intensity, and (2) reproductive impact, by investigating whether sexual and parthenogenetic species react differently. We collected 32,542 adult oribatid mites in 60 forests and grasslands of known land-use intensity in two regions of Germany. Diversity and total abundance as well as the proportion of sexual species were higher in forests than in grasslands. Diversity declined with higher land-use intensity in forests, but increased with higher mowing and fertilization in grasslands. Depending on land-use parameter and region, abundance either declined or remained unaffected by increasing intensity. Gravidity was higher in sexual than in parthenogenetic species and sexuals had 1.6× more eggs per gravid female. Proportions of sexual species and gravid females decreased with land-use intensity in forests, but increased with mowing in grasslands. At the species level, 75% of sexuals and 87.5% of parthenogens were ‘losers’ of higher percentages of dead wood originating from management-related disturbances. Across land-use parameters and habitats, a similar proportion of sexual and parthenogenetic oribatid mite species were ‘losers’ of high land-use intensity. However, ‘winner’ species were more common among sexuals. Supplementary information The online version of this article (10.1007/s10493-020-00586-z) contains supplementary material, which is available to authorized users.

Temperature influences all biochemical and biophysiological processes within an organism. By extension, it also affects those ecological interactions that are mediated by gland-produced chemical compounds, such as reservoir-based chemical defense. Herein, we investigate how environmental temperature affects the regeneration of defensive secretions and influences the efficacy of chemical defense in a model predator-prey system: the oribatid mite Archegozetes longisetosus and the predaceous rove beetle Stenus juno. Through a combination of chemical analyses, non-linear regression modeling and theoretical simulations we show that the amount of defensive secretion responded to temperature in a unimodal optimum curve: the regeneration rate followed a positive, linear relationship up to 35 °C, but rapidly broke down beyond this temperature (“tipping point” effect). Using functional response simulations, there is an initially positive dampening effect on the predation rate when regeneration is optimal, but at higher temperatures chemical defense does not counteract the previously described effects of elevated predatory pressure. In a larger context, our results demonstrate the need to integrate relevant environmental factors in predator-prey modeling approaches.

We present Biomedisa, a free and easy-to-use open-source online platform developed for semi-automatic segmentation of large volumetric images. The segmentation is based on a smart interpolation of sparsely pre-segmented slices taking into account the complete underlying image data. Biomedisa is particularly valuable when little a priori knowledge is available, e.g. for the dense annotation of the training data for a deep neural network. The platform is accessible through a web browser and requires no complex and tedious configuration of software and model parameters, thus addressing the needs of scientists without substantial computational expertise. We demonstrate that Biomedisa can drastically reduce both the time and human effort required to segment large images. It achieves a significant improvement over the conventional approach of densely pre-segmented slices with subsequent morphological interpolation as well as compared to segmentation tools that also consider the underlying image data. Biomedisa can be used for different 3D imaging modalities and various biomedical applications., Manual segmentation of biological images is a time-consuming task. Here the authors present Biomedisa, an open-source online platform for segmentation of large volumetric images starting from sparsely presegmented slices.

The fatty acid (FA) composition of lipids in animals is influenced by factors such as species, life stage, availability and type of food, as well as the ability to synthesize certain FAs de novo. We investigated the effect of starvation on the neutral lipid (NLFA) and phospholipid (PLFA) fatty acid patterns of the oribatid mite Archegozetes longisetosus Aoki. Furthermore, we performed stable-isotope labeled precursors feeding experiments under axenic conditions to delineate de novo FA synthesis by profiling 13C and deuterium incorporation via single-ion monitoring. Starvation of mites resulted in a decline in the total amount of NLFAs and significantly changed the fatty acid patterns, indicating that NLFAs were metabolized selectively. Biochemical tracer experiments confirmed that oribatid mites, like other animals, can produce stearic (18:0) and oleic acid (18:1ω9) de novo. Mass spectrometric data also revealed that they appear to synthesize linoleic acid [18:2ω6,9 = (9Z,12Z)-octadeca-9,12-dienoic acid]-an ability restricted only to a few arthropod taxa, including astigmatid mites. The physiological and biosynthesis processes revealed here are crucial to understand the potential biomarker function of fatty acids-especially 18:2ω6,9-in oribatid mites and their applicability in soil animal food web studies.

Numerous animal species use defense mechanisms such as chemical secretion to defend against attacks of predators. Although defense mechanisms have the potential to considerably change the dynamics and stability of a system, few theoretical studies exist. In this paper, we focus on predator-prey systems with reservoir-based chemical defense, which is also called “reducible defense” and is widespread among invertebrates. The predator has to attack often enough to disarm and consume prey, and prey can biosynthetically restore lost secretion. The model includes these features in the functional response, and in a separate equation for the stored amount of secretion. Additionally, our model takes into account that defense involves metabolic costs, reducing population growth of the prey. By performing computer simulations, we show that the defense mechanism causes the predator to take more time to consume prey. This time is increased more efficiently when the prey invests in a large reservoir rather than in fast restoration of secretion. We also investigate the stationary states resulting on longer time scales, finding that both predator and prey can become considerably more abundant due to the defense mechanism. However, investment into defenses pays off only when predator density is large enough and costs of defense are not too high.

Size scaling phenomena occur on different levels, from organisms to ecosystems. In predictive ecology, empirical data on body size relation have been used for decades to explain large-scale tempora...

Reservoir-based chemical defense (= reducible defense) is a widespread mechanism to repel predators in many invertebrates. We investigated the influence of macronutrients on the availability and regeneration of defensive secretions and parametrize a theoretical functional response model for reducible defense to predict nutritional effects on predator–prey dynamics. Our modeling approach showed that initially high amounts of defensive secretions provided an effective short-time defense, while higher regeneration rates were favorable under permanent predation pressure. Regeneration rates were correlated to the amount of dietary fat and carbohydrates, indicating an adaptive connection of macronutrients on chemical defense and predatory success—an effect covering two trophic levels. Our results underpin the urgent need to integrate dynamical aspects of chemical defense into the modeling of predator–prey interactions in food webs.

Olfactory cues are important for many heterotrophic organisms to find and identify food. In soil ecosystems, however, olfactory food selection has only been fragmentarily explored and it remains to be uncovered whether olfactory signals are involved in finding suitable food sources in microarthropods. We addressed this basic question in laboratory food-choice bioassays with two oribatid mite species [ Archegozetes longisetosus (opportunistic feeder) and Scheloribates sp. (myco-/phytophagous feeder)] and bacteria, fungi, lichen and litter as resources. We found that both oribatid mite species used olfactory cues to find and differentiate among food resources. While A. longisetosus preferred bacterial diet, Scheloribates sp. mainly fed on fungal-based food sources (fungi and lichen). We analysed volatiles and nutrients of the resources and used modified food, synthetic compounds and amino/fatty acid mixtures in a second food-choice experiment. A. longisetosus preferred fatty acids (and their preferred bacterial diet was also rich in fatty acids), while Scheloribates was highly attracted by mushroom-alcohol (1-octen-3-ol). Our experiments showed that olfactory signals contribute to the trophic ecology of oribatid mites in soil ecosystems.

Biomarkers (e.g. fatty acids, amino acids, stable isotopes, and molecular barcodes) have become increasingly important for investigating food web structure and nutrient flow in soil ecosystems. While the biomarker function of fatty acids has been investigated for some soil animal taxa (e.g. collembolans and nematodes), their role in soil-dwelling oribatid mites remained unknown. Here, we investigate the biomarker function and nutritional stoichiometry of neutral lipid fatty acids (NLFA) and amino acids in oribatid mites. We reared the opportunistic model oribatid mite species Archegozetes longisetosus on ten different resources of animal, bacterial, fungal and herbal origin. We analyzed the neutral lipid fatty acid and amino acid compositions of resources and consumers with gas chromatography/mass spectrometry (GC/MS) and ion-exchange chromatography (IEC), respectively. We found diet-dependent amounts and compositions of NLFA in the oribatid mites, but amino acids were stable and independent of diet. Consumer NLFA composition could be used as a reliable predictor of diet using data mining approaches (i.e., Random Forest), while amino acid profiles reflected diet-independent intrinsic physiological properties and confirm the homeostatic protein stoichiometry hypothesis for oribatid mites.

The so-called “glandulate Oribatida” (including Astigmata) possess large opisthonotal oil glands, which produce semiochemicals as potent agents for chemical defence against predators (allomones) as well as for intraspecific communication (pheromones). The oil gland reservoirs and their contents remain with shed exuviae, so secretions need to be synthesized de novo after each moult. The qualitative composition of chemical profiles may change dramatically between the last juvenile instar (tritonymph) and adult (e.g. Hermannia convexa Koch, Scheloribates azumaensis Enami, Nakamura & Katsumata, Oribotritia berlesei Michael), but reports about quantitative ontogenetic shifts are ambiguous. Here, we analysed the complete ontogenetic sequence (larva, protonymph, deutonymph, tritonymph, and adult) of oil gland secretions in the parthenogenetic oribatid model species Archegozetes longisetosus Aoki using gas chromatography–mass spectrometry. We show that absolute and body mass-corrected amounts of oil gland...

Members of the genus Stenus (Coleoptera, Staphylinidae) possess a unique adhesive labial prey-capture apparatus as an adaptation to their predatory behaviour. In order to examine the relationships between the morphology of the prey-capture apparatus, its adhesive performance and the prey-capture success, we combined force measurements, morphological and behavioural investigations of representatives of 14 Central European species of this genus. The direct relationship between these traits was studied by using phylogenetic generalized least squares and a molecular phylogeny generated from mitochondrial cytochrome c oxidase I partial sequences. Force measurements revealed strong interspecific differences in the adhesive forces generated during the predatory attack; these differences entail significant differences in the prey-capture success. The interspecific differences in adhesive performance were functionally correlated with the pad morphology and divergences in the compressive forces generated during the predatory strike. Allometric analyses revealed that the pad area scaled with positive allometry with respect to body size, whereas the adhesive forces scaled with negative allometry with respect to body size, that is, the pads' efficiency decreased with body size. Our experimental approach demonstrates a direct functional relationship between the morphology of the prey-capture device of Stenus beetles and its performance in a natural behavioural context., This study was partly financed by the German Science Foundation (project PAK 478: BE 2233/10–1). LZG was supported by funds from The Ministry of Economy and Competitiveness (Spain) (CGL2015-70639-P) and The National Research, Development and Innovation Office (NKFIH, K-115970).

Food webs in soil differ fundamentally from those aboveground; they are based on inputs from both living plants via root exudates, and from detritus, which is a complex mixture of fungi, bacteria, and dead plant remains. Trophic relationships are difficult to disentangle due to the cryptic lifestyle of soil animals and inevitable microbial contributions to their diet. Compound‐specific isotope analysis of amino acids (AAs) is increasingly used to explore complex food webs. The combined use of AA δ^(13)C and δ^(15)N values is a promising new approach to disentangle trophic relationships since it provides independent but complementary information on basal resources, as well as the trophic position of consumers. We conducted a controlled feeding study in which we reconstructed trophic chains from main basal resources (bacteria, fungi, plants) to primary consumers (springtails, oribatid mites) and predators (gamasid mites, spiders). We analyzed dual compound‐specific isotope AA values of both resources and consumers. By applying an approach termed “stable isotope (^(13)C) fingerprinting” we identified basal resources, and concomitantly calculated trophic positions using ^(15)N values of trophic and source AAs in consumers. In the ^(13)C fingerprinting analysis, consumers in general grouped close to their basal resources. However, higher than usual offsets in AA δ^(13)C between diet and consumers suggest either gut microbial supplementation or the utilization of specific resource fractions. Identification of trophic position crucially depends on correct estimates of the trophic discrimination factor (TDF_(Glu‐Phe)), which was close to the commonly applied value of 7.6‰ in primary consumers feeding on microbial resources, but considerably lower in arachnid predators (~2.4‰), presumably due to higher diet quality, excretion of guanine, and fluid feeding. While our feeding study demonstrates that dual compound‐specific AA analyses hold great promise in delineating trophic linkages among soil‐dwelling consumers and their resources, it also highlights that a “one‐size‐fits‐all” approach to TDF_(Glu‐Phe) does not apply to soil food webs.

Compositional data are commonly used in chemical ecology to describe the biological role of chemical compounds in communication, defense or other behavioral modifications. Statistical analyses of compositional data, however, are challenging due to several constraints (e.g., constant sum constraint). We use an ontogenetic series of defensive gland secretions from larvae, three nymphal stages and adults of the oribatid model species Archegozetes longisetosus as a typical chemo-ecological data set to prepare a practical guide for compositional data analyses in chemical ecology. We compare various common and less common statistical and ordination methods to depict small quantitative and/or qualitative differences in compositional datasets: principal component analysis (PCA), non-metric multidimensional scaling (NMDS), multivariate statistical tests (Anderson’s permutational multivariate analyses of variance = PERMANOVA; permutational analyses of multivariate dispersions = PERMDIPS), linear discriminant analysis (LDA), the data mining algorithm Random Forests, bipartite network analysis and dynamic range boxes (dynRB). We summarize which methods are suitable for different research questions and how data needs to be structured and pre-processed. Network analyses and dynamic range boxes are promising tools for analyzing compositional data beyond the “classical” methods and provide additional information.

Stable isotope analysis has become an analytical tool of central importance in trophic ecology. The actual degree of isotopic fractionation, however, remains a black-box in most studies. Hence, mean values for trophic enrichment from other taxa are commonly used to delimitate trophic levels. On the other hand, resource composition as well as consumer physiology both influence fractionation patterns. Especially in soil food webs, high variability of isotopic fractionation has been found for both 15 N and 13 C. Here, we investigate effects of diet on trophic enrichment in a no-choice feeding experiment with the oribatid mite model species Archegozetes longisetosus and a set of fungal, animal, algal and plant resources (seeds and vegetative tissues). We found consistent trophic enrichment for nitrogen irrespective of diet (Δ 15 N = 3.9‰), but no reliable fractionation for carbon being negative for fungi (Δ 13 C = −1.8‰), neutral for algae, and positive for the remaining plant and animal resources (Δ 13 C = 2.3‰). The results suggest that δ 15 N is a reliable marker for delimiting the trophic level of oribatid mites and presumably other soil detritivores, while understanding δ 13 C signals needs a priori knowledge about isotopic fractionation with respect to consumed resources.

Body mass, volume and surface area are important for many aspects of the physiology and performance of species. Whereas body mass scaling received a lot of attention in the literature, surface areas of animals have not been measured explicitly in this context. We quantified surface area-volume (SA/V) ratios for the first time using 3D surface models based on a structured light scanning method for 126 species of pollinating insects from 4 orders (Diptera, Hymenoptera, Lepidoptera, and Coleoptera). Water loss of 67 species was measured gravimetrically at very dry conditions for 2 h at 15 and 30 °C to demonstrate the applicability of the new 3D surface measurements and relevance for predicting the performance of insects. Quantified SA/V ratios significantly explained the variation in water loss across species, both directly or after accounting for isometric scaling (residuals of the SA/V ∼ mass2/3 relationship). Small insects with a proportionally larger surface area had the highest water loss rates. Surface scans of insects to quantify allometric SA/V ratios thus provide a promising method to predict physiological responses, improving the potential of body mass isometry alone that assume geometric similarity.

Cheese infested with cheese mites is usually treated as unpalatable. Nevertheless, some traditional cheese manufactories in Germany and France intentionally use mites for fermentation of special varieties (i.e. Milbenkäse and Mimolette). While their production includes different mite species, both are characterized by a "lemon-like" flavor. However, the chemical nature and origin of this flavor-component is unknown. The cheese mites possess a pair of opisthosomal glands producing blends of hydrocarbons, terpenes and aromatics. Here, we describe the chemical profiles of the astigmatid mite species Tyrolichus casei (Milbenkäse) and Acarus siro (Mimolette). Although the chemical profiles differ in several aspects, both mite species produce neral (a volatile flavor component of lemon oil), which was absent from the headspace of both cheeses without mites. We conclude that the lemon-like flavor of mite cheese is not a consequence of fermentation of the cheese itself but a component from secretions of the cheese mites.

The ability to synthesize simple aromatic compounds is well known from bacteria, fungi and plants, which all share an exclusive biosynthetic route—the shikimic acid pathway. Some of these organisms further evolved the polyketide pathway to form core benzenoids via a head-to-tail condensation of polyketide precursors. Arthropods supposedly lack the ability to synthesize aromatics and instead rely on aromatic amino acids acquired from food, or from symbiotic microorganisms. The few studies purportedly showing de novo biosynthesis via the polyketide synthase (PKS) pathway failed to exclude endosymbiotic bacteria, so their results are inconclusive. We investigated the biosynthesis of aromatic compounds in defence secretions of the oribatid mite Archegozetes longisetosus . Exposing the mites to a diet containing high concentrations of antibiotics removed potential microbial partners but did not affect the production of defensive benzenoids. To gain insights into benzenoid biosynthesis, we fed mites with stable-isotope labelled precursors and monitored incorporation with mass spectrometry. Glucose, malonic acid and acetate, but not phenylalanine, were incorporated into the benzenoids, further evidencing autogenous biosynthesis. Whole-transcriptome sequencing with hidden Markov model profile search of protein domain families and subsequent phylogenetic analysis revealed a putative PKS domain similar to an actinobacterial PKS, possibly indicating a horizontal gene transfer.

Background: Oribatid mites are among the primordial decomposer faunal elements and potential prey organisms insoil. Among their myriad morphological defenses are strong sclerotization and mineralization, cuticular tecta, and the ���ptychoid��� body-form, which allows to attain an encapsulated, seed-like appearance. Most oribatid mites possess a pair of exocrine glands that produce blends of hydrocarbons, terpenes, aromatics, alkaloids and cyanogenic compounds.Many species evolved ���holistic��� defensive strategies by combining several morphological and chemical traits. Methods: We describe the morphological and chemical bases of defense in the ptychoid oribatid Euphthiracarus reticulatus. The functional morphology was investigated with synchrotron X-ray microtomography (SR��CT) and highspeed life-radiography. Gland secretions were collected from 20,000 adult specimens, purified and fractionated by preparative capillary gas chromatography (pcGC) and analyzed by gas chromatography / mass spectrometry (GC/MS), high-resolution mass spectrometry (HRMS), and nuclear magnetic resonance spectroscopy (NMR). The adaptive values of morphological and chemical defenses were estimated in bioassays against three predators: a similar-sized gamasid mite (Stratiolaelaps miles, ca. 0.8 mm, with slender chelicera for piercing membranous cuticular regions), and two larger staphylinid beetles, Stenus juno (ca. 7 mm, bearing a harpoon-like sticky labium and sickle-shaped mandibles) and Othius punctulatus (ca. 14 mm, bearing plesiomorphic chewing mandibles). Results: The secretions comprised two components: the diterpene ��-springene and a novel compound with a mass of 276 g/mol ��� eventually elucidated as 2-(but-1-en-1-yl)-4-butylidene-3-(pent-2-en-1-yl)-pentanedial, to which we assign the trivial name ��-acaridial. Upon attacks by S. juno, E. reticulatus reacted quickly: within 150 ms from the first contact the encapsulation was almost completed ��� less time than the beetle needed to retract the labium and transfer the mite to the mandibles. Chemically-defended specimens of E. reticulatus effectively repelled all predators. After depletion of oil-gland reservoirs, however, O. punctulatus easily fed on the mites while S. miles and S. juno were not able to overcome the morphological barrier of strong cuticle and ptychoid body form. Conclusion: Such an effective, holistic defense strategy, involving both morphological and chemical traits, probably carries high resource-costs, but it allows adult euphthiracaroid mites to occupy an almost ���enemy-free space��� despite the high diversity of predators in soil.

Small arthropods show a highly condensed central nervous system, which is accompanied by the loss of the ancestral metameric organization. This results in the formation of one solid mass, a synganglion. Although numerous studies investigated the morphology of Archegozetes longisetosus, the organization of the nervous system is to date unknown. Using synchrotron X-ray microtomography, we investigated the organization of the nervous system in the adult stage and the development of the synganglion over all five free-living life stages (larva, proto-, deuto-, tritonymph and adult). The general morphology of the synganglion resembles that of other studied mites (in the classic sense) and ticks, being subdivided into a sub- and supraesophageal region, and consisting of cortex and neuropil. All nerves entering the walking legs except the first consist of two rami. This split is not based on a functional division into a motor and a sensory ramus, but both rami contain motor and sensory neurites. Within the synganglion, we found structures that resemble the ancestral metameric organization of the nervous system of arthropods. The development of the synganglion of A. longisetosus shows a more or less linear increase in volume, but cortex and neuropil grow at different rates over the five life stages. Between the second and third nymphal stage, the volume of the neuropil increases at a faster rate than the cortex.

Modern applications for analysing 2D/3D data require complex visual output features which are often based on the multi-platform OpenGL® API for rendering vector graphics. Instead of providing classical workstations, the provision of powerful virtual machines (VMs) with GPU support in a scientific cloud with direct access to high performance storage is an efficient and cost effective solution. However, the automatic deployment, operation and remote access of OpenGL® API-capable VMs with professional visualization applications is a non-trivial task. In this chapter the authors demonstrate the concept of such a flexible cloud-like analysis infrastructure within the framework of the project ASTOR. The authors present an Analysis-as-a-Service (AaaS) approach based on VMware™-ESX for on demand allocation of VMs with dedicated GPU cores and up to 256 GByte RAM per machine.

Morphological and chemical defences are widespread anti-predator mechanisms in most domains of life, and play an important role in understanding predator–prey interactions. Classical concepts of dynamical protection (‘inducible defence’) include the morphological changes in certain crustaceans or the production of chemicals in many plants. Permanently stored defensive secretions are, to our knowledge, ignored in food web ecology. We show that this kind of chemical defence is highly dynamic and may loose its effect over time (‘reducible defence’). Combining experimental and theoretical approaches, we show that chemical defence also changes the time budget of predators and decreases the strength of the functional response. However, this may be counteracted by increasing predator density—an effect we call ‘apparent facilitation’. The interplay of ‘reducible defence’ and ‘apparent facilitation’ may substantially contribute to stability in terrestrial ecosystems.

The most complex mechanical defense of oribatid mites is ptychoidy, in which the animals can retract their legs and gnathosoma into the idiosoma and encapsulate by deflecting the prodorsum. Since Acari lack most antagonistic musculature, extension of appendages is facilitated through hemolymph pressure that in mites mostly is generated by dorso-ventral compression of the opisthosoma. The hardened notogaster of box mites requires a different system of pressure generation that is also able to accommodate huge hemolymph movement accompanying ptychoidy. We compared the functional morphology of ptychoidy in one model species from each of the two ptyctime superfamilies, Euphthiracaroidea and Phthiracaroidea, using synchrotron X-ray microtomography and high-speed videography. We show that the two groups evolved very different functional modes of hydrostatic pressure control. While euphthiracaroids employ a lateral compression of the notogaster using all muscles of the opisthosomal compressor system, phthiracaroids employ a dorsoventral compression generated by only the notogaster lateral compressor and additionally the postanal muscle; these retract the temporarily unified ventral plates into the idiosoma, revealing the poam as an integral part of the opisthosomal compressor system in this group. The primitive mode of operation for generating hemolymph pressure in the Ptyctima probably was lateral compression, as molecular studies indicate that Phthiracaroidea evolved within Euphthiracaroidea. In this hypothesis, dorsoventral compression evolved secondarily in phthiracaroid mites, but whether the immediate ancestors of Ptyctima used lateral or dorsoventral compression remains to be determined.

Oribatid mites are abundant and diverse decomposers in almost all terrestrial microhabitats, especially in temperate forests. Although their functional importance in the decomposition system in these forests has been investigated, spatio-temporal patterns of oribatid mite communities inhabiting different microhabitats have largely been neglected. Therefore, we (i) investigated seasonal fluctuation (monthly over one year) in oribatid-mite community structure and specificity to three microhabitats (moss, dead wood and litter) and (ii) analyzed the influence of air temperature and overall air humidity on seasonal community changes. In total, 57,398 adult oribatid mite individuals were collected. Total abundance, species richness and diversity differed among microhabitats. Seasonal changes were most pronounced in moss and least in litter. While overall air humidity had no influence on species distribution and community changes, air temperature positively influenced species richness and diversity, again most pronounced in moss. The calculated environmental temperature occurrence niche showed that 35% of adult oribatid mite species occurred at higher air temperatures. Furthermore, interaction/bipartite networks were more generalized - i.e., species were more equally distributed among moss, dead wood and litter - when ambient air temperatures were higher. This pattern is probably due to the dispersal ability of adult oribatid mites, i.e., species enter a dispersal mode only at higher air temperatures.

Cyanogenesis denotes a chemical defensive strategy where hydrogen cyanide (HCN, hydrocyanic or prussic acid) is produced, stored, and released toward an attacking enemy. The high toxicity and volatility of HCN requires both chemical stabilization for storage and prevention of accidental self-poisoning. The few known cyanogenic animals are exclusively mandibulate arthropods (certain myriapods and insects) that store HCN as cyanogenic glycosides, lipids, or cyanohydrins. Here, we show that cyanogenesis has also evolved in the speciose Chelicerata. The oribatid mite Oribatula tibialis uses the cyanogenic aromatic ester mandelonitrile hexanoate (MNH) for HCN storage, which degrades via two different pathways, both of which release HCN. MNH is emitted from exocrine opisthonotal oil glands, which are potent organs for chemical defense in most oribatid mites.

International audience; With about 10,000 described species and densities reaching 400,000 ind/m2, the Oribatida (without Astigmata) represent the most prevalent group of soil mites. However, with the exception of their taxonomy, many aspects of the biology of oribatid mites have been poorly studied. This might be explained in part by the previous lack of a model species. However, in the last 20 years, more and more non-taxonomic studies regarding development, genetics, morphology, chemical ecology and ecotoxicology have become available, with a significant number focused on the trhypochthoniid oribatid mite Archegozetes longisetosus. A well-defined laboratory strain of this pantropical parthenogenetic species was established in 1993 by one of us (RAN), and has since spread through numerous laboratories worldwide. In this review, we summarize the scientific achievements this lineage has enabled while becoming a model system for general zoology, ecology and evolution.

The speciose staphylinid subfamily Steninae comprises more than 2700 species of the two genera Stenus and Dianous. Whereas the labium of Dianous beetles is short and unspecialized, the members of Stenus are characterized by a protruding elongated labium that functions as a prey-capture apparatus. This is considered the derived state and the most prominent apomorphic character for Stenus . To elucidate the phylogenetic relationship of Stenus and Dianous , we analyzed 807 bp of the mitochondrial cytochrome c oxidase I (COI) gene in 30 Stenus and 12 Dianous species. Our analysis indicates the evolutionary origin of Dianous within Stenus , suggesting a secondary loss of the specialized prey-capture apparatus. Whereas the derived phylogenetic position of Dianous within Stenus is supported by maximum parsimony, neighbor joining, maximum likelihood, and Bayesian analyses, the resolution of COI seems to be insufficient to consistently resolve basal relationships of Stenus species.