Global arthropod beta-diversity is spatially and temporally structured by latitude

Global biodiversity gradients are generally expected to reflect greater species replacement closer to the equator. However, empirical validation of global biodiversity gradients largely relies on vertebrates, plants, and other less diverse taxa. Here we assess the temporal and spatial dynamics of global arthropod biodiversity dynamics using a beta-diversity framework. Sampling includes 129 sampling sites whereby malaise traps are deployed to monitor temporal changes in arthropod communities. Overall, we encountered more than 150,000 unique barcode index numbers (BINs) (i.e. species proxies). We assess between site differences in community diversity using beta-diversity and the partitioned components of species replacement and richness difference. Global total beta-diversity (dissimilarity) increases with decreasing latitude, greater spatial distance and greater temporal distance. Species replacement and richness difference patterns vary across biogeographic regions. Our findings support long-standing, general expectations of global biodiversity patterns. However, we also show that the underlying processes driving patterns may be regionally linked.

Higher-order species interactions cause time-dependent niche and fitness differences: Experimental evidence in plant-feeding arthropods

Species interact in different ways, including competition, facilitation and predation. These interactions can be non-linear or higher order and may depend on time or species densities. Although these higher-order interactions are virtually ubiquitous, they remain poorly understood, as they are challenging both theoretically and empirically. We propose to adapt niche and fitness differences from modern coexistence theory and apply them to species interactions over time. As such, they may not merely inform about coexistence, but provide a deeper understanding of how species interactions change. Here, we investigated how the exploitation of a biotic resource (plant) by phytophagous arthropods affects their interactions. We performed monoculture and competition experiments to fit a generalized additive mixed model to the empirical data, which allowed us to calculate niche and fitness differences. We found that species switch between different types of interactions over time, including intra- and interspecific facilitation, and strong and weak competition.

DNA metabarcoding reveals seasonal changes in diet composition across four arthropod-eating lizard species (Phrynosomatidae: Sceloporus)

Diet composition and its ecological drivers are rarely investigated in coexisting closely related species. We used a molecular approach to characterize the seasonal variation in diet composition in four spiny lizard species inhabiting a mountainous ecosystem. DNA metabarcoding revealed that the lizards Sceloporus aeneus, S. bicanthalis, S. grammicus, and S. spinosus mostly consumed arthropods of the orders Hemiptera, Araneae, Hymenoptera, and Coleoptera. The terrestrial lizards S. aeneus and S. bicanthalis mostly predated ants and spiders, whereas the arboreal-saxicolous S. grammicus and saxicolous S. spinosus largely consumed grasshoppers and leafhoppers. The taxonomic and phylogenetic diversity of the prey was higher during the dry season than the rainy season, likely because reduced prey availability in the dry season forced lizards to diversify their diets to meet their nutritional demands. Dietary and phylogenetic composition varied seasonally depending on the species, but only dietary composition varied with altitude. Seasonal dietary turnover was greater in S. spinosus than in S. bicanthalis, suggesting site-specific seasonal variability in prey availability; no other differences among species were observed. S. bicanthalis, which lives at the highest altitude in our study site, displayed interseasonal variation in diet breadth. Dietary differences were correlated with the species' feeding strategies and elevational distribution, which likely contributed to the coexistence of these lizard species in the studied geographic area and beyond.

Tree diversity enhances predation by birds but not by arthropods across climate gradients

Tree diversity can promote both predator abundance and diversity. However, whether this translates into increased predation and top-down control of herbivores across predator taxonomic groups and contrasting environmental conditions remains unresolved. We used a global network of tree diversity experiments (TreeDivNet) spread across three continents and three biomes to test the effects of tree species richness on predation across varying climatic conditions of temperature and precipitation. We recorded bird and arthropod predation attempts on plasticine caterpillars in monocultures and tree species mixtures. Both tree species richness and temperature increased predation by birds but not by arthropods. Furthermore, the effects of tree species richness on predation were consistent across the studied climatic gradient. Our findings provide evidence that tree diversity strengthens top-down control of insect herbivores by birds, underscoring the need to implement conservation strategies that safeguard tree diversity to sustain ecosystem services provided by natural enemies in forests.

Land-use change in the past 40 years explains shifts in arthropod community traits

Understanding how anthropogenic activities induce changes in the functional traits of arthropod communities is critical to assessing their ecological consequences. However, we largely lack comprehensive assessments of the long-term impact of global-change drivers on the trait composition of arthropod communities across a large number of species and sites. This knowledge gap critically hampers our ability to predict human-driven impacts on communities and ecosystems. Here, we use a dataset of 1.73 million individuals from 877 species to study how four functionally important traits of carabid beetles and spiders (i.e. body size, duration of activity period, tolerance to drought, and dispersal capacity) have changed at the community level across ~40 years in different types of land use and as a consequence of land use changes (that is, urbanisation and loss of woody vegetation) at the landscape scale in Switzerland. The results show that the mean body size in carabid communities declined in all types of land use, with particularly stronger declines in croplands compared to forests. Furthermore, the length of the activity period and the tolerance to drought of spider communities decreased in most land use types. The average body size of carabid communities in landscapes with increased urbanisation in the last ~40 years tended to decrease. However, the length of the activity period, the tolerance to drought, and the dispersal capacity did not change significantly. Furthermore, urbanisation promoted increases in the average dispersal capacities of spider communities. Additionally, urbanisation favoured spider communities with larger body sizes and longer activity periods. The loss of woody areas at the landscape level was associated with trait shifts to carabid communities with larger body sizes, shorter activity periods, higher drought tolerances and strongly decreased dispersal capacities. Decreases in activity periods and dispersal capacities were also found in spider communities. Our study demonstrates that human-induced changes in land use alter key functional traits of carabid and spider communities in the long term. The detected trait shifts in arthropod communities likely have important consequences for their functional roles in ecosystems.

Intra and interspecific differences in desiccation tolerance in native and alien Antarctic springtails in geothermal grounds

The extreme low humidity and temperatures in Antarctica make it one of the harsher areas for life on our planet. In a global change context, environmental barriers that prevented the arrival of alien species in Antarctica are weakening. Deception Island, one of the four active volcanoes of Antarctica, is especially vulnerable to the impacts of alien species. Geothermal areas (GA) in this Island offer unique microclimatic conditions that could differentially affect native and alien soil arthropods. Here we explore the desiccation tolerance of a native (Cryptopygus antarcticus) and an alien (Proisotoma minuta) springtail (Collembola) species to these extreme environmental conditions. GA and non-geothermal areas (NGA) were selected to evaluate intra- and interspecific variation in desiccation tolerance. Populations of P. minuta from GA had greater desiccation tolerance than populations from NGA. However, desiccation tolerance of C. antarcticus did not differ between GA and NGA. This native species had greater desiccation tolerance than the alien P. minuta, but also greater body size. Our findings show that the alien P. minuta responds differently to environmental conditions than the native C. antarcticus. Furthermore, body size may influence desiccation tolerance in these two springtail species.

Microplastics promote the accumulation of negative fungal groups and cause multigenerational effects in springtails

The environmental persistence of microplastics (MPs) is ubiquitous and problematic. Despite an increase in research on the soil ecotoxicity of MPs, the response of springtails to MP pollution remains unexplored. We hypothesized that MPs promote the accumulation of negative soil fungal groups and cause multigenerational effects in springtails. We performed a multigenerational study of high-density polyethylene MPs using springtail Folsomia candida and analyzed the soil fungal community. We found that soil entomopathogenic fungi and negative soil fungal groups accumulated in springtail F. candida due to soil MP pollution; subsequently, MPs negatively affected F. candida in the F2 generation. To the best of our knowledge, this is the first study to investigate the correlations between MP pollution, soil fungi, and fungi-feeding springtails. The study provides evidence of the accumulation of soil entomopathogenic fungi and negative soil fungal groups in F. candida caused by soil MP pollution.

An update and review of arthropod vector sensory systems: Potential targets for behavioural manipulation by parasites and other disease agents

For over a century, vector ecology has been a mainstay of vector-borne disease control. Much of this research has focused on the sensory ecology of blood-feeding arthropods (black flies, mosquitoes, ticks, etc.) with terrestrial vertebrate hosts. Of particular interest are the cues and sensory systems that drive host seeking and host feeding behaviours as they are critical for a vector to locate and feed from a host. An important yet overlooked component of arthropod vector ecology are the phenotypic changes observed in infected vectors that increase disease transmission. While our fundamental understanding of sensory mechanisms in disease vectors has drastically increased due to recent advances in genome engineering, for example, the advent of CRISPR-Cas9, and high-throughput "big data" approaches (genomics, proteomics, transcriptomics, etc.), we still do not know if and how parasites manipulate vector behaviour. Here, we review the latest research on arthropod vector sensory systems and propose key mechanisms that disease agents may alter to increase transmission.

Drivers of arthropod biodiversity in an urban ecosystem

Our world is becoming increasingly urbanized with a growing human population concentrated around cities. The expansion of urban areas has important consequences for biodiversity, yet the abiotic drivers of biodiversity in urban ecosystems have not been well characterized for the most diverse group of animals on the planet, arthropods. Given their great diversity, comparatively small home ranges, and ability to disperse, arthropods make an excellent model for studying which factors can most accurately predict urban biodiversity. We assessed the effects of (i) topography (distance to natural areas and to ocean) (ii) abiotic factors (mean annual temperature and diurnal range), and (iii) anthropogenic drivers (land value and amount of impervious surface) on the occurrence of six arthropod groups represented in Malaise trap collections run by the BioSCAN project across the Greater Los Angeles Area. We found striking heterogeneity in responses to all factors both within and between taxonomic groups. Diurnal temperature range had a consistently negative effect on occupancy but this effect was only significant in Phoridae. Anthropogenic drivers had mixed though mostly insignificant effects, as some groups and species were most diverse in highly urbanized areas, while other groups showed suppressed diversity. Only Phoridae was significantly affected by land value, where most species were more likely to occur in areas with lower land value. Los Angeles can support high regional arthropod diversity, but spatial community composition is highly dependent on the taxonomic group.

Uniquely preserved gut contents illuminate trilobite palaeophysiology

Trilobites are among the most iconic of fossils and formed a prominent component of marine ecosystems during most of their 270-million-year-long history from the early Cambrian period to the end Permian period1. More than 20,000 species have been described to date, with presumed lifestyles ranging from infaunal burrowing to a planktonic life in the water column2. Inferred trophic roles range from detritivores to predators, but all are based on indirect evidence such as body and gut morphology, modes of preservation and attributed feeding traces; no trilobite specimen with internal gut contents has been described3,4. Here we present the complete and fully itemized gut contents of an Ordovician trilobite, Bohemolichas incola, preserved three-dimensionally in a siliceous nodule and visualized by synchrotron microtomography. The tightly packed, almost continuous gut fill comprises partly fragmented calcareous shells indicating high feeding intensity. The lack of dissolution of the shells implies a neutral or alkaline environment along the entire length of the intestine supporting digestive enzymes comparable to those in modern crustaceans or chelicerates. Scavengers burrowing into the trilobite carcase targeted soft tissues below the glabella but avoided the gut, suggesting noxious conditions and possibly ongoing enzymatic activity.

Sleep: An Essential and Understudied Process in the Biology of Blood-Feeding Arthropods

Understanding the biology of blood-feeding arthropods is critical to managing them as vectors of etiological agents. Circadian rhythms act in the regulation of behavioral and physiological aspects such as blood feeding, immunity, and reproduction. However, the impact of sleep on these processes has been largely ignored in blood-feeding arthropods, but recent studies in mosquitoes show that sleep-like states directly impact host landing and blood feeding. Our focus in this review is on discussing the relationship between sleep and circadian rhythms in blood-feeding arthropods along with how unique aspects such as blood gluttony and dormancy can impact sleep-like states. We highlight that sleep-like states are likely to have profound impacts on vector-host interactions but will vary between lineages even though few direct studies have been conducted. A myriad of factors, such as artificial light, could directly impact the time and levels of sleep in blood-feeding arthropods and their roles as vectors. Lastly, we discuss underlying factors that make sleep studies in blood-feeding arthropods difficult and how these can be bypassed. As sleep is a critical factor in the fitness of animal systems, a lack of focus on sleep in blood-feeding arthropods represents a significant oversight in understanding their behavior and its role in pathogen transmission.

Histologic lesions of giant African millipedes (Archispirostreptus gigas) from a zoological institution

Histopathologic data of millipedes are scarce. Little is known about health and disease of these invertebrates despite their exhibition at zoological institutions and use in ecotoxicological studies. In a retrospective study of 69 zoo-housed giant African millipedes (Archispirostreptus gigas) submitted between 2018 and 2021, most deaths occurred during midwinter and in 2021. The most common lesion was inflammation (n = 55; 80%). Necrosis was seen concurrently in 31 (45%) millipedes and of these, bacteria (20; 29%) and fungi (7; 10%) were detected in lesions. Inflammation was seen in the head/collum (20; 29%), hemocoel (16; 23%), and appendages (9; 13%), specifically in perivisceral fat body (42; 61%), gut (16; 23%), tracheae (26; 38%), skeletal muscle (24; 35%), and ventral nerve (17; 25%). Inflammatory cell types and patterns included agranular hemocytes (61; 88%), granular hemocytes (39; 57%), and nodulation/encapsulation (47; 68%) often accompanied by melanization. The oral cavity or gut (ingestion), spiracles (inhalation), or cuticular defects were considered plausible routes of bacterial entry. Metazoan parasites (adult nematodes: 2, 3%; trematode ova: 2, 3%; and arthropods: 1, 1%) were associated with gut necrosis and inflammation in 5 millipedes. In addition, adult nematodes were noted in the gut of 4 millipedes without lesions. Neoplasia was not detected in any millipedes. Speculatively, environmental factors may have predisposed to disease, as most deaths occurred during winter months. Disease surveillance of millipedes is critical to optimize husbandry practices in zoo populations and investigate potential impacts of environmental degradation and climate change on wild millipedes.

Context-dependent responses of terrestrial invertebrates to anthropogenic nitrogen enrichment: A meta-analysis

Anthropogenic increases in nitrogen (N) concentrations in the environment are affecting plant diversity and ecosystems worldwide, but relatively little is known about N impacts on terrestrial invertebrate communities. Here, we performed an exploratory meta-analysis of 4365 observations from 126 publications reporting on the richness (number of taxa) or abundance (number of individuals per taxon) of terrestrial arthropods or nematodes in relation to N addition. We found that the response of invertebrates to N enrichment is highly dependent on both species' traits and local climate. The abundance of arthropods with incomplete metamorphosis, including agricultural pest species, increased in response to N enrichment. In contrast, arthropods exhibiting complete or no metamorphosis, including pollinators and detritivores, showed a declining abundance trend with increasing N enrichment, particularly in warmer climates. These contrasting and context-dependent responses may explain why we detected no overall response of arthropod richness. For nematodes, the abundance response to N enrichment was dependent on mean annual precipitation and varied between feeding guilds. We found a declining trend in abundance with N enrichment in dry areas and an increasing trend in wet areas, with slopes differing between feeding guilds. For example, at mean levels of precipitation, bacterivore abundance showed a positive trend in response to N addition while fungivore abundance declined. We further observed an overall decline in nematode richness with N addition. These N-induced changes in invertebrate communities could have negative consequences for various ecosystem functions and services, including those contributing to human food production.

Functional morphology and biomechanics of arthropods

Representatives of arthropods, the largest animal phylum, occupy terrestrial, aquatic, arboreal, and subterranean niches. Their evolutionary success depends on specific morphological and biomechanical adaptations related to their materials and structures. Biologists and engineers have become increasingly interested in exploring these natural solutions to understand relationships between structures, materials, and their functions in living organisms. The aim of this special issue is to present the state-of-the-art research in this interdisciplinary field using modern methodology, such as imaging techniques, mechanical testing, movement capture, and numerical modeling. It contains nine original research reports covering diverse topics, including flight, locomotion, and attachment of the arthropods. The research achievements are essential not only to understand ecological adaptations, and evolutionary and behavioral traits, but also to drive prominent advances for engineering from exploitation of numerous biomimetic ideas.

Host-pathogen interaction in arthropod vectors: Lessons from viral infections

Haematophagous arthropods can harbor various pathogens including viruses, bacteria, protozoa, and nematodes. Insects possess an innate immune system comprising of both cellular and humoral components to fight against various infections. Haemocytes, the cellular components of haemolymph, are central to the insect immune system as their primary functions include phagocytosis, encapsulation, coagulation, detoxification, and storage and distribution of nutritive materials. Plasmatocytes and granulocytes are also involved in cellular defense responses. Blood-feeding arthropods, such as mosquitoes and ticks, can harbour a variety of viral pathogens that can cause infectious diseases in both human and animal hosts. Therefore, it is imperative to study the virus-vector-host relationships since arthropod vectors are important constituents of the ecosystem. Regardless of the complex immune response of these arthropod vectors, the viruses usually manage to survive and are transmitted to the eventual host. A multidisciplinary approach utilizing novel and strategic interventions is required to control ectoparasite infestations and block vector-borne transmission of viral pathogens to humans and animals. In this review, we discuss the arthropod immune response to viral infections with a primary focus on the innate immune responses of ticks and mosquitoes. We aim to summarize critically the vector immune system and their infection transmission strategies to mammalian hosts to foster debate that could help in developing new therapeutic strategies to protect human and animal hosts against arthropod-borne viral infections.

Introduction to the Collection: Climate Change, Insect Pests, and Beneficial Arthropods in Production Systems

Climate change is expected to alter pressure from insect pests and the abundance and effectiveness of insect pollinators across diverse agriculture and forestry systems. In response to warming, insects are undergoing or are projected to undergo shifts in their geographic ranges, voltinism, abundance, and phenology. Drivers include direct effects on the focal insects and indirect effects mediated by their interactions with species at higher or lower trophic levels. These climate-driven effects are complex and variable, sometimes increasing pest pressure or reducing pollination and sometimes with opposite effects depending on climatic baseline conditions and the interplay of these drivers. This special collection includes several papers illustrative of these biological effects on pests and pollinators. In addition, in response to or anticipating climate change, producers are modifying production systems by introducing more or different crops into rotations or as cover crops or intercrops or changing crop varieties, with potentially substantial effects on associated insect communities, an aspect of climate change that is relatively understudied. This collection includes several papers illustrating these indirect production system-level effects. Together, biological and management-related effects on insects comprise the necessary scope for anticipating and responding to the effects of climate change on insects in agriculture and forest systems.

Collembola are Among the Most Pesticide-Sensitive Soil Fauna Groups: A Meta-Analysis

Pesticides are a major concern because of their deleterious impacts on biodiversity and on the ecological functions provided by living organisms. Although earthworms are well studied, smaller-sized organisms, such as Collembola, also contribute to the agroecosystem functioning, and their sensitivity to pesticides makes them good bioindicators of soil quality. Using data from 21 publications, we performed a meta-analysis to compare the pesticide sensitivity of Collembola with other soil invertebrate groups and discuss the relevance of including tests on representatives of this microarthropods group in European regulation tests. We defined a paired observation as the median lethal concentration or the median effect concentration values for both Collembola species and another soil fauna group (Acari, enchytraeids, earthworms, isopods, and nematodes) under a unique combination of author, year, substance, and type of soil (61 and 57 paired observations for reproduction and lethal effects). In some studies, paired comparisons were available for several groups of soil fauna. We demonstrated that Collembola are among the most sensitive soil fauna groups to a variety of pesticides, notably for effects on reproduction, mostly compared with earthworms and enchytraeids. Because there are several modes of exposure and explaining factors, we suggest moving from a single-species study to a food-chain approach integrating different taxonomic groups. Differences between soil fauna groups in sensitivity or response to pesticides could have effects on soil communities and also on soil functions. Environ Toxicol Chem 2022;41:2333-2341. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Habitat Type Affects Elevational Patterns in Ground-dwelling Arthropod Communities

Understanding factors that drive biodiversity distributions is central in ecology and critical to conservation. Elevational gradients are useful for studying the effects of climate on biodiversity but it can be difficult to disentangle climate effects from resource differences among habitat types. Here we compare elevational patterns and influences of environmental variables on ground-dwelling arthropods in open- and forested-habitats. We examine these comparisons in three arthropod functional groups (detritivores, predators, and herbivores) and two taxonomic groups (beetles and arachnids). We sampled twelve sites spanning 1,132 m elevation and four life zones, collecting 4,834 individual ground arthropods identified to 123 taxa. Elevation was a strong predicator for arthropod composition, however, patterns differed among functional and taxonomic groups and individual species between open- and forested-habitats. Beetles, arachnids, and predators decreased with elevation in open habitats but increased in forests showing a significant interaction between habitat type and elevation. Detritivores and herbivores showed no elevational patterns. We found 11 arthropod taxa with linear elevational patterns, seven that peaked in abundance at high elevations, and four taxa at low elevations. We also found eight taxa with parabolic elevational patterns that peaked in abundance at mid-elevations. We found that vegetation composition and productivity had stronger explanatory power for arthropod composition in forested habitats, while ground cover was a stronger predictor in open habitats. Temperature and precipitation were important in both habitats. Our findings demonstrate that relationships between animal diversity and elevation can be mediated by habitat type, suggesting that physiological restraints and resource limitations work differently between habitat types.

Diversity and Abundance of Predatory Arthropods on Immature and Mature Oil Palm (Elaeis guineensis) Plantations

BACKGROUND AND OBJECTIVE

Predatory arthropods may play a crucial role in decreasing the pest population that causes a significant loss in oil palm production. In this study, we investigated the diversity of predatory arthropods and their abundance on immature and mature oil palm plantation grown in Aceh Tamiang, Sumatra, Indonesia.

MATERIALS AND METHODS

Arthropod predators were collected by using light trap, yellow-pan trap and pitfall trap that were placed on an immature and mature oil palm plantation. Specimens were sorted and identified in the Laboratory.

RESULTS

The results showed that there were 674 individuals arthropod predators (insects and spiders) consisted of 7 orders, 22 families and 37 morphospecies collected in the immature plantation. While in mature plantation, arthropod predators found were 740 individuals consisted of 6 orders 23 families and 42 morphospecies. Ants (Hymenoptera: Formicidae) dominated other families regarding morphospecies and individual numbers. There was no significant difference in term of species richness and abundance of predators between both phases of the plantation which implied that the two plantations hosted a similar composition and abundance of predators. The diversity indices of predators calculated in both plantations showed that the predators were categorized as middle level of diversity and middle level of individual distribution, However, the community is unstable.

CONCLUSION

Our results suggested that predatory predators were present in similar structure in both phases of oil palm plantations. Efforts to conserve them are needed to enhance their performance as part of a sustainable and environmentally friendly method for controlling pests in oil palm plantation.

Effects on Life-History Traits of Hypogastrura viatica (Collembola) Exposed to Imidacloprid Through Soil or Diet

Collembola (springtails) are important members of soil communities worldwide by contributing to degradation of organic matter. In nature, Collembola might be exposed to the neonicotinoid insecticide imidacloprid, which is fairly persistent in soil. We exposed the widespread Hypogastrura viatica to imidacloprid through soil or food and monitored the animals during exposure and a post exposure period. We recorded effects on life-history traits affecting individual fitness, that is, mortality, behavioral activity, several reproduction traits, and molting frequency. Exposure through soil led to a concentration-dependent mortality, while the mortality from dietary exposure possibly reflected reduced feeding activity. The body burden of imidacloprid in the Collembola did not differ between treatments. We found no sign of recovery in behavioral activity following exposure in either experiment. The egg production of H. viatica was not significantly affected by imidacloprid at 0.01 mg/kg dry soil but showed a tendency to reduce number of eggs per batch and reduced hatching success. At higher concentrations, reproduction was close to, or completely, stopped. The molting frequency decreased during exposure, while in the post exposure period, we saw milder effects at the highest concentrations, suggesting elimination through molting or reduced toxic response as a result of reduced feeding activity. Overall, H. viatica was more sensitive to imidacloprid than previously studied Collembola, which highlights the importance of considering species sensitivities when risk-assessing soil environments. Environ Toxicol Chem 2021;40:3111-3122. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

The Evolutionary Relevance of Social Learning and Transmission in Non-Social Arthropods with a Focus on Oviposition-Related Behaviors

Research on social learning has centered around vertebrates, but evidence is accumulating that small-brained, non-social arthropods also learn from others. Social learning can lead to social inheritance when socially acquired behaviors are transmitted to subsequent generations. Using oviposition site selection, a critical behavior for most arthropods, as an example, we first highlight the complementarities between social and classical genetic inheritance. We then discuss the relevance of studying social learning and transmission in non-social arthropods and document known cases in the literature, including examples of social learning from con- and hetero-specifics. We further highlight under which conditions social learning can be adaptive or not. We conclude that non-social arthropods and the study of oviposition behavior offer unparalleled opportunities to unravel the importance of social learning and inheritance for animal evolution.

The inter-individual variance can provide additional information for the ecotoxicologists beside the mean

The hypothesis that the inter-individual parameter variability is an unexploited area of ecotoxicology was proposed several decades ago. Although some illustrative examples were presented to support this hypothesis in the last decades, it has never been tested on an extensive, coherent database. In this study, variance changes of 105 dose-response curves were analysed. All data originated from the same experiment, where the effects of the insecticide Trebon EC were investigated in a dose-response manner on 15 traits of the collembolan Folsomia candida in four subsequent generations and two types of insecticide treatments. A consistent relationship between inter-individual variance and insecticide application was found in 2 (first clutch size and growth-reproduction trade-off) out of the 15 of the parameters. Contrary to the mean, the variance of the first clutch size showed consistent differences compared to the control. Furthermore, the variance of the growth-reproduction trade-off was consistently different from the control except in one case (F3 generation of the transgenerational treatment). Higher first clutch size variances were found in F1 and a lower one in the F2 and F3 generations than in that of the control. This overall pattern of the variance changes of the first clutch size and the trade-off seems to be a quick response to the insecticide application. In the short term, we have found that variance increased with insecticide treatment (P and F1 generation), because phenotypic variance generally increases due to environmental stress. Disruptive selection could be another mechanism between the more detoxification less reproduction strategy and the more reproduction less detoxification strategy. However, in the later generations (F2-F3) the variance decreases compared to the control, which could be because on short term selection stronger on the viability parameters and in long-term selection on reproduction becomes stronger. According to our results, analysis of the variance changes of some parameters may give information about the effects of the pesticide even when the mean does not predict any impact. Testing variance changes are important in ecotoxicology because variance change can signalise toxicant impact even when the mean does not change in certain cases.

The toxicity and toxicokinetics of imidacloprid and a bioactive metabolite to two aquatic arthropod species

Previous studies have explored effects of imidacloprid and its metabolites on terrestrial species, such as bees, and indicated the importance of some active metabolites. However, the biotransformation of IMI and the toxicity of its metabolites to aquatic arthropods are largely unknown, especially the mechanisms driving species sensitivity differences and time-cumulative toxicity effects. To assess the potential effects of the metabolization of IMI and the toxicokinetics and toxicity of the metabolite(s) on aquatic arthropods, we first studied the acute toxicity of IMI and relevant metabolites to the mayfly species Cloen dipterum (sensitive to IMI) and the amphipod species Gammarus pulex (less sensitive to IMI). Secondly, toxicokinetic experiments were conducted using both the parent compound and imidacloprid-olefin (IMI-ole), a metabolite assessed as toxic in the acute tests and defined as bioactive. Of the four tested metabolites, only IMI-ole was readily biotransformed from the parent IMI and showed similar toxicity to C. dipterum as IMI. However, C. dipterum was hardly able to eliminate IMI-ole from its body. For G. pulex, IMI-ole was also the only detected metabolite causing toxicity, but the biotransformation of IMI to IMI-ole was slower and lower in G. pulex compared to C. dipterum, and G. pulex eliminated IMI-ole quicker than C. dipterum. Our results on internal kinetics of IMI and IMI-ole, and on biotransformation of IMI indicated that the metabolite IMI-ole was toxic and was rather persistent inside the body tissue of both invertebrate species, especially for C. dipterum. In conclusion, as IMI and IMI-ole have similar toxicity and IMI was replaced rapidly by IMI-ole which in turn was poorly eliminated by C. dipterum, the overall toxicity is a function of dose and time. As a result, no long-term threshold of effects of IMI may exist for C. dipterum as the poor elimination results in an ongoing increase of toxicity over time for mayflies as also found experimentally in previous published papers.

Time course of acclimation of critical thermal limits in two springtail species (Collembola)

Critical thermal limits are one of the most important sources of information on the possible impacts of climate change on soil microarthropods. The extent of plasticity of tolerance limits can provide valuable insights about the likely responses of ectotherms to environmental change. Although many studies have investigated various aspects of the acclimatory response of thermal limits to temperature changes in arthropods, the number of studies focusing on the temporal dynamics of this plastic response is relatively small. Collembola, one of the key microarthropods groups in almost all soil ecosystems around the world, have been the focus of several thermal acclimation studies. Yet the time course of acclimation and its reversal have not been widely studied in this group. Here we investigated the time course of acclimation of critical thermal maxima (CT_max) and minima (CT_min) of two springtail species. We exposed a Cryptopygus species from temperate southern Australia to high and low temperature conditions and Mucrosomia caeca from Sub-Antarctic Macquarie Island to high temperature conditions. Upper thermal limits in both species were found to be highly constrained, as CT_max did not show substantial response to high and low temperature acclimation both in the Cryptopygus species and M. caeca, whereas CT_min showed significant responses to high and low temperature conditions. The acclimation begins to stabilize in approximately seven days in all treatments except for the acclimation of CT_min under high temperature conditions, where the pattern of change suggests that this acclimation might take longer to be completed. Although reversal of this acclimation also begins to stabilize under 7 days, re-acclimation was relatively slow as we did not observe a very clear settling point in 2 of the 3 re-acclimation treatments. The observed limits on the plasticity of CT_max indicate that both of these species may be very limited in their ability to respond plastically to short-term rapid changes in temperature (i.e temperature extremes).

An overview on trilobite eyes and their functioning

Great progress has been made during the last decades in understanding visual systems of arthropods living today. Thus it seems worthwhile to review what is known about structure and function of the eyes of trilobites, the most important group of marine arthropods during the Paleozoic. There are three types of compound eyes in trilobites. The oldest and most abundant is the so-called holochroal eye. The sensory system represents a typical apposition eye, and all units are covered by one cornea in common. The so-called abathochroal eye (only in eodiscid trilobites) consists of small lenses, each individually covered by a thin cuticular cornea. The schizochroal eye is represented just in the suborder Phacopina, and probably is a highly specialized visual system. We discuss the calcitic character of trilobite lenses, the phylogenetic relevance of the existence of crystalline cones in trilobites, and consider adaptations of trilobite's compound eyes to different ecological constraints. The aim of this article is to give a resumé of what is known so far about trilobite vision, and to open perspectives to what still might be done.

Protaspis larva of an aglaspidid-like arthropod from the Ordovician of Siberia and its habitat

A fossil larva lacking segmentation of the calcified carapace, closely resembling the trilobite protaspis, has been found associated with other skeletal elements of an angarocaridid Girardevia species in the mid Darriwilian of central Siberia. The presence of protaspis larvae in the angarocaridids, generally believed to represent a branch of the Aglaspidida, supports their proximity to trilobites and proves a low position on the arthropod phylogenetic tree but does not necessarily contradict the chelicerate affinity. The cephalic appendages of angarocaridids bore massive gnathobases with detachable spines, closely similar to those known in extant xiphosurans and in their probable Cambrian relatives. The stratigraphic succession of the angarocaridids, their phosphatized cuticle pieces being abundant in the Ordovician strata of Siberia, shows a gradual improvement of mechanical resistance of their carapaces, eventually resulting in a honeycomb structure. The associated benthic mollusc assemblage is dominated with the bellerophontids showing high mortality at metamorphosis and only the limpet-like Pterotheca, infaunal bivalves, and scaphopods being able to survive this in a substantial number. This suggests a strong selective pressure from predators equipped with well-skeletonised oral apparatuses able to crush mineralized body covers of their prey. Possibly, these were some of the associated conodonts of appropriate size and co-evolving towards their ability to crush more and more resistant cuticle. Less likely candidates for durophagy are endoceratid or orthoceratid cephalopods. Also the angarocaridids themselves, equipped with robust gnathobases of cephalic appendages, apparently predated on benthic shelly animals.

Comparative transcriptomics reveals hidden issues in the plant response to arthropod herbivores

Plants experience different abiotic/biotic stresses, which trigger their molecular machinery to cope with them. Besides general mechanisms prompted by many stresses, specific mechanisms have been introduced to optimize the response to individual threats. However, these key mechanisms are difficult to identify. Here, we introduce an in-depth species-specific transcriptomic analysis and conduct an extensive meta-analysis of the responses to related species to gain more knowledge about plant responses. The spider mite Tetranychus urticae was used as the individual species, several arthropod herbivores as the related species for meta-analysis, and Arabidopsis thaliana plants as the common host. The analysis of the transcriptomic data showed typical common responses to herbivory, such as jasmonate signaling or glucosinolate biosynthesis. Also, a specific set of genes likely involved in the particularities of the Arabidopsis-spider mite interaction was discovered. The new findings have determined a prominent role in this interaction of the jasmonate-induced pathways leading to the biosynthesis of anthocyanins and tocopherols. Therefore, tandem individual/general transcriptomic profiling has been revealed as an effective method to identify novel relevant processes and specificities in the plant response to environmental stresses.

Assessing single effects of sugarcane pesticides fipronil and 2,4-D on plants and soil organisms

The continuous growth in global population since the beginning of the 20th century result in the necessity of food and energy provision favoring the intensive use of agricultural products such as pesticides. Although pesticides are important to prevent losses in the conventional chemically based agriculture, they frequently present side effects, which goes against agricultural production. The use of pesticides cause direct and indirect effects to soil organisms unbalancing essential soil processes (e.g. primary production, organic matter decomposition, nutrient cycling). Under tropical conditions, very little is known regarding the effects of pesticides to terrestrial organisms. Hence, the aim of the present study was to assess the ecotoxicological effects of the herbicide DMA® 806 BR (active ingredient: 2,4-D) and the insecticide Regent® 800 WG (active ingredient: fipronil), on terrestrial plant species (the dicot Raphanus sativus var. acanthioformis and the monocot Allium cepa), and soil invertebrates (the collembolan Folsomia candida and the enchytraeid Enchytraeus crypticus), using natural (NS) and artificial soils (TAS). For both pesticides, negative effects on non-target species were observed at concentrations lower than the doses recommended to prevent pests in sugarcane fields. For both soils, the dicot species was the most affected by the herbicide (R. sativus > A. cepa > F. candida > E. crypticus) and the collembolan species was the most affected by the insecticide (F. candida > E. crypticus = R. sativus = A. cepa). Although the order of the organisms' sensitivity for both pesticides was the same in both soils, results showed that the extent of the effects was soil dependent. Considering the ecologically relevant concentrations tested, and their severe effects to non-target organisms, it may be concluded that the use of fipronil and 2,4-D under recommended conditions may pose a risk to the terrestrial environment.

Tree canopy arthropods have idiosyncratic responses to plant ecophysiological traits in a warm temperate forest complex

Biodiversity studies on forest canopies often have narrow arthropod taxonomic focus, or refer to a single species of tree. In response, and to better understand the wide range of drivers of arthropod diversity in tree canopies, we conducted a large-scale, multi-taxon study which (a) included effect of immediate surroundings of an individual tree on plant physiological features, and (b), how these features affect compositional and functional arthropod diversity, in a warm, southern Afro-temperate forest. We found that tree species differed significantly in plant physiological features and arthropod diversity patterns. Surprisingly, we found negative correlation between surrounding canopy cover, and both foliar carbon and arthropod diversity in host trees, regardless of tree species. Subtle, tree intraspecific variation in physiological features correlated significantly with arthropod diversity measures, but direction and strength of correlations differed among tree species. These findings illustrate great complexity in how canopy arthropods respond to specific tree species, to immediate surroundings of host trees, and to tree physiological features. We conclude that in natural forests, loss of even one tree species, as well as homogenization of the crown layer and/or human-induced environmental change, could lead to profound and unpredictable canopy arthropod biodiversity responses, threatening forest integrity.

Survey of biomechanical aspects of arthropod terrestrialisation - Substrate bound legged locomotion

Arthropods are the most diverse clade on earth with regard to both species number and variability of body plans. Their general body plan is characterised by variable numbers of legs, and many-legged locomotion is an essential aspect of many aquatic and terrestrial arthropod species. Moreover, arthropods belong to the first groups of animals to colonise subaerial habitats, and they did so repeatedly and independently in a couple of clades. Those arthropod clades that colonised land habitats were equipped with highly variable body plans and locomotor apparatuses. Proceeding from their respective specific anatomies, they were challenged with strongly changing environmental conditions as well as altered physical and physiological constraints. This review explores the transitions from aquatic to terrestrial habitats across the different arthropod body plans and explains the major mechanisms and principles that constrain design and function of a range of locomotor apparatuses. Important aspects of movement physiology addressed here include the effects of different numbers of legs, different body sizes, miniaturisation and simplification of body plans and different ratios of inertial and damping forces. The article's focus is on continuous legged locomotion, but related ecological and behavioural aspects are also taken into account.

Arthropods and climate change - arctic challenges and opportunities

The harsh climate, limited human infrastructures, and basic autecological knowledge gaps represent substantial challenges for studying arthropods in the Arctic. At the same time, rapid climate change, low species diversity, and strong collaborative networks provide unique and underexploited Arctic opportunities for understanding species responses to environmental change and testing ecological theory. Here, I provide an overview of individual, population, and ecosystem level responses to climate change in Arctic arthropods. I focus on thermal performance, life history variation, population dynamics, community composition, diversity, and biotic interactions. The species-poor Arctic represents a unique opportunity for testing novel, automated arthropod monitoring methods. The Arctic can also potentially provide insights to further understand and mitigate the effects of climate change on arthropods worldwide.

Understanding the Mechanisms Underlying Host Restriction of Insect-Specific Viruses

Arthropod-borne viruses contribute significantly to global mortality and morbidity in humans and animals. These viruses are mainly transmitted between susceptible vertebrate hosts by hematophagous arthropod vectors, especially mosquitoes. Recently, there has been substantial attention for a novel group of viruses, referred to as insect-specific viruses (ISVs) which are exclusively maintained in mosquito populations. Recent discoveries of novel insect-specific viruses over the past years generated a great interest not only in their potential use as vaccine and diagnostic platforms but also as novel biological control agents due to their ability to modulate arbovirus transmission. While arboviruses infect both vertebrate and invertebrate hosts, the replication of insect-specific viruses is restricted in vertebrates at multiple stages of virus replication. The vertebrate restriction factors include the genetic elements of ISVs (structural and non-structural genes and the untranslated terminal regions), vertebrate host factors (agonists and antagonists), and the temperature-dependent microenvironment. A better understanding of these bottlenecks is thus warranted. In this review, we explore these factors and the complex interplay between ISVs and their hosts contributing to this host restriction phenomenon.

Arthropod exosomes as bubbles with message(s) to transmit vector-borne diseases

Ticks and mosquitoes are medically important vectors that transmit several pathogens, including arboviruses, to humans. Understanding how these blood-feeding arthropods transmit pathogens to humans requires knowledge on the molecular and cellular interplay at vector-host interface. Recent studies have highlighted the role of tick and mosquito small extracellular vesicles (EVs), including exosomes, facilitating arbovirus transmission within arthropod cells and from arthropod to mammalian cells. In this review, we summarize this emerging line of investigation in understanding the role of tick and mosquito exosomes in vector-pathogen-host tripartite interactions. Understanding the role of arthropod exosomes in pathogen interactions could lead to the discovery of novel therapeutic targets to interfere with the life cycle of several pathogens transmitted by vectors.

Three-way Interactions between Plants, Microbes, and Arthropods (PMA): Impacts, Mechanisms, and Prospects for Sustainable Plant Protection

plantcell;32/7/tpc.120.tt0720/FIG1F1fig1Three-way Interactions between Plants, Microbes, and Arthropods (PMA): Impacts, Mechanisms, and Prospects for Sustainable Plant Protection (By Maria J. Pozo, Benedicte R. Albrectsen, Eduardo R. Bejarano, Eduardo de la Peña, Salva Herrero, Ainhoa Martinez-Medina, Victoria Pastor, Sabine Ravnskov, Mary Williams and Arjen Biere)Plants constantly interact with numerous of organisms and the outcome of these interactions determines plant health and growth. In other words, the phenotype of a plant is not only the result of the plant's interaction with abiotic conditions, but also of multiple interactions in the living environment surrounding the plant, the phytobiome. In this Teaching Tool, we have focused on interactions between plants, microbes and arthropods (PMA). The organism groups that contribute to PMA interactions are presented as well as types of interactions between them, along with multiple examples of simple and more complex PMA interactions. The underlying mechanisms of plant responses are described in detail as well as the evolutionary aspects of PMA interactions. Finally, the use of PMA interactions for crop protection in sustainable plant production that supports the UN Sustainable Development Goals for 2030 is proposed.(Posted July 6, 2020)Click HERE to access Teaching Tool ComponentsRECOMMENDED CITATION STYLE:Pozo, M.J., Albrectsen, B.R., Bejarano, E.R., de la Peña, E., Herrero, S., Martinez-Medina, A., Pastor, V., Ravnskov, S., Williams, M., and Biere, A. (July NN, 2020). Three-way interactions between plants, microbes, and arthropods (PMA): Impacts, mechanisms, and prospects for sustainable plant protection. Teaching Tools in Plant Biology: Lecture Notes. The Plant Cell (online), doi/10.1105/tpc.120.tt0720.

Effects of arthropod inquilines on growth and reproductive effort among metacommunities of the purple pitcher plant (Sarracenia purpurea var. montana)

Many plant species harbor communities of symbionts that release nutrients used by their host plants. However, the importance of these nutrients to plant growth and reproductive effort is not well understood. Here, we evaluate the relationship between the communities that colonize pitcher plant phytotelmata and the pitcher plants’ vegetative growth and flower production to better understand the symbiotic role played by phytotelma communities. We focus on the mountain variety purple pitcher plant (Sarracenia purpurea var. montana), which occurs in small and isolated populations in Western North Carolina. We found that greater symbiont community diversity is associated with higher flower production the following season. We then examined geographic variation in communities and found that smaller plant populations supported less diverse symbiont communities. We relate our observations to patterns of community diversity predicted by community ecology theory.

Impact of temperature on the toxicity of Kraft 36 EC® (a.s. abamectin) and Score 250 EC® (a.s. difenoconazole) to soil organisms under realistic environmental exposure scenarios

Pesticides can affect all receiving compartments, especially soils, and their fate and effects may be enhanced by temperature, increasing their risk to ecological functions of soils. In Brazil, the most widely used pesticides are the insecticide Kraft 36 EC® (a.s. abamectin) and the fungicide Score 250 EC® (a.s. difenoconazole), which are commonly used in strawberry, often simultaneously as a mixture. The aim of this study was to evaluate the toxicity of realistic environmental applications, single and in mixtures, for both pesticides to the springtail Folsomia candida and the plant species Allium cepa (onion) and Lycopersicum esculentum (tomato). Mesocosms filled with Brazilian natural soil (lattosolo) were dosed with water (control), Kraft (10.8 g a.s/ha), Score (20 g.a.s/ha) and Kraft + Score (10.8 + 20 g a.s./ha). The applications were repeated every 7 days, during 18 days of experiment, and simulating rainfall twice a week. Collembola reproduction tests were conducted with soils from the first (day 1) and last day (day 18) of experiment for each treatment. Plant toxicity tests were carried out in the experimental units. The experiments were run at 23 °C and 33 °C. Kraft, alone and in the binary mixture, showed high toxicity to the springtails in soils from both days 1 and 18, especially at 23 °C where it caused 100% mortality. Score however, was not toxic to the springtails. Plant growth was reduced by Score, but responses varied depending on temperature. This study indicates a high environmental risk of the insecticide Kraft, particularly at lower temperatures (23 °C), and an influence of temperature on pesticide fate and effects.

Aquatic stem group myriapods close a gap between molecular divergence dates and the terrestrial fossil record

Identifying marine or freshwater fossils that belong to the stem groups of the major terrestrial arthropod radiations is a longstanding challenge. Molecular dating and fossils of their pancrustacean sister group predict that myriapods originated in the Cambrian, much earlier than their oldest known fossils, but uncertainty about stem group Myriapoda confounds efforts to resolve the timing of the group's terrestrialization. Among a small set of candidates for membership in the stem group of Myriapoda, the Cambrian to Triassic euthycarcinoids have repeatedly been singled out. The only known Devonian euthycarcinoid, Heterocrania rhyniensis from the Rhynie and Windyfield cherts hot spring complex in Scotland, reveals details of head structures that constrain the evolutionary position of euthycarcinoids. The head capsule houses an anterior cuticular tentorium, a feature uniquely shared by myriapods and hexapods. Confocal microscopy recovers myriapod-like characters of the preoral chamber, such as a prominent hypopharynx supported by tentorial bars and superlinguae between the mandibles and hypopharynx, reinforcing an alliance between euthycarcinoids and myriapods recovered in recent phylogenetic analysis. The Cambrian occurrence of the earliest euthycarcinoids supplies the oldest compelling evidence for an aquatic stem group for either Myriapoda or Hexapoda, previously a lacuna in the body fossil record of these otherwise terrestrial lineages until the Silurian and Devonian, respectively. The trace fossil record of euthycarcinoids in the Cambrian and Ordovician reveals amphibious locomotion in tidal environments and fills a gap between molecular estimates for myriapod origins in the Cambrian and a post-Ordovician crown group fossil record.

Effects of α-pinene on life history traits and stress tolerance in the springtail Folsomia candida

Volatile monoterpenes are emitted in large quantities to both air and soil by many plant species. While studies have addressed effects of monoterpenes on aboveground invertebrates, we have much poorer understanding of the possible effects of monoterpenes on soil invertebrates. Monoterpenes play a protective role in some plant species during heat and water stress, and therefore may provide similar protection against abiotic stress to soil invertebrates. The aim of the present study was to investigate the effects of the common monoterpene, α-pinene, on the soil living springtail, Folsomia candida (Collembola; Isotomidae). We hypothesized that exposure to α-pinene would lower the transition temperature of membranes, and thereby improve cold tolerance. Controlled exposure to α-pinene, which is a volatile liquid at room temperature, was made possible by passive dosing through the air-phase using a lipid donor. This lipid-based passive dosing approach also allows linking observed effects to concentrations in membrane when equilibrium is achieved. Equilibrium membrane concentrations above 116 mmol kg^-1 caused springtails to become comatose, and coma recovery time was proportional to exposure concentration. Alpha-pinene delayed time to first egg laying, while the number of eggs laid and hatchability was unaffected. Springtails exposed to α-pinene showed increased survival of cold shock (-6 °C, 2 h), but no effects on heat (34 °C, 2 h) or drought tolerance (98.2% relative humidity, 7d) were observed. The present study has demonstrated that α-pinene has direct toxic effects to F. candida, but on the other hand can improve their cold tolerance considerably at membrane concentrations above 87 mmol kg^-1.

Antifreeze protein complements cryoprotective dehydration in the freeze-avoiding springtail Megaphorura arctica

The springtail, Megaphorura arctica, is freeze-avoiding and survives sub-zero temperatures by cryoprotective dehydration. At the onset of dehydration there is some supercooling of body fluids, and the danger of inoculative freezing, which would be lethal. To see if the springtails are protected by antifreeze proteins in this pre-equilibrium phase, we examined extracts from cold-acclimated M. arctica and recorded over 3 °C of freezing point depression. Proteins responsible for this antifreeze activity were isolated by ice affinity. They comprise isoforms ranging from 6.5 to 16.9 kDa, with an amino acid composition dominated by glycine (>35 mol%). Tryptic peptide sequences were used to identify the mRNA sequence coding for the smallest isoform. This antifreeze protein sequence has high similarity to one characterized in Hypogastrura harveyi, from a different springtail order. If these two antifreeze proteins are true homologs, we suggest their origin dates back to the Permian glaciations some 300 million years ago.

Subterranean Deuteraphorura Absolon, 1901, (Hexapoda, Collembola) of the Western Carpathians - Troglomorphy at the northern distributional limit in Europe

An integrative approach employing molecular, morphological and geographical data were applied to species delimitation among Deuteraphorura congeners occupying caves of the Western Carpathian Mts. A new species of Deuteraphorura from the Western Carpathians is described. D. muranensis sp. nov. belongs among species with 4 pso at the hind margin of the head and possesses highly troglomorphic features. It is conspicuous with its distinctly elongated claws and long, hair-like body chaetae. The status of the new species was confirmed by DNA barcoding based on the mitochondrial COI marker. Populations of D. kratochvili (Nosek, 1963), the most widespread species, were studied in detail. Both ABGD and PTP analyses brought results congruent with geography, i.e. the molecular and geographic distance of the populations were positively correlated. However, some molecular separation based on pairwise distance and the number of substitutions was indicated within two of the studied populations. Despite the indistinct morphological differences, the tested populations were well isolated both geographically and genetically, which indicates that each studied population may represent a cryptic species. The troglomorphy of cave Collembola at the northernmost border of the distribution of cave-adapted species in the Europe is discussed. It is clear that the level of troglomorphy is closely associated with conditions of the microhabitat occupied by the individual subterranean species. The results of our study enhance the importance of the Western Carpathians regarding the diversity pattern of obligate cave species in Europe.

Long-term ecological research in southern Brazil grasslands: Effects of grazing exclusion and deferred grazing on plant and arthropod communities

Grazing exclusion may lead to biodiversity loss and homogenization of naturally heterogeneous and species-rich grassland ecosystems, and these effects may cascade to higher trophic levels and ecosystem properties. Although grazing exclusion has been studied elsewhere, the consequences of alleviating the disturbance regime in grassland ecosystems remain unclear. In this paper, we present results of the first five years of an experiment in native grasslands of southern Brazil. Using a randomized block experimental design, we examined the effects of three grazing treatments on plant and arthropod communities: (i) deferred grazing (i.e., intermittent grazing), (ii) grazing exclusion and (iii) a control under traditional continuous grazing, which were applied to 70 x 70 m experimental plots, in six regionally distributed blocks. We evaluated plant community responses regarding taxonomic and functional diversity (life-forms) in separate spatial components: alpha (1 x 1 m subplots), beta, and gamma (70 x 70 m plots), as well as the cascading effects on arthropod high-taxa. By estimating effect sizes (treatments vs. control) by bootstrap resampling, both deferred grazing and grazing exclusion mostly increased vegetation height, plant biomass and standing dead biomass. The effect of grazing exclusion on plant taxonomic diversity was negative. Conversely, deferred grazing increased plant taxonomic diversity, but both treatments reduced plant functional diversity. Reduced grazing pressure in both treatments promoted the break of dominance by prostrate species, followed by fast homogenization of vegetation structure towards dominance of ligneous and erect species. These changes in the plant community led to increases in high-taxa richness and abundance of vegetation-dwelling arthropod groups under both treatments, but had no detectable effects on epigeic arthropods. Our results indicate that decision-making regarding the conservation of southern Brazil grasslands should include both intensive and alleviated levels of grazing management, but not complete grazing exclusion, to maximize conservation results when considering plant and arthropod communities.

Genital morphology and the mechanics of copulation in the millipede genus Pseudopolydesmus (Diplopoda: Polydesmida: Polydesmidae)

Mate choice, copulation, genital morphology, and sperm storage are not very well understood in millipedes. The use of three-dimensional x-ray computed tomography (μCT) provides new morphological data regarding millipede reproductive systems in both the female and male, including chitinous sclerites and membranes, muscles, glands, oviducts, and sperm conduits. Here we present a complete integrated account of the morphology and function of the female genital organs in the family Polydesmidae (Diplopoda: Polydesmida) using μCT, UV fluorescence imaging, and scanning electron microscopy. These data allow us to consider competing hypotheses regarding millipede vulva formation. We additionally present the morphology of copulatory interface in Pseudopolydesmus Attems, 1898 using images of a mating pair in copula and by simulating the interface of the organs using 3D models from μCT, allowing us to tentatively identify a lock-and-key-like mechanism. Finally, we use μCT to reveal the topology of the seminal canal in the gonopod of male Pseudopolydesmus, a topic that has remained unresolved for nearly 80 years.

Synergistic interaction between effects of phenanthrene and dynamic heat stress cycles in a soil arthropod

Climatic stressors and chemicals should not be treated as isolated problems since they often occur simultaneously, and their combined effects must be evaluated including their possible interactive effects. In the present study we subjected springtails (Folsomia candida) to combined exposure to phenanthrene and dynamic heat cycles in a full factorial experiment. In a microcosm experiment, we studied the population growth of springtails subjected to a range of sub-lethal concentrations of phenanthrene. During the 28-day experiment we further subjected microcosms to varying numbers of repeated dynamic heat cycles (0-5 cycles) simulating repeated heat waves. We found a synergistic interaction between the effects of phenanthrene and the number of heat waves on both body mass of adults and juvenile production of F. candida showing that the negative effects of phenanthrene were intensified when animals were heat stressed, and/or vice versa. This interaction was not related to internal concentrations of phenanthrene in adult springtails, nor was it due to altered degradation of phenanthrene in soil. We argue that both phenanthrene (by its partitioning into membrane bilayers) and heat have detrimental effects on the physical conditions of cellular membranes in a dose-dependent manner, which, under extreme circumstances, can increase membrane fluidity to a level which is sub-optimal for normal membrane functioning. We discuss the possibility that the synergistic interactions subsequently reduce life-history parameters such as growth and reproduction.

Recovery period of Folsomia candida influence the impact of nonylphenol and phenanthrene on the tolerance of drought and heat shock

Soil organisms are exposed to natural and anthropogenic stressors, such as xenobiotics. However, to simplify and make laboratory experiments easily reproducible, natural stressors are often excluded from ecotoxicological studies and risk assessment. This might underestimate the effect of chemicals, since synergistic interactions between chemicals and natural stressors might occur, creating a more severe impact than expected. Several studies have addressed simultaneous exposure to natural and chemical stressors, but very little is known of about the persistence of these interactions during recovery. Here, we examined if recovery after chemical stress exposure was important for the ability of springtails (Folsomia candida) to tolerate subsequent drought- and heat stress. Nonylphenol (NP) and phenanthrene (PHE) was tested and their isolated toxicity resulted in LC₅₀ values of 206 mg NP kg^-1 dry soil and 109 mg PHE kg^-1 dry soil in a 7-day test. Elimination of NP and PHE was rapid and only trace amounts remained in springtail tissues after 3-7 days of recovery. Isolated studies of drought and heat shock on Folsomia candida resulted in a lethal effect for 50% of the animals (LRH₅₀) at a relative humidity (RH) of 97.9%, and 190 min at 34 °C was shown to be lethal for 50% of the test species (LT₅₀). The results showed, as expected, significant synergistic interactions between the effects of the chemicals and the effects of drought and heat stress. The negative effects of NP and PHE on the drought tolerance disappeared within 7 days post exposure. Springtails exposed to PHE also recovered their heat tolerance within 7 days post exposure, while NP exposed animals had not fully recovered their heat tolerance 14 days after exposure. Overall, a recovery period post chemical exposure was found to be very important for springtails in order to cope with natural stressors like heat and drought.

Eprinomectin antiparasitic affects survival, reproduction and behavior of Folsomia candida biomarker, and its toxicity depends on the type of soil

The objective of this study was to evaluate the toxicity of the antiparasitic agent eprinomectin in two subtropical soils, using ecotoxicological lethality, reproduction and avoidance behavior tests with springtails (Folsomia candida). Eprinomectin concentrations were 0 (control), 0.5, 1, 2, 4, 8, 12, 16 and 20 mg kg^-1 of dry soil combined with either Entisol or Oxisol soils. Statistically significant toxic effects of eprinomectin on springtails were observed in both soils. Eprinomectin was lethal starting at 8 mg kg^-1 of dry soil in Entisol, and 20 mg kg^-1 of dry soil in Oxisol, with effects less than 50% at lethal concentrations. Reductions in the reproduction rate of the springtails were also observed starting at 8 mg kg^-1 of dry soil in Entisol, and 0.5 mg kg^-1 of dry soil in Oxisol. EC_repr50 value calculated for Entisol was 4.38 ± 0.62 mg kg^-1 of dry soil; for Oxisol the EC_repr50 was above the highest tested concentration. For avoidance behavior, the effect occurred from 0.5 mg kg^-1 of dry soil for both soils. In Entisol, all concentrations caused avoidance of more than 95%, and in Oxisol the EC_avoi50 value was 1.33 ± 0.83 mg kg^-1 of dry soil. We conclude that eprinomectin affected survival, reproduction and caused avoidance behavior of F. candida in both soils. The toxic effects were greater as the concentration in the soils increased. The effects in Oxisol were less intense than those in Entisol with respect to the affected springtails. This discrepancy may be attributed to the different physicochemical characteristics of the soils that determine the retention capacity for eprinomectin; in particular, there are greater contents of clay, organic matter and cation exchange capacity in Oxisol.

Quantitative assessment of plant-arthropod interactions in forest canopies: A plot-based approach

Research on canopy arthropods has progressed from species inventories to the study of their interactions and networks, enhancing our understanding of how hyper-diverse communities are maintained. Previous studies often focused on sampling individual tree species, individual trees or their parts. We argue that such selective sampling is not ideal when analyzing interaction network structure, and may lead to erroneous conclusions. We developed practical and reproducible sampling guidelines for the plot-based analysis of arthropod interaction networks in forest canopies. Our sampling protocol focused on insect herbivores (leaf-chewing insect larvae, miners and gallers) and non-flying invertebrate predators (spiders and ants). We quantitatively sampled the focal arthropods from felled trees, or from trees accessed by canopy cranes or cherry pickers in 53 0.1 ha forest plots in five biogeographic regions, comprising 6,280 trees in total. All three methods required a similar sampling effort and provided good foliage accessibility. Furthermore, we compared interaction networks derived from plot-based data to interaction networks derived from simulated non-plot-based data focusing either on common tree species or a representative selection of tree families. All types of non-plot-based data showed highly biased network structure towards higher connectance, higher web asymmetry, and higher nestedness temperature when compared with plot-based data. Furthermore, some types of non-plot-based data showed biased diversity of the associated herbivore species and specificity of their interactions. Plot-based sampling thus appears to be the most rigorous approach for reconstructing realistic, quantitative plant-arthropod interaction networks that are comparable across sites and regions. Studies of plant interactions have greatly benefited from a plot-based approach and we argue that studies of arthropod interactions would benefit in the same way. We conclude that plot-based studies on canopy arthropods would yield important insights into the processes of interaction network assembly and dynamics, which could be maximised via a coordinated network of plot-based study sites.

The rotating magnetocaloric effect as a potential mechanism for natural magnetic senses

Many animals are able to sense the earth’s magnetic field, including varieties of arthropods and members of all major vertebrate groups. While the existence of this magnetic sense is widely accepted, the mechanism of action remains unknown. Building from recent work on synthetic magnetoreceptors, we propose a new model for natural magnetosensation based on the rotating magnetocaloric effect (RME), which predicts that heat generated by magnetic nanoparticles may allow animals to detect features of the earth’s magnetic field. Using this model, we identify the conditions for the RME to produce physiological signals in response to the earth’s magnetic field and suggest experiments to distinguish between candidate mechanisms of magnetoreception.

Complexity of the relationship between global warming and urbanization - an obscure future for predicting increases in vector-borne infectious diseases

Arthropod vectors are responsible for the transmission of many infectious diseases. Currently, more than three billion people living in endemic areas are exposed to vector-borne pathogens. Substantial differences in the biology of arthropod vectors make it extremely challenging to predict the incidence of vector-borne diseases in the future. However, global warming and urbanization both profoundly affect the ecology and distribution of arthropod vectors. Such processes often result in a biotic homogenization of species in a non-random process of biodiversity loss. The data presently available indicate a trend towards progressive increases in the presence and abundance of vectors capable of thriving in urban environments amongst humans, thus, increasing the contact between vectors and human hosts. As a consequence, we expect the incidence of vector-borne diseases to increase. In our opinion, resources should be made available and directed to strategies within the Integrated Vector Management framework, focusing on proven vector control tools. Besides, a substantial reduction of IVM costs would be achieved by observing environmental guidelines and providing basic sanitary infrastructure at early stages of its development. This could help to increase IVM effectiveness in attenuating social determinants of health and social inequities due to exposure to vectors.