Discovery of diverse Pectocaris species at the Cambrian series 2 Hongjingshao formation Xiazhuang section (Kunming, SW China) and its ecological, taphonomic, and biostratigraphic implications

Pectocaris species are intermediate- to large-sized Cambrian bivalved arthropods. Previous studies have documented Pectocaris exclusively from the Cambrian Series 2 Stage 3 Chengjiang biota in Yu'anshan Formation, Chiungchussu Stage in SW China. In this study, we report Pectocaris paraspatiosa sp. nov., and three other previously known Pectocaris from the Xiazhuang section in Kunming, which belongs to the Hongjingshao Formation and is a later phase within Cambrian Stage 3 than the Yu'anshan Formation. The new species can be distinguished from its congeners by the sparsely arranged endopodal endites and the morphologies of the abdomen, telson, and telson processes. We interpret P. paraspatiosa sp. nov. as a filter-feeder and a powerful swimmer adapted to shallow, agitated environments. Comparison among the Pectocaris species reinforces previous views that niche differentiation had been established among the congeneric species based on morphological differentiation. Our study shows the comprehensive occurrences of Pectocaris species outside the Chengjiang biota for the first time. With a review of the shared fossil taxa of Chengjiang and Xiaoshiba biotas, we identify a strong biological connection between the Yu'anshan and Hongjingshao Formations.

Virome profiling of fig wasps (Ceratosolen spp.) reveals virus diversity spanning four realms

We investigated the virome of agaonid fig wasps (Ceratosolen spp.) inside syconia ("fruits") of various Ficus trees fed upon by frugivores such as pteropodid bats in Sub-Saharan Africa. This virome includes representatives of viral families spanning four realms and includes near-complete genome sequences of three novel viruses and fragments of five additional potentially novel viruses evolutionarily associated with insects, fungi, plants, and vertebrates. Our study provides evidence that frugivorous animals are exposed to a plethora of viruses by coincidental consumption of fig wasps, which are obligate pollinators of figs worldwide.

Cloning, expression and molecular analysis of recombinant Netrin-A protein of Lucilia sericata Meigen (Diptera: Calliphoridae) larvae

Objectives

Lucilia sericata (Diptera: Calliphoridae) is used in larval therapy for wound healing. Netrin-A is an enzyme secreted from the salivary glands of these larvae, and has a central role in neural regeneration and angiogenesis. This study aimed to produce the recombinant Netrin-A protein from Lucilia sericata larvae by the baculovirus expression vector system in the Sf9 insect cell line.

Methods

The coding sequence of Netrin-A was cloned, amplified in the pTG19 vector, and then cloned in the pFastBac HTA vector. It was then transformed into DH10Bac, and the recombinant Bacmid was subsequently transfected into Sf9 cells. The recombinant Netrin-A was purified by Ni-NTA agarose. The evaluation was done using SDS-PAGE and western blot, respectively. Finally, its concentration was calculated with the Bradford assay.

Results

The molecular weight of this protein was 52 kDa with 404 amino acids. The signal peptide was located between amino acids 24 and 25. The concentration of Netrin-A was calculated to be 48.8 μg/ml. It reaffirmed the characterized gene codes of Lucilia sericata Netrin-A in a previous study.

Conclusions

The generation of recombinant Netrin-A could be used in larval therapy, and as a biomarker in certain diseases. The netrin-A of Lucilia sericata was unprecedentedly cloned and expressed in a eukaryotic cell line. Given that this larva is FDA-approved, and non-pathogenic, it conduces to research on the development of maggot therapy in future.

Molecular Evolution of Malacostracan Short Wavelength Sensitive Opsins

Investigations of the molecular mechanisms behind detection of short, and particularly ultraviolet, wavelengths in arthropods have relied heavily on studies from insects due to the relative ease of heterologous expression of modified opsin proteins in model organisms like Drosophila. However, species outside of the Insecta can provide information on mechanisms for spectral tuning as well as the evolutionary history of pancrustacean visual pigments. Here we investigate the basis of spectral tuning in malacostracan short wavelength sensitive (SWS) opsins using phylogenetic comparative methods. Tuning sites that may be responsible for the difference between ultraviolet (UV) and violet visual pigment absorbance in the Malacostraca are identified, and the idea that an amino acid polymorphism at a single site is responsible for this shift is shown to be unlikely. Instead, we suggest that this change in absorbance is accomplished through multiple amino acid substitutions. On the basis of our findings, we conducted further surveys to identify spectral tuning mechanisms in the order Stomatopoda where duplication of UV opsins has occurred. Ancestral state reconstructions of stomatopod opsins from two main clades provide insight into the amino acid changes that lead to differing absorption by the visual pigments they form, and likely contribute the basis for the wide array of UV spectral sensitivities found in this order.

Minimal resin embedding of SBF-SEM samples reduces charging and facilitates finding a surface-linked region of interest

BACKGROUND

For decoding the mechanism of how cells and organs function information on their ultrastructure is essential. High-resolution 3D imaging has revolutionized morphology. Serial block face scanning electron microscopy (SBF-SEM) offers non-laborious, automated imaging in 3D of up to ~ 1 mm3 large biological objects at nanometer-scale resolution. For many samples there are obstacles. Quality imaging is often hampered by charging effects, which originate in the nonconductive resin used for embedding. Especially, if the imaged region of interest (ROI) includes the surface of the sample and neighbours the empty resin, which insulates the object. This extra resin also obscures the sample's morphology, thus making navigation to the ROI difficult.

RESULTS

Using the example of small arthropods and a fish roe we describe a workflow to prepare samples for SBF-SEM using the minimal resin (MR) embedding method. We show that for imaging of surface structures this simple approach conveniently tackles and solves both of the two major problems-charging and ROI localization-that complicate imaging of SBF-SEM samples embedded in an excess of overlying resin. As the surface ROI is not masked by the resin, samples can be precisely trimmed before they are placed into the imaging chamber. The initial approaching step is fast and easy. No extra trimming inside the microscope is necessary. Importantly, charging is absent or greatly reduced meaning that imaging can be accomplished under good vacuum conditions, typically at the optimal high vacuum. This leads to better resolution, better signal to noise ratio, and faster image acquisition.

CONCLUSIONS

In MR embedded samples charging is minimized and ROI easily targeted. MR embedding does not require any special equipment or skills. It saves effort, microscope time and eventually leads to high quality data. Studies on surface-linked ROIs, or any samples normally surrounded by the excess of resin, would benefit from adopting the technique.

Olfactory navigation in arthropods

Using odors to find food and mates is one of the most ancient and highly conserved behaviors. Arthropods from flies to moths to crabs use broadly similar strategies to navigate toward odor sources-such as integrating flow information with odor information, comparing odor concentration across sensors, and integrating odor information over time. Because arthropods share many homologous brain structures-antennal lobes for processing olfactory information, mechanosensors for processing flow, mushroom bodies (or hemi-ellipsoid bodies) for associative learning, and central complexes for navigation, it is likely that these closely related behaviors are mediated by conserved neural circuits. However, differences in the types of odors they seek, the physics of odor dispersal, and the physics of locomotion in water, air, and on substrates mean that these circuits must have adapted to generate a wide diversity of odor-seeking behaviors. In this review, we discuss common strategies and specializations observed in olfactory navigation behavior across arthropods, and review our current knowledge about the neural circuits subserving this behavior. We propose that a comparative study of arthropod nervous systems may provide insight into how a set of basic circuit structures has diversified to generate behavior adapted to different environments.

Transcriptomic and targeted immune transcript analyses confirm localized skin immune responses in Atlantic salmon towards the salmon louse

Atlantic salmon (Salmo salar) are highly susceptible to infestations with the ectoparasite Lepeophtheirus salmonis, the salmon louse. Infestations elicit an immune response in the fish, but the response does not lead to parasite clearance, nor does it protect against subsequent infestations. It is, however, not known why the immune response is not adequate, possibly because the local response directly underneath the louse has been poorly evaluated. The present study describes the transcriptomic response by RNA sequencing of skin at the site of copepodid attachment. Analysing differentially expressed genes, 2864 were higher and 1357 were lower expressed at the louse attachment site compared to uninfested sites in the louse infested fish, while gene expression at uninfested sites were similar to uninfested control fish. The transcriptional patterns of selected immune genes were further detailed in three skin compartments/types: Whole skin, scales only and fin tissue. The elevation of pro-inflammatory cytokines and immune cell marker transcripts observed in whole skin and scale samples were not induced in fin, and a higher cytokine transcript level in scale samples suggest it can be used as a nonlethal sampling method to enhance selective breeding trials. Furthermore, the immune response was followed in both skin and anterior kidney as the infestation developed. Here, newly moulted preadult 1 stage lice induced a higher immune response than chalimi and adult lice. Overall, infestation with salmon louse induce a modest but early immune response with an elevation of mainly innate immune transcripts, with the response primarily localized to the site of attachment.

Invasive investigation: uptake and transport of l-leucine in the gill epithelium of crustaceans

Many aquatic species are well known as extremely successful invaders. The green crab (Carcinus maenas) is an arthropod native to European waters; however, it is now known to be a globally invasive species. Recently, it was discovered that the C. maenas could transport nutrients in the form of amino acids across their gill from the surrounding environment, a feat previously thought to be impossible in arthropods. We compared the ability for branchial amino acid transport of crustacean's native to Canadian Pacific waters to that of the invasive C. maenas, determining if this was a novel pathway in an extremely successful invasive species, or a shared trait among crustaceans. Active transport of l-leucine was exhibited in C. maenas, Metacarcinus gracilis, Metacarcinus magister, and Cancer productus across their gill epithelia. Carcinus maenas exhibited the highest maximum rate of branchial l-leucine transport at 53.7 ± 6.24 nmolg-1 h-1, over twice the rate of two native Canadian crustaceans. We also examined the influence of feeding, gill specificity, and organ accumulation of l-leucine. Feeding events displayed a heavy influence on the branchial transport rate of amino acids, increasing l-leucine transport rates by up to 10-fold in C. maenas. l-leucine displayed a significantly higher accumulation rate in the gills of C. maenas compared to the rest of the body at 4.15 ± 0.78 nmolg-1 h-1, with the stomach, hepatopancreas, eyestalks, muscle tissue, carapace and heart muscle exhibiting accumulation under 0.15 nmolg-1 h-1. For the first time, the novel transport of amino acids in Canadian native arthropods is described, suggesting that branchial amino acid transport is a shared trait among arthropods, contrary to existing literature. Further investigation is required to determine the influence of environmental temperature and salinity on transport in each species to outline any competitive advantages of the invasive C. maenas in a fluctuating estuarine environment.

Appearance of a transparent protrusion containing two pairs of legs on the apodous ring preceding the anamorphic molt in a millipede, Niponia nodulosa

BACKGROUND

Arthropods gradually change their forms through repeated molting events during postembryonic development. Anamorphosis, i.e., segment addition during postembryonic development, is seen in some arthropod lineages. In all millipede species (Myriapoda, Diplopoda), for example, postembryonic processes go through anamorphosis. Jean-Henri Fabre proposed 168 years ago the "law of anamorphosis", that is, "new rings appear between the penultimate ring and the telson" and "all apodous rings in a given stadium become podous rings in the next stadium", but the developmental process at the anamorphic molt remains largely unknown. In this study, therefore, by observing the morphological and histological changes at the time of molting, the detailed processes of leg- and ring-addition during anamorphosis were characterized in a millipede, Niponia nodulosa (Polydesmida, Cryptodesmidae).

RESULTS

In the preparatory period, a few days before molting, scanning electron microscopy, confocal laser scanning microscopy, and histological observations revealed that two pairs of wrinkled leg primordia were present under the cuticle of each apodous ring. In the rigidation period, just prior to molt, observations of external morphology showed that a transparent protrusion was observed on the median line of the ventral surface on each apodous ring. Confocal laser scanning microscopy and histological observations revealed that the transparent protrusion covered by an arthrodial membrane contained a leg bundle consisting of two pairs of legs. On the other hand, ring primordia were observed anterior to the telson just before molts.

CONCLUSIONS

Preceding the anamorphic molt in which two pairs of legs are added on an apodous ring, a transparent protrusion containing the leg pairs (a leg bundle) appears on each apodous ring. The morphogenetic process of the rapid protrusion of leg bundles, that is enabled by thin and elastic cuticle, suggested that millipedes have acquired a resting period and unique morphogenesis to efficiently add new legs and rings.

A deeper insight into the sialome of male and female Culex quinquefasciatus mosquitoes

INTRODUCTION

During evolution, blood-feeding arthropods developed a complex salivary mixture that can interfere with host haemostatic and immune response, favoring blood acquisition and pathogen transmission. Therefore, a survey of the salivary gland contents can lead to the identification of molecules with potent pharmacological activity in addition to increase our understanding of the molecular mechanisms underlying the hematophagic behaviour of arthropods. The southern house mosquito, Culex quinquefasciatus, is a vector of several pathogenic agents, including viruses and filarial parasites that can affect humans and wild animals.

RESULTS

Previously, a Sanger-based transcriptome of the salivary glands (sialome) of adult C. quinquefasciatus females was published based on the sequencing of 503 clones organized into 281 clusters. Here, we revisited the southern mosquito sialome using an Illumina-based RNA-sequencing approach of both male and female salivary glands. Our analysis resulted in the identification of 7,539 coding DNA sequences (CDS) that were functionally annotated into 25 classes, in addition to 159 long non-coding RNA (LncRNA). Additionally, comparison of male and female libraries allowed the identification of female-enriched transcripts that are potentially related to blood acquisition and/or pathogen transmission.

CONCLUSION

Together, these findings represent an extended reference for the identification and characterization of the proteins containing relevant pharmacological activity in the salivary glands of C. quinquefasciatus mosquitoes.

Low Endosymbiont Incidence in Drosophila Species Across Peninsula Thailand

Arthropods are known to harbor several endosymbionts, such as Cardinium, Rickettsia, Spiroplasma, and Wolbachia. Wolbachia, for example, are the most widespread known endosymbionts in the world, which are found in about half of all arthropod species. To increase their transmission, these endosymbionts must manipulate their hosts in several ways such as cytoplasmic incompatibility and male killing. In tropical regions, endosymbiont diversity has not been studied exhaustively. Here, we checked four endosymbionts, including Cardinium, Rickettsia, Spiroplasma, and Wolbachia, in eleven Drosophila species found in Thai Peninsula. The Wolbachia strain wRi-like was found in all populations of Drosophila ananassae and Drosophila simulans. Furthermore, we found two new strains, wMalA and wMalB, in two populations of Drosophila malerkotliana. Besides Wolbachia, we did not find any of the above endosymbionts in all fly species. This work reveals the hidden diversity of endosymbionts in Drosophila and is the first exhaustive study on Drosophila in the region.

Morpho-physiological and biochemical responses of cotton (Gossypium hirsutum L.) genotypes upon sucking insect-pest infestations

The effects of sucking insect-pests on the morpho-physiological and biochemical changes in the leaves of four cotton genotypes-Bio 100 BG-II and GCH-3 (highly tolerant); KDCHH-9810 BG-II and HS-6 (highly susceptible)-were examined. Compared to tolerant genotypes, susceptible genotypes showed a decrease in relative water content, specific leaf weight, leaf area, photosynthetic rate, and total chlorophyll content, with an increase in electrolyte leakage. Hydrogen peroxide and total soluble sugar content were higher in susceptible plants. In contrast, resistant plants had higher levels of total soluble protein, total phenolic content, gossypol content, tannin content, peroxidase activity, and polyphenol oxidase. The findings demonstrated that the Bio 100 BG-II and GCH-3 genotypes effectively offset the impact of sucking insect-pests by modifying the factors mentioned above. The KDCHH-9810 BG-II and HS-6 genotypes could not completely negate the effects of sucking insect-pests. Customized metabolites and total soluble protein are more efficient in protecting cotton plants from damage brought on by infestations of sucking insects and pests.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-022-01253-w.

Transfer of elements into boreal forest ants at a former uranium mining site

Ants can influence ecological processes, such as the transfer of elements or radionuclides, in several ways. For example, they redistribute materials while foraging and maintaining their nests and have an important role in terrestrial food webs. Quantitative data of the transfer of elements into ants is needed, e.g., for developing improved radioecological models. In this study, samples of red wood ants (genus Formica), nest material, litter and soil were collected from a former uranium mining site in Eastern Finland. Concentrations of 33 elements were analyzed by Inductively Coupled Plasma-Mass Spectroscopy/Optical Emission Spectroscopy. Estimated element concentrations in spruce needles were used as a proxy for studying the transfer of elements into ants via aphids because spruces host the most important aphid farms in boreal forests. Empirically determined organism/medium concentration ratios (CRs) are commonly used in radioecological models. Ant/soil CRs were calculated and the validity of the fundamental assumption behind the of use of CRs (linear transfer) was evaluated. Elements that accumulated in ants in comparison to other compartments were cadmium, potassium, phosphorus, sulfur, and zinc. Ant uranium concentrations were low in comparison to soil, litter, or nest material but slightly elevated in comparison to spruce needles. Ant element concentrations were quite constant regardless of the soil concentrations. Non-linear transfer models could therefore describe the soil-to-ant transfer better than conventional CRs.

Research of Rickettsia spp. and Borrelia spp. in dogs in Southeast Brazil

Dogs are important in the epidemiology of tick-borne diseases, playing a significant role mainly in endemic areas of rickettsiosis and borreliosis, and serving as sentinels in epidemiological surveys. We analyzed the distribution of Rickettsia and Borrelia spp. in dogs and their ticks in the municipalities of Guaxupé, Minas Gerais, and Tapiratiba, São Paulo, Brazil, two areas non-endemic for Baggio-Yoshinari Syndrome (BYS) and rickettsiosis. Serum from 242 dogs of different ages (>12 months) and breeds were tested by the Indirect Immunofluorescence Assay (IFA) using specific antigens for Rickettsia rickettsii, Rickettsia parkeri, Rickettsia amblyommatis, Rickettsia rhipicephali, and Rickettsia bellii, and by an indirect Enzyme Linked Immunosorbent Assay (ELISA) for the detection of homologous IgG antibodies against Borrelia burgdorferi American strain G39/40. Ticks were collected from the animals and subjected to PCR and nested PCR for detection of Rickettsia spp. (synthase citrate gene) and Borrelia spp. (flagellin gene). Serological data showed that 7.85% (19/242) of the analyzed dogs were seropositive for at least one of the five Rickettsia antigens tested; one (0.41%) was considered seropositive for R. parkeri (1:64) and one (0.41%) for R. rickettsii (1:256). Nine (3.72%) were considered seropositive for R. bellii and one (0.41%) for R. amblyommatis; a seroprevalence of 13.64% (33/242) for IgG class immunoreactive antibodies against B. burgdorferi was observed. A total of 148 ticks were collected from the dogs; among these 3.40% were identified as larvae of the genus Rhipicephalus and 0.70% of the genus Amblyomma; 89.8% were identified as Rhipicephalus sanguineus, 4.70% Amblyomma sculptum and 1.40% Amblyomma ovale; all negative for PCR of Rickettsia spp. and nested PCR for Borrelia spp.. The serological findings of this study suggest the circulation of Rickettsiae associated with the spotted fever group and vector ticks, just like Borrelia spp. in a non-endemic Brazilian area, drawing attention to the possibility of a zoonotic cycle in the region.

Acknowledging extraordinary women in the history of medical entomology

Throughout history, women have been actively involved in the advancement of science, while struggling to overcome challenges to participate and a lack of recognition. Prior to 1950, most women were not included in the lists of "classical" descriptions of the iconic scientific figures nor included in the most relevant historical accounts. Since the second half of the twentieth century, great efforts have been made to recognize the contributions of women to the advancement of science, especially since formal scientific careers have been dominated by men, with limited (or no) access to women. Despite these challenging social, political and cultural contexts, many women have succeeded in making significant advancements, and their contributions are now being acknowledged. Such efforts have led to the publication of recent reviews and compilations on outstanding women in biological sciences. The field of medical entomology is inherently interdisciplinary, focusing on insects and other arthropods that affect human health, with input primarily from the biological and medical sciences and a strong public health perspective. Several reviews and book chapters describing the history of medical entomology have been published over the decades, but few women are mentioned in these publications, even though many women have contributed to this field. Much of the information on these women is currently scattered throughout the published literature and historical records on a wide range of topics, including activism, virology, vector control and even acarology. Considering that there is no single available compilation of women contributors in the history of medical entomology, this review aims to provide a list of 22 women and their contributions to this field. The list includes women from diverse backgrounds, born in the late 1800s and before 1950, who directly impacted medical entomology in various ways and in different regions of the world. This compilation is far from exhaustive, but it aims to identify role models and examples of extraordinary women to motivate the evolving future of this field.

Performance of the SSI development function compared with 33 other functions applied to 79 arthropod species' datasets

The development rates of arthropods are temperature-dependent. Studies aiming to predict the dynamics of arachnid, crustacean, and insect populations in nature often require the derivation of development functions representing this phenomenon. A previous study (Quinn, B.K., 2017, J. Therm. Biol. 63, 65-77) identified 33 development functions commonly used in past studies on temperature-dependent development of arthropods, and illustrated that: (1) most of 99 past studies only applied one or few (2-5) development functions to their data without considering others; and (2) most of a subset of 79 studies' data were not fit with the actual best function for them, resulting in sometimes substantial differences in model performance and predictive ability. However, that study did not test the class of development functions based on theoretical enzyme thermodynamics, including the Sharpe-Schoolfield-Ikemoto (SSI) function. Herein, the meta-analyses done in that previous study were redone, after fitting all 79 reanalyzed datasets with the SSI function. Estimates of the intrinsic optimum temperature (T_Φ) for development of each tested species were also derived using the SSI function and compared among taxa. Including the SSI function in analyses did not change the conclusions of the previous study concerning development function usage, choice, and consequences. Notably, the SSI function performed as well as or relatively better than other functions of comparable or lower complexity in terms of R², AIC_C-based rankings, ΔAIC_C values, and prediction errors, which may recommend its more widespread use in future studies. Overall differences in T_Φ were found among arthropod subphyla, as well as between most species pairs. Most T_Φ estimates produced herein were novel, and could be used to make inferences about or comparisons among arthropod taxa in future studies.

Development of genus-specific universal primers for the detection of flaviviruses

Background

Flaviviruses are representative arboviruses carried by arthropods and/or vertebrates; these viruses can pose a public health concern in many countries. By contrast, it is known that a novel virus group called insect-specific flaviviruses (ISFs) also infects arthropods, although no such virus has yet been isolated from vertebrates. The characteristics of ISFs, which affect replication of human-pathogenic flaviviruses within co-infected mosquito cells or mosquitoes without affecting the mosquitoes themselves, mean that we should pay attention to both ISFs and human-pathogenic flaviviruses, despite the fact that ISFs appear not to be directly hazardous to human health. To assess the risk of diseases caused by flaviviruses, and to better understand their ecology, it is necessary to know the extent to which flaviviruses are harbored by arthropods.

Methods

We developed a novel universal primer for use in a PCR-based system to detect a broad range of flaviviruses. We then evaluated its performance. The utility of the novel primer pair was evaluated in a PCR assay using artificially synthesized oligonucleotides derived from a template viral genome sequence. The utility of the primer pair was also examined by reverse transcription PCR (RT-PCR) using cDNA templates prepared from virus-infected cells or crude supernatants prepared from virus-containing mosquito homogenates.

Results

The novel primer pair amplified the flavivirus NS5 sequence (artificially synthesized) in all samples tested (six species of flavivirus that can cause infectious diseases in humans, and flaviviruses harbored by insects). In addition, the novel primer pair detected viral genomes in cDNA templates prepared from mosquito cells infected with live flavivirus under different infectious conditions. Finally, the viral genome was detected with high sensitivity in crude supernatants prepared from pooled mosquito homogenates.

Conclusion

This PCR system based on a novel primer pair makes it possible to detect arthropod-borne flaviviruses worldwide (the primer pair even detected viruses belonging to different genetic subgroups). As such, an assay based on this primer pair may help to improve public health and safety, as well as increase our understanding of flavivirus ecology.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12985-021-01646-5.

The genome of the extremophile Artemia provides insight into strategies to cope with extreme environments

BACKGROUND

Brine shrimp Artemia have an unequalled ability to endure extreme salinity and complete anoxia. This study aims to elucidate its strategies to cope with these stressors.

RESULTS AND DISCUSSION

Here, we present the genome of an inbred A. franciscana Kellogg, 1906. We identified 21,828 genes of which, under high salinity, 674 genes and under anoxia, 900 genes were differentially expressed (42%, respectively 30% were annotated). Under high salinity, relevant stress genes and pathways included several Heat Shock Protein and Leaf Embryogenesis Abundant genes, as well as the trehalose metabolism. In addition, based on differential gene expression analysis, it can be hypothesized that a high oxidative stress response and endocytosis/exocytosis are potential salt management strategies, in addition to the expression of major facilitator superfamily genes responsible for transmembrane ion transport. Under anoxia, genes involved in mitochondrial function, mTOR signalling and autophagy were differentially expressed. Both high salt and anoxia enhanced degradation of erroneous proteins and protein chaperoning. Compared with other branchiopod genomes, Artemia had 0.03% contracted and 6% expanded orthogroups, in which 14% of the genes were differentially expressed under high salinity or anoxia. One phospholipase D gene family, shown to be important in plant stress response, was uniquely present in both extremophiles Artemia and the tardigrade Hypsibius dujardini, yet not differentially expressed under the described experimental conditions.

CONCLUSIONS

A relatively complete genome of Artemia was assembled, annotated and analysed, facilitating research on its extremophile features, and providing a reference sequence for crustacean research.

Challenges at the host-arthropod-coronavirus interface and COVID-19: a One Health approach

Background: The world faces the challenge posed by the interaction between hosts and Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) with potential role for arthropod vectors, and the effect of SARS-CoV-2 variants on acquired immunity, vaccine efficacy and coronavirus disease-19 (COVID-19) pandemic control. Proposal: The characterization of the role played by animal hosts and host-virus interactions is essential to address this challenge. Zoonotic (animal-to-human) and reverse zoonotic (human-to-animal) routes may be involved in virus transmission with a possible still unconfirmed role for arthropod vectors. Herein we propose to consider the risks posed by the possible role of arthropod vectors in COVID-19 and that immunity against SARS-CoV-2 may increase the risk for zoonotic virus transmission. These risks should be considered when evaluating vaccine efficacy and monitoring animal SARS-CoV-2 variants. Conclusion: Virus surveillance, epidemiology, sequencing and evaluation of susceptibility to antibodies and other protective immune mechanisms from vaccinated individuals should be improved. A One Health approach such as the one applied by our group SaBio is necessary for a more effective control of COVID-19 and prevention of future pandemics.

The evolution of the gene regulatory networks patterning the Drosophila Blastoderm

The Drosophila blastoderm gene regulatory network is one of the best studied networks in biology. It is composed of a series of tiered sub-networks that act sequentially to generate a primary segmental pattern. Many of these sub-networks have been studied in other arthropods, allowing us to reconstruct how each of them evolved over the transition from the arthropod ancestor to the situation seen in Drosophila today. I trace the evolution of each of these networks, showing how some of them have been modified significantly in Drosophila relative to the ancestral state while others are largely conserved across evolutionary timescales. I compare the putative ancestral arthropod segmentation network with that found in Drosophila and discuss how and why it has been modified throughout evolution, and to what extent this modification is unusual.

The salmon louse genome: Copepod features and parasitic adaptations

Copepods encompass numerous ecological roles including parasites, detrivores and phytoplankton grazers. Nonetheless, copepod genome assemblies remain scarce. Lepeophtheirus salmonis is an economically and ecologically important ectoparasitic copepod found on salmonid fish. We present the 695.4 Mbp L. salmonis genome assembly containing ≈60% repetitive regions and 13,081 annotated protein-coding genes. The genome comprises 14 autosomes and a ZZ-ZW sex chromosome system. Assembly assessment identified 92.4% of the expected arthropod genes. Transcriptomics supported annotation and indicated a marked shift in gene expression after host attachment, including apparent downregulation of genes related to circadian rhythm coinciding with abandoning diurnal migration. The genome shows evolutionary signatures including loss of genes needed for peroxisome biogenesis, presence of numerous FNII domains, and an incomplete heme homeostasis pathway suggesting heme proteins to be obtained from the host. Despite repeated development of resistance against chemical treatments L. salmonis exhibits low numbers of many genes involved in detoxification.

Comparative and functional genomics of the ABC transporter superfamily across arthropods

BACKGROUND

The ATP-binding cassette (ABC) transporter superfamily is comprised predominantly of proteins which directly utilize energy from ATP to move molecules across the plasma membrane. Although they have been the subject of frequent investigation across many taxa, arthropod ABCs have been less well studied. While the manual annotation of ABC transporters has been performed in many arthropods, there has so far been no systematic comparison of the superfamily within this order using the increasing number of sequenced genomes. Furthermore, functional work on these genes is limited.

RESULTS

Here, we developed a standardized pipeline to annotate ABCs from predicted proteomes and used it to perform comparative genomics on ABC families across arthropod lineages. Using Kruskal-Wallis tests and the Computational Analysis of gene Family Evolution (CAFE), we were able to observe significant expansions of the ABC-B full transporters (P-glycoproteins) in Lepidoptera and the ABC-H transporters in Hemiptera. RNA-sequencing of epithelia tissues in the Lepidoptera Helicoverpa armigera showed that the 7 P-glycoprotein paralogues differ substantially in their tissue distribution, suggesting a spatial division of labor. It also seems that functional redundancy is a feature of these transporters as RNAi knockdown showed that most transporters are dispensable with the exception of the highly conserved gene Snu, which is probably due to its role in cuticular formation.

CONCLUSIONS

We have performed an annotation of the ABC superfamily across > 150 arthropod species for which good quality protein annotations exist. Our findings highlight specific expansions of ABC transporter families which suggest evolutionary adaptation. Future work will be able to use this analysis as a resource to provide a better understanding of the ABC superfamily in arthropods.

Effects of temperature, fungal infection and weight on intermoult duration and survival of starving earwig larvae

Moulting is a cornerstone of arthropods development. It can be determined by numerous factors such as body mass, temperature, and immunity. However, the effects of these factors can be dependent on each other, so that it is often difficult to predict whether and how they shape moulting, and whether their effects are additive or interactive. In this study, we addressed these questions by testing the effects of body mass, ambient temperature, fungal infection and their interaction on intermoult duration and survival in starved juveniles of the European earwig Forficula auricularia. We recorded the date of moult and death of a total of 207 earwig juveniles that were weighed, exposed to different doses of the entomopathogenic fungus Metarizium brunneum and then maintained at either 20 °C or 24 °C. Our results first reveal that juveniles moulted earlier when they were heavy compared to light on the day of exposure, as well as earlier when maintained at 24 °C compared to 20 °C. By contrast, pathogen exposure did not affect the moulting date. We also found that nymphs died faster when they were light compared to heavy on the day of exposure, when they were exposed to high (10⁶ and 10⁷ spores/ml) compared to low (10⁴, 10⁵ and 0 spores/ml) pathogen concentrations, and when they were maintained at 24 °C compared to 20 °C. We detected no sign of interaction between temperature, fungal infection and body mass on both moulting and survival. Overall, these findings shed light on the limited importance of infection on moulting in starved juveniles, and reveal that weight, temperature, and infection have additive effects on their survival. More generally, this study emphasizes that the three tested factors do not necessarily interact to shape key physiological processes in an insect.

Roles of three putative salmon louse (Lepeophtheirus salmonis) prostaglandin E2 synthases in physiology and host-parasite interactions

BACKGROUND

The salmon louse (Lepeophtheirus salmonis) is a parasite of salmonid fish. Atlantic salmon (Salmo salar) exhibit only a limited and ineffective immune response when infested with this parasite. Prostaglandins (PGs) have many biological functions in both invertebrates and vertebrates, one of which is the regulation of immune responses. This has led to the suggestion that prostaglandin E₂ (PGE₂) is important in the salmon louse host-parasite interaction, although studies of a salmon louse prostaglandin E₂ synthase (PGES) 2 gene have not enabled conformation of this hypothesis. The aim of the present study was, therefore, to characterize two additional PGES-like genes.

METHODS

Lepeophtheirus salmonis microsomal glutathione S-transferase 1 like (LsMGST1L) and LsPGES3L were investigated by sequencing, phylogenetics, transcript localization and expression studies. Moreover, the function of these putative PGES genes in addition to the previously identified LsPGES2 gene was analyzed in double stranded (ds) RNA-mediated knockdown (KD) salmon louse.

RESULTS

Analysis of the three putative LsPGES genes showed a rather constitutive transcript level throughout development from nauplius to the adult stages, and in a range of tissues, with the highest levels in the ovaries or gut. DsRNA-mediated KD of these transcripts did not produce any characteristic changes in phenotype, and KD animals displayed a normal reproductive output. The ability of the parasite to infect or modulate the immune response of the host fish was also not affected by KD.

CONCLUSIONS

Salmon louse prostaglandins may play endogenous roles in the management of reproduction and oxidative stress and may be a product of salmon louse blood digestions.

The influence of vector-borne disease on human history: socio-ecological mechanisms

Vector-borne diseases (VBDs) are embedded within complex socio-ecological systems. While research has traditionally focused on the direct effects of VBDs on human morbidity and mortality, it is increasingly clear that their impacts are much more pervasive. VBDs are dynamically linked to feedbacks between environmental conditions, vector ecology, disease burden, and societal responses that drive transmission. As a result, VBDs have had profound influence on human history. Mechanisms include: (1) killing or debilitating large numbers of people, with demographic and population-level impacts; (2) differentially affecting populations based on prior history of disease exposure, immunity, and resistance; (3) being weaponised to promote or justify hierarchies of power, colonialism, racism, classism and sexism; (4) catalysing changes in ideas, institutions, infrastructure, technologies and social practices in efforts to control disease outbreaks; and (5) changing human relationships with the land and environment. We use historical and archaeological evidence interpreted through an ecological lens to illustrate how VBDs have shaped society and culture, focusing on case studies from four pertinent VBDs: plague, malaria, yellow fever and trypanosomiasis. By comparing across diseases, time periods and geographies, we highlight the enormous scope and variety of mechanisms by which VBDs have influenced human history.

Accurate and sensitive detection of microbial eukaryotes from whole metagenome shotgun sequencing

BACKGROUND

Microbial eukaryotes are found alongside bacteria and archaea in natural microbial systems, including host-associated microbiomes. While microbial eukaryotes are critical to these communities, they are challenging to study with shotgun sequencing techniques and are therefore often excluded.

RESULTS

Here, we present EukDetect, a bioinformatics method to identify eukaryotes in shotgun metagenomic sequencing data. Our approach uses a database of 521,824 universal marker genes from 241 conserved gene families, which we curated from 3713 fungal, protist, non-vertebrate metazoan, and non-streptophyte archaeplastida genomes and transcriptomes. EukDetect has a broad taxonomic coverage of microbial eukaryotes, performs well on low-abundance and closely related species, and is resilient against bacterial contamination in eukaryotic genomes. Using EukDetect, we describe the spatial distribution of eukaryotes along the human gastrointestinal tract, showing that fungi and protists are present in the lumen and mucosa throughout the large intestine. We discover that there is a succession of eukaryotes that colonize the human gut during the first years of life, mirroring patterns of developmental succession observed in gut bacteria. By comparing DNA and RNA sequencing of paired samples from human stool, we find that many eukaryotes continue active transcription after passage through the gut, though some do not, suggesting they are dormant or nonviable. We analyze metagenomic data from the Baltic Sea and find that eukaryotes differ across locations and salinity gradients. Finally, we observe eukaryotes in Arabidopsis leaf samples, many of which are not identifiable from public protein databases.

CONCLUSIONS

EukDetect provides an automated and reliable way to characterize eukaryotes in shotgun sequencing datasets from diverse microbiomes. We demonstrate that it enables discoveries that would be missed or clouded by false positives with standard shotgun sequence analysis. EukDetect will greatly advance our understanding of how microbial eukaryotes contribute to microbiomes. Video abstract.

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.

Aboveground herbivores drive stronger plant species-specific feedback than belowground fungi to regulate tree community assembly

Ectomycorrhizal (EcM) tree species often become more dominant than arbuscular mycorrhizal (AM) tree species in temperate forests, but they generally coexist. Theory predicts that ecological feedback mediated by aboveground herbivory and/or belowground microbes could explain these dominance/coexistence patterns. An experimental test of how aboveground/belowground organisms associated with AM/EcM trees mediate ecological feedbacks has been lacking at the community-level. By establishing AM and EcM tree sapling assemblages in mesocosms and then introducing seedlings of each type in a reciprocal planting experiment, we compared seedling performance under varying sapling species (conspecifics, heterospecifics within the same and different mycorrhizal types), using traits that reflect either aboveground herbivory-mediated feedback or belowground fungal-mediated feedback or both. When examining seedling traits that reflect aboveground herbivory-mediated feedbacks (i.e., foliar damage), AM plants tended to experience less foliar damage and EcM plants more damage under conspecific versus heterospecific saplings within the same mycorrhizal types, and aboveground herbivory-mediated feedback was species-specific rather than mycorrhizal type-specific. Conversely, when examining traits that reflect belowground fungal-mediated feedbacks, both AM and EcM plant species often exhibited mycorrhizal type-specific feedbacks (e.g., greater aboveground biomass under the same versus different mycorrhizal-type saplings) rather than species-specific feedbacks. Furthermore, tree species affected by herbivory-mediated feedback were less affected by belowground feedback, indicating that the relative importance of the feedbacks varied among plant species. Analysis of plant-associated organisms verified that the feedback outcomes corresponded with species accumulation of belowground fungi (but not of aboveground herbivores). Thus, aboveground herbivores drive stronger plant species-specific feedback than belowground fungi to regulate temperate tree diversity.

Mechanisms underlying gut microbiota-host interactions in insects

Insects are the most diverse group of animals and colonize almost all environments on our planet. This diversity is reflected in the structure and function of the microbial communities inhabiting the insect digestive system. As in mammals, the gut microbiota of insects can have important symbiotic functions, complementing host nutrition, facilitating dietary breakdown or providing protection against pathogens. There is an increasing number of insect models that are experimentally tractable, facilitating mechanistic studies of gut microbiota-host interactions. In this Review, we will summarize recent findings that have advanced our understanding of the molecular mechanisms underlying the symbiosis between insects and their gut microbiota. We will open the article with a general introduction to the insect gut microbiota and then turn towards the discussion of particular mechanisms and molecular processes governing the colonization of the insect gut environment as well as the diverse beneficial roles mediated by the gut microbiota. The Review highlights that, although the gut microbiota of insects is an active field of research with implications for fundamental and applied science, we are still in an early stage of understanding molecular mechanisms. However, the expanding capability to culture microbiomes and to manipulate microbe-host interactions in insects promises new molecular insights from diverse symbioses.

Are arthropod communities in grassland ecosystems affected by the abundance of an invasive plant?

Invasive plants cause changes to native plant communities and nutrient cycling, and by doing so, may alter the amount and quality of habitat available for animals at multiple trophic levels, including arthropods. Arthropods are generally abundant, diverse, and contribute to energy flow and nutrient cycling and are, therefore, an important group to study as a way of determining the effects of changes to ecosystem functioning. Spotted knapweed (Centaurea stoebe L.), a perennial forb native to Eastern Europe, is considered one of the most ecologically harmful invasive species in Western North America. Here, we test if spotted knapweed alters plant community, ground litter and ground temperature, and arthropod functional group structure and biomass in grassland habitats in British Columbia, Canada. Pitfall traps, installed at 20 sites that differed in spotted knapweed density, were sorted into herbivores, omnivores, predators, detritivores, and parasites. Decreases in herbivore and detritivore biomass was associated with increasing spotted knapweed density. The first two coordinates of a Principle Coordinates Analysis explained a cumulative 60% of the variation, and herbivores were separated from predators on both axes. The results suggest that spotted knapweed density may affect arthropod functional groups through changes in plant community composition, and surface soil temperatures. The results suggest that in terms of relative abundance and biomass, increasing knapweed density had positive effects on some arthropod functional groups, neutral effects on others, and negative effects on others. Thus, not all arthropod functional groups responded equally to knapweed invasion, and knapweed invasion does not necessarily decrease arthropod functional group diversity.

A trace fossil made by a walking crayfish or crayfish-like arthropod from the Lower Jurassic Moenave Formation of southwestern Utah, USA

New invertebrate trace fossils from the Lower Jurassic Moenave Formation at the St. George Dinosaur Discovery Site at Johnson Farm (SGDS) continue to expand the ichnofauna at the site. A previously unstudied arthropod locomotory trace, SGDS 1290, comprises two widely spaced, thick, gently undulating paramedial impressions flanked externally by small, tapered to elongate tracks with a staggered to alternating arrangement. The specimen is not a variant of any existing ichnospecies, but bears a striking resemblance to modern, experimentally generated crayfish walking traces, suggesting a crayfish or crayfish-like maker for the fossil. Because of its uniqueness, we place it in a new ichnospecies, Siskemia eurypyge. It is the first fossil crayfish or crayfish-like locomotion trace ever recorded.

The Neurobiology of Ocean Change - insights from decapod crustaceans

The unprecedented rate of carbon dioxide accumulation in the atmosphere has led to increased warming, acidification and oxygen depletion in the world's oceans, with projected impacts also on ocean salinity. In this perspective article, we highlight potential impacts of these factors on neuronal responses in decapod crustaceans. Decapod crustaceans comprise more than 8,800 marine species which have colonized a wide range of habitats that are particularly affected by global ocean change, including estuarine, intertidal, and coastal areas. Many decapod species have large economic value and high ecological importance because of their global invasive potential and impact on local ecosystems. Global warming has already led to considerable changes in decapod species' behavior and habitat range. Relatively little is known about how the decapod nervous system, which is the ultimate driver of all behaviors, copes with environmental stressors. We use select examples to summarize current findings and evaluate the impact of current and expected environmental changes. While data indicate a surprising robustness against stressors like temperature and pH, we find that only a handful of species have been studied and long-term effects on neuronal activity remain mostly unknown. A further conclusion is that the combined effects of multiple stressors are understudied. We call for greater research efforts towards long-term effects on neuronal physiology and expansion of cross-species comparisons to address these issues.

From bioaccumulation to biodecumulation: Nickel movement from Odontarrhena lesbiaca (Brassicaceae) individuals into consumers

Hyperaccumulation describes plants' ability to take up high amounts of soil metals such as Ni and allocate them to aboveground tissues. Little is known, however, about the rate at which Ni is allocated to different plant parts, or about the consumers related to these parts, including their pollinator mutualists. In this study, we examine the interface between the serpentine endemic Ni-hyperaccumulator Odontarrhena lesbiaca and its consumers of different plant parts: leaves (consumers), floral parts (consumers and primitive pollinators), and floral rewards (true pollinators). The study was conducted at two serpentine areas on Lesvos, Greece. Over 13 rounds of sampling during the flowering period of O. lesbiaca in both areas we collected plant stems with flowers, consumers of different plant parts, and flower visitors. Collected animals were mainly insects and some spiders. Chemical analyses showed negligible Ni-concentration differences between the two areas. Among all plant parts, the lowest Ni concentration was found in pollen and the highest in leaves. Regarding animal dietary habits, folivores accumulated the highest Ni concentrations, therefore characterized as "high-Ni insects", while floral-reward consumers, both primary (bees) and secondary (Eristalis tenax, Pygopleurus spp., and wasps), bore low Ni loads. Ni-body load of predators that fed on animals that were passing by was also low. Among floral-reward consumers, short-range fliers (bees of the genera Andrena and Lasioglossum) accumulated higher Ni loads than long-range fliers (Apis mellifera, Bombus terrestris, Eristalis tenax). Solitary Andrena bees accumulated higher Ni concentration than eusocial honeybees (Apis mellifera) and bumblebees (Bombus terrestris); a group of Lasioglossum specimens encompassing both solitary and eusocial bees lay in between. Our results show that diet, foraging distance, and sociality are important factors for Ni transferred into consumers and mutualists, mostly insects that are directly associated with different plant parts of O. lesbiaca.

Coronavirus in cat flea: findings and questions regarding COVID-19

The coronavirus disease 19 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has affected millions of people worldwide. Recent evidence raised the question about the possibility that cats may be a domestic host for SARS-CoV-2 with unknown implications in disease dissemination. Based on the fact that the domestic cat flea, Ctenocephalides felis, are abundant ectoparasites infesting humans, companion animals and wildlife and that coronavirus-like agents have been identified in the ectoparasite tick vector, Ixodes uriae of seabirds, herein we considered the presence of coronaviruses in general and SARS-CoV-2 in particular in C. felis. We identified coronavirus-derived and cell receptor angiotensin-converting enzyme RNA/proteins in C. felis. Although current evidence suggests that pets are probably dead-end-hosts with small risk of transmission to humans, our results suggested that cat flea may act as biological and/or mechanical vectors of SARS-CoV. Although preliminary, these results indicate a possibility of ectoparasites acting as reservoirs and vectors of SARS-CoV and related beta-coronavirus although with little disease risk due to systemic transmission route, low viremia, virus attenuation or other unknown factors. These results support the need to further study the role of animal SARS-CoV-2 hosts and their ectoparasite vectors in COVID-19 disease spread.

Geriatric Invertebrates

Invertebrates are becoming more popular and, as collections age, clients may seek veterinary intervention where the welfare of the animal must be considered. This article covers aging in many invertebrate species but with a focus on species likely to be seen in general practice. Supportive care may be an option to prolong life, but euthanasia must be considered for invertebrates with age-related unmanageable conditions.

The interactions of Trichoderma at multiple trophic levels: inter-kingdom communication

Trichoderma spp. are universal saprotrophic fungi in terrestrial ecosystems, and as rhizosphere inhabitants, they mediate interactions with other soil microorganisms, plants, and arthropods at multiple trophic levels. In the rhizosphere, Trichoderma can reduce the abundance of phytopathogenic microorganisms, which involves the action of potent inhibitory molecules, such as gliovirin and siderophores, whereas endophytic associations between Trichoderma and the seeds and roots of host plants can result in enhanced plant growth and crop productivity, as well as the alleviation of abiotic stress. Such beneficial effects are mediated via the activation of endogenous mechanisms controlled by phytohormones such as auxins and abscisic acid, as well as by alterations in host plant metabolism. During either root colonization or in the absence of physical contact, Trichoderma can trigger early defense responses mediated by Ca²⁺ and reactive oxygen species, and subsequently stimulate plant immunity by enhancing resistance mechanisms regulated by the phytohormones salicylic acid, jasmonic acid, and ethylene. In addition, Trichoderma release volatile organic compounds and nitrogen or oxygen heterocyclic compounds that serve as signaling molecules, which have effects on plant growth, phytopathogen levels, herbivorous insects, and at the third trophic level, play roles in attracting the natural enemies (predators and parasitoids) of herbivores. In this paper, we review some of the most recent advances in our understanding of the environmental influences of Trichoderma spp., with particular emphasis on their multiple interactions at different trophic levels.

In Silico Identification of Chemicals Capable of Binding to the Ecdysone Receptor

The process of molting, known alternatively as ecdysis, is a feature integral in the life cycles of species across the arthropod phylum. Regulation occurs as a function of the interaction of ecdysteroid hormones with the arthropod nuclear ecdysone receptor-a process preceding the triggering of a series of downstream events constituting an endocrine signaling pathway highly conserved throughout environmentally prevalent insect, crustacean, and myriapod organisms. Inappropriate ecdysone receptor binding and activation forms the essential molecular initiating event within possible adverse outcome pathways relating abnormal molting to mortality in arthropods. Definition of the characteristics of chemicals liable to stimulate such activity has the potential to be of great utility in mitigation of hazards posed toward vulnerable species. Thus the aim of the present study was to develop a series of rule-sets, derived from the key structural and physicochemical features associated with identified ecdysone receptor ligands, enabling construction of Konstanz Information Miner (KNIME) workflows permitting the flagging of compounds predisposed to binding at the site. Data describing the activities of 555 distinct chemicals were recovered from a variety of assays across 10 insect species, allowing for formulation of KNIME screens for potential binding activity at the molecular initiating event and adverse outcome level of biological organization. Environ Toxicol Chem 2020;39:1438-1450. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

The hallmarks of GSK-3 in morphogenesis and embryonic development metabolism in arthropods

Several research groups around the world have studied diverse aspects of energy metabolism in arthropod disease vectors, with the aim of discovering potential control targets. As in all oviparous organisms, arthropod embryonic development is characterized by the mobilization of maternally-derived metabolites for the formation of new tissues and organs. Glycogen synthase kinase-3 (GSK-3) is a serine-threonine kinase described as an important regulator of metabolism and development in a wide range of organisms. GSK-3 was first identified based on its action upon glycogen synthase, a central enzyme in glycogen biosynthesis. Currently, it is recognized as a key component of multiple cellular processes such as glucose metabolism, apoptosis, cell proliferation, transcription, cell migration, and immune response. The present review will describe the current knowledge on GSK-3 activation and its role in morphogenesis and embryonic metabolism in arthropods. Altogether, the information discussed here can spark new approaches and strategies for further studies, enhancing our understanding of these important arthropod vectors and strengthening the resources in the search for novel control methods.

Consequences of HSF knockdown on gene expression during the heat shock response in Tigriopus californicus

Although the existence of a cellular heat shock response is nearly universal, its relationship to organismal thermal tolerance is not completely understood. Many of the genes involved are known to be regulated by the highly conserved heat shock transcription factor-1 (HSF-1), yet the regulatory network is not fully characterized. Here, we investigated the role of HSF-1 in gene expression following thermal stress using knockdown of HSF-1 by RNA interference in the intertidal copepod Tigriopus californicus We observed some evidence for decreased transcription of heat shock protein genes following knockdown, supporting the widely acknowledged role of HSF-1 in the heat shock response. However, the majority of differentially expressed genes between the control and HSF-1 knockdown groups were upregulated, suggesting that HSF-1 normally functions to repress their expression. Differential expression observed in genes related to chitin and cuticle formation lends support to previous findings that these processes are highly regulated following heat stress. We performed a genome scan and identified a set of 396 genes associated with canonical heat shock elements. RNA-seq data did not find those genes to be more highly represented in our HSF-1 knockdown treatment, indicating that requirements for binding and interaction of HSF-1 with a given gene are not simply predicted by the presence of HSF-1 binding sites. Further study of the pathways implicated by these results and future comparisons among populations of T. californicus may help us understand the role and importance of HSF-1 in the heat shock response and, more broadly, in organismal thermal tolerance.

Dataset on gene expressions affected by simultaneous knockdown of Hedgehog and Dpp signaling components in embryos of the spider Parasteatoda tepidariorum

Simultaneous, parental RNA interference (pRNAi) mediated knockdown of Hedgehog and Decapentaplegic (Dpp) signaling components, Pt-patched (Pt-ptc) and Pt-dpp, respectively, exhibited serious defects in the formation of the major embryonic axes in the model spider Parasteatoda tepidariorum. This paper describes a dataset of a custom oligonucleotide two-color microarray analysis that was carried out to compare the transcript expression levels between untreated (normal) and Pt-ptc + Pt-dpp double pRNAi embryos at late stage 5. Array spots that showed the intensity ratio of [Pt-ptc + Pt-dpp double pRNAi]/[normal] <0.6 were categorized as positive. The expressions of most, not all, of the transcripts related to the positive array spots were examined in embryos by whole-mount in situ hybridization. Some of the stained embryos showed distinct patterns of gene expression. The data presented may be useful for characterizing the mechanisms of embryonic patterning in spider embryos.

Elongation during segmentation shows axial variability, low mitotic rates, and synchronized cell cycle domains in the crustacean, Thamnocephalus platyurus

Background

Segmentation in arthropods typically occurs by sequential addition of segments from a posterior growth zone. However, the amount of tissue required for growth and the cell behaviors producing posterior elongation are sparsely documented.

Results

Using precisely staged larvae of the crustacean, Thamnocephalus platyurus, we systematically examine cell division patterns and morphometric changes associated with posterior elongation during segmentation. We show that cell division occurs during normal elongation but that cells in the growth zone need only divide ~ 1.5 times to meet growth estimates; correspondingly, direct measures of cell division in the growth zone are low. Morphometric measurements of the growth zone and of newly formed segments suggest tagma-specific features of segment generation. Using methods for detecting two different phases in the cell cycle, we show distinct domains of synchronized cells in the posterior trunk. Borders of cell cycle domains correlate with domains of segmental gene expression, suggesting an intimate link between segment generation and cell cycle regulation.

Conclusions

Emerging measures of cellular dynamics underlying posterior elongation already show a number of intriguing characteristics that may be widespread among sequentially segmenting arthropods and are likely a source of evolutionary variability. These characteristics include: the low rates of posterior mitosis, the apparently tight regulation of cell cycle at the growth zone/new segment border, and a correlation between changes in elongation and tagma boundaries.

Post-feeding behavior in crayfish (Procambarus clarkii): Description of an invertebrate behavioral satiety sequence

Previous studies have demonstrated that food consumption induces the behavioral satiety sequence (BSS) in some animals, a characteristic series of activities which include exploration, grooming, and resting. The BSS, while valuable in assessing the effects of drugs on food intake, has not been widely studied in non-mammalian species. Our experiment examined post-feeding behavior in crayfish using continuous recording of five behaviors: feeding, walking, grooming, leg wave, and quiescence. We found that food intake, but not sham feeding, significantly decreased feeding behavior, increased leg wave, and increased quiescence. Walking and grooming were not significantly altered by food intake. These findings indicate that post-feeding behaviors in crayfish share some characteristics with the mammalian BSS. Detailed descriptions of post-ingestive behavior in invertebrates may contribute to the development of drugs targeting feeding behaviors in medically and economically important species.

Microarray data on the comparison of transcript expression between normal and Pt-Delta RNAi embryos in the common house spider Parasteatoda tepidariorum

We conducted a custom microarray experiment to detect the differences in the transcript expression levels between untreated (normal) and Pt-Delta-RNAi embryos at late stage 6 in the common house spider Parasteatoda tepidariorum. The array probes were designed based on accumulated EST and cDNA sequences. The microarray dataset has been deposited in the Gene Expression Omnibus (GEO) Database at the National Center for Biotechnology Information (NCBI) under the accession GSE113064. The expression of the transcripts selected based on the detected differences was examined in embryos by whole-mount in situ hybridization.

Acaricidal efficacy of Calotropis procera (Asclepiadaceae) and Taraxacum officinale (Asteraceae) against Rhipicephalus microplus from Mardan, Pakistan

Medicinal plants are used by traditional folk healers, modern physicians, and veterinarians as an alternative to conventional drugs to treat a wide range of disorders including parasitic diseases. Some compounds from these plants have been shown to have acaricidal activity and repel arthropods. The cattle tick Rhipicephalus microplus is one of the most destructive pests to the livestock industry in tropical and subtropical parts of the world. The potential to develop herbal acaricides to control R. microplus infestations is critical in maintaining cattle herd productivity, reducing economic losses, and curtailing the overuse of synthetic chemical acaricides. Calotropis procera, the apple of Sodom, and Taraxacum officinale, the common dandelion, were evaluated for acaricidal activity against R. microplus larvae and adults in vitro. Both plant species tested are common indigenous species of Pakistan where R. microplus infestations are widespread across livestock species including cattle, sheep, and goats. Whole-plant extracts derived from C. procera and T. officinale significantly reduced the index of egg laying (P < 0.01) and increased the percent inhibition of oviposition of adult female ticks at a concentration of 40 mg/mL when assessed by the adult immersion test (AIT). Calotropis procera and T. officinale treatments at the same concentration also resulted in larval mortality of 96.0% ± 0.57 and 96.7% ± 0.88, respectively, as measured using the larval packet test (LPT). An increasing range of extract concentrations was tested to determine the LD₅₀ and LD₉₀ for C. procera, 3.21 and 21.15 mg/mL, respectively, and T. officinale, 4.04 and 18.92 mg/mL, respectively. These results indicate that further studies are warranted to determine the relative contribution of individual phytochemicals from whole-plant extracts on acaricidal activity. This information will guide the design of further acaricidal efficacy tests using livestock infested with R. microplus.

Exoskeleton Repair in Invertebrates

This article focuses on exoskeleton repair in invertebrates presented due to physical trauma with impairment of the integument and often with hemolymph loss. Invertebrates, especially the larger-bodied arthropods, can severely damage their exoskeleton if dropped or if they are handled during ecdysis. Clinicians are encouraged to familiarize themselves with the basic first-aid techniques for invertebrate exoskeleton repair. With simple techniques and using items found in most homes, clients can be guided through basic first-aid procedures to prevent fatalities from hemolymph loss until the animal can be properly attended by a clinician.

The Natural History of Teneurins: A Billion Years of Evolution in Three Key Steps

The entire evolutionary history of the animal gene family, Teneurin, can be summed up in three key steps, plus three salient footnotes. In a shared ancestor of all bilaterians, the first step began with gene fusions that created a protein with an amino-terminal intracellular domain bridged via a single transmembrane helix to extracellular EGF-like domains. This first step was completed with a further gene fusion: an additional carboxy-terminal stretch of about 2000 amino acids (aa) was adopted, as-a-whole, from bacteria. The 2000 aa structure in Teneurin was recently solved in three dimensions. The 2000 aa region appears in a number of bacteria, yet was co-opted solely into Teneurin, and into no other eukaryotic proteins. Outside of bilaterian animals, no Teneurins exist, with a “Monosiga brevicollis caveat” brought below, as ‘the third footnote.” Subsequent to the “urTeneurin’s” genesis-by-fusions, all bilaterians bore a single Teneurin gene, always encoding an extraordinarily conserved Type II transmembrane protein with invariant domain content and order. The second key step was a duplication that led to an exception to singleton Teneurin genomes. A pair of Teneurin paralogs, Ten-a and Ten-m, are found in representatives of all four Arthropod sub-phyla, in: insects, crustaceans, myriapods, and chelicerates. In contrast, in every other protostome species’ genome, including those of all non-Arthropod ecdysozoan phyla, only a single Teneurin gene occurs. The closest, sister, phylum of arthropods, the Onychophorans (velvet worms), bear a singleton Teneurin. Ten-a and Ten-m therefore arose from a duplication in an urArthropod only after Arthropods split from Onychophorans, but before the splits that led to the four Arthropod sub-phyla. The third key step was a quadruplication of Teneurins at the root of vertebrate radiation. Four Teneurin paralogs (Teneurins 1 through 4) arose first by a duplication of a single chordate gene likely leading to one 1/4–type gene, and one 2/3-type gene: the two copies found in extant jawless vertebrates. Relatively soon thereafter, a second duplication round yielded the -1, -2, -3, and -4 paralog types now found in all jawed vertebrates, from sharks to humans. It is possible to assert that these duplication events correlate well to the Ohno hypothesized 2R (two round) vertebrate whole genome duplication (WGD), as refined in more recent treatments. The quadruplication can therefore be placed at approximately 400 Myr ago. Echinoderms, hemichordates, cephalochordates, and urochordates have only a single copy of Teneurin in their genomes. These deuterostomes and non-vertebrate chordates provide the anchor showing that the quadruplication happened at the root of vertebrates. A first footnote must be brought concerning some of the ‘invertebrate’ relatives of vertebrates, among Deuterostomes. A family of genes that encode 7000 aa proteins was derived from, but is distinct from, the Teneurin family. This distinct family arose early in deuterostomes, yet persists today only in hemichordate and cephalochordate genomes. They are named here TRIPs (Teneurin-related immense proteins). As a second of three ‘footnotes’: a limited number of species exist with additional Teneurin gene copies. However, these further duplications of Teneurins occur for paralog types (a, m, or 1–4) only in specific lineages within Arthropods or Vertebrates. All examples are paralog duplications that evidently arose in association with lineage specific WGDs. The increased Teneurin paralog numbers correlate with WGDs known and published in bony fish, Xenopus, plus select Chelicerates lineages and Crustaceans. The third footnote, alluded to above, is that a Teneurin occurs in one unicellular species: Monosiga brevicollis. Teneurins are solely a metazoan, bilaterian-specific family, to the exclusion of the Kingdoms of prokaryotes, plants, fungi, and protists. The single exception occurs among the unicellular, opisthokont, closest relatives of metazoans, the choanoflagellates. There is a Teneurin in Monosiga brevicollis, one species of the two fully sequenced choanoflagellate species. In contrast, outside of triploblast-bilaterians, there are no Teneurins in any diploblast genomes, including even sponges – those metazoans closest to choanoflagellates. Perhaps the ‘birth’ of the original Teneurin occurred in a shared ancestor of M. brevicollis and metazoans, then was lost in M. brevicollis’ sister species, and was serially and repeatedly lost in all diploblast metazoans. Alternatively, and as favored above, it first arose in the ‘urBilaterian,’ then was subsequently acquired from some bilaterian via horizontal transfer by a single choanoflagellate clade. The functional partnership of Teneurins and Latrophilins was discovered in rodents through the LPH1-TENM2 interaction. Recent work extends this to further members of each family. Surveying when the interacting domains of Teneurins and Latrophilins co-exist within different organisms can give an indication of how widespread their functional cooperation might be, across bilaterians. Paralog number for the two families is relatively correlated among bilaterians, and paralog numbers underwent co-increase in the WGDs mentioned above. With co-increasing paralog numbers, the possible combinatorial pairs grow factorially. This should have a significant impact for increasing nervous system complexity. The 3 key events in the ‘natural history’ of the Teneurins and their Latrophilin partners coincide with the ascendance of particularly successful metazoan clades: bilaterians; arthropods; and vertebrates. Perhaps we can attribute some of this success to the unique Teneurin family, and to its partnership with Latrophilins.

Occurrence and predictive utility of isochronal, equiproportional, and other types of development among arthropods

In isochronal (ICD) and equiproportional development (EPD), the proportion of total immature (egg, larval, and/or juvenile) development spent in each stage (developmental proportion) does not vary among stages or temperatures, respectively. ICD and EPD have mainly been reported in copepods, and whether they occur in other arthropods is not known. If they did, then rearing studies could be simplified because the durations of later developmental stages could be predicted based on those of earlier ones. The goal of this study was to test whether different taxa have ICD, EPD, or an alternative development type in which stage-specific proportions depend on temperature, termed 'variable proportional' development (VPD), and also how well each development type allowed later-stage durations to be predicted from earlier ones. Data for 71 arthropods (arachnids, copepod and decapod crustaceans, and insects) were tested, and most (85.9%) species were concluded to have VPD, meaning that ICD and EPD do not occur generally. However, EPD predicted later-stage durations comparably well to VPD (within 19-23%), and thus may still be useful. Interestingly, some species showed a 'mixed' form of development, where some stages' developmental proportions varied with temperature while those of others did not, which should be further investigated.

The distribution of important sero-complexes of flaviviruses in Malaysia

Flaviviruses (FVs) are arthropod-borne viruses of medical and veterinary importance. Numerous species of FVs have been isolated from various host; mainly humans, animals, ticks, and mosquitoes. Certain FVs are extremely host-specific; at the same time, some FVs can infect an extensive range of species. Based on published literatures, 11 species of FVs have been detected from diverse host species in Malaysia. In humans, dengue virus and Japanese encephalitis virus have been reported since 1901 and 1942. In animals, the Batu Cave virus, Sitiawan virus, Carey Island, Tembusu virus, Duck Tembusu virus, and Japanese encephalitis viruses were isolated from various species. In mosquitoes, Japanese encephalitis virus and Kunjin virus were isolated from Culex spp., while Zika virus and Jugra virus were isolated from Aedes spp. In ticks, the Langat virus was isolated from Ixodes spp. One of the major challenges in the diagnosis of FVs is the presence of sero-complexes as a result of cross-reactivity with one or more FV species. Subsequently, the distribution of specific FVs among humans and animals in a specific population is problematic to assess and often require comprehensive and thorough analyses. Molecular assays such as quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) and digital droplet RT-PCR (ddRT-PCR) have been used for the differentiation of flavivirus infections to increase the accuracy of epidemiological data for disease surveillance, monitoring, and control. In situations where sero-complexes are common in FVs, even sensitive assays such as qRT-pCR can produce false positive results. In this write up, an overview of the various FV sero-complexes reported in Malaysia to date and the challenges faced in diagnosis of FV infections are presented.

Age-related responses to injury and repair in insect cuticle

We evaluated the ability of female adult desert locusts (Schistocerca gregaria) to repair injuries to their exoskeletons and restore mechanical strength over the course of their natural life. We discovered that younger insects are more capable of repairing injuries, displaying no significant decreases in failure strength, stiffness or bending moment to failure after 3 weeks of repair. Older insects, in contrast, were only capable of repairing to ∼70% of their original strength. Both older and younger insects carry out targeted deposition to repair injuries. We also examined different mechanisms of failure, and we discovered that the cuticle of older insects is more susceptible to crack growth due to a large decrease in fracture toughness with age, making them more sensitive to scalpel cuts and punctures. The biological mechanisms that drive these changes are still under investigation.