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Background: Tick-borne encephalitis (TBE) is a severe human neuroinfection caused by TBE virus (TBEV). TBEV is transmitted by tick bites and by the consumption of unpasteurized dairy products from infected asymptomatic ruminants. In France, several food-borne transmission events have been reported since 2020, raising the question of the level of exposure of domestic ungulates to TBEV. In this study, our objectives were (i) to estimate TBEV seroprevalence and quantify antibodies titres in cattle in the historical endemic area of TBEV in France using the micro virus neutralisation test (MNT) and (ii) to compare the performance of two veterinary cELISA kits with MNT for detecting anti-TBEV antibodies in cattle in various epidemiological contexts. A total of 344 cattle sera from four grid cells of 100 km² in Alsace-Lorraine (endemic region) and 84 from western France, assumed to be TBEV-free, were investigated. Results: In Alsace-Lorraine, cattle were exposed to the virus with an overall estimated seroprevalence of 57.6% (95% CI: 52.1–62.8%, n = 344), varying locally from 29.9% (95% CI: 21.0–40.0%) to 92.1% (95% CI: 84.5–96.8%). Seroprevalence did not increase with age, with one- to three-year-old cattle being as highly exposed as older ones, suggesting a short-life duration of antibodies. The proportion of sera with MNT titres lower than 1:40 per grid cell decreased with increased seroprevalence. Both cELISA kits showed high specificity (> 90%) and low sensitivity (less than 78.1%) compared with MNT. Sensitivity was lower for sera with neutralising antibodies titres below 1:40, suggesting that sensitivity of these tests varied with local virus circulation intensity. Conclusions: Our results highlight that cattle were highly exposed to TBEV. Screening strategy and serological tests should be carefully chosen according to the purpose of the serological study and with regard to the limitations of each method. [ABSTRACT FROM AUTHOR]

Division of labour through the formation of morphologically and functionally distinct castes is a recurring theme in the evolution of animal sociality. The mechanisms driving the differentiation of individuals into distinct castes remain poorly understood, especially for animals forming clonal colonies. We test the association between microbiomes and caste formation within the social trematode Philophthalmus attenuatus, using a metabarcoding approach targeting the bacterial 16S SSU rRNA gene. Clonal colonies of this trematode within snail hosts comprise large reproductive individuals which produce dispersal stages, and small, non‐reproducing soldiers which defend the colony against invaders. In colonies extracted directly from field‐collected snails, reproductives harboured more diverse bacterial communities than soldiers, and reproductives and soldiers harboured distinct bacterial communities, at all taxonomic levels considered. No single bacterial taxon showed high enough prevalence in either soldiers or reproductives to be singled out as a key driver, indicating that the whole microbial community contributes to these differences. Other colonies were experimentally exposed to antibiotics to alter their bacterial communities, and sampled shortly after treatment and weeks later after allowing for turnover of colony members. At those time points, bacterial communities of the two castes still differed across all antibiotic treatments; however, the caste ratio within colonies changed: after antibiotic disruption and turnover of individuals, new individuals were more likely to become reproductives than in undisturbed control colonies. Our results reveal that each caste has a distinct microbiome; whether the social context affects the microbiota, or whether microbes contribute to modulating the phenotype of individuals, remains to be determined. [ABSTRACT FROM AUTHOR]

Gilthead seabream represents a species of importance in Mediterranean aquaculture. The larval stage is particularly sensitive and frequently impacted in suboptimal environmental or sanitary conditions. In the present study, investigations were carried out in a seabream hatchery following an unusual mortality reaching 70% among 50‐day post‐hatching. Anorexia, loss of appetite and abnormal swimming behaviour were observed in absence of parasites or pathogenic bacteria. Proliferation of rod‐shaped bacteria in the gut lumen was associated with focal degeneration in the intestinal mucosa. Cytopathic effects on an EK‐1 cell line after 21 days of culture at 14°C and 20°C in contact with homogenized affected larvae revealed the presence of a viral agent. Molecular characterization by high‐throughput sequencing showed a typical picornavirus genome organization with a polyprotein precursor of 2276 amino acids sharing 46.3% identity with that of the Eel Picornavirus‐1. A specific real‐time PCR confirmed the presence of the viral genome in affected larval homogenate and corresponding cell culture supernatant. We propose the name Potamipivirus daurada for this novel species within the genus Potamipivirus. The etiological role of this virus remains uncertain at this time, and future studies will be necessary to investigate its prevalence in natural and aquaculture‐reared populations as well as its ability to cause diseases in gilthead seabream. [ABSTRACT FROM AUTHOR]

Technical advances in metagenomics and metatranscriptomics have dramatically accelerated virus discovery in recent years. "Chuviruses" were first described in 2015 as obscure negative-sense RNA viruses of diverse arthropods. Although "chuviruses" first appeared to be members of the negarnaviricot order Mononegavirales in phylogenetic analyses using RNA-directed RNA polymerase sequences, further characterization revealed unusual gene orders in genomes that are nonsegmented, segmented, and/or possibly circular. Consequently, a separate order, Jingchuvirales, was established to include a monospecific family, Chuviridae. Recently, it has become apparent that jingchuvirals are broadly distributed and are therefore likely of ecological and economic importance. Here, we describe recent and ongoing efforts to create the necessary taxonomic framework to accommodate the expected flood of novel viruses belonging to the order. [ABSTRACT FROM AUTHOR]

A growing literature demonstrates the impact of helminths on their host gut microbiome. We investigated whether the stickleback host microbiome depends on ecoevolutionary variables by testing the impact of exposure to the cestode parasite Schistocephalus solidus with respect to infection success, host genotype, parasite genotype, and parasite microbiome composition. We observed constitutive differences in the microbiome of sticklebacks of different origin, and those differences increased when sticklebacks exposed to the parasite resisted infection. In contrast, the microbiome of successfully infected sticklebacks varied with parasite genotype. More specifically, we revealed that the association between microbiome and immune gene expression increased in infected individuals and varied with parasite genotype. In addition, we showed that S. solidus hosts a complex endomicrobiome and that bacterial abundance in the parasite correlates with expression of host immune genes. Within this comprehensive analysis we demonstrated that (i) parasites contribute to modulating the host microbiome through both successful and unsuccessful infection, (ii) when infection is successful, the host microbiome varies with parasite genotype due to genotype‐dependent variation in parasite immunomodulation, and (iii) the parasite‐associated microbiome is distinct from its host and impacts the host immune response to infection. [ABSTRACT FROM AUTHOR]

Epidemiological traits of host–parasite associations depend on the effects of the host, the parasite and their interaction. Parasites evolve mechanisms to infect and exploit their hosts, whereas hosts evolve mechanisms to prevent infection and limit detrimental effects. The reasons why and how these traits differ across populations still remain unclear. Using experimental cross-infection of three-spined stickleback Gasterosteus aculeatus and their species-specific cestode parasites Schistocephalus solidus from Alaskan and European populations, we disentangled host, parasite and interaction effects on epidemiological traits at different geographical scales. We hypothesized that host and parasite main effects would dominate both within and across continents, although interaction effects would show geographical variation of natural selection within and across continents. We found that mechanisms preventing infection (qualitative resistance) occurred only in a combination of hosts and parasites from different continents, while mechanisms limiting parasite burden (quantitative resistance) and reducing detrimental effects of infection (tolerance) were host-population specific. We conclude that evolution favours distinct defence mechanisms on different geographical scales and that it is important to distinguish concepts of qualitative resistance, quantitative resistance and tolerance in studies of macroparasite infections. [ABSTRACT FROM AUTHOR]

Abstract Background Research using the Pacific oyster Crassostrea gigas as a model organism has experienced rapid growth in recent years due to the development of high-throughput molecular technologies. As many as 56,268 EST sequences have been sequenced to date, representing a genome-wide resource that can be used for transcriptomic investigations. Results In this paper, we developed a Pacific oyster microarray containing oligonucleotides representing 31,918 transcribed sequences selected from the publicly accessible GigasDatabase. This newly designed microarray was used to study the transcriptome of male and female gonads, mantle, gills, posterior adductor muscle, visceral ganglia, hemocytes, labial palps and digestive gland. Statistical analyses identified genes differentially expressed among tissues and clusters of tissue-enriched genes. These genes reflect major tissue-specific functions at the molecular level, such as tissue formation in the mantle, filtering in the gills and labial palps, and reproduction in the gonads. Hierarchical clustering predicted the involvement of unannotated genes in specific functional pathways such as the insulin/NPY pathway, an important pathway under study in our model species. Microarray data also accurately identified reference genes whose mRNA level appeared stable across all the analyzed tissues. Adp-ribosylation factor 1 (arf1) appeared to be the most robust reference for normalizing gene expression data across different tissues and is therefore proposed as a relevant reference gene for further gene expression analysis in the Pacific oyster. Conclusions This study provides a new transcriptomic tool for studies of oyster biology, which will help in the annotation of its genome and which identifies candidate reference genes for gene expression analysis.

Strong and ongoing artificial selection in domestic animals has resulted in amazing phenotypic responses that benefit humans, but often at a cost to an animal's health, and problems related to inbreeding depression, including a higher incidence of cancer. Despite high rates of cancer in domesticated species, little attention has been devoted to exploring the hypothesis that persistent artificial selection may also favour the evolution of compensatory anticancer defences. Indeed, there is evidence for effective anti‐cancer defences found in several domesticated species associated with different cancer types. We also suggest that artificial selection can favour the "domestication" of inherited oncogenic mutations in rare instances, retaining those associated to late and/or less aggressive cancers, and that by studying these seemingly rare anticancer adaptations, novel cancer treatments may be found. [ABSTRACT FROM AUTHOR]

Animal microbiomes influence their development, behavior and interactions with other organisms. Parasitic metazoans also harbor microbial communities; although they are likely to modulate host–parasite interactions, little is known about parasite microbiomes. The persistence of microbial communities throughout the life of a parasite is particularly challenging for helminths with complex life cycles. These parasites undergo major morphological changes during their life, and parasitize host species that are immunologically, physiologically, and phylogenetically very different. Here, using 16S amplicon sequencing, we characterize the microbiome of the trematode Coitocaecum parvum across four of its life stages: sporocysts, metacercariae and adults inhabiting (respectively) snails, crustaceans and fish, as well as free-living cercariae. Our results demonstrate that, at each life stage, the parasite possesses a phylogenetically diverse microbiome, distinct from that of its hosts or the external environment. The parasite's microbiome comprises bacterial taxa specific to each life stage in different hosts, as well as a small core set of taxa that persists across the parasite's whole life. The apparent existence of an ontogenetically and vertically transmitted core microbiome is supported by the findings that the diversity and taxonomic composition of the microbiome does not vary significantly among life stages, and that the main source of microbial taxa at any life stage is the previous life stage. Our results suggest that microbes are an integrated component of the trematode, possibly shaping its phenotype and host–parasite interactions. [ABSTRACT FROM AUTHOR]

In order to gain an evolutionary perspective on host-parasite-microbe interactions, evolutionary studies encompassing microbes across host and parasite species are necessary to identify patterns of cospeciation and speciation following host shifts. With appropriate experimental systems, geographic variations affecting the role of microbes in host-parasite interactions can be assessed by using a complete cross-experimental design, in which hosts from different localities are infected with parasites from their corresponding localities in the presence of either microbes isolated from the same localities or microbes from different test localities. Finally, when possible, experimental evolution of parasites and hosts in the presence or absence of the identified microbes can been used to test the effect of specific microbes on the evolution of the system and to identify mechanisms involved in parasite-microbe interaction. Phase one will compile information on previously characterized parasite-associated microbes and parasite-microbe interactions (already partially reviewed in [[15]-[16], [53]]), mine genomic and transcriptomic databases to detect microbial sequences, and characterize the complete microbiome of a set of parasites representing diverse taxa and environments. [Extracted from the article]

The article offers information on the natural selection act on parasites to compromise barriers to cancer risks. Topics discussed the factors that disrupt the cellular barriers to cancer as cell-cycle arrest, apoptosis, repression of telomerase, and cell adhesion; highlights high prevalence of microbes with oncogenic potential and focuses that parasites can modulate the oncogenicity of host-associated microbes.

The complete genome sequence of an RNA virus was assembled from RNA sequencing of virus particles purified from threespine stickleback intestine tissue samples. This new virus is most closely related to the Eel Picornavirus and can be assigned to the genus Potamipivirus in the family Picornaviridae. Its unique genetic properties are enough to establish a new species, dubbed the Threespine Stickleback Picornavirus (TSPV). Due to their broad geographic distribution throughout the northern hemisphere and parallel adaptation to freshwater, threespine sticklebacks have become a model in evolutionary ecology. Further analysis using diagnostic PCRs revealed that TSPV is highly prevalent in both anadromous and freshwater populations of threespine sticklebacks, infects almost all fish tissues and is transmitted vertically to offspring obtained from in vitro fertilization in laboratory settings. Finally, TSPV was found in Sequence Read Archives of transcriptome of G. aculeatus further demonstrating its wide distribution and unsought prevalence in samples. It is thus necessary to test the impact of TSPV on the biology of threespine sticklebacks as this widespread virus could interfere with the behavioral, physiological, or immunological studies that employ this fish as model system. [ABSTRACT FROM AUTHOR]

Selective pressures between hosts and their parasites can result in reciprocal evolution or adaptation of specific life history traits. Local adaptation of resident hosts and parasites should lead to increase parasite infectivity/virulence (higher compatibility) when infecting hosts from the same location (in sympatry) than from a foreign location (in allopatry). Analysis of geographic variations in compatibility phenotypes is the most common proxy used to infer local adaptation. However, in some cases, allopatric host-parasite systems demonstrate similar or greater compatibility than in sympatry. In such cases, the potential for local adaptation remains unclear. Here, we study the interaction between Schistosoma and its vector snail Biomphalaria in which such discrepancy in local versus foreign compatibility phenotype has been reported. Herein, we aim at bridging this gap of knowledge by comparing life history traits (immune cellular response, host mortality, and parasite growth) and molecular responses in highly compatible sympatric and allopatric Schistosoma/Biomphalaria interactions originating from different geographic localities (Brazil, Venezuela and Burundi). We found that despite displaying similar prevalence phenotypes, sympatric schistosomes triggered a rapid immune suppression (dual-RNAseq analyses) in the snails within 24h post infection, whereas infection by allopatric schistosomes (regardless of the species) was associated with immune cell proliferation and triggered a non-specific generalized immune response after 96h. We observed that, sympatric schistosomes grow more rapidly. Finally, we identify miRNAs differentially expressed by Schistosoma mansoni that target host immune genes and could be responsible for hijacking the host immune response during the sympatric interaction. We show that despite having similar prevalence phenotypes, sympatric and allopatric snail-Schistosoma interactions displayed strong differences in their immunobiological molecular dialogue. Understanding the mechanisms allowing parasites to adapt rapidly and efficiently to new hosts is critical to control disease emergence and risks of Schistosomiasis outbreaks. [ABSTRACT FROM AUTHOR]

Until recently, parasitic infections have been primarily studied as interactions between the parasite and the host, leaving out crucial players: microbes. The recent realization that microbes play key roles in the biology of all living organisms is not only challenging our understanding of host-parasite evolution, but it also provides new clues to develop new therapies and remediation strategies. In this paper we provide a review of promising and advanced experimental organismal systems to examine the dynamic of hostparasite-microbe interactions. We address the benefits of developing new experimental models appropriate to this new research area and identify systems that offer the best promises considering the nature of the interactions among hosts, parasites, and microbes. Based on these systems, we identify key criteria for selecting experimental models to elucidate the fundamental principles of these complex webs of interactions. It appears that no model is ideal and that complementary studies should be performed on different systems in order to understand the driving roles of microbes in host and parasite evolution. [ABSTRACT FROM AUTHOR]

Discoveries made over the past ten years have provided evidence that invertebrate antiparasitic responses may be primed in a sustainable manner, leading to the failure of a secondary encounter with the same pathogen. This phenomenon called “immune priming” or "innate immune memory" was mainly phenomenological. The demonstration of this process remains to be obtained and the underlying mechanisms remain to be discovered and exhaustively tested with rigorous functional and molecular methods, to eliminate all alternative explanations. In order to achieve this ambitious aim, the present study focuses on the Lophotrochozoan snail, Biomphalaria glabrata, in which innate immune memory was recently reported. We provide herein the first evidence that a shift from a cellular immune response (encapsulation) to a humoral immune response (biomphalysin) occurs during the development of innate memory. The molecular characterisation of this process in Biomphalaria/Schistosoma system was undertaken to reconcile mechanisms with phenomena, opening the way to a better comprehension of innate immune memory in invertebrates. This prompted us to revisit the artificial dichotomy between innate and memory immunity in invertebrate systems. [ABSTRACT FROM AUTHOR]

Vibrio harveyi is a marine bacterial pathogen responsible for episodic abalone mortalities in France, Japan and Australia. In the European abalone, V. harveyi invades the circulatory system in a few hours after exposure and is lethal after 2 days of infection. In this study, we investigated the responses of European abalone immune cells over the first 24 h of infection . Results revealed an initial induction of immune gene expression including Rel/NF-kB, Mpeg and Clathrin. It is rapidly followed by a significant immuno-suppression characterized by reduced cellular hemocyte parameters, immune response gene expressions and enzymatic activities. Interestingly, Ferritin was overexpressed after 24 h of infection suggesting that abalone attempt to counter V. harveyi infection using soluble effectors. Immune function alteration was positively correlated with V. harveyi concentration. This study provides the evidence that V. harveyi has a hemolytic activity and an immuno-suppressive effect in the European abalone. [ABSTRACT FROM AUTHOR]

Understanding parasite strategies for evasion, manipulation or exploitation of hosts is crucial for many fields, from ecology to medical sciences. Generally, research has focused on either the host response to parasitic infection, or the parasite virulence mechanisms. More recently, integrated studies of host–parasite interactions have allowed significant advances in theoretical and applied biology. However, these studies still provide a simplistic view of these as mere two-player interactions. Host and parasite are associated with a myriad of microorganisms that could benefit from the improved fitness of their partner. Illustrations of such complex multi-player interactions have emerged recently from studies performed in various taxa. In this conceptual article, we propose how these associated microorganisms may participate in the phenotypic alterations induced by parasites and hence in host–parasite interactions, from an ecological and evolutionary perspective. Host- and parasite-associated microorganisms may participate in the host–parasite interaction by interacting directly or indirectly with the other partner. As a result, parasites may develop (i) the disruptive strategy in which the parasite alters the host microbiota to its advantage, and (ii) the biological weapon strategy where the parasite-associated microorganism contributes to or modulates the parasite’s virulence. Some phenotypic alterations induced by parasite may also arise from conflicts of interests between the host or parasite and its associated microorganism. For each situation, we review the literature and propose new directions for future research. Specifically, investigating the role of host- and parasite-associated microorganisms in host–parasite interactions at the individual, local and regional level will lead to a holistic understanding of how the co-evolution of the different partners influences how the other ones respond, both ecologically and evolutionary. The conceptual framework we propose here is important and relevant to understand the proximate basis of parasite strategies, to predict their evolutionary dynamics and potentially to prevent therapeutic failures. [ABSTRACT FROM AUTHOR]

Background: Triploidy can occur in many animal species but is often lethal. Among invertebrates, amphibians and fishes, triploids are viable although often sterile or infertile. Most triploids of the Pacific oyster Crassostrea gigas are almost sterile (named “3nβ”) yet a low but significant proportion show an advanced gametogenesis (named “3nα”). These oysters thus constitute an interesting model to study the effect of triploidy on germ cell development. We used microarrays to compare the gonad transcriptomes of diploid 2n and the abovementioned triploid 3nβ and 3nα male and female oysters throughout gametogenesis. Results: All triploids displayed an upregulation of genes related to DNA repair and apoptosis and a downregulation of genes associated with cell division. The comparison of 3nα and 3nβ transcriptomes with 2n revealed the likely involvement of a cell cycle checkpoint during mitosis in the successful but delayed development of gonads in 3nα individuals. In contrast, a disruption of sex differentiation mechanisms may explain the sterility of 3nβ individuals with 3nβ females expressing male-specific genes and 3nβ males expressing female-specific genes. Conclusions: The disruption of sex differentiation and mitosis may be responsible for the impaired gametogenesis of triploid Pacific oysters. The function of the numerous candidate genes identified in our study should now be studied in detail in order to elucidate their role in sex determination, mitosis/meiosis control, pachytene cell cycle checkpoint, and the control of DNA repair/apoptosis. [ABSTRACT FROM AUTHOR]

Global change and its associated temperature increase has directly or indirectly changed the distributions of hosts and pathogens, and has affected host immunity, pathogen virulence and growth rates. This has resulted in increased disease in natural plant and animal populations worldwide, including scleractinian corals. While the effects of temperature increase on immunity and pathogen virulence have been clearly identified, their interaction, synergy and relative weight during pathogenesis remain poorly documented. We investigated these phenomena in the interaction between the coral Pocillopora damicornis and the bacterium Vibrio coralliilyticus, for which the infection process is temperature-dependent. We developed an experimental model that enabled unraveling the effects of thermal stress, and virulence vs. non-virulence of the bacterium. The physiological impacts of various treatments were quantified at the transcriptome level using a combination of RNA sequencing and targeted approaches. The results showed that thermal stress triggered a general weakening of the coral, making it more prone to infection, non-virulent bacterium induced an ‘efficient’ immune response, whereas virulent bacterium caused immuno-suppression in its host. [ABSTRACT FROM AUTHOR]

Since the preindustrial era, the average surface ocean pH has declined by 0.1 pH units and is predicted to decline by an additional 0.3 units by the year 2100. Although subtle, this decreasing pH has profound effects on the seawater saturation state of carbonate minerals and is thus predicted to impact on calcifying organisms. Among these are the scleractinian corals, which are the main builders of tropical coral reefs. Several recent studies have evaluated the physiological impact of low pH, particularly in relation to coral growth and calcification. However, very few studies have focused on the impact of low pH at the global molecular level. In this context we investigated global transcriptomic modifications in a scleractinian coral (Pocillopora damicornis) exposed to pH 7.4 compared to pH 8.1during a 3-week period. The RNAseq approach shows that 16% of our transcriptome was affected by the treatment with 6% of upregulations and 10% of downregulations. A more detailed analysis suggests that the downregulations are less coordinated than the upregulations and allowed the identification of several biological functions of interest. In order to better understand the links between these functions and the pH, transcript abundance of 48 candidate genes was quantified by q-RT-PCR (corals exposed at pH 7.2 and 7.8 for 3 weeks). The combined results of these two approaches suggest that pH≥7.4 induces an upregulation of genes coding for proteins involved in calcium and carbonate transport, conversion of CO2 into HCO3− and organic matrix that may sustain calcification. Concomitantly, genes coding for heterotrophic and autotrophic related proteins are upregulated. This can reflect that low pH may increase the coral energy requirements, leading to an increase of energetic metabolism with the mobilization of energy reserves. In addition, the uncoordinated downregulations measured can reflect a general trade-off mechanism that may enable energy reallocation. [ABSTRACT FROM AUTHOR]

Background: The Pacific oyster Crassostrea gigas (Mollusca, Lophotrochozoa) is an alternative and irregular protandrous hermaphrodite: most individuals mature first as males and then change sex several times. Little is known about genetic and phenotypic basis of sex differentiation in oysters, and little more about the molecular pathways regulating reproduction. We have recently developed and validated a microarray containing 31,918 oligomers (Dheilly et al., 2011) representing the oyster transcriptome. The application of this microarray to the study of mollusk gametogenesis should provide a better understanding of the key factors involved in sex differentiation and the regulation of oyster reproduction. Methodology/Principal Findings: Gene expression was studied in gonads of oysters cultured over a yearly reproductive cycle. Principal component analysis and hierarchical clustering showed a significant divergence in gene expression patterns of males and females coinciding with the start of gonial mitosis. ANOVA analysis of the data revealed 2,482 genes differentially expressed during the course of males and/or females gametogenesis. The expression of 434 genes could be localized in either germ cells or somatic cells of the gonad by comparing the transcriptome of female gonads to the transcriptome of stripped oocytes and somatic tissues. Analysis of the annotated genes revealed conserved molecular mechanisms between mollusks and mammals: genes involved in chromatin condensation, DNA replication and repair, mitosis and meiosis regulation, transcription, translation and apoptosis were expressed in both male and female gonads. Most interestingly, early expressed male-specific genes included bindin and a dpy-30 homolog and female-specific genes included foxL2, nanos homolog 3, a pancreatic lipase related protein, cd63 and vitellogenin. Further functional analyses are now required in order to investigate their role in sex differentiation in oysters. Conclusions/Significance: This study allowed us to identify potential markers of early sex differentiation in the oyster C. gigas, an alternative hermaphrodite mollusk. We also provided new highly valuable information on genes specifically expressed by mature spermatozoids and mature oocytes. [ABSTRACT FROM AUTHOR]

Abstract: Echinoderms evolved early in the deuterostome lineage, and as such constitute model organisms for comparative physiology and immunology. The sea urchin genome sequence (Strongylocentrotus purpuratus) revealed a complex repertoire of genes with similarities to the immune response genes of other species. To complement these genomic data, we investigated the responses of sea urchins to the injection of bacteria using a comparative proteomics approach on a closely related species. In the sea urchin, Heliocidaris erythrogramma, the relative abundance of many proteins was altered in response to the injection of both bacteria and saline, suggesting their involvement in wounding responses, while others were differentially altered in response to bacteria only. The identities of 15 proteins that differed in relative abundance were determined by mass spectrometry. These proteins revealed a significant modification in energy metabolism in coelomocytes towards the consumption of glutamate and the production of NADPH after injection, as well as an increased concentration of cell signalling molecules, such as heterotrimeric guanine nucleotide-binding protein. The injection of bacteria specifically increased the abundance of apextrin and calreticulin, suggesting that these two proteins are involved in the sequestration or inactivation of bacteria. [ABSTRACT FROM AUTHOR]

Pharmaceuticals and personal care products are emerging contaminants that are increasingly detected in the environment worldwide. Certain classes of pharmaceuticals, such as selective serotonin reuptake inhibitors (SSRIs), are a major environmental concern due to their widespread use and the fact that these compounds are designed to have biological effects at low doses. A complication in predicting toxic effects of SSRIs in nontarget organisms is that their mechanism of action is not fully understood. To better understand the potential toxic effects of SSRIs, we employed an ultra-low input RNA-sequencing method to identify potential pathways that are affected by early exposure to two SSRIs (fluoxetine and paroxetine). We exposed wildtype zebrafish (Danio rerio) embryos to 100 μg/L of either fluoxetine or paroxetine for 6 days before extracting and sequencing mRNA from individual larval brains. Differential gene expression analysis identified 1550 genes that were significantly affected by SSRI exposure with a core set of 138 genes altered by both SSRIs. Weighted gene co-expression network analysis identified 7 modules of genes whose expression patterns were significantly correlated with SSRI exposure. Functional enrichment analysis of differentially expressed genes as well as network module genes repeatedly identified various terms associated with mitochondrial and neuronal structures, mitochondrial respiration, and neurodevelopmental processes. The enrichment of these terms indicates that toxic effects of SSRI exposure are likely caused by mitochondrial dysfunction and subsequent neurodevelopmental effects. To our knowledge, this is the first effort to study the tissue-specific transcriptomic effects of SSRIs in developing zebrafish, providing specific, high resolution molecular data regarding the sublethal effects of SSRI exposure. • Ultra-low input RNA-seq methods assayed brain gene expression after SSRI exposure. • >1500 genes were differentially expressed in brain tissue with SSRI exposure. • Weighted co-expression network analysis expanded list of key genes to >10,000. • Gene ontology implicates mitochondrial & neurodevelopmental effects as a toxic mechanism. [ABSTRACT FROM AUTHOR]

Parasitic arthropods have not typically been included in conservation and management strategies, possibly because the most well-known blood-feeding arthropods are associated with human and livestock disease. However, the vast majority of parasitic arthropods pose no threat to human health and instead contribute to the overall stability of communities to which they belong. The loss of parasitic arthropod biodiversity likely has repercussions for host health, population density, and community structure. The need for parasitic arthropod conservation is urgent given they represent the majority of parasitic animal biodiversity and environmental change is expected to pose a significant threat to their survival. We urge that microbial associations of host–parasitic arthropod assemblages be considered in conservation efforts. Parasitic arthropods are dependent on their microbial associates for development, nutrient acquisition, immune function, and reproduction. The microbiome also mediates the interactions between a parasitic arthropod and a host, and the role of a parasitic arthropod in vectoring pathogens to its host. The microbiome may therefore represent a "weak link" that increases the susceptibility of parasitic arthropods to environmental change. Fundamental knowledge is missing, precluding assessment of this complex association between microbes and parasitic arthropods. We highlight broad areas of future research that focus on building primary knowledge, developing experimental protocols and novel statistics, and leveraging new techniques to increase the resolution at which we can examine microbial communities of parasites. Conservation of parasitic arthropods that accounts for microbiota will likely be more effective at maintaining parasite biodiversity and at controlling arthropod-vectored disease emergence. Unlabelled Image • Parasitic arthropods are expected to suffer high extinction due to climate change. • Parasites depend on microbes for access to and their function within suitable habitat. • Environmental alteration of microbiomes may decrease suitable habitat for parasites. • Successful parasite conservation will depend on knowledge of parasite microbiomes. [ABSTRACT FROM AUTHOR]

Jingchuvirales is an order of negative-sense RNA viruses with genomes of 9.1-15.3 kb that have been associated with arachnids, barnacles, crustaceans, insects, fish and reptiles in Africa, Asia, Australia, Europe, North America and South America. The jingchuviral genome has two to four open reading frames (ORFs) that encode a glycoprotein (GP), a nucleoprotein (NP), a large (L) protein containing an RNA-directed RNA polymerase (RdRP) domain, and/or proteins of unknown function. Viruses in the order are only known from their genome sequences. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the order Jingchuvirales and on the families Aliusviridae , Chuviridae , Crepuscuviridae , Myriaviridae and Natareviridae , which are available at ictv.global/report/jingchuvirales, ictv.global/report/aliusviridae, ictv.global/report/chuviridae, ictv.global/report/crepuscuviridae, ictv.global/report/myriaviridae and ictv.global/report/natareviridae, respectively.

For parasites with complex multi-host life cycles, the facultative truncation of the cycle represents an adaptation to challenging conditions for transmission. However, why certain individuals are capable of abbreviating their life cycle while other conspecifics are not remains poorly understood. Here, we test whether conspecific trematodes that either follow the normal three-host life cycle or skip their final host by reproducing precociously (via progenesis) in an intermediate host differ in the composition of their microbiomes. Characterization of bacterial communities based on sequencing of the V4 hypervariable region of the 16S SSU rRNA gene revealed that the same bacterial taxa occur in both normal and progenetic individuals, independent of host identity and temporal variation. However, all bacterial phyla recorded in our study, and two-thirds of bacterial families, differed in abundance between the two morphs, with some achieving higher abundance in the normal morph and others in the progenetic morph. Although the evidence is purely correlative, our results reveal a weak association between microbiome differences and intraspecific plasticity in life cycle pathways. Advances in functional genomics and experimental microbiome manipulation will allow future tests of the significance of these findings.

Because parasites have an inextricable relationship with their host, they have the potential to serve as viral reservoirs or facilitate virus host shifts. And yet, little is known about viruses infecting parasitic hosts except for blood-feeding arthropods that are well-known vectors of zoonotic viruses. Herein, we uncovered viruses of flatworms (phylum Platyhelminthes, group Neodermata) that specialize in parasitizing vertebrates and their ancestral free-living relatives. We discovered 115 novel viral sequences, including 1 in Macrostomorpha, 5 in Polycladida, 44 in Tricladida, 1 in Monogenea, 15 in Cestoda, and 49 in Trematoda, through data mining. The majority of newly identified viruses constitute novel families or genera. Phylogenetic analyses show that the virome of flatworms changed dramatically during the transition of neodermatans to a parasitic lifestyle. Most Neodermata viruses seem to codiversify with their host, with the exception of rhabdoviruses, which may switch hosts more often, based on phylogenetic relationships. Neodermata rhabdoviruses also have a position ancestral to vertebrate-associated rhabdo viruses, including lyssaviruses, suggesting that vertebrate-associated rhabdoviruses emerged from a flatworm rhabdovirus in a parasitized host. This study reveals an extensive diversity of viruses in Platyhelminthes and highlights the need to evaluate the role of viral infection in flatworm-associated diseases. IMPORTANCE Little is known about the diversity of parasite-associated viruses and how these viruses may impact parasite fitness, parasite-host interactions, and virus evolution. The discovery of over a hundred viruses associated with a range of free-living and parasitic flatworms, including parasites of economic and clinical relevance, allowed us to compare the viromes of flatworms with contrasting lifestyles. The results suggest that flatworms acquired novel viruses after their transition to a parasitic lifestyle and highlight the possibility that they acquired viruses from their hosts and vice versa. An interesting example is the discovery of flatworm rhabdoviruses that have a position ancestral to rabies viruses and other vertebrate-associated rhabdoviruses, demonstrating that flatworm-associated viruses have emerged in a vertebrate host at least once in history. Therefore, parasitic flatworms may play a role in virus diversity and emergence. The roles that parasite-infecting viruses play in parasite-associated diseases remain to be investigated.

The concept of a holobiont, a host organism and its associated microbial communities, encapsulates the vital role the microbiome plays in the normal functioning of its host. Parasitic infections can disrupt this relationship, leading to dysbiosis. However, it is increasingly recognized that multicellular parasites are themselves holobionts. Intestinal parasites share space with the host gut microbiome, creating a system of nested microbiomes within the primary host. However, how the parasite, as a holobiont, interacts with the host holobiont remains unclear, as do the consequences of these interactions for host health. Here, we used 16S amplicon and shotgun metagenomics sequencing to characterize the microbiome of the intestinal cestode Eubothrium and its effect on the gut microbiome of its primary host, Atlantic salmon. Our results indicate that cestode infection is associated with salmon gut dysbiosis by acting as a selective force benefiting putative pathogens and potentially introducing novel bacterial species to the host. Our results suggest that parasitic cestodes may themselves be holobionts nested within the microbial community of their holobiont host, emphasizing the importance of also considering microbes associated with parasites when studying intestinal parasitic infections. IMPORTANCE The importance of the parasite microbiome is gaining recognition. Of particular concern is understanding how these parasite microbiomes influence host-parasite interactions and parasite interactions with the vertebrate host microbiome as part of a system of nested holobionts. However, there are still relatively few studies focusing on the microbiome of parasitic helminths in general and almost none on cestodes in particular, despite the significant burden of disease caused by these parasites globally. Our study provides insights into a system of significance to the aquaculture industry, cestode infections of Atlantic salmon and, more broadly, expands our general understanding of parasite-microbiome-host interactions and introduces a new element, the microbiome of the parasite itself, which may play a critical role in modulating the host microbiome, and, therefore, the host response, to parasite infection.