A new strain of Volutella citrinella with nematode predation and nematicidal activity, isolated from the cysts of potato cyst nematodes in China.

BACKGROUND: Plant parasitic nematodes (PPNs) are responsible for causing many plant diseases and are extremely difficult to control at present. Currently, due to the negative effects of chemical agents on the environment and human health, the development of new biological pesticides has become an important part of plant nematode control. Nematophagous fungi refers to a class of fungi that kill plant nematodes. Notably, a large number of nematophagous fungi resources remain to be studied. The objective of our study was to use in vitro screening to identify nematophagous fungi and select strains that were highly active against nematodes, providing a primary research for the development and utilization of new nematophagous fungi. RESULTS: A new nematophagous fungal strain (GUCC2219) was isolated from cysts of possibly Globodera spp. and Heterodera spp., identified as Volutella citrinella. The hyphae of V. citrinella produced ring structures of variable size and exhibited predatory and nematicidal activity. The hyphal predation rates (in vitro) against three species of nematodes, Aphelenchoides besseyi, Bursaphelenchus xylophilus, and Ditylenchus destructor, averaged 59.45, 33.35, and 50.95%, respectively, while the fermentation broth produced by the fungus exhibited mortality rates of 100, 100, and 55.63%, respectively, after 72 h. CONCLUSION: V. citrinella is a new strain with nematophagous properties, which are a novel discovery. At the same time, this is the first report of nematicidal and nematode predation activity in the genus Volutella.

On the role of dauer in the adaptation of nematodes to a parasitic lifestyle.

Nematodes are presumably the most abundant Metazoa on Earth, and can even be found in some of the most hostile environments of our planet. Various types of hypobiosis evolved to adapt their life cycles to such harsh environmental conditions. The five most distal major clades of the phylum Nematoda (Clades 8-12), formerly referred to as the Secernentea, contain many economically relevant parasitic nematodes. In this group, a special type of hypobiosis, dauer, has evolved. The dauer signalling pathway, which culminates in the biosynthesis of dafachronic acid (DA), is intensively studied in the free-living nematode Caenorhabditis elegans, and it has been hypothesized that the dauer stage may have been a prerequisite for the evolution of a wide range of parasitic lifestyles among other nematode species. Biosynthesis of DA is not specific for hypobiosis, but if it results in exit of the hypobiotic state, it is one of the main criteria to define certain behaviour as dauer. Within Clades 9 and 10, the involvement of DA has been validated experimentally, and dauer is therefore generally accepted to occur in those clades. However, for other clades, such as Clade 12, this has hardly been explored. In this review, we provide clarity on the nomenclature associated with hypobiosis and dauer across different nematological subfields. We discuss evidence for dauer-like stages in Clades 8 to 12 and support this with a meta-analysis of available genomic data. Furthermore, we discuss indications for a simplified dauer signalling pathway in parasitic nematodes. Finally, we zoom in on the host cues that induce exit from the hypobiotic stage and introduce two hypotheses on how these signals might feed into the dauer signalling pathway for plant-parasitic nematodes. With this work, we contribute to the deeper understanding of the molecular mechanisms underlying hypobiosis in parasitic nematodes. Based on this, novel strategies for the control of parasitic nematodes can be developed.

REVIEW OF THE DAUER HYPOTHESIS: WHAT NON-PARASITIC SPECIES CAN TELL US ABOUT THE EVOLUTION OF PARASITISM.

Parasitic lineages have acquired suites of new traits compared to their nearest free-living relatives. When and why did these traits arise? We can envision lineages evolving through multiple stable intermediate steps such as a series of increasingly exploitative species interactions. This view allows us to use non-parasitic species that approximate those intermediate steps to uncover the timing and original function of parasitic traits, knowledge critical to understanding the evolution of parasitism. The dauer hypothesis proposes that free-living nematode lineages evolved into parasites through two intermediate steps, phoresy and necromeny. Here we delve into the proposed steps of the dauer hypothesis by collecting and organizing data from genetic, behavioral, and ecological studies in a range of nematode species. We argue that hypotheses on the evolution of parasites will be strengthened by complementing comparative genomic studies with ecological studies on non-parasites that approximate intermediate steps.

Wolbachia: endosymbiont of onchocercid nematodes and their vectors.

BACKGROUND: Wolbachia is an obligate intracellular maternally transmitted, gram-negative bacterium which forms a spectrum of endosymbiotic relationships from parasitism to obligatory mutualism in a wide range of arthropods and onchocercid nematodes, respectively. In arthropods Wolbachia produces reproductive manipulations such as male killing, feminization, parthenogenesis and cytoplasmic incompatibility for its propagation and provides an additional fitness benefit for the host to protect against pathogens, whilst in onchocercid nematodes, apart from the mutual metabolic dependence, this bacterium is involved in moulting, embryogenesis, growth and survival of the host. METHODS: This review details the molecular data of Wolbachia and its effect on host biology, immunity, ecology and evolution, reproduction, endosymbiont-based treatment and control strategies exploited for filariasis. Relevant peer-reviewed scientic papers available in various authenticated scientific data bases were considered while writing the review. CONCLUSIONS: The information presented provides an overview on Wolbachia biology and its use in the control and/or treatment of vectors, onchocercid nematodes and viral diseases of medical and veterinary importance. This offers the development of new approaches for the control of a variety of vector-borne diseases.

Resistance of strongylid nematodes to anthelmintic drugs and driving factors at Czech goat farms.

BACKGROUND: Strongylid nematode infections may negatively affect both animal health and welfare, with deleterious consequences for livestock productivity. Many farmers in recent decades have relied on anthelmintics as the sole strategy of control, but the intensive use of these chemotherapeutics has led to the development of anthelmintic resistance (AR). Knowledge of both the efficacy of anthelmintics and factors promoting AR are essential to effectively control nematode infections, but no information on these topics for goats in the Czech Republic (CR) is available. This survey aimed to determine the occurrence of AR at Czech goat farms and to identify risk factors for the development of AR. A total of 24 herds of dairy goats across the CR were evaluated using in vitro tests for detecting AR, and a questionnaire survey was carried out to evaluate factors associated with AR. RESULTS: Resistance against benzimidazoles was confirmed at 18 (75%) farms, and the level of resistance was high in four (22%) of the affected herds based on the egg hatch test. Ivermectin-resistant nematodes were detected in 13 (54%) herds using the larval development test; Teladorsagia/Trichostrongylus and Haemonchus were the predominant types of resistant larvae. Eight (62%) of the affected herds were evaluated as highly resistant to ivermectin. Eleven (46%) of the herds were resistant to both benzimidazoles and ivermectin. This report is the first on dual AR in the CR. A univariate logistic regression analysis indicated that a high stocking rate and farmer inexperience were significantly associated with ivermectin and benzimidazole resistance, respectively. CONCLUSIONS: The results of our survey suggest that AR is widespread amongst herds of dairy goats in the CR, likely due to inappropriate practices of pasture and health management. AR may be an issue for expanding dairy-goat production in the CR in the near future unless both veterinary practitioners and farmers widely adopt strategies to prevent the development of AR.

Parabronema skrjabini (Nematoda: Habronematidae) infection and development in the intermediate host-Haematobia irritans (Linnaeus, 1758) in Inner Mongolia, China.

Parabronemosis is a disease that severely threatens camel health, causing huge economic losses to industries involved in camel husbandry. Previous studies have reported that horn flies (Haematobia irritans) act as intermediate hosts of Parabronema skrjabini; however, the infection and developmental processes of P. skrjabini in horn flies remain unclear. In the present study, the infection rates of P. skrjabini were determined in morphologically and molecularly identified horn flies collected from Bactrian camels (Camelus bactrianus) producing regions in Inner Mongolia, China that have high P. skrjabini infection rates. The horn flies were dissected to obtain the nematode larvae at various instar stages. The P. skrjabini found in the different instar stages of horn fly instars were counted and identified to assess the infection and developmental status. Nematode larvae at different developmental stages were obtained from the horn fly instars for further molecular analysis. Sequencing results confirmed that the nematode larvae were P. skrjabini. Furthermore, we found that the mean growth rate of the nematode larva increased as the horn fly instars develops. The results suggested that P. skrjabini infected the horn flies at the larval instar stage, and that the nematode larvae developed simultaneously with the horn fly instars stages. Our findings provide useful information into the elucidation of P. skrjabini infection and life history by studying horn fly development.

Prevalence of anthelmintic resistance of gastrointestinal nematodes in Polish goat herds assessed by the larval development test.

BACKGROUND: Helminthic infections, in particular those caused by gastrointestinal nematodes (GIN), are found worldwide and are among the most economically important diseases of goats. Anthelmintic resistance (AR) in GIN of goats is currently present worldwide, and single- or multidrug resistant species are widespread. The aim of this study was to determine the prevalence of AR to benzimidazoles (BZ), macrocyclic lactones (ML) and imidazothiazoles represented by levamisole (LEV) in the Polish goat herds by using an in vitro larval development test, which is useful especially in large-scale epidemiological surveys. RESULTS: This cross-sectional study was conducted from September 2018 to June 2019 and enrolled 42 dairy goat herds scattered over the entire country. The most commonly used anthelmintic class in goat herds in Poland were BZ (92%), followed by ML (85%) and LEV (13%). BZ-resistant GIN populations were found in 37 herds (88%, CI 95%: 75 to 95%), ML-resistant GIN populations in 40 herds (95%, CI 95, 84 to 99%), and LEV-resistant GIN populations in 5 herds (12%, CI 95%: 5 to 25%). Multidrug resistance involving all three anthelmintic classes was found in 5 herds (12%, CI 95, 5 to 25%). Based on the morphological features of stage 3 larvae the main resistant GIN turned out to be Haemonchus contortus and Trichostrongylus spp. The use of BZ and frequency of anthelmintic treatments were significantly related to the presence of AR to BZ in Polish goat herds. CONCLUSIONS: This cross-sectional study demonstrates the existence of AR to BZ, ML and LEV on Polish goat farms. Resistance to BZ and ML is widespread, while AR to LEV is currently at a low level. A considerable proportion of herds harbours multidrug resistant GIN, which requires further consideration. An effective anthelmintic treatment strategy, reasonable preventive measures and better understanding of the resistance-related management practices by farmers and veterinarians may delay further development of AR.

Investigating Neolithic caprine husbandry in the Central Pyrenees: Insights from a multi-proxy study at Els Trocs cave (Bisaurri, Spain).

Sheep remains constitute the main archaeozoological evidence for the presence of Early Neolithic human groups in the highlands of the Southern Pyrenees but understanding the role of herding activities in the Neolithisation process of this mountain ecosystem calls for the analysis of large and well-dated faunal assemblages. Cova de Els Trocs (Bisaurri, Huesca, Spain), a cave located at 1564 m a.s.l on the southern slopes of the Central Pyrenees, is an excellent case study since it was seasonally occupied throughout the Neolithic (ca. 5312-2913 cal. BC) and more than 4000 caprine remains were recovered inside. The multi-proxy analytical approach here presented has allowed us to offer new data elaborating on vertical mobility practices and herd management dynamics as has not been attempted up until now within Neolithic high-mountain sites in the Iberian Peninsula. For the first time, δ18O and δ13C stable isotope analyses offer direct evidence on both the regular practice of altitudinal movements of sheep flocks and the extended breeding season of sheep. Autumn births are recorded from the second half of the fifth millennium cal. BC onwards. Age-at-death distributions illustrate the progressive decline in caprine perinatal mortality together with the rising survival rate of individuals older than six months of age and the larger frequency of adults. This trend alongside the 'off-season' lambing signal at the implementation of husbandry techniques over time, probably aiming to increase the size of the flocks and their productivity. Palaeoparasitological analyses of sediment samples document also the growing reliance on herding activities of the human groups visiting the Els Trocs cave throughout the Neolithic sequence. In sum, our work provides substantial arguments to conclude that the advanced herding management skills of the Early Neolithic communities arriving in Iberia facilitated the anthropisation process of the subalpine areas of the Central Pyrenees.

An Animal Able To Tolerate D2 O.

It is possible to gain a deeper insight into the role of water in biology by using physicochemical variant molecules, such as deuterium oxide (D2 O); however, D2 O is toxic to multicellular organisms in high concentrations. By using a unique desiccation-rehydration process, we demonstrate that the anhydrobiotic nematode Panagrolaimus superbus is able to tolerate and proliferate in 99 % D2 O. Moreover, we analysed P. superbus' water-channel protein (aquaporin; AQP), which is associated with dehydration/rehydration, by comparing its primary structure and modelling its tertiary structure in silico. Our data evidence that P. superbus' AQP is an aquaglyceroporin, a class of water channel known to display a wider pore; this helps to explain the rapid and successful organismal influx of D2 O into this species. This is the first demonstration of an animal able to withstand high D2 O levels, thus paving a way for the investigation of the effects D2 O on higher levels of biological organization.

Soil nematode functional diversity, successional patterns, and indicator taxa associated with vertebrate decomposition hotspots.

Decomposition of vertebrate remains is a dynamic process that creates localized soil enrichment zones. A growing body of literature has documented effects of vertebrate decomposition on soil pH, electrical conductivity, oxygen levels, nitrogen and carbon speciation, microbial biomass, and microbial successional patterns. However, relatively few studies have examined the microfaunal members of the soil food web that function as secondary consumers, specifically nematodes. Nematodes are often used as indicators of enrichment in other systems, and initial observations from vertebrate decomposition zones have indicated there is an effect on nematode communities. Our goal was to catalog decomposition-induced nematode succession and changes to alpha, beta, and functional diversity, and identify potential indicator taxa associated with decomposition progression. Six adult beaver (Castor canadensis) carcasses were allowed to decompose in a forest ecosystem for one year. During this period soil temperature, moisture, and electrical conductivity were monitored. Soils samples were taken at two depths in order to assess nematode community dynamics: 30-cm cores and 1-cm interface samples. Nematode abundance, alpha, beta, and functional diversity all responded to soil enrichment at the onset of active decay, and impacts persisted through skeletonization. After one year, nematode abundances and alpha diversity had recovered to original levels, however both community membership and functional diversity remained significantly altered. We identified seven indicator taxa that marked major transitions in decomposition progression. Enrichment of Rhabditidae (B1) and Diplogasteridae (B1) coupled with depletion in Filenchus (F2) characterized active and advanced decay prior to skeletonization in both cores and interface soils. Enrichment of Acrobeloides (B2), Aphelenchoides (F2), Tylencholaimidae (F4) and Seinura (P2) occurred during a narrow period in mid-skeletonization (day 153). Our study has revealed soil nematode successional patterns during vertebrate decomposition and has identified organisms that may function as indicator taxa for certain periods during decomposition.

Arthrobotrys cladodes and Pochonia chlamydosporia: Nematicidal effects of single and combined use after passage through cattle gastrointestinal tract.

Nematodiosis are responsible for financial losses in cattle production systems due to treatment costs, falling production rates and animal deaths. The incorporation of sodium alginate pellets containing nematophagous fungi in the bovine diet is a method for the control of nematodiosis. The aims of this study were to evaluate the viability of Arthrobotrys cladodes and Pochonia chlamydosporia contained in sodium alginate pellets after passage through the bovine gastrointestinal tract, as well as to evaluate the effects of single and combined use of these fungi against bovine parasitic nematodes. The reduction in parasitic nematode infective larvae of bovines by the combined use of Arthrobotrys cladodes and Pochonia chlamydosporia was more than the reduction in infective larvae by Arthrobotrys cladodes or Pochonia chlamydosporia alone in the collections 12, 24 and 36 h after giving the pellets to the animals. Arthrobotrys cladodes and Pochonia chlamydosporia combined promoted maximum reduction of infective larvae of 86.3%. Therefore, the combination of Arthrobotrys cladodes and Pochonia chlamydosporia may be an effective method to control gastrointestinal nematodiosis affecting grazing cattle.

High levels of third-stage larvae (L3) overwinter survival for multiple cattle gastrointestinal nematode species on western Canadian pastures as revealed by ITS2 rDNA metabarcoding.

BACKGROUND: The ability of infective larvae of cattle gastrointestinal nematode (GIN) species to overwinter on pastures in northerly climatic zones with very cold dry winters is poorly understood. This is an important knowledge gap with critical implications for parasite risk assessment and control. METHODS: Infective third-stage larvae (L3) were quantified in samples of fecal pats, together with adjacent grass and soil, before and after winter on three farms in southern, central and northern Alberta. Nemabiome ITS2 metabarcoding was then performed on the harvested L3 populations to determine the species composition. Finally, parasite-free tracer calves were used to investigate if the L3 surviving the winter could infect calves and develop to adult worms in spring. RESULTS: Farm level monitoring, using solar powered weather stations, revealed that ground temperatures were consistently higher, and less variable, than the air temperatures; minimum winter air and ground temperatures were - 32.5 °C and - 24.7 °C respectively. In spite of the extremely low minimum temperatures reached, L3 were recovered from fecal pats and grass before and after winter with only a 38% and 61% overall reduction over the winter, respectively. Nemabiome ITS2 metabarcoding assay revealed that the proportion of L3 surviving the winter was high for both Cooperia oncophora and Ostertagia ostertagi although survival of the former species was statistically significantly higher than the latter. Nematodirus helvetinaus and Trichostrongylus axei could be detected after winter whereas Haemonchus placei L3 could not overwinter at all. Adult C. oncophora, O. ostertagi and N. helvetianus could be recovered from tracer calves grazing after the winter. CONCLUSIONS: The largest proportion of L3 were recovered from fecal pats suggesting this is important refuge for L3 survival. Results also show that L3 of several GIN parasite species can survive relatively efficiently on pastures even in the extreme winter conditions in western Canada. Tracer calf experiments confirmed that overwintered L3 of both C. oncophora and O. ostertagi were capable of establishing a patent infection in the following spring. These results have important implications for the epidemiology, risk of production impact and the design of effective control strategies. The work also illustrates the value of applying ITS2 nemabiome metabarcoding to environmental samples.

Novel Polyketide-Terpenoid Hybrid Metabolites from a Potent Nematicidal Arthrobotrys oligospora Mutant ΔAOL_s00215g278.

Here, we reported that detailed investigation on trace targeted metabolites from nematode-trapping fungus Arthrobotrys oligospora mutant with deletion of P450 gene AOL_s00215g278 led to isolation of 9 new polyketide-terpenoid hybrid derivatives, including four new glycosides of the key precursor farnesyl hydrotoluquinol (1) and, surprisingly, four new sesquiterpenyl epoxy-cyclohexenoids (SECs) analogues. Among them, two major target metabolites 1 and 14 displayed moderate nematode inhibitory ability. Moreover, the mutant lacking AOL_s00215g278 could form far more nematode-capturing traps within 6 h in contact with nematodes and show rapid potent nematicidal activity with killing 93.7% preys, though deletion of the P450 gene resulted in dramatic decrease in fungal colony growth and failure to produce fungal conidia. The results unequivocally revealed that gene AOL_s00215g278 should be involved in not only the SEC biosynthetic pathway in the nematode-trapping fungus A. oligospora but also fungal conidiation and nematicidal activity.

The Possible Biotechnological Use of Edible Mushroom Bioproducts for Controlling Plant and Animal Parasitic Nematodes.

The present paper reviewed publications on the nematocidal activity of edible mushrooms (EM) and their potential use as sustainable tools for the control of parasitic nematodes affecting agriculture and livestock industry. Nematodes are organisms living in the soil and animals' guts where they may live as parasites severely affecting economically important crops and farm animals, thus causing economic losses to worldwide agriculture. Traditionally, parasitic nematodes have been controlled using commercial pesticides and anthelmintic (AH) drugs. Over the years, nematodes developed resistance to the AH drugs, reducing the usefulness of many commercial drugs. Also, the use of pesticides/anthelmintic drugs to control nematodes can have important negative impacts on the environment. Different EM have been not only used as food but also studied as alternative methods for controlling several diseases including parasitic nematodes. The present paper reviewed publications from the last decades about the nematocidal activity of EM and assessed their potential use as sustainable tools for the control of nematodes affecting agriculture and livestock industry. A reduced number of reports on the effect of EM against nematodes were found, and an even smaller number of reports regarding the potential AH activity of chemical compounds isolated from EM products were found. However, those studies have produced promising results that certainly deserve further investigation. It is concluded that EM, their fractions and extracts, and some compounds contained in them may have biotechnological application for the control of animal and plant parasitic nematodes.

Demographic and reproductive associations with nematode infection in a long-lived mammal.

Infection by macroparasites, such as nematodes, varies within vertebrate host systems; elevated infection is commonly observed in juveniles and males, and, for females, with different reproductive states. However, while such patterns are widely recognized in short-lived model systems, how they apply to long-lived hosts is comparatively understudied. Here, we investigated how infection varies with host age, sex, and female reproduction in a semi-captive population of individually marked Asian elephants Elephas maximus. We carried out 1,977 faecal egg counts (FECs) across five years to estimate nematode loads for 324 hosts. Infection patterns followed an established age-infection curve, whereby calves (5 years) exhibited the highest FECs and adults (45 years) the lowest. However, males and females had similar FECs across their long lifespan, despite distinct differences in life-history strategy and clear sexual dimorphism. Additionally, although mothers invest two years in pregnancy and a further three to five years into lactation, nematode load did not vary with four different measures of female reproduction. Our results provide a much-needed insight into the host-parasite dynamics of a long-lived host; determining host-specific associations with infection in such systems is important for broadening our knowledge of parasite ecology and provides practical applications for wildlife medicine and management.

Comparison of ITS-2 rDNA nemabiome sequencing with morphological identification to quantify gastrointestinal nematode community species composition in small ruminant feces.

Mixed gastrointestinal nematode (GIN) infections are a common and significant cause of financial loss for small ruminant producers. Morphologic examination of third-stage larvae (L3) can be used to identify species composition in feces but has limitations due to the requirement for specialized expertise and the extensive time (8-15 d depending on method used) and labour involved. Moreover, differential development and survival of larvae during coproculture to the third stage often occurs. Deep amplicon sequencing of the ITS-2 rDNA locus of first-stage larvae (L1) allows for higher throughput with reduced specialist labour and reduces the risk of misidentification. Harvesting of L1 soon after hatching is also faster and further reduces labour as well as biases that can occur due to differential larval development and survival. This study compares the results of morphologic examination of L3 with those of ITS-2 rDNA deep amplicon sequencing of L1 from a set of pooled fecal samples. The proportions of eggs that were successfully recovered as larvae following culture to L3 and L1 were also compared. Larval recovery rate was significantly lower from L3 cultures than from L1 cultures (p < 0.001); eggs were 238.7 times less likely to develop to L3 than to L1 (95 % confidence interval for odds ratio 80.0-712.0). Significantly lower proportions of Teladorsagia circumcincta (odds ratio = 3.1, p = 0.008) and higher proportions of Trichostrongylus spp. (p = 0.009) were identified using morphologic examination of L3 compared with deep amplicon sequencing of L1 on the same samples. This is consistent with previous reports of differential survival of these species in L3 cultures. These results indicate that deep amplicon sequencing of L1 may reduce bias introduced by differential GIN survival to L3 in small ruminants.

Elucidating the molecular and developmental biology of parasitic nematodes: Moving to a multiomics paradigm.

In the past two decades, significant progress has been made in the sequencing, assembly, annotation and analyses of genomes and transcriptomes of parasitic worms of socioeconomic importance. This progress has somewhat improved our knowledge and understanding of these pathogens at the molecular level. However, compared with the free-living nematode Caenorhabditis elegans, the areas of functional genomics, transcriptomics, proteomics and metabolomics of parasitic nematodes are still in their infancy, and there are major gaps in our knowledge and understanding of the molecular biology of parasitic nematodes. The information on signalling molecules, molecular pathways and microRNAs (miRNAs) that are known to be involved in developmental processes in C. elegans and the availability of some molecular resources (draft genomes, transcriptomes and some proteomes) for selected parasitic nematodes provide a basis to start exploring the developmental biology of parasitic nematodes. Indeed, some studies have identified molecules and pathways that might associate with developmental processes in related, parasitic nematodes, such as Haemonchus contortus (barber's pole worm). However, detailed information is often scant and 'omics resources are limited, preventing a proper integration of 'omic data sets and comprehensive analyses. Moreover, little is known about the functional roles of pheromones, hormones, signalling pathways and post-transcriptional/post-translational regulations in the development of key parasitic nematodes throughout their entire life cycles. Although C. elegans is an excellent model to assist molecular studies of parasitic nematodes, its use is limited when it comes to explorations of processes that are specific to parasitism within host animals. A deep understanding of parasitic nematodes, such as H. contortus, requires substantially enhanced resources and the use of integrative 'omics approaches for analyses. The improved genome and well-established in vitro larval culture system for H. contortus provide unprecedented opportunities for comprehensive studies of the transcriptomes (mRNA and miRNA), proteomes (somatic, excretory/secretory and phosphorylated proteins) and lipidomes (e.g., polar and neutral lipids) of this nematode. Such resources should enable in-depth explorations of its developmental biology at a level, not previously possible. The main aims of this review are (i) to provide a background on the development of nematodes, with a particular emphasis on the molecular aspects involved in the dauer formation and exit in C. elegans; (ii) to critically appraise the current state of knowledge of the developmental biology of parasitic nematodes and identify key knowledge gaps; (iii) to cover salient aspects of H. contortus, with a focus on the recent advances in genomics, transcriptomics, proteomics and lipidomics as well as in vitro culturing systems; (iv) to review recent advances in our knowledge and understanding of the molecular and developmental biology of H. contortus using an integrative multiomics approach, and discuss the implications of this approach for detailed explorations of signalling molecules, molecular processes and pathways likely associated with nematode development, adaptation and parasitism, and for the identification of novel intervention targets against these pathogens. Clearly, the multiomics approach established recently is readily applicable to exploring a wide range of interesting and socioeconomically significant parasitic worms (including also trematodes and cestodes) at the molecular level, and to elucidate host-parasite interactions and disease processes.

Effects of synthetic fertilizer and farm compost on soil nematode community in long-term crop rotation plots: A morphological and metabarcoding approach.

Soil biodiversity plays a key regulation role in the ecosystem services that underpin regenerative sustainable agriculture. It can be impacted by agricultural management techniques, both positively (through measures such as compost application) and negatively (through, for example, application of synthetic nitrogen). As one of the most numerous members of the soil biota, nematodes are well established as indicators for the soil food web. However, compost application also includes the addition of nematodes present in compost and their subsequent survival in soil is unknown. Nematode communities within the compost applied to soil, and nematode communities in the soil of a multi-year rotational cropping field trial in Melle (Belgium) were studied using morphological and metabarcoding techniques. Compost (C) and nitrogen fertilizer (NF) treated plots were compared. Three replicate plots were investigated for each of the following treatments: C application only; C and NF application; NF only; no C and no NF (control). Plots were sampled six times between 2015-2017, before and after C or NF were added each spring and after crop harvest (except for 2017). NF treatment resulted in a significant decrease of fungal feeding and predatory nematodes, while herbivorous nematodes were positively affected. Remarkably, we did not find compost addition to exert any noticeable effects on the soil nematode community. The morphological and metabarcoding data resulted in different results of the nematode community composition. However, trends and patterns in the two data sets were congruent when observed with NMDS plots and using the nematode maturity index. Metabarcoding of individual compost nematode taxa demonstrated that nematodes originating from compost did not persist in soil.

In Vitro Anthelmintic Activity of Saponins from Medicago spp. Against Sheep Gastrointestinal Nematodes.

Gastrointestinal strongyle nematodes (GIS) are included among the most important parasites of small ruminants. The widespread drug resistance and drug residues in products of animal origin have increased the interest in the search for natural compounds with anthelmintic activity as a valid alternative to current synthetic drugs. The aim of the present investigation was to test the 'in vitro' anthelmintic activity of saponins and prosapogenins from different Medicago species, selected for their importance as a forage crop worldwide for animal feeding. From these plants, saponin mixtures were extracted, purified and used at scalar concentrations to evaluate their anthelmintic activities against sheep gastrointestinal strongyles (GISs), by the egg hatch test. Treated and untreated controls were used as the comparison. Data were statistically analyzed, and EC50 and EC90 were also calculated. All saponins and prosapogenins showed inhibiting effects on GIS eggs in a concentration-dependent manner. At higher concentrations, most of them showed an efficacy comparable to the reference drug (Thiabendazole 3 µg/mL) (P < 0.001). With 1.72 mg/mL EC50 and 3.84 mg/mL EC90, saponin from M. polymorpha cultivars Anglona was the most active. Obtained results encourage further studies aimed at evaluating the efficacy 'in vivo' of saponins which resulted as most effective 'in vitro' in this study.

Sensitivity to Copper and Development of Culturing and Toxicity Test Procedures for the Antarctic Terrestrial Nematode Plectus murrayi.

Environmental quality guideline values and remediation targets, specific to Antarctic ecosystems, are required for the risk assessment and remediation of contaminated sites in Antarctica. Ecotoxicological testing with Antarctic soil organisms is fundamental in determining reliable contaminant effect threshold concentrations. The present study describes the development of optimal culturing techniques and aqueous toxicity test procedures for an endemic Antarctic soil nematode, Plectus murrayi, which lives within interstitial waters between soil particles. Toxicity tests were of extended duration to account for the species' physiology and life-history characteristics. Plectus murrayi was sensitive to aqueous copper with a 50% effective concentration for egg-hatching success of 139 µg/L. Hatched juveniles that were first exposed to copper as eggs appeared to be less sensitive than those first exposed at the hatched J2 stage, indicating a potential protective effect of the egg. Sensitivity of juveniles to copper increased with exposure duration, with 50% lethal concentrations of 478 and 117 µg/L at 21 and 28 d, respectively. The present study describes new methods for the application of an environmentally relevant test species to the risk assessment of contaminants in Antarctic soil and provides the first estimates of sensitivity to a toxicant for an Antarctic terrestrial microinvertebrate. Environ Toxicol Chem 2020;39:482-491. © 2019 SETAC.