Nematodes As Soil Stress Indicators for Polycyclic Aromatic Hydrocarbons: a Review

Polycyclic aromatic hydrocarbons (PAHs) are an important group of organic pollutants present in all parts of the environment, affecting ecosystems and human health. PAHs, which have a strong affinity for organic carbon, are found in large quantities in soil, which is one of the most important sinks for these contaminants. Their impact on the soil biotic compartments depends on a number of different factors in combination with PAH behaviour and can be assessed using soil monitoring. Soil fauna have already shown excellent properties for biomonitoring of contaminants with most promising indicator frameworks based on nematodes, which are involved in essential processes in this environment. Nematodes respond to PAHs at multiple levels, including molecular, individual and community levels. At the molecular level, this is associated with activation of metabolic pathways for xenobiotics and increased demand for energy and resources. At the individual level, this is reflected in the slowing down of various physiological processes, which has consequences at the individual and community level for sensitive taxa. In this review, the toxicity and the direct and indirect effects of PAHs on soil nematode communities are discussed. It also considers the perspectives and challenges in assessing the toxicity of PAHs and their indication using soil nematodes.

Helminths Infecting Sympatric Congeneric Treefrogs in Northeastern Brazil

PURPOSE

We aimed to describe the helminth fauna associated with two sympatric congeneric treefrogs species (Boana multifasciata and Boana raniceps) from a highland marsh in northeastern Brazil. In addition, we investigate the body size influence on parasitological descriptors in these treefrogs, in which we expected that larger frogs would have greater abundance and richness helminths too, and no differences with respect to helminth composition once both hosts are exposed to similar environmental conditions.

METHODS

We collected anurans during the rainy season from 11 January to 09 February 2019, using visual and auditory searches in breeding environments. We analysed the presence of ectoparasites under an epidermis, oral cavity, and endoparasites present in the organs. Using a Linear mixed-effects model we tested the relationship between the host body size (length and weight) and helminths abundance and richness. In addition, we used the ANOSIM R test to investigate the differences between the hosts with respect to helminth composition.

RESULTS

We recorded 37 individuals (15 specimens of B. multifasciata and 22 of B. raniceps), in which 89.1% of them were infected by at least one helminth species. We found 355 helminths from 12 taxa parasitizing the two treefrogs, but just three parasite taxa were common to both species. All identified helminth species found in B. multifasciata are new records and four are new records for B. raniceps. In addition, we present the first record of Cosmocerca paraguayensis in Brazil. We found no support for the hypothesis that larger frogs tend to be more parasitized, at least for congeneric species, and sympatric hosts species have similar helminth composition. We also present a compilation of helminths occurring in treefrogs belonging to the Boana genus in South American, increasing our knowledge of the parasitic diversity of Neotropical anurans.

CONCLUSION

Our results suggest a lack of knowledge about helminth fauna associated with amphibians even for common and widely distributed species, such as Boana spp., and demonstrate the need to deepen our knowledge about host parasitic relationships, especially in the Neotropical region.

Occurrence of Eustrongylides sp. (Nematoda: Dioctophymatidae) in Fish Species Collected in the Peruvian Amazonia and Its Implications for Public Health

PURPOSE

The present study aims to report the occurrence of Eustrongylides sp. in some neotropical fish species commercialized in the Peruvian Amazonia.

METHODS

Samples of young farmed Arapaima gigas were collected from a fish farmer; young Brachyplatystoma tigrinum were acquired from a fish exporter and samples of adult specimens of Acestrorhynchus falcirostris, Pseudoplatystoma punctifer, Cichla monoculus, Hoplias malabaricus, Hydrolycus scomberoides, Raphiodon vulpinus, and Serrasalmus rhombeus were acquired from a fish market of Iquitos, Loreto-Peru. Samples were transported to the "Laboratorio de Parasiología y Sanidad Acuícola" from "Instituto de Investigaciones de la Amazonía Peruana" located in Iquitos, Peru.

RESULTS

Larvae L4 of Eustrongylides sp. were found in the host body, in the muscle, and in the visceral cavity of studied fish species. Notorious damages were reported in young A. gigas (lumps in the muscle, inflammation and severe redness of the skin) and in young B. tigrinum (perforation of the abdominal cavity), while in adult specimens of the remaining species, no external damage was reported.

CONCLUSION

The presence of Eustrongylides sp. in various fish species collected in the city of Iquitos-Peru contributes to the distribution of this parasite in the Peruvian Amazon, reporting it, for the first time in this country. Its presence in the muscle of various fish species commercialized in fish markets, warm a possible public health concern and implications for their marketability in the city of Iquitos, Peru.

Host-dependent impairment of parasite development and reproduction in the acanthocephalan model

BACKGROUND

A central question in parasitology is why parasites mature and reproduce in some host species but not in others. Yet, a better understanding of the inability of parasites to complete their life cycles in less suitable hosts may hold clues for their control. To shed light on the molecular basis of parasite (non-)maturation, we analyzed transcriptomes of thorny-headed worms (Acanthocephala: Pomphorhynchus laevis), and compared developmentally arrested worms excised from European eel (Anguilla anguilla) to developmentally unrestricted worms from barbel (Barbus barbus).

RESULTS

Based on 20 RNA-Seq datasets, we demonstrate that transcriptomic profiles are more similar between P. laevis males and females from eel than between their counterparts from barbel. Impairment of sexual phenotype development was reflected in gene ontology enrichment analyses of genes having differential transcript abundances. Genes having reproduction- and energy-related annotations were found to be affected by parasitizing either eel or barbel. According to this, the molecular machinery of male and female acanthocephalans from the eel is less tailored to reproduction and more to coping with the less suitable environment provided by this host. The pattern was reversed in their counterparts from the definitive host, barbel.

CONCLUSIONS

Comparative analysis of transcriptomes of developmentally arrested and reproducing parasites elucidates the challenges parasites encounter in hosts which are unsuitable for maturation and reproduction. By studying a gonochoric species, we were also able to highlight sex-specific traits. In fact, transcriptomic evidence for energy shortage in female acanthocephalans associates with their larger body size. Thus, energy metabolism and glycolysis should be promising targets for the treatment of acanthocephaliasis. Although inherently enabling a higher resolution in heterosexuals, the comparison of parasites from definitive hosts and less suitable hosts, in which the parasites merely survive, should be applicable to hermaphroditic helminths. This may open new perspectives in the control of other helminth pathogens of humans and livestock.

Comprehensive analysis of codon usage pattern in Withania somnifera and its associated pathogens: Meloidogyne incognita and Alternaria alternata

Meloidogyne incognita (Root-knot nematode) and Alternaria alternata (fungus) were among the dominant parasites of the medicinal plant Withania somnifera. Despite the fatal nature of their infection, a comprehensive study to explore their evolution and adaptation is lacking. The present study elucidates evolutionary and codon usage bias analysis of W. somnifera (host plant), M. incognita (root-knot nematode) and A. alternata (fungal parasite). The results of the present study revealed a weak codon usage bias prevalent in all the three organisms. Based on the nucleotide analysis, genome of W. somnifera and M. incognita was found to be A-T biased while A. alternata had GC biased genome. We found high similarity of CUB pattern between host and its nematode pathogen as compared to the fungal pathogen. Inclusively, both the evolutionary forces influenced the CUB in host and its associated pathogens. However, neutrality plot indicated the pervasiveness of natural selection on CUB of the host and its pathogens. Correspondence analysis revealed the dominant effect of mutation on CUB of W. somnifera and M. incognita while natural selection was the main force affecting CUB of A. alternata. Taken together the present study would provide some prolific insight into the role of codon usage bias in the adaptability of pathogens to the host’s environment for establishing parasitic relationship.

Morphology, genetic characterization and molecular phylogeny of the poorly known nematode parasite Cissophyllus leytensis Tubangui & Villaamil, 1933 (Nematoda: Ascaridida) from the Philippine sailfin lizard Hydrosaurus pustulatus (Eschscholtz, 1829) (Reptilia: Squamata)

Background

The genus Cissophyllus (Cosmocercoidea: Kathlaniidae) is a rare group of nematodes parasitic in turtles and lizards. To date, only four species have been reported in Asia and North America. However, most of them are inadequately described. The species Cissophyllus leytensis has never been reported since it was originally described by Tubangui and Villaamil in 1933 from the Philippine sailfin lizard Hydrosaurus pustulatus (Eschscholtz, 1829) (Reptilia: Squamata). Furthermore, the systematic status of Cissophyllus/Cissophyllinae in the family Kathlaniidae of the superfamily Cosmocercoidea remains under debate.

Methods

The detailed morphology of C. leytensis was studied using light microscopy (LM) and, for the first time, scanning electron microscopy (SEM), based on newly collected specimens from the type host H. pustulatus. Six different genetic markers, including nuclear sequences [small ribosomal subunit (18S), internal transcribed spacer (ITS) and large ribosomal subunit (28S)], plus mitochondrial genes [cytochrome c oxidase subunit 1 (cox1), cytochrome c oxidase subunit 2 (cox2) and 12S small subunit ribosomal RNA gene] of C. leytensis were sequenced. Additionally, in order to test the validity of the subfamily Cissophyllinae and clarify the phylogenetic relationships of Cissophyllus and the other genera in the family Kathlaniidae, phylogenetic analyses based on 18S + 28S and ITS sequence data were performed using maximum likelihood (ML) and Bayesian inference (BI) analyses, respectively.

Results

Our observations using LM and SEM revealed some previously unreported morphological features, necessitating the redescription of this poorly known species. The presence of remarkable morphological variation in the isthmus and the position of excretory pore among different individuals was found. Molecular analysis showed no intraspecific nucleotide divergence detected in the 18S, ITS, 28S, cox2 and 12S regions among different individuals of C. leytensis, but a low level of intraspecific genetic variation was found in the cox1 (0.52%). Our phylogenetic results showed the representatives of the Cosmocercoidea divided into four large clades (Cosmocerca + Aplectana + Cosmocercoides representing the family Cosmocercidae, Cruzia representing the subfamily Cruzinae of Kathlaniidae, Falcaustra + Cissophyllus + Megalobatrachonema representing the subfamily Kathlaniinae of Kathlaniidae, and Orientatractis + Rondonia representing the family Atractidae). The genus Cissophyllus clustered together with the genus Megalobatrachonema in both the ML and BI trees using ITS sequence data, but displayed a sister relationship to the genus Falcaustra in the ML tree and to the genera Falcaustra + Megalobatrachonema in the BI tree using 18S + 28S sequence data.

Conclusions

Molecular phylogenetic results further confirmed that the family Kathlaniidae is not a monophyletic group. The subfamily Cruziinae should be moved from the hitherto-defined family Kathlaniidae and elevated as a separate family Cruziidae. The present phylogenetic results also negated the validity of the subfamily Cissophyllinae and supported the genus Cissophyllus assigned in the subfamily Kathlaniinae. Molecular analysis indicated that the morphological variation in the isthmus and position of excretory pore among different individuals should be considered as intraspecific variation. Moreover, some characters important for the specific diagnosis of C. leytensis are reported for the first time: the number of acuminate denticles (lamellae) on each lip, the chitinized pharynx with three flabellate pharyngeal plates, the presence of single medioventral precloacal papilla and the detailed morphology of caudal papillae. The present study is only the second record of C. leytensis.

Graphical Abstract

REVIEW OF DIOCTOPHYME RENALE: ETIOLOGY, MORPHOLOGY, BIOLOGY, ECOEPIDEMIOLOGY, PATHOGENESIS, SYMPTOMATOLOGY, DIAGNOSIS, TREATMENT, AND PREVENTION

Dioctophyme renale has a worldwide distribution and has been diagnosed in several wild and domestic animals as well as in humans. As numerous reports in the literature exist concerning the presence of D. renale in different animal species, as well as its diagnosis, treatment, and confirmation in new geographic areas, we reviewed existing information to contribute to the knowledge of the etiology, biology, epidemiology, pathogenesis, symptoms, diagnosis, treatment, and prevention of D. renale. Results of dioctophymosis may range from asymptomatic infection to even death of the host. Diagnosis is based on data from morphology, imaging, and antibody testing, with surgical treatment being the most effective. A high potential for infection of pets exists when there is overlap with wild parasitized animals; given common risk factors for infections in humans, D. renale should be considered as having zoonotic potential.

Lurking in the water: testing eDNA metabarcoding as a tool for ecosystem-wide parasite detection

In the light of global biodiversity change and emerging disease, there is an urgent need to establish efficient monitoring programmes of parasites in aquatic ecosystems. However, parasite identification is time-consuming, requires a high degree of taxonomic expertize and in general requires lethal sampling. The use of environmental DNA methodology to identify parasites has the potential to circumvent these limitations. This study evaluates the use of eDNA metabarcoding to detect the presence of all species of nematode and platyhelminth parasites in two New Zealand lakes. We developed two novel metabarcoding primer pairs targeting a region of cytochrome oxidase I gene (COI) specific to platyhelminths and nematodes. We successfully detected parasite DNA in both lakes. Platyhelminth DNA yield was in general greater than nematode DNA yield. This most likely results from the larger biomass of the former quantified using traditional methods, or the presence of free-swimming life stages in the life cycle of many platyhelminths. By using eDNA, we did not detect all expected parasite families revealed through traditional methods, likely due to a lack of sequencing data available from public databases such as GenBank. As such, genetic resources need to include full reference sequences if parasitology is to truly harness eDNA to characterize and monitor parasite biodiversity in natural systems.

Gleasonian structure in the helminth metacommunity of the opossum Didelphis albiventris in two extremes of the Atlantic Forest

Didelphis albiventris is the opossum with the largest geographic distribution in Brazil and has a wide spectrum of helminth parasites. This study aimed to describe the species composition and analyse the structure of helminth communities of D. albiventris in two extremes of the Atlantic Forest in Brazil. The influence of host sex, body mass, age, helminth species richness and locality on the abundance and prevalence of the most prevalent helminth species was investigated. Ninety-five per cent of the animals were infected with at least one species. Nine helminth species were found: the nematodes Aspidodera raillieti, Cruzia tentaculata, Trichuris didelphis and Trichuris minuta in the large intestine; Turgida turgida in the stomach; Travassostrongylus orloffi and Viannaia hamata; and the trematodes Brachylaima advena and Rhopalias coronatus in the small intestine. Three helminth morphospecies were also recovered: the nematodes Hoineffia sp. and Viannaia sp. and a cestode in the small intestine. Cruzia tentaculata and V. hamata were the species with the highest mean abundances and intensities, while the most prevalent species were A. raillieti, C. tentaculata, T. turgida and V. hamata, forming the central nucleus of the helminth component community. The analysis of the helminth metacommunity structure indicated a Gleasonian pattern for the total set of infracommunities, corroborating the beta diversity indices, which indicated more species replacement than loss between localities and infracommunities, although at a low level. The results indicated a stronger influence of host attributes than geographical distance on the community structure.

Three new species of Cosmocerca Diesing, 1861 (Nematoda: Cosmocercidae) parasitising frogs Cacosternum boettgeri Boulenger, 1882, Kassina senegalensis Dumeril and Bibron, 1841 and Phrynomantis bifasciatus Smith, 1847 from South Africa

Cosmocercid nematodes have been documented with much criticism due to the numerous inaccurate descriptions, redescriptions and synonymisation of found species. This is due to indistinguishable characters of females and the lack of male specimens found. Consequently, the species C. ornata is the most commonly found species worldwide and the only species of the genus reported in South Africa. In the present study, we found Cosmocerca in three different amphibian species, namely Cacosternum boettgeri, Kassina senegalensis and Phrynomantis bifasciatus. Based on differences in the shape of the gubernaculum and number of papillae, the found nematodes were assigned to three new species namely C. daly n. sp., C. monicae n. sp. and C. makhadoensis n. sp. Descriptions of species are followed by pairwise and phylogenetic analysis of partial ITS-28S sequences. All three species were found only in their host types from distant localities. Therefore, we hypothesise that host specificity of Cosmocerca from South African amphibians might be rather high and that the presence of C. ornata throughout South Africa is rather doubtful.

Endohelminth Fauna of Teleost Fishes from Coasts of Şile Region of the Black Sea

A total of 508 fish specimens belonging to 19 species collected in the coast of Şile region of the Black sea were examined to detect the presence of endohelminths. Of this, 357 (70.27%) were found to be infected with parasites. 15 distinct helminths species were recovered including four species of nematodes, seven digenean species, one species of cestodes and three species of acanthocephalans. It was also determined that the species of nematode Hysterothylacium aduncum was the most common parasite and the most diverse endohelminth fauna was found in Gobius niger and Solea vulgaris, with five species. Furthermore, it should be noted that Capillaria gracilis is reported for the first time from the Turkish coasts. The infection rates, hosts, and parasites are listed in this paper.

Benchmarking Australian sheep parasite control: Changes in gastrointestinal nematode control practices reported from surveys between 2003 and 2019

Cross-sectional surveys of sheep parasite control practices in Australia were conducted in 2004, 2012 and 2019 to document parasite problems, control practices and measure change over time. This article reports the results pertaining to gastrointestinal nematode infection; comparisons between years are mostly descriptive and not based on statistical inference. There was a general increase in the use of grazing management to prepare clean pastures for sheep to control gastrointestinal nematode infections with the largest increases in the use of: cropping, long acting anthelmintics to prepare clean pastures, feeding strategies, selecting rams for resistance to nematodes, and leaving some sheep untreated. The proportion of respondents using faecal worm egg count monitoring (WEC) and the number of WEC monitors per year were similar in 2003 (weaners: 3.0 WEC/year, adult ewes: 2.6 WEC/year) and 2018 (lambs and weaners and adult ewes both 3.1 WEC/year) but lower in 2011(lambs and weaners: 2.0 WEC/year, adult ewes: 2.9 WEC/year), whilst there was a higher number of anthelmintic treatments given in 2011 than 2003 and 2018 which were similar. There was an increase in the proportion of respondents carrying out WEC monitors themselves from 2011 (21%) to 2018 (30%) and a corresponding reduction in the use of private laboratories, government laboratories and veterinarians with regional differences in who carried out WECs. The top three anthelmintic groups used did not differ between the three survey years with macrocyclic lactones the most used followed by benzimidazoles (BZ) and levamisole (LEV) although the percentage of MLs used in 2011 and 2018 was lower than in 2003 with higher proportions of respondents using BZ and LEV groups in the latter two survey years. Moxidectin was in the most commonly used active in all survey years. There was an increase in the use of combination of anthelmintics from different groups, especially for a combination of three anthelmintics (2003: 4.4%, 2011: 19.1%, 2018: 21.5%), with lower use of single anthelmintics in 2011 (57.0%) and 2018 (55.4%) compared with 2003 (74.5%). The use of testing for anthelmintic resistance was generally low across the survey years with a lower proportion of respondents using tests in 2011 and 2018 than in 2003 (2003:48%, 2011: 29%, 2018: 37%). Time of year, results from WEC and seasonal weather condition were the most important factors when deciding when to apply anthelmintic treatment.

Helminth fauna and histopathology associated with parasitic infections in Phrynops geoffroanus (Schweigger, 1812) (Testudines, Chelidae) in a Brazilian river subjected to anthropogenic activities

The objective of this study was to determine the structure of the helminth fauna and identify the macroscopic and histopathological alterations associated with parasitic infections in Phrynops geoffroanus. Freshwater turtles of both sexes were captured during the dry and rainy seasons in four municipalities along the Capibaribe River. The study included 63 animals, of which 79.37% (50/63) were parasitized by one or more helminths. In total, 933 helminths of seven taxa were recovered: Serpinema monospiculatus, Spiroxys figueiredoi, Nematophila grandis, Polystomoides brasiliensis, Cheloniodiplostomum testudinis, Telorchis birabeni, and Prionosomoides scalaris. Monogeneans and digenetic trematodes were more sensitive to environmental pressures, since the prevalences varied significantly between areas. Nematodes proved to be more resistant to environmental pressure and caused severe injuries to their hosts: nodules in the stomach and small intestine, adhesions in the liver capsule, and pulmonary emphysema. Parasitic granulomas were recorded at the infection sites and in the lungs and liver, the latter caused by migration of S. figueiredoi larvae. This is the first record of P. brasiliensis, N. grandis, C. testudinis, and T. birabeni parasitizing P. geoffroanus in the state of Pernambuco. Histopathology proved to be an important tool for studies on the impact of parasites at the individual, population, and ecosystem levels. Considering the use of the Capibaribe River for public water supply, fishing, and other activities, within the One Health perspective, this study demonstrates that the anthropogenic impact affects parasites and their hosts, in addition to the human population that uses this ecosystem.

Diversity and Ecology of Endohelminth Parasites in a Fish Assemblage of an Amazon River Tributary in Brazil

PURPOSE

This study investigated the diversity and ecology of endohelminth parasites in an assemblage of 15 omnivorous and four piscivorous fish species in a tributary of the Amazon River (Brazil).

METHODS

Fish were collected bimonthly to evaluate the diversity and ecology of endohelminth parasites in omnivorous and piscivorous fish species in a tributary of the Amazon River using traditional methods and other methods.

RESULTS

A total of 4,234 parasites of 19 species (8 Nematoda, 5 Acanthocephala, 4 Digenea and 2 Cestoda) were sampled from 531 fish specimens. Procamallanus (Spirocamallanus) inopinatus and Contracaecum sp. were the predominant parasite species, and the parasites showed an aggregated dispersion pattern. Positive correlation was shown between the abundance of Contracaecum sp., Hysterothylacium patagonense and P. (S.) inopinatus, and the body size of 15.8% of the host fish examined. No difference was shown for Shannon diversity index and evenness between omnivorous and piscivorous hosts, but the richness, abundance and intensity of parasites were greater in piscivorous host fish.

CONCLUSION

In the fish assemblage, the presence of parasites in the larval and adult stages suggests that these are intermediate, paratenic and definitive hosts, reflecting the feeding habits of the omnivorous and piscivorous host species. 74.1% of the parasite species were new records for the different host species examined. The size of the hosts, trophic level and diet had an influence on the structuring of endohelminth communities and infracommunities.

Helminths of the Antarctic dragonfish, Parachaenichthys charcoti (Perciformes, Notothenioidei, Bathydraconidae) Studied near Galindez Island (Argentine Islands, West Antarctica)

PURPOSE

The Antarctic dragonfish, Parachaenichthys charcoti is a notothenioid teleost fish endemic to the Southern Ocean surrounding Antarctica. It is a relatively rare fish species; therefore, published data on the parasite communities of P. charcoti are limited. The present study was performed on the Ukrainian Antarctic Station "Akademik Vernadsky", Argentine Islands, West Antarctica and the purpose was to examine the species diversity of the parasites of P. charcoti and to identify the parameters of helminth infection and helminth component community.

METHODS

Fifteen specimens of P. charcoti were caught at a depth of 10-30 m and examined using standard parasitological techniques. All helminths (6251 specimens) were collected manually, fixed in 70% ethanol and identified based on their morphology.

RESULTS

All examined specimens of P. charcoti were found to be infected with helminths; each fish harboured 10-20 helminth species (mean 13.2; median 13) and 237-804 helminth specimens (mean 417; median 401). Twenty-seven helminth species were found, including nine species of trematodes, 4 of cestodes, 4 of nematodes and 10 of acanthocephalans. P. charcoti is the definitive host for 11 out of 27 helminth species recorded. In the helminth component community, the diversity indices were 2.03 (Shannon's index) and 0.79 (Simpson's index); Pielou evenness index was 0.61, and Berger-Parker dominance index was 0.38.

CONCLUSIONS

Our results indicate a high species diversity and complex structure of the helminth community in Antarctic dragonfish P. charcoti in the Argentine Islands.

Pseudocapillaria (Ichthyocapillaria) bumpi n. sp. (Nematoda: Capillariidae) Parasitising West African Lungfish Protopterus annectens (Owen, 1839) (Lepidosireniformes: Protopteridae) in Mozambique and Its Phylogenetic Position Within Capillariid Nematodes

INTRODUCTION

Pseudocapillaria (Ichthyocapillaria) bumpi n. sp. (Nematoda: Capillariidae) is described from specimens infecting the digestive tract of the West African lungfish, Protopterus annectens (Owen) (Lepidosireniformes: Protopteridae).

METHODS

Nematodes were collected in Karingani Game Reserve, Southern Mozambique and studied using light microscopy; obtained sequences of the 18S ribosomal (18S rRNA) gene used for phylogenetic studies.

RESULTS

The new species is assigned to Pseudocapillaria Freitas, 1959 by having a stichosome consisting of a single row of stichocytes and ventrolateral lobes on the male tail as well as by lacking spines on the specular sheath, caudal alae, a membranous caudal bursa, and a lateral expansion of the caudal end. It is also assigned to the sub-genus Ichthyocapillaria Moravec, 1982 by having a membrane between the ventrolateral lobes and by lacking a vulvar appendage. Pseudocapillaria (I.) bumpi n. sp. differs from its nominal congeners by having a comparatively large body size with relatively long spicule, bearing the thin membrane non-extending further than ventrolateral lobes in males and relatively smaller eggs without protruding polar plugs. It is the 20th species of the genus, the first from the Afrotropical Realm, and the first from any lungfish species. Phylogenetic analyses suggested that P. (I.) bumpi is deeply nested in a clade that associates species of the genera Pearsonema, Aonchotheca and Baruscapillaria.

Soil invertebrates of coniferous forests along a gradient of air pollution (Komi Republic)

Background

The role of soil invertebrates in the cycle of substances, soil-forming processes and the provision of ecosystem services is undeniable. Therefore, soil invertebrates are valuable in bioindication studies. Comprehensive research of soil invertebrates in the production area of Mondi Syktyvkar JSC as the largest pulp and paper enterprise in the European part of Russia was initiated in 2003. A huge amount of data about composition, abundance and structure of soil macro- and mesofauna along an impact gradient was accumulated during the period from 2003 to 2019 years. These data can be used to study local biodiversity, monitor the state of soil invertebrate communities and assess the impact of the pulp and paper industry on the environment.

New information

Datasets here presented include information from a monitoring programme for soil invertebrates that inhabit coniferous forests in the production area of Mondi Syktyvkar JSC (Komi Republic). The assemblages' structure of macrofauna, collembolans and nematodes are described. Information on the number of individuals of springtail species, nematodes genera and macrofauna taxa is given. A total of 11146 sampling events of macrofauna, 6673 sampling events of Collembola, and 2592 sampling events of Nematoda are recorded along a gradient of air pollution from pulp and paper industry emissions.

Morphological and molecular characterization of Paraleptus chiloscyllii Yin & Zhang, 1983 (Nematoda: Physalopteridae) from the brownbanded bambooshark Chiloscyllium punctatum Müller & Henle (Elasmobranchii: Orectolobiformes)

Paraleptus (Spirurida: Physalopteridae) is a small genus of nematodes, parasitic in fishes, most species of which are inadequately described. Genetic data for these congeners have not been reported. The detailed morphology of P. chiloscyllii was studied using light and scanning electron microscopy, based on newly collected specimens from the brownbanded bambooshark C. punctatum Müller & Henle (Elasmobranchii: Orectolobiformes) in the Taiwan Strait. Some previously unreported morphological features of taxonomic significance were observed, i.e., pseudolabium with two sublateral rows of 6-7 small spines, 7-8 small spines on each lower rim between pseudolabia, deirids not distally bifurcated, vulva with remarkable protruding lip, presence of 1 pair medio-ventral precloacal papillae and 1 pair of discoid protrusions of postcloacal lip in male. The specimens described by González-Solís & Ali's (2015) as P. chiloscyllii from the Arabian carpetshark C. arabicum off Iraq are considered a new species, for which the name P. moraveci n. sp. is proposed. The genetic characterization of the partial small (18S) and large (28S) ribosomal DNA, and the partial mitochondrial cytochrome c oxidase subunit 1 (cox1) of P. chiloscyllii are provided for the first time. There was no intraspecific nucleotide divergence detected in the 18S and 28S regions among different individuals of P. chiloscyllii, but a low level of intraspecific genetic variation was found in the cox1 (0.62-0.92%). The present genetic data is very important for molecular identification, and will be valuable for further invertigantions on the population genetics and phylogeny of this group.

Morphology, genetic characterization and phylogeny of Aplectana dayaoshanensis n. sp. (Nematoda: Ascaridida) from frogs

Cosmocercoid nematodes are common parasites in the digestive tract of amphibians. However, our knowledge of the species diversity, genetic data and molecular phylogeny of the superfamily Cosmocercoidea are far from being well understood. In the present study, large numbers of cosmocercoid nematodes were collected from the fine-spined frog Sylvirana spinulosa (Smith) (Anura: Ranidae) and the white-spotted thigh tree-frog Polypedates megacephalus (Hallowell) (Anura: Rhacophoridae) in Guangxi Province, China. Integrated morphological and genetic evidence reveals these nematode specimens to be a new species of the genus Aplectana, A. dayaoshanensis n. sp. (Cosmocercoidea: Cosmocercidae). The molecular characterization of small ribosomal DNA (18S), internal transcribed spacer (ITS) and large ribosomal DNA (28S) of A. dayaoshanensis n. sp., together with the 28S of A. chamaeleonis (Baylis, 1929) (collected from Hyperolius kivuensis Ahl in Rwanda), were reported for the first time. Moreover, phylogenetic analyses using maximum likelihood (ML) inference based on 18S + 28S and ITS sequence data, respectively, both supported the family Cosmocercidae to be a monophyletic group and the family Kathlaniidae to be a paraphyletic group. Our phylogenetic results rejected the monophyly of the genus Aplectana. The present results contribute to the knowledge of the species diversity and genetic data of cosmocercoid nematodes, and preliminarily revealed the phylogenetic relationships of the major families and some genera in the Cosmocercoidea.

New free-living nematode species and records (Chromadorea: Plectida and Desmodorida) from the edge and axis of Kermadec Trench, Southwest Pacific Ocean

One new nematode species is described and two new species records are provided from the edge (6,080 m depth) and axis (7,132 m) of Kermadec Trench, Southwest Pacific. Leptolaimus hadalis sp. nov. is characterised by medium body 587-741 μm long, labial region not offset from body contour, inconspicuous labial sensilla, amphid located 12-19 μm from anterior end, female without supplements, male with four tubular precloacal supplements (alveolar supplements absent), tubular supplements almost straight with dentate tip, arcuate spicules and weakly cuticularized dorsal gubernacular apophyses strongly bent distally. In a previously published ecological survey of Kermadec Trench, L. hadalis sp. nov. was the most abundant species in a core obtained at 8,079 m water depth and third most abundant species in a core obtained at 7,132 m, while only one individual was found at 6,096 m depth, and none at 9,175 m depth (Leduc & Rowden, 2018). Alaimella aff. cincta and Desmodora aff. pilosa are recorded for the first time from the Southwest Pacific region. Prior to the present study, Alaimella had only been recorded from coastal locations and from the Weddell sea to a depth of 2,000 m. The record of Desmodora aff. pilosa at 6,080 m depth is the deepest record of a Desmodora species to date, although unidentified Desmodora specimens have been found as deep as 6,300 m in the South Sandwich Trench. The morphology of the Kermadec Trench Alaimella aff. cincta and Desmodora aff. pilosa specimens bear a strong resemblance to their respective type populations from the Northern Hemisphere, but further morphological and molecular data are required to ascertain whether they in fact represent distinct species.

What is the difference between marine and limnetic-terrestrial associations of nematodes with invertebrates?

Zoo- and phyto-parasitic nematodes of the order Rhabditida and zooparasites of the subclass Dorylaimia are well known, due largely to their medical, veterinarian and agricultural significance. However, there have been many switches from a free-living to a symbiotic (including parasitism) mode of existence in the evolutionary trajectories of various nematode clades. Here, we attempt to summarize all known cases of symbioses (from commensalism to true parasitism) between marine nematodes representing nonparasitic taxa and various larger animals, ranging from protists to vertebrates. Most cases are of nematodes relating to dwelling on crustaceans (ectocommensalism) or living in the body cavity and internal organs of various invertebrates (endoparasitism or parasitoidism). Ectocommensal species may differ from their free-living relatives in their longer filiform bodies and enlarged ventral and caudal glands, which may be interpreted as adaptations for the purpose of fixation on the body surface of a motile host. Endoparasitic species are characterized by deep anatomical modification, including rudimentation of the alimentary tract and hypertrophy of reproductive organs. Unlike terrestrial and limnetic invertebrates, marine invertebrates have almost no intestinal nematode dwellers. The evolutionary trajectories of nematode dwellers of marine and nonmarine invertebrates are compared.

A longitudinal survey of gastrointestinal parasites of the black-eared opossum Didelphis aurita at an urban-sylvatic interface area in Southeast Brazil: a morphological and ecological characterization based on helminth eggs

Parasites are important organisms in ecosystem dynamics and take part in the regulation and structure of host populations. The prevalence, abundance, and distribution of parasites in their host species may be affected by biotic and abiotic factors. Most studies of helminths of Brazilian marsupials are taxonomic descriptions or re-descriptions and records of occurrence. The use of noninvasive techniques for studying parasitic worms of vertebrate hosts is more common in large or threatened species. The aims of this study were to describe and identify the helminth morphotypes and to analyse the parasitological parameters of gastrointestinal helminth eggs obtained in faecal samples of marsupial Didelphis aurita at the Fiocruz Atlantic Forest Biological Station and surroundings, municipality of Rio de Janeiro, southeast Brazil. The common opossums were sampled during a capture-mark-recapture study. Faecal samples collected from each animal were analysed for helminth egg diagnosis using the methods of flotation in sugar solution and sedimentation. Eggs were compared with samples obtained from the uterus of adult worms obtained from a previous study carried out in the same area. Eleven helminth egg morphotypes were found. Among them, seven were identified at the species level. The highest values of parasitic load and prevalence were observed for the families Viannaiidae and Trichuridae. A significant relationship was found between the number of morphotypes and host body size in females. The influence of parasite load on host condition factor or body size was not observed.

Gastrointestinal Helminths in Amietia sp. (Anura: Pyxicephalidae) from the Albertine Rift of Central Africa

Fourteen Amietia sp. (Pyxicephalidae), from the Albertine Rift of Democratic Republic of the Congo were examined for helminths. Five species of Nematoda were found: Amphibiophilus chabaudi, Aplectana praeputialis, Falcaustra congoensis, Foleyellides duboisi and Orneoascaris chrysanthemoides. Amphibiophilus chabaudi was the most numerous nematode (n = 40) with the highest prevalence (57 %). Five new host records are reported.

Spiroxys ankarafantsika Roca et Garcia, 2008 (Nematoda: Gnathostomatidae) and Other Nematodes Parasitising Pelusios spp. (Testudines: Pelomedusidae) from South Africa and Mozambique

INTRODUCTION

The nematode Spiroxys ankarafantsika was described parasitising freshwater turtles Pelusios castanoides and Pelomedusa subrufra from Madagascar. During parasitological surveys at different localities in Mozambique and South Africa the species was recovered from the digestive tract of Pelusios sinuatus, P. subniger and P. castanoides.

METHODS

The species were identified based on the morphology of the anterior extremity (absence of additional teeth on pseudolabia) and the male caudal end (number and arrangement of caudal papillae, size and shape of spicules). Molecular data included a 720 bp sequence fragment of 18S rDNA, the entire internal transcribed spacer 1 (ITS1), 5.8S rRNA, and internal transcribed spacer 2 (ITS), flanked by a 288 bp 18S rDNA sequence and about 1000 bp 28S rDNA sequence, and the mitochondrial cytochrome c oxidase subunit I (cox1) gene marker obtained in the present study.

RESULTS

All specimen recovered were identical, based on morphological and molecular data, with the exception of two specimens showing an intraspecific divergence of 9% based on a 694 bp sequence fragment of the cox1 gene. Additionally, a Contracaecum sp. third stage larva and an unidentified larva with mushroom-shaped anterior extremity were found. Descriptions of S. ankarafantsika and the two above-mentioned larval stages, supported by photomicrographs and molecular data 18S rDNA, ITS1-5.8S-ITS2-28S and cox1 gene fragments are presented herein.

Genus-level evolutionary relationships of FAR proteins reflect the diversity of lifestyles of free-living and parasitic nematodes

Background

Nematodes are a widespread and diverse group comprising free-living and parasitic species, some of which have major detrimental effects on crops, animals, and human health. Genomic comparisons of nematodes may help reveal the genetic bases for the evolution of parasitic lifestyles. Fatty acid and retinol-binding proteins (FARs) are thought to be unique to nematodes and play essential roles in their development, reproduction, infection, and possibly parasitism through promoting the uptake, transport, and distribution of lipid and retinol. However, the evolution of FAR family proteins across the phylum Nematoda remains elusive.

Results

We report here the evolutionary relationship of the FAR gene family across nematodes. No FAR was found in Trichocephalida species and Romanomermis culicivorax from Clade I, and FAR could be found in species from Clades III, IV, and V. FAR proteins are conserved in Clade III species and separated into three clusters. Tandem duplications and high divergence events lead to variable richness and low homology of FARs in Steinernema of Clade IVa, Strongyloides of Clade IVb, and intestinal parasitic nematodes from Clades Vc and Ve. Moreover, different richness and sequence variations of FARs in pine wood, root-knot, stem, and cyst nematodes might be determined by reproduction mode or parasitism. However, murine lungworm Angiostrongylus and bovine lungworm Dictyocaulus viviparus from Clade Vd have only 3–4 orthologs of FAR. RNA-seq data showed that far genes, especially far-1 and far-2, were highly expressed in most nematodes. Angiostrongylus cantonensis FAR-1 and FAR-3 have low sequence homology and distinct ligand-binding properties, leading to differences in the cavity volume of proteins. These data indicate that FAR proteins diverged early and experienced low selective pressure to form genus-level diversity. The far genes are present in endophyte or root-colonized bacteria of Streptomyces, Kitasatospora sp., Bacillus subtilis, and Lysobacter, suggesting that bacterial far genes might be derived from plant-parasitic nematodes by horizontal gene transfer.

Conclusions

Data from these comparative analyses have provided insights into genus-level diversity of FAR proteins in the phylum Nematoda. FAR diversification provides a glimpse into the complicated evolution history across free-living and parasitic nematodes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-021-01111-3.