Three new species of Pharygodonidae (Nematoda: Oxyuridea) in Laudakia tuberculata (Squamata: Agamidae) from Dehradun, Uttarakhand, India

Parapharyngodon tuberculata sp. nov., Thelandros tuberculata sp. nov. and Thelandros dehradunensis sp. nov. (Nematoda: Pharyngodonidae) from the large intestine of a rock lizard, Laudakia tuberculata Gray, 1827), are described and illustrated. Parapharyngodon tuberculata sp. nov. is the 8th Oriental species and 59th species assigned to the genus Parapharyngodon and differs from other species of the genus by possessing 3 pairs of caudal papillae, an echinate cloacal lip, 112-115 µm spicule length and postbulbar ovary. Thelandros tuberculata sp. nov. is the 5th and Thelandros dehradunensis sp. nov. the 6th Oriental species, respectively, and they are the 40th and 41st species assigned to the genus Thelandros. They differ from other species of the genus in caudal papillae arrangement, length of spicules, and structure of the anterior end of the esophagus. We transfer Parapharyngodon arequipensis Calisaya and Cordova, 1997 to Thelandros arequipensis (Calisaya and Cordova, 1997) comb. n. based upon the presence of a terminal operculum in the egg and large, pendant, caudal papillae.

Distinct genetic differentiation and species diversification within two marine nematodes with different habitat preference in Antarctic sediments

Background

Dispersal ability, population genetic structure and species divergence in marine nematodes are still poorly understood, especially in remote areas such as the Southern Ocean. We investigated genetic differentiation of species and populations of the free-living endobenthic nematode genera Sabatieria and Desmodora using nuclear 18S rDNA, internal transcribed spacer (ITS) rDNA, and mitochondrial cytochrome oxidase I (COI) gene sequences. Specimens were collected at continental shelf depths (200–500 m) near the Antarctic Peninsula, Scotia Arc and eastern side of the Weddell Sea. The two nematode genera co-occurred at all sampled locations, but with different vertical distribution in the sediment. A combination of phylogenetic (GMYC, Bayesian Inference, Maximum Likelihood) and population genetic (AMOVA) analyses were used for species delimitation and assessment of gene flow between sampling locations.

Results

Sequence analyses resulted in the delimitation of four divergent species lineages in Sabatieria, two of which could not be discriminated morphologically and most likely constitute cryptic species. Two species were recognised in Desmodora, one of which showed large intraspecific morphological variation. Both genera comprised species that were restricted to one side of the Weddell Sea and species that were widely spread across it. Population genetic structuring was highly significant and more pronounced in the deeper sediment-dwelling Sabatieria species, which are generally less prone to resuspension and passive dispersal in the water column than surface Desmodora species.

Conclusions

Our results indicate that gene flow is restricted at large geographic distance in the Southern Ocean, which casts doubt on the efficiency of the Weddell gyre and Antarctic Circumpolar Current in facilitating circum-Antarctic nematode species distributions. We also show that genetic structuring and cryptic speciation can be very different in nematode species isolated from the same geographic area, but with different habitat preferences (surface versus deeper sediment layers).

Electronic supplementary material

The online version of this article (doi:10.1186/s12862-017-0968-1) contains supplementary material, which is available to authorized users.

Integrative taxonomy of Goezia spinulosa (Nematoda: Raphidascarididae) from arapaimas in the northwestern Brazil

Arapaima gigas, a fish with a high market value, has been farmed in different localities within Brazil. Among its parasites, adults of Goezia spinulosa are reported to cause ulcers in the stomach and to result in the death of farmed fingerlings. Due to the veterinary importance of this nematode in cultured arapaimas, an integrative taxonomic study is proposed, combining morphological, ultrastructural and genetic profiles of this parasite. The fish were obtained from semi-intensive fish farming in Acre State, Brazil. The fish measured 7-42cm in total length and the intensity of infection was 1-60 parasites per fish. The site of infection was mainly the stomach. Morphological and ultrastructural analyses of G. spinulosa showed the importance of its spiny body in firmly attaching the worm to the gastric mucosa, resulting in lesions, ulcers and deep gastric perforations of the stomach wall. New sequences for partial 18S rDNA, ITS1, 5.8S and ITS2 rDNA, partial 28S rDNA, cox1 mtDNA and for cox2 mtDNA are presented. Phylogenetic reconstructions based on the partial 18S and 28S rDNA shows species of Goezia occur in a clade well separated from other genera in both analyses. Both the partial 18S and 28S rDNA genes represented good genetic markers for distinguishing genera of the Raphidascarididae, with exception of Hysterothylacium. This integrated taxonomic study produced a robust profile for G. spinulosa that will aid the diagnosis of both adults and larval stages from arapaimas and possible intermediate hosts.

Nematode distributions as spatial null models for macroinvertebrate species richness across environmental gradients: A case from mountain lakes

Nematode species are widely tolerant of environmental conditions and disperse passively. Therefore, the species richness distribution in this group might largely depend on the topological distribution of the habitats and main aerial and aquatic dispersal pathways connecting them. If so, the nematode species richness distributions may serve as null models for evaluating that of other groups more affected by environmental gradients. We investigated this hypothesis in lakes across an altitudinal gradient in the Pyrenees. We compared the altitudinal distribution, environmental tolerance, and species richness, of nematodes with that of three other invertebrate groups collected during the same sampling: oligochaetes, chironomids, and nonchironomid insects. We tested the altitudinal bias in distributions with t-tests and the significance of narrow-ranging altitudinal distributions with randomizations. We compared results between groups with Fisher's exact tests. We then explored the influence of environmental factors on species assemblages in all groups with redundancy analysis (RDA), using 28 environmental variables. And, finally, we analyzed species richness patterns across altitude with simple linear and quadratic regressions. Nematode species were rarely biased from random distributions (5% of species) in contrast with other groups (35%, 47%, and 50%, respectively). The altitudinal bias most often shifted toward low altitudes (85% of biased species). Nematodes showed a lower portion of narrow-ranging species than any other group, and differed significantly from nonchironomid insects (10% and 43%, respectively). Environmental variables barely explained nematode assemblages (RDA adjusted R2 = 0.02), in contrast with other groups (0.13, 0.19 and 0.24). Despite these substantial differences in the response to environmental factors, species richness across altitude was unimodal, peaking at mid elevations, in all groups. This similarity indicates that the spatial distribution of lakes across altitude is a primary driver of invertebrate richness. Provided that nematodes are ubiquitous, their distribution offers potential null models to investigate species richness across environmental gradients in other ecosystem types and biogeographic regions.

Two new species of nematode parasites, Cucullanus epinepheli sp. n. (Cucullanidae) and Procamallanus (Spirocamallanus) sinespinis sp. n. (Camallanidae), from marine serranid and haemulid fishes off New Caledonia

Based on light and scanning electron microscopical studies, two new species of parasitic nematodes are described from marine perciform fishes off New Caledonia: Cucullanus epinepheli sp. n. (Cucullanidae) from the intestine of the brownspotted grouper Epinephelus chlorostigma (Valenciennes) (Serranidae) and Procamallanus (Spirocamallanus) sinespinis sp. n. from the intestine of the silver grunt Pomadasys argenteus (Forsskål) (Haemulidae). Cucullanus epinepheli sp. n. differs from its congeners mainly in possessing a unique structure of the anterior, elevated cloacal lip with a large posterior outgrowth covering the cloacal aperture and in the presence of cervical alae and two small preanal papillae on the median dome-shaped precloacal elevation. This is the second known nominal species of this genus parasitising fishes of the family Serranidae and the second representative of Cucullanus Müller, 1777 recorded from fishes in New Caledonian waters. Procamallanus (Spirocamallanus) sinespinis sp. n. is mainly characterised by 10-12 spiral ridges in the buccal capsule, the presence of wide caudal alae, three pairs of pedunculate preanal papillae, two unequally long spicules (465-525 µm and 218-231 µm) and by the tail tip with a knob-like structure in the male, and the broad, rounded tail with a terminal digit-like protrusion without cuticular spikes in the female. This is the fifth nominal species of the subgenus Spirocamallanus Olsen, 1952 reported from fishes in New Caledonian waters.

Understanding trophic interactions in host-parasite associations using stable isotopes of carbon and nitrogen

BACKGROUND

Stable isotope analysis of carbon and nitrogen can deliver insights into trophic interactions between organisms. While many studies on free-living organisms are available, the number of those focusing on trophic interactions between hosts and their associated parasites still remains scarce. In some cases information about taxa (e.g. acanthocephalans) is completely missing. Additionally, available data revealed different and occasionally contrasting patterns, depending on the parasite's taxonomic position and its degree of development, which is most probably determined by its feeding strategy (absorption of nutrients through the tegument versus active feeding) and its localization in the host.

METHODS

Using stable isotope analysis of carbon and nitrogen we provided first data on the trophic position of an acanthocephalan species with respect to its fish host. Barbels (Barbus barbus) infected only with adult acanthocephalans Pomphorhynchus laevis as well as fish co-infected with the larval (L4) nematodes Eustrongylides sp. from host body cavity were investigated in order to determine the factors shaping host-parasite trophic interactions. Fish were collected in different seasons, to study also potential isotopic shifts over time, whereas barbels with single infection were obtained in summer and co-infected ones in autumn.

RESULTS

Acanthocephalans as absorptive feeders showed lower isotope discrimination values of δ 15N than the fish host. Results obtained for the acanthocephalans were in line with other parasitic taxa (e.g. cestodes), which exhibit a similar feeding strategy. We assumed that they feed mainly on metabolites, which were reprocessed by the host and are therefore isotopically lighter. In contrast, the nematodes were enriched in the heavier isotope δ 15N with respect to their host and the acanthocephalans, respectively. As active feeders they feed on tissues and blood in the body cavity of the host and thus showed isotope discrimination patterns resembling those of predators. We also observed seasonal differences in the isotope signatures of fish tissues and acanthocephalans, which were attributed to changes in food composition of the host and to seasonality in the transmission and development of acanthocephalans.

CONCLUSIONS

This study provided first data on trophic interaction between an acanthocephalan species and its associated host, which support the tendency already described for other taxa with similar nutrition strategy (e.g. cestodes). Actively feeding taxa such as larval Eustrongylides sp., appear to act like predators as it can be seen from their isotope discrimination values. However, future research on additional host-parasite systems and especially on acanthocephalans is needed in order to corroborate these conclusions.

Skin parasitism by Paratrichosoma recurvum in wild American crocodiles and its relation to environmental and biological factors

Paratrichosma spp. are capillarid worms that parasitize the abdominal skin of crocodiles. They are likely not a threat to crocodiles' health, but they affect the skins' commercial value. No successful treatment exists against this parasite, and present knowledge of its life cycle is limited. Herein we report new information on Paratrichosoma recurvum occurrence in wild American crocodiles Crocodylus acutus from Mexican Caribbean islands and its relation to environmental (water salinity, temperature, climatic events) and biological (body condition) factors. The percentage of parasitized crocodiles (30.3%) is among the highest recorded in wild crocodilian populations. Small (<40.8 cm total length [TL]) and large (>270 cm TL) crocodiles are less parasitized, probably due to the characteristics of their skin or of the parasite life cycle. Two individuals appeared to have eliminated worms naturally between their capture and recapture. The thorax-abdomen is the most parasitized area of the body of crocodiles. The risk of infection is not associated with the sex of the crocodile, but there was a difference in the proportion of parasitized crocodiles between sites, which could be related to different environmental conditions. The body condition of a crocodile does not seem to be affected by the parasite. Climatic events and water temperature show no effect on the parasitism of crocodiles, but salinity could have an effect. The infection of crocodiles by P. recurvum could depend more on an individual's behavior than on environmental conditions.

Metabarcoding of marine nematodes - evaluation of similarity scores used in alignment-based taxonomy assignment approach

BACKGROUND

The diversity of organisms is being commonly accessed using metabarcoding of environmental samples. Reliable identification of barcodes is one of the critical steps in the process and several taxonomy assignment methods were proposed to accomplish this task, including alignment-based approach that uses Basic Local Alignment Search Tool (BLAST) algorithm. This publication evaluates the variability of 5' end of 18S rRNA barcoding region as expressed by similarity scores (alignment score and identity score) produced by BLAST, and its impact on barcode identification to family-level taxonomic categories.

NEW INFORMATION

In alignment-based taxonomy assignment approach, reliable identification of anonymous OTUs to supraspecific taxa depends on the correct application of similarity thresholds. Since various taxa show different level of genetic variation, practical application of alignment-based approach requires the determination and use of taxon-specific similarity thresholds.

Orientatractis moraveci n. sp. and Rondonia rondoni Travassos, 1920 (Nematoda: Atractidae), parasites of Pimelodus blochii (Osteichthyes, Pimelodidae) from the Acre and Xapuri Rivers, Western Amazon, Brazil

The fish fauna in the State of Acre represents 10·7% of all fish species recorded from Brazil, but, despite this, there are few fish parasite studies in this area. The recent expansion of fish farming in Acre prompted a need for helminthological studies of the most commonly consumed fish species in the area, Pimelodus blochii (Pimelodidae). The aim of this study was to analyse the helminth fauna of P. blochii from the Acre and Xapuri Rivers in Northwestern Brazil. Numerous nematodes were collected from the intestine and two species of the family Atractidae were identified: Rondonia rondoni Travassos, 1920 and Orientatractis moraveci n. sp. The new species is distinguished from its congeners mainly by having: 10 pairs of caudal papillae (3 pairs pre-cloacal, 2 pairs ad-cloacal and 5 pairs post-cloacal); unequal spicules of 161-198 and 69-100 µ m long; and a gubernaculum 38-58 µ m long with an antero-lateral process. Morphological and ultrastructural data on O. moraveci n. sp. and R. rondoni are presented, in addition to new genetic data based on partial 18S rDNA and 28S rDNA. The taxonomic status of Labeonema synodontisi (Vassiliadès, 1973) is discussed, suggesting that it should be returned to the genus Raillietnema.

Gender and developmental specific N-glycomes of the porcine parasite Oesophagostomum dentatum

BACKGROUND

The porcine nodule worm Oesophagostomum dentatum is a strongylid class V nematode rather closely related to the model organism Caenorhabditis elegans. However, in contrast to the non-parasitic C. elegans, the parasitic O. dentatum is an obligate sexual organism, which makes both a gender and developmental glycomic comparison possible.

METHODS

Different enzymatic and chemical methods were used to release N-glycans from male and female O. dentatum as well as from L3 and L4 larvae. Glycans were analysed by MALDI-TOF MS after either 2D-HPLC (normal then reversed phase) or fused core RP-HPLC.

RESULTS

Whereas the L3 N-glycome was simpler and more dominated by phosphorylcholine-modified structures, the male and female worms express a wide range of core fucosylated N-glycans with up to three fucose residues. Seemingly, simple methylated paucimannosidic structures can be considered 'male', while methylation of fucosylated glycans was more pronounced in females. On the other hand, while many of the fucosylated paucimannosidic glycans are identical with examples from other nematode species, but simpler than the tetrafucosylated glycans of C. elegans, there is a wide range of phosphorylcholine-modified glycans with extended HexNAc_2-4PC_2-4 motifs not observed in our previous studies on other nematodes.

CONCLUSION

The interspecies tendency of class V nematodes to share most, but not all, N-glycans applies also to O. dentatum; furthermore, we establish, for the first time in a parasitic nematode, that glycomes vary upon development and sexual differentiation.

GENERAL SIGNIFICANCE

Unusual methylated, core fucosylated and phosphorylcholine-containing N-glycans vary between stages and genders in a parasitic nematode.

Metabarcoding of marine nematodes - evaluation of reference datasets used in tree-based taxonomy assignment approach

Background

Metabarcoding is becoming a common tool used to assess and compare diversity of organisms in environmental samples. Identification of OTUs is one of the critical steps in the process and several taxonomy assignment methods were proposed to accomplish this task. This publication evaluates the quality of reference datasets, alongside with several alignment and phylogeny inference methods used in one of the taxonomy assignment methods, called tree-based approach. This approach assigns anonymous OTUs to taxonomic categories based on relative placements of OTUs and reference sequences on the cladogram and support that these placements receive.

New information

In tree-based taxonomy assignment approach, reliable identification of anonymous OTUs is based on their placement in monophyletic and highly supported clades together with identified reference taxa. Therefore, it requires high quality reference dataset to be used. Resolution of phylogenetic trees is strongly affected by the presence of erroneous sequences as well as alignment and phylogeny inference methods used in the process. Two preparation steps are essential for the successful application of tree-based taxonomy assignment approach.

Completing the above mentioned preparation steps is expected to decrease the number of unassigned OTUs and thus improve the results of the tree-based taxonomy assignment approach.

Stable isotope analysis (δ (13)C and δ (15)N) of soil nematodes from four feeding groups

Soil nematode feeding groups are a long-established trophic categorisation largely based on morphology and are used in ecological indices to monitor and analyse the biological state of soils. Stable isotope ratio analysis (¹³C/¹²C and ¹⁵N/¹⁴N, expressed as δ¹³C and δ¹⁵N) has provided verification of, and novel insights into, the feeding ecology of soil animals such as earthworms and mites. However, isotopic studies of soil nematodes have been limited to date as conventional stable isotope ratio analysis needs impractically large numbers of nematodes (up to 1,000) to achieve required minimum sample weights (typically >100 µg C and N). Here, micro-sample near-conventional elemental analysis–isotopic ratio mass spectrometry (μEA–IRMS) of C and N using microgram samples (typically 20 µg dry weight), was employed to compare the trophic position of selected soil nematode taxa from four feeding groups: predators (Anatonchus and Mononchus), bacterial feeders (Plectus and Rhabditis), omnivores (Aporcelaimidae and Qudsianematidae) and plant feeder (Rotylenchus). Free-living nematodes were collected from conventionally and organically managed arable soils. As few as 15 nematodes, for omnivores and predators, were sufficient to reach the 20 µg dry weight target. There was no significant difference in δ¹⁵N (p = 0.290) or δ¹³C (p = 0.706) between conventional and organic agronomic treatments but, within treatments, there was a significant difference in N and C stable isotope ratios between the plant feeder, Rotylenchus (δ¹⁵N = 1.08 to 3.22 mUr‰, δ¹³C = –29.58 to –27.87 mUr) and all other groups. There was an average difference of 9.62 mUr in δ¹⁵N between the plant feeder and the predator group (δ¹⁵N = 9.89 to 12.79 mUr, δ¹³C = –27.04 to –25.51 mUr). Isotopic niche widths were calculated as Bayesian derived standard ellipse areas and were smallest for the plant feeder (1.37 mUr²) and the predators (1.73 mUr²), but largest for omnivores (3.83 mUr²). These data may reflect more preferential feeding by the plant feeder and predators, as assumed by classical morphology-based feeding groups, and indicate that omnivory may be more widespread across detritivore groups i.e. bacterial feeders (3.81 mUr²). Trophic information for soil nematodes derived from stable isotope analysis, scaled as finely as species level in some cases, will complement existing indices for soil biological assessment and monitoring, and can potentially be used to identify new trophic interactions in soils. The isotopic technique used here, to compare nematode feeding group members largely confirm their trophic relations based on morphological studies.

Parasite fauna of Antarctic Macrourus whitsoni (Gadiformes: Macrouridae) in comparison with closely related macrourids

BACKGROUND

The extreme, isolated environment within the Antarctic Convergence has fuelled the evolution of a highly endemic fauna with unique adaptations. One species known from this area is the Whitson's grenadier Macrourus whitsoni (Regan, 1913). While closely related species occurring in the Northern Hemisphere were targets of a variety of studies, knowledge on M. whitsoni is scarce, including not only its ecology but also its parasite fauna. Parasites, an often overlooked but important component of every ecosystem, can provide important insights into host ecology, including feeding habits, food web interactions and distribution patterns. The aim of our study was to increase the currently limited knowledge on the ecology of M. whitsoni and its parasite life-cycles.

METHODS

In this study, parasite fauna and stomach content of 50 specimens of M. whitsoni were sampled off Elephant and King George Islands. Fish samples were morphological, food ecological and parasitological examined and parasites morphological and partly molecular identified. To evaluate the findings, results were compared with other macrourid species.

RESULTS

The parasite fauna of M. whitsoni revealed 9 genera and 17 species. Stomach content analysis indicated Amphipoda and Mysida as the primary food source. Considering the parasites of M. whitsoni, the highest diversity was found within the Digenea, while prevalence was highest for the Acanthocephala and Nematoda. The diverse parasite fauna of M. whitsoni together with the stomach content analysis, suggests a benthopelagic mode of life. Furthermore, an extensive evaluation of the parasite fauna of species of the Macrourinae was conducted, which is probably the most thorough one yet, to compare the findings with closely related host fish species. A similarity analysis revealed a strong connection between the parasite fauna composition and geographical distribution, with a clear separation between the parasite faunas in fishes sampled in the Pacific and the Atlantic Oceans.

CONCLUSIONS

Due to the isolated habitat within the Antarctic Conversion, the parasite fauna of M. whitsoni differs clearly from those of closely related and closely occurring species of the genus Macrourus. Our study revealed an endemically dominated parasite fauna, with parasites often host-specific to M. whitsoni. The comparison with the faunas of other species of the Macrourinae revealed a largely endemic parasite fauna, which emphasizes again the isolated character of the Antarctic shelf regions.

F200Y polymorphism of the β-tubulin isotype 1 gene in Haemonchus contortus and sheep flock management practices related to anthelmintic resistance in eastern Amazon

The objective of the present study was to determine the frequency of the F200Y polymorphism in the β-tubulin isotype 1 gene of Haemonchus contortus from various sheep flocks in eastern Amazon, and to identify management practices that may favor the emergence of resistance to anthelmintic drugs in the same area. In total, 305 specimens of H. contortus were collected from sheep at 12 farms located in the state of Pará. An allele-specific PCR was performed to detect the F200Y polymorphism, and questionnaires were used to obtain information about the farms and flocks. All genotypes were detected as follows: 31% of the parasites were RR, 37% of the parasites were SR, and 32% were SS. The completed questionnaires revealed that all farms employed semi-intensive farming systems, performed suppressive anthelmintic treatment, and based their choice of drug on cost and availability rather than on any knowledge regarding drugs that remained effective on their property. It can thus be concluded that the SNP in codon 200 of the β-tubulin isotype 1 gene is present in the H. contortus populations from eastern Amazon, and that a series of management practices that favor the emergence of anthelmintic resistance are employed on these farms.

Taxonomic status of Syngamus nematodes parasitizing passeriform hosts from Central Europe: Morphological, morphometric and molecular identification

The systematic position and validity of species within genus Syngamus have always been controversial. In this present work, we evaluated the taxonomic status and phylogenetic relationships between three species of Syngamus nematodes (Syngamus trachea, Syngamus taiga and Syngamus merulae) and one taxa, determined only to the generic level, collected from respiratory tracts of passeriform hosts from Central Europe using newly obtained sequences of 2 nuclear markers (internal transcribed spacers 1 and 2 [ITS1, ITS2]) and a fragment of mitochondrial cytochrome oxidase I [COI] gene. Our results clearly showed that S. trachea, S. taiga and S. merulae are valid, molecularly and morphologically distinct species. Moreover, molecular analysis of adult female of Syngamus sp. collected from tracheae of the European robin Erithacus rubecula clearly indicate that these comprise separate species. In the derived phylogeny, the Syngamus clade is divided into two sub-clades: one comprised Syngamus species with a characteristic, well-developed cuticular collar around the oral opening (S. trachea and S. taiga) and a second that groups taxa without or with rudimentary collar (S. merulae and currently sequenced Syngamus sp. from Erithacus rubecula). These results clearly suggest that the degree of collar development (well-developed vs. rudimentary/absent) may be an important phylogenetic feature for determining the structure of the genus Syngamus on subgeneric level. Additionally, our results support historical division of the genus Syngamus into two subgenera S. (Syngamus) and S. (Ornithogamus).

A systematic review of pentacyclic triterpenes and their derivatives as chemotherapeutic agents against tropical parasitic diseases

Parasitic infections are among the leading global public health problems with very high economic and mortality burdens. Unfortunately, the available treatment drugs are beset with side effects and continuous parasite drug resistance is being reported. However, new findings reveal more promising compounds especially of plant origin. Among the promising leads are the pentacyclic triterpenes (PTs) made up of the oleanane, ursane, taraxastane, lupane and hopane types. This paper reviews the literature published from 1985 to date on the in vitro and in vivo anti-parasitic potency of this class of phytochemicals. Of the 191 natural and synthetic PT reported, 85 have shown high anti-parasitic activity against various species belonging to the genera of Plasmodium, Leishmania, Trypanosoma, as well as various genera of Nematoda. Moreover, structural modification especially at carbon 3 (C3) and C27 of the parent backbone of PT has led to improved anti-parasitic activity in some cases and loss of activity in others. The potential of this group of compounds as future alternatives in the treatment of parasitic diseases is discussed. It is hoped that the information presented herein will contribute to the full exploration of this promising group of compounds as possible drugs for parasitic diseases.

Early development of the root-knot nematode Meloidogyne incognita

BACKGROUND

Detailed descriptions of the early development of parasitic nematodes are seldom available. The embryonic development of the plant-parasitic nematode Meloidogyne incognita was studied, focusing on the early events.

RESULTS

A fixed pattern of repeated cell cleavages was observed, resulting in the appearance of the six founder cells 3 days after the first cell division. Gastrulation, characterized by the translocation of cells from the ventral side to the center of the embryo, was seen 1 day later. Approximately 10 days after the first cell division a rapidly elongating two-fold stage was reached. The fully developed second stage juvenile hatched approximately 21 days after the first cell division.

CONCLUSIONS

When compared to the development of the free-living nematode Caenorhabditis elegans, the development of M. incognita occurs approximately 35 times more slowly. Furthermore, M. incognita differs from C. elegans in the order of cell divisions, and the early cleavage patterns of the germ line cells. However, cytoplasmic ruffling and nuclear migration prior to the first cell division as well as the localization of microtubules are similar between C. elegans and M. incognita.

Free-living marine nematodes from San Antonio Bay (Río Negro, Argentina)

The dataset of free-living marine nematodes of San Antonio Bay is based on sediment samples collected in February 2009 during doctoral theses funded by CONICET grants. A total of 36 samples has been taken at three locations in the San Antonio Bay, Santa Cruz Province, Argentina on the coastal littoral at three tidal levels. This presents a unique and important collection for benthic biodiversity assessment of Patagonian nematodes as this area remains one of the least known regions. In total 7,743 specimens of free-living marine nematodes belonging to two classes, eight orders, 37 families, 94 genera and 104 species were collected.

A checklist of helminth parasites of Elasmobranchii in Mexico

A comprehensive and updated summary of the literature and unpublished records contained in scientific collections on the helminth parasites of the elasmobranchs from Mexico is herein presented for the first time. At present, the helminth fauna associated with Elasmobranchii recorded in Mexico is composed of 132 (110 named species and 22 not assigned to species), which belong to 70 genera included in 27 families (plus 4 incertae sedis families of cestodes). These data represent 7.2% of the worldwide species richness. Platyhelminthes is the most widely represented, with 128 taxa: 94 of cestodes, 22 of monogeneans and 12 of trematodes; Nematoda and Annelida: Hirudinea are represented by only 2 taxa each. These records come from 54 localities, pertaining to 15 states; Baja California Sur (17 sampled localities) and Baja California (10), are the states with the highest species richness: 72 and 54 species, respectively. Up to now, 48 elasmobranch species have been recorded as hosts of helminths in Mexico; so, approximately 82% of sharks and 67% of rays distributed in Mexican waters lack helminthological studies. The present list provides the host, distribution (with geographical coordinates), site of infection, accession number in scientific collections, and references for the parasites. A host-parasite list is also provided.

The complete mitochondrial genome of Koerneria sudhausi (Diplogasteromorpha: Nematoda) supports monophyly of Diplogasteromorpha within Rhabditomorpha

Testing hypotheses of monophyly for different nematode groups in the context of broad representation of nematode diversity is central to understanding the patterns and processes of nematode evolution. Herein sequence information from mitochondrial genomes is used to test the monophyly of diplogasterids, which includes an important nematode model organism. The complete mitochondrial genome sequence of Koerneria sudhausi, a representative of Diplogasteromorpha, was determined and used for phylogenetic analyses along with 60 other nematode species. The mtDNA of K. sudhausi is comprised of 16,005 bp that includes 36 genes (12 protein-coding genes, 2 ribosomal RNA genes and 22 transfer RNA genes) encoded in the same direction. Phylogenetic trees inferred from amino acid and nucleotide sequence data for the 12 protein-coding genes strongly supported the sister relationship of K. sudhausi with Pristionchus pacificus, supporting Diplogasteromorpha. The gene order of K. sudhausi is identical to that most commonly found in members of the Rhabditomorpha + Ascaridomorpha + Diplogasteromorpha clade, with an exception of some tRNA translocations. Both the gene order pattern and sequence-based phylogenetic analyses support a close relationship between the diplogasterid species and Rhabditomorpha. The nesting of the two diplogasteromorph species within Rhabditomorpha is consistent with most molecular phylogenies for the group, but inconsistent with certain morphology-based hypotheses that asserted phylogenetic affinity between diplogasteromorphs and tylenchomorphs. Phylogenetic analysis of mitochondrial genome sequences strongly supports monophyly of the diplogasteromorpha.

Checklist of the helminth parasites of the genus Profundulus Hubbs, 1924 (Cyprinodontiformes, Profundulidae), an endemic family of freshwater fishes in Middle-America

From December 2012 to November 2014, 267 fish belonging to the family Profundulidae (representing nine of the 11 species of the genus Profundulus) were collected in 26 localities of Middle-America, across southern Mexico, Guatemala, and Honduras, comprising the distribution range of the genus, and analyzed for helminth parasites. Additionally, a database with all ten available published accounts of the helminth parasite fauna of this genus (the only genus within the family) was assembled. Based on both sources of information, a checklist containing all the records was compiled as a tool to address future questions in the areas of evolutionary biology, biogeography, ecology and phylogeography of this host-parasite association. The helminth parasite fauna of this fish group consists of 20 nominal species, classified in 17 genera and 14 families. It includes six species of adult digeneans, five metacercariae, two monogeneans, one adult cestode, three adult nematodes and three larval nematodes. The profundulid fishes are parasitized by a specialized group of helminth species (e.g.ParacreptotremablancoisensuSalgado-Maldonado et al. (2011b), Paracreptotremaprofundulusi Salgado-Maldonado, Caspeta-Mandujano & Martínez Ramírez, 2011, Phyllodistomumspinopapillatum Pérez-Ponce de León, Pinacho-Pinacho, Mendoza-Garfias & García-Varela, 2015, Spinitectushumbertoi Mandujano-Caspeta & Moravec, 2000, Spinitectusmariaisabelae Caspeta-Mandujano Cabañas-Carranza & Salgado-Maldonado, 2007 and Rhabdochonasalgadoi Mandujano-Caspeta & Moravec, 2000), representing the core helminth fauna that are not shared with other Middle-American fish species.

Fenxiang biota: a new Early Ordovician shallow-water fauna with soft-part preservation from China

Our perception of biodiversity in the geological past is incomplete and biased because most organisms did not have mineralized skeletons and therefore had little chance of fossilization. This especially refers to shallow-water marine environments, rarely represented by localities with exceptional preservation of fossil material (known as taphonomic windows or Konservat-Lagerstätten). Such extraordinary “windows” may markedly broaden our knowledge of biodiversity of the past. Here, we show a review of the invertebrate fossils from recently discovered locality in the Lower Ordovician Fenxiang Formation of Hubei Province in southern China revealing exceptional preservation of soft tissues. The fauna, generally of shallow-water aspect, contains linguloid brachiopods with a remarkably preserved pedicle, the oldest traces of nematode life activities, the oldest reliable record of hydroids, the first fossil antipatharian corals, a pyritized colonial organism of unknown affinity, supposed arthropod appendages, probable phosphatized scalidophoran worm embryo and other fossils. Our discovery supports the opinion that the famous soft-bodied preservation of Burgess Shale- or Chengjiang-type did not vanish from the fossil record in post-Cambrian times. The new finding represents a prelude to the Great Ordovician Biodiversification Event and provides evidence for calibration of molecular clock of several invertebrate lineages.

Role of biogenic amines in the post-mortem migration of Anisakis pegreffii (Nematoda: Anisakidae Dujardin, 1845) larvae into fish fillets

Infective third-stage larvae (L3) of nematode Anisakis spp. have been recognized as one of the major food-borne threats in lightly processed fish products in Europe, particularly in the Mediterranean region. Therefore, the effect of different storage temperatures of fish on larval post-mortem migration from visceral cavity into fillets is an important parameter to take into account when evaluating the risk for consumer safety. The European anchovy (Engraulis encrasicolus) were caught during fishing season, a subsample of fillets was checked for the presence of Anisakis larvae at capture (mean abundance=0.07), and the rest was stored at four different temperatures (-18, 0, 4 and 22°C) in order to count migrating larvae and measure the production of biogenic amines over a period of time. Larvae were identified by morphological features and molecular tools. Post-mortem migration was observed in fillets stored at 0 and 4°C after three and five days, respectively, but not at 22 and -18°C. In case of storage at 22°C for two days, at the onset of putrefaction of the visceral organs, larvae migrated out of the visceral cavity towards the fish surface. Measured pH and biogenic amine profile during storage indicated that certain biochemical conditions trigger larval migration into fillets. Likewise, migration was observed at pH ~6.4 when sensory degradation of the fish was markedly visible. Although larval migration was delayed for approximately four days at a temperature of <4°C the correlation between pH and abundance of A. pegreffii larvae in the fillet was high and statistically significant at both 0 (r=0.998, p<0.01) and 4°C (r=0.946, p<0.05). Out of eight biogenic amines measured, cadaverine and putrescine levels correlated the most with the post-mortem migration at 4°C, while tyramine levels were significant at both temperatures.

Molecular Phylogeny of Nematodes (Oxyurida: Travassosinematidae) from Orthoptera (Gryllotalpidae) Inferred by Mitochondrial Cytochrome C Oxidase Subunit 1 Gene

In this study, we sequenced mt Cox 1 gene sequences of five nematode spp. that were infective to arthropod, Gryllotalpa africana. The nematode belongs to Thelastomatoidea, a group of pinworms that parasitizes only invertebrates. Currently, in India spp. of this group are distinguished mainly on the basis of morphological characters that present possible confusions. Therefore, we identified the species through morphological and genetic analysis. We selected mt Cox 1 gene region to show their phylogenetic position with closely related spp. and confirmed their molecular validation. The present findings are important to confirm the phylogenetic position and relationship among five nematode spp. and avoid misidentification regarding their validation, as it is more necessary in that case when many species harbours the same host.

A low-cost technique to manufacture a container to process meiofauna for scanning electron microscopy

An easy and low-cost method to elaborate a container to dehydrate nematodes and other meiofauna in order to process them for scanning electron microscopy (SEM) is presented. Illustrations of its elaboration, step by step, are included. In addition, a brief methodology to process meiofauna, especially nematodes and kinorhynchs, and illustrations are provided. With this methodology it is possible to easily introduce the specimens, to lock them in a closed chamber allowing the infiltration of fluids and gases (ethanol, acetone, carbon dioxide) but avoiding losing the specimens. After using this meiofauna basket for SEM the results are efficient. Examples of nematode and kinorhynch SEM pictures obtained using this methodology are also included.