Description of Hemienchytraeus wuhanensis sp. nov. (Annelida, Clitellata, Enchytraeidae) from central China, with comments on species records of Hemienchytraeus from China

Hemienchytraeus wuhanensissp. nov. is described from hardwood forest soil in Wuhan, China. This moderately sized enchytraeid species of 6–9 mm body length is characterized by: (1) an oesophageal appendage with tertiary branches, (2) three pairs of secondary pharyngeal gland lobes in V, VI, VII, (3) five pairs preclitellar nephridia, from 5/6 to 9/10, (4) dorsal vessel originating in clitellar segments, (5) a girdle-shaped clitellum, (6) a relatively small male reproductive apparatus without seminal vesicle, and (7) spermathecae that extend to VI–VII. DNA barcodes of paratype specimens of the new species are provided. Previous species records of Hemienchytraeus from China are critically discussed.

Molecular and morphological characterisation of Trichodorus species (Nematoda: Trichodoridae), with description of T. pseudoaequalis n. sp. from California and other states of the USA

Summary During surveys for stubby root nematodes in the natural vegetation of California, Oregon and Washington, USA, three known species, viz., Trichodorus californicus, T. intermedius and T. obscurus were recovered together with ten unidentified Trichodorus species. The three known and one new species were studied using an integrated approach. Trichodorus pseudoaequalis n. sp. is characterised by a medium-sized body about 800 μm long on average, male with two ventromedian cervical papillae anterior to secretory-excretory pore and three precloacal supplements all located anterior to the retracted spicules; spicules 39 μm long (average), slightly ventrally curved, more so in head region and blade with slight indentation mid-way and striation more pronounced in posterior half. Females possess a rather short (average 33% of corresponding body diam.) pear-shaped vagina with small vaginal sclerotised pieces (ca 1.5 μm long), rounded triangular in shape, obliquely orientated and close together; one pair of sublateral body pores anterior (about four vulval body diam.) to vulva and one pair of post-advulvar sublateral body pores. Trichodorus pseudoaequalis n. sp. differs from the most similar species, T. aequalis, in male characters like general spicule shape and ornamentation and in the position of the dorsal pharyngeal gland nucleus in both sexes (at same level of posterior ventrosublateral pair vs clearly separated). The phylogenetic relationships of the recovered species were reconstructed using the ITS2 rRNA and the D2-D3 expansion segments of 28S rRNA gene sequences.

Conserved nuclear receptors controlling a novel trait target fast-evolving genes expressed in a single cell

Environment shapes development through a phenomenon called developmental plasticity. Deciphering its genetic basis has implications for understanding evolution and adaptation to novel environments, yet molecular studies are scarce. Here, we expanded the gene regulatory network controlling predatory vs. non-predatory morphology in the nematode Pristionchus pacificus. First, we isolated a mutant in the nuclear hormone receptor nhr-1 with a previously unseen phenotypic effect. It disrupts mouth-form determination and results in animals combining features of both wild-type morphs. Further, we identified common targets of NHR-1 and the previously identified nuclear hormone receptor NHR-40 through transcriptomics. Unlike their highly conserved regulators, the target genes have no orthologs in Caenorhabditis elegans and likely result from lineage-specific expansions. An array of transcriptional reporters revealed co-expression of all tested targets in the same pharyngeal gland cell. The morphological remodeling of this cell accompanied the evolution of teeth and predation, linking rapid gene turnover with morphological innovations.

Description of Globodera sandveldensis n. sp. (Nematoda: Heteroderidae) from South Africa

A new cyst nematode, herein described as Globodera sandveldensis n. sp., was found in the Sandveld, Western Cape Province, South Africa. As the host plant of G. sandveldensis n. sp. is currently unknown, the species is represented by cysts and second-stage juveniles (J2) only. The J2 are characterised by a well developed stylet of 26.4 (24.8-28.5) μm with rounded to anteriorly flattened knobs. The distance from the dorsal pharyngeal gland outlet to the stylet knobs is 4.5 (2.4-7.2) μm. The tail is 64 (56-77) μm long and the length of the hyaline region is 33 (22-39) μm. The cysts are characterised by their ovate to spherical shape, short neck, and the presence of subcuticular punctations and bullae or vulval bodies. Six to 14 cuticular ridges/lines are present on the outer surface of the cyst between the anus and vulval basin. Granek’s ratio is 1.7 (0.9-3.0), the vulval basin diam. is 20.4 (13.1-34.6) μm and the distance between vulval basin and anus is 33.5 (19.7-54.0) μm. Phylogenetic relationships with other species of the genus, inferred from ITS-rDNA sequences, indicate that G. sandveldensis n. sp. is included in the clade of Globodera sp. that parasitise non-solanaceous plants and is closely related to unidentified Globodera spp. from Portugal, G. millefolii, and G. artemisiae.

Morphological and molecular data support the monophyletic nature of the genus Pratylenchoides Winslow, 1958 (Nematoda: Merliniidae) and reveal its intrageneric structuring

The genus Pratylenchoides has recently been transferred from the family Pratylenchidae to Merliniidae. To investigate further the relationship between these ‘Pratylenchus-like’ species (residing in the subfamily Pratylenchoidinae) and the subfamily Merliniinae, more than 500 soil samples were collected from various natural and agronomic habitats in the northern and north-western provinces of Iran. In this study, paratypes or populations of 22 species of Pratylenchoides, including the Iranian populations of P. alkani, P. crenicauda, P. erzurumensis, P. laticauda, P. nevadensis, P. ritteri and an undescribed species, were studied. Intra- and interspecies variation of the following characters were investigated: position of the pharyngeal gland nuclei, shape of female and male head, striation of female tail terminus, number of lateral lines at mid-body and in phasmid region for females, presence of intestinal fasciculi, and shape of sperm. Combining morphological and molecular data prompted us to propose two clusters of related Pratylenchoides species. One cluster includes P. crenicauda, P. variabilis and P. erzurumensis, whereas the second cluster consists of P. alkani, P. nevadensis and P. ritteri. Our data point to a sister positioning of P. magnicauda vis-à-vis all Pratylenchoides species included in this research. Analyses of SSU rDNA (for family and subfamily relationships) and partial LSU rDNA sequences (for intrageneric relationships) data revealed: i) the distal and nested positioning of all Pratylenchoidinae within the Merliniidae; ii) the single transition from ectoparasitism to migratory endoparasitism within the family Merliniidae corresponds with the current subfamily partitioning; and iii) support for the monophyletic nature of the genus Pratylenchoides.

Characterization of glutathione S-transferases from the pine wood nematode, Bursaphelenchus xylophilus

We have previously identified two secreted glutathione S-transferases (GST) expressed in the pharyngeal gland cell of Bursaphelenchus xylophilus, which are upregulated post infection of the host. This study examines the functional role of GSTs in B. xylophilus biology. We analysed the expression profiles of all predicted GSTs in the genome and the results showed that they belong to kappa and cytosolic subfamilies and the majority are upregulated post infection of the host. A small percentage is potentially secreted and none is downregulated post infection of the host. One secreted protein was confirmed as a functional GST and is within a cluster that showed the highest expression fold change in infection. This enzyme has a protective activity that may involve host defences, namely in the presence of terpenoid compounds and peroxide products. These results suggest that GSTs secreted into the host participate in the detoxification of host-derived defence compounds and enable successful parasitism.

First report of, and additional information on, Meloidogyne konaensis (Nematoda: Meloidogyninae) parasitising various crops in Brazil

In a survey for Meloidogyne spp. in different crops from 11 regions in Ceará State, Brazil, using esterase isozyme electrophoresis as a specific identification method, four atypical populations were characterised from cabbage, papaya, noni and canapum plants, all of which showed an esterase profile different from those previously detected in Brazil. Morphological studies showed typical characteristics of Meloidogyne konaensis. Perineal patterns of females were variable, similar to M. arenaria and M. incognita, stylet length 14-20 μm. In females, the knobs gradually merged with the shaft and the dorsal pharyngeal gland orifice (DGO) ranged from 4 to 7 μm. Although males are not frequently found, the stylet morphology provides the most useful source of diagnostic character for the species, having 6-12 large projections protruding from the shaft. The esterase pattern K3 is unique and species-specific with three major bands Rm 1.0, 1.17, 1.27 and a secondary band Rm 1.10. Some confusion about the true identity of this species was clarified in this study, including differentiation from M. paranaensis. A species-specific SCAR marker developed for M. paranaensis was tested and no amplification products were observed. In Neighbour-Joining analyses of ITS and D2-D3 rRNA sequences, M. konaensis from Brazil appeared clearly separated from M. paranaensis. Pathological tests indicated that coffee is not a host of M. konaensis as previously reported in the original description of this species.