Description of Aphelenchoides persicus sp. n. (Nematoda: Aphelenchoididae) from Iran

During a survey on the soil nematodes, a population of the genus Aphelenchoides was collected around the rhizosphere of persimmon in Guilan Province, Iran. The morphological and molecular characters confirmed the new species, namely A. persicus sp. n. The new species is characterized by a female body length (699-1068 μm), lip region offset from the rest of the body by a slight constriction, lateral fields with six incisures, stylet 12-13.5 μm long, with a clear basal swelling, excretory pore ca 1.5 metacorpal length posterior to base of the metacorpus, post uterine sac elongate, about 4-7 times than the vulval body diameter; conical female tail with a single centrally located mucron with tiny projection close to the tail tip, male body length (663-908 μm), and spicule well developed with rounded condylus, blunt conical rostrum, and a hook-like tip of dorsal limb. The new species belongs to the Group 2 category of Aphelenchoides species and was similar to seven known species with six lateral field incisures, including A. allius, A. chinensis, A. meghalayensis, A. nechaleos, A. paranechaleos, A. parasexlineatus, and A. sexlineatus. The molecular phylogeny based on 28S rDNA revealed that the new species stands close to A. hamospiculatus (MN931591; MN931592) and two unidentified Aphelenchoides (KY769057; LC583315). The measurements, line illustrations, LM photographs, and phylogenetic analysis are given for the new species.

Highlighting Potential Physical and Chemical Cues Involved in Conspecific Recognition System in a Predator Nematode, Seinura caverna

Conspecific recognition is the ability to distinguish and respond to individuals of the same species. In nematodes, this behavior can mediate aggregation, feeding behavior, or mating. Here, we investigated whether and how the predatory nematode Seinura caverna recognizes and avoids conspecifics to prey on. In predation assays, S. caverna did not kill conspecifics, but killed nematodes of three heterospecific species. Interestingly, S. caverna did not kill Ektaphelenchoides spondylis nematodes. Seinura caverna did not eject its stylet when encountering conspecifics or E. spondylis. The characterization of the internal cuticle structure of 13 nematode species suggested that the cuticle may play a role in the preying decision, as E. spondylis and S. caverna exhibited similar, type III, cuticle layers. Chemical extracts from S. caverna further repelled conspecifics. We discuss the potential hierarchical use of physical and chemical cues in S. caverna predation behavior and provide insights into the evolutionary adaptations and behavior of this organism.

Ultrastructural study of anther parasitism of Ficus laevigata by Ficophagus laevigatus (Aphelenchoididae)

Transmission electron microscopy (TEM) was used to compare the ultrastructural differences between healthy male florets (anthers) and one floret parasitized by Ficophagus laevigatus in late phase C syconia of Ficus laevigata from southern Florida. Previous light-microscopic examination of paraffin-sectioned material showed that F. laevigatus-infested anthers of F. laevigata manifested as malformed, often with aberrant pollen and hypertrophied epidermal cells closest to regions containing propagating nematodes. Female florets or fig wasp-parasitized female florets were not observed to be parasitized by nematodes. Considering that plant-feeding in the Aphelenchoididae is purportedly much less specialized than in certain groups of the Tylenchomorpha, where specialized hypertrophied feeder cells are produced in response to nematode feeding, we examined the putative induced response in this unusual aphelenchoidid system with the higher resolution afforded by TEM. TEM confirmed the expression of significant epidermal cell hypertrophy of the anther and anther filament in the presence of propagating nematodes, which was expressed as cell enlargement (2-5X), fractionation of large electron-dense stores into smaller aggregates, irregularly shaped nuclei enclosed by an elongated nuclear envelope, nucleolus enlargement, increased organelle production, and apparent metabolism with increased numbers of mitochondria, pro-plastids, and endoplasmic reticulum, as well as increased thickening of the cell walls. Pathological effects were observed in adjacent cells/tissue (e.g., anther and anther filament parenchymal cells, pollen tubes, pollen, and endothecium) with apparent diminishment as the distance from propagating nematodes increased (which was also probably affected by number of nematodes). Some TEM sections captured previously undocumented ultrastructural highlights of propagating individuals of F. laevigatus.

Phylogenetic position of Ptychaphelenchus eucalypticola Hodda, 2009 within the Aphelenchoidoidea Skarbilovich, 1947 (Siddiqi, 1980) inferred from partial 18S and 28S rDNA gene sequences

At the time of description, the morphology of Ptychaphelenchus eucalypticola Hodda, 2009 indicated it could be assigned to either the Aphelenchoididae Skarbilovich, 1947 (Paramonov, 1953) or the Parasitaphelenchidae Ruehm, 1956 (Siddiqi, 1980) within the Aphelenchoidoidea Skarbilovich, 1947 (Siddiqi, 1980). Although P. eucalypticola was, tentatively, and remains assigned to the Aphelenchoididae, its relationships with other aphelenchoids have not been reassessed, and no molecular data were previously available for this species. We re-collected P. eucalypticola from its type host and locality, Eucalyptus macrorhyncha F. Muell. ex Benth., from Mount Ainslie, ACT, Australia. We performed Bayesian inference and maximum likelihood analyses of a concatenated 18S + 28S rDNA gene sequence dataset to determine the position of P. eucalypticola within the Aphelenchoidoidea, followed by 18S and 28S single-gene analyses to further assess relationships between this species and an expanded set of close relatives. All analyses indicated P. eucalypticola is correctly assigned to the Aphelenchoididae, in a clade comprising all species of Ficophagus Davies & Bartholomaeus, 2015 and some species presently assigned to Aphelenchoides Fisher, 1894, sister to Martininema Davies & Bartholomaeus, 2015 and additional species of Aphelenchoides. Our 18S single-gene analyses did not resolve the position of P. eucalypticola relative to Aphelenchoides and Ficophagus; however, our 28S single-gene analyses indicated a sister relationship between P. eucalypticola and Ficophagus. This sister relationship is plausible as the former species shares many characteristics with species of the latter genus; however, there are sufficient morphological differences to consider P. eucalypticola as representative of a distinct lineage within the Aphelenchoidoidea.

Ficophagus giblindavisi n. sp. (Nematoda: Aphelenchoididae), an associate of Ficus variegata in China

A new species of the genus Ficophagus was recovered from the syconia of Ficus variegata from Shenzhen, Guangdong province, China. It is described herein as Ficophagus giblindavisi n. sp. and is characterised by possessing the longest stylet in males (35.1-45.8 μm) and most lateral incisures (5) of all currently described species in the genus, a short PUS (8.4-11.4 μm or 0.3 VBD long), excretory pore situated at or posterior to the nerve ring, amoeboid sperm, three pairs of subventral papillae on the male tail, rounded male tail tip with a mucron, absence of gubernaculum and sickle-shaped spicules with a terminal cucullus. Ficophagus giblindavisi n. sp. was differentiated from other sequenced species by the partial small subunit (SSU) rRNA gene and D2-D3 expansion segments of the large subunit (LSU) rRNA gene. Phylogenetic analysis with the LSU D2-D3 expansion segment sequence suggested that F. giblindavisi n. sp. is clustered in the same highly supported monophyletic clade with F. auriculatae and F. fleckeri.

Characterisation of Ficophagus virens (Bartholomaeus, Davies, Kanzaki, Ye & Giblin-Davis, 2009) Davies & Bartholomaeus, 2015 from Ficus virens (Moraceae) in India with a tabular key for the Indian species of Ficophagus

A population of Ficophagus was recovered from white fig (Ficus virens) in New Delhi, India. We further described the population as Ficophagus virens based on morphological and morphometric characters, and molecular data. A detailed description of key morphological features, measurements of taxonomic characters, and photomicrography of the male and female specimens are given here. The study also included additional parameters such as lip diam. and height, conus stylet, shaft stylet, knobs diam. and height, vulva position from anterior end, length and width of spermatheca, anal/cloacal body diam., vulval width, and ovary/testis length for better characterisation of species. In addition to 28S rDNA (D2/D3), new sequence data from small subunit rDNA (18S) and mitochondrial cytochrome oxidase I COI marker gene were added. The D2/D3 sequence of F. virens was most similar to the sequence available for the Australian population of F. virens in GenBank. Maximum likelihood (ML) and Bayesian methods were used to analyse phylogenetic relationships of the Indian population of F. virens with those of the Australian populations and other Ficophagus species. This species is a new record from Delhi, India, and hence this report provides a new geographical location for the F. virens nematode after the first report from Australia.

Bursaphelenchus suri n. sp.: A second Bursaphelenchus syconial parasite of figs supports adaptive radiation among section Sycomorus figs

The nematode genus Bursaphelenchus is a highly divergent group. This genus mainly consists of mycophagous entomophilic species, but some species have specialized as obligate or facultative plant parasites, facultative insect parasites, or exhibit feeding dimorphism (phenotypic plasticity) leading to mycophagous and predatory forms. In the present study, a new Bursaphelenchus species, B. suri n. sp. was isolated from fresh syconia (figs) of Ficus sur and is described and illustrated based on its typological characters and molecular phylogenetic status. The new species is characterized by its highly derived feeding structures found in obligate plant parasites, lip possessing a labial disc and a long and thick stylet with a long conus and extremely well-developed basal swellings. In addition, slender body of both sexes is characteristic of the species. The new species is phylogenetically and typologically closely related to B. sycophilus, i.e., these two species share the characteristic feeding structures and form a well-supported clade within the B. fungivorus group in the genus. Biologically, these two species are both isolated from fresh figs of the section Sycomorus. However, the new species differs from B. sycophilus by the length of the female post-uterine sac and the shape of the male spicule, i.e., the new species has a long post-uterine sac and spicule condylus without dorsal recurvature. Thus, the new species is the second obligate fig parasite of the genus, and the evolutionary relationship between the B. suri n. sp. and B. sycophilus clade and section Sycomorus figs is hypothesized as an example of adaptive radiation with more species to be discovered.

Association of Fig Pollinating Wasps and Fig Nematodes inside Male and Female Figs of a Dioecious Fig Tree in Sumatra, Indonesia

Simple Summary

It has been known that fig pollinating wasps can transfer nematodes when they enter receptive figs to deposit their eggs (male figs in male trees) and pollinate the flowers (female figs in female trees) of a dioecious fig tree. However, the fate of nematodes transferred into female figs was unknown, since the pollinating wasps that enter female figs cannot reproduce. This study examined whether the nematodes transferred by pollinating wasps into female figs of Ficus hispida could develop and reproduce in the same way as in male figs. Three species of nematodes were found to develop within the male and female figs of F. hispida, with populations peaking at about the same time for both sexes of figs. Our findings showed that the female figs could support the growth and reproduction of the three nematodes; however, there was no pollinator offspring to transfer the nematodes out of the figs. The results provide a better understanding of the development of nematodes in male and female figs of a dioecious fig tree, which may also influence the biodiversity of the tropical ecosystem.

Abstract

Nematodes can grow within the inflorescences of many fig trees (Ficus spp., Moraceae); however, the feeding behaviour of most nematodes is not known. Fig pollinating wasps (Hymenoptera: Agaonidae) transfer nematodes into young figs upon the wasps’ entry into the figs to deposit their eggs. Most Asian fig trees, however, are functionally dioecious, and the pollinating wasps that enter female figs are unable to reproduce. They fail to produce the offspring required to carry the new generations of nematodes. We examined whether female figs of F. hispida can nonetheless support the development of phoretic nematode populations. Nematodes were extracted from male and female figs sampled in Sumatra, Indonesia, to compare the growth of their populations within the figs. We found three species of nematodes that grew within figs of male and female trees of F. hispida: Ficophagus cf. centerae (Aphelenchoididae), Martininema baculum (Aphelenchoididae) and Caenorhabditis sp (Rhabditidae). The latter species (Caenorhabditis sp.) has never been reported to be associated with F. hispida before. Nematode populations peaked at around 120–140 individuals in both sexes of figs, at the time when a succeeding generation of adult fig wasps appeared within male figs. The female figs could support the growth and reproduction of the three nematodes species; however, the absence of vectors meant that female figs remained as traps from which there could be no escape.

Phylum Nematoda: trends in species descriptions, the documentation of diversity, systematics, and the species concept

This paper summarizes the trends in nematode species description and systematics emerging from a comparison of the latest comprehensive classification and census of Phylum Nematoda (Hodda 2022a, b) with earlier classifications (listed in Hodda 2007).   It also offers some general observations on trends in nematode systematics emerging from the review of the voluminous literature used to produce the classification.   The trends in nematodes can be compared with developments in the systematics of other organisms to shed light on many of the general issues confronting systematists now and into the future.  

Phylum Nematoda: a classification, catalogue and index of valid genera, with a census of valid species

A classification of the entire Phylum Nematoda is presented, based on current molecular, developmental and morphological evidence. The classification reflects the evolutionary relationships within the phylum, as well as significant areas of uncertainty, particularly related to the early evolution of nematodes.   It includes 3 classes, 8 subclasses, 12 superorders, 32 orders, 53 suborders, 101 superfamilies, 276 families, 511 subfamilies, 3030 genera, and 28537 species.   All valid species named from the time of publication of the previous classification and census (2010) to the end of 2019 are listed, along with the number of valid species in each genus.   Taxonomic authorities are provided for taxon names of all ranks.   The habitats where the species in each genus are found are listed, and an alphabetic index of genus names is provided.   The systematics of nematodes is reviewed, along with a history of nematode classification; evolutionary affinities and origins of nematodes; and the current diagnosis of the group.   Short overviews of the general biology, ecology, scientific and economic importance of the group are presented.  

Molecular diversity and relationships of fig associated nematodes from South Africa

Nematodes of figs and fig wasps have received limited attention in Africa since their discovery in 1973. Sixteen of the 25 species of native South African figs were sampled for nematode associates using molecular barcoding with three loci (SSU, LSU D2-D3 and mtCOI) and fourteen (93%) were positive for at least one nematode species. Thirty-three putative species of nematodes were identified and classified according to the loci that were amplified and successfully sequenced. Fourteen putative nematode species were classified as Aphelenchoididae, of which nine were identified as Ficophagus from four species of Ficus from the section Galoglychia (i.e., five ex F. burkei including one shared with F. natalensis, one ex F. glumosa, one ex F. lutea, and one ex F. stuhlmannii) and one species ex F. sur from the section Sycomorus. In addition, there were four nematode species classified as Schistonchus s.s. from section Galoglychia figs (i.e., one ex F. burkei, two ex F. trichopoda, and one ex F. glumosa). There was also one species of Bursaphelenchus nematode recovered from F. sur from the section Sycomorus. Sixteen putative nematode species were classified as Diplogastridae, of which eight occurred in two clades of what is currently called Parasitodiplogaster with one (P. salicifoliae) being recovered from two Ficus species in the section Urostigma (F. salicifolia and F. ingens) and seven diplogastrids being associated with six species of Ficus from the section Galoglychia (i.e., two ex F. burkei including P. sycophilon, one ex F. stuhlmannii, one ex F. burtt-davyi, one ex F. trichopoda, one ex F. abutilifolia and one ex F. sansibarica). Three Acrostichus spp., a Teratodiplogaster and a Pristionchus species were recovered from F. sur and two Teratodiplogaster spp. and Pristionchus sycomori were recovered from F. sycomorus with both Ficus species belonging to the subgenus and section Sycomorus. The identities of the previously described T. martini and Parasitodiplogaster doliostoma (= Pristionchus sp. 35) are discussed. Lastly, there was a panagrolaimid identified from F. petersii.

Basilaphelenchus hyrcanus n. sp. (Rhabditida: Tylaphelenchinae) associated with bark of a beech tree (Fagus orientalis Lipsky) from northern Iran

Basilaphelenchus hyrcanus n. sp., the sixth species of the newly established genus was isolated during a nematode survey associated with bark samples of beech tree in northern Iran, which differs from the other species by body size, stylet length, metacorpus structure, and tail characters of both genders. The new species is also characterized by elevated cephalic region with sclerotised vestibule, posteriorly directed stylet knobs, well-developed metacorpus filling corresponding body region, position of excretory pore at the level of base of metacarpus, length of post uterine sac by 38–60 μm long, conoid elongate tail by sharp to finely rounded tip in female. Based upon the morphological characteristics and phylogenetic analyses of partial 18 S and D2-D3 28 S rDNA segments, the new species mostly resembles B. magnabulbus. However, B. hyrcanus n. sp. is clearly different from this species by having a longer stylet, different position of the excretory pore, a different male tail tip characters and 4.4 and 13.2% sequence divergences in 18 S and D2-D3 28 S, respectively.

The Scent of Life: Phoretic Nematodes Use Wasp Volatiles and Carbon Dioxide to Choose Functional Vehicles for Dispersal

Hitchhikers (phoretic organisms) need vehicles to disperse out of unsuitable habitats. Therefore, finding vehicles with the right functional attributes is essential for phoretic organisms. To locate these vehicles, phoretic organisms employ cues within modalities, ranging from visual to chemical senses. However, how hitchhikers discriminate between individual vehicles has rarely been investigated. Using a phoretic nematode community associated with an obligate fig-fig wasp pollination mutualism, we had earlier established that hitchhiking nematodes make decisions based on vehicle species identity and number of conspecific hitchhikers already present on the vehicle. Here we investigate if hitchhikers can differentiate between physiological states of vehicles. We asked whether phoretic nematodes choose between live or dead vehicles present in a chemically crowded environment and we investigated the basis for any discrimination. We conducted two-choice and single-choice behavioral assays using single nematodes and found that plant- and animal-parasitic nematodes preferred live over dead vehicles and used volatiles as a sensory cue to make this decision. However, in single-choice assays, animal-parasitic nematodes were also attracted towards naturally dead or freeze-killed wasps. The volatile profile of the wasps was dominated by terpenes and spiroketals. We examined the volatile blend emitted by the different wasp physiological states and determined a set of volatiles that the phoretic nematodes might use to discriminate between these states which is likely coupled with respired CO₂. We determined that CO₂ levels emitted by single wasps are sufficient to attract nematodes, demonstrating the high sensitivity of nematodes to this metabolic product.

Hopping on: Conspecific traveller density within a vehicle regulates parasitic hitchhiking between ephemeral microcosms

Hitchhikers (phoretic organisms) identify their vehicles using species-specific visual, chemical and vibrational cues. However, what factors influence their choice between vehicles of the same species has rarely been investigated. Hitchhikers must not only avoid overcrowded vehicles but may also need to travel with conspecifics to ensure mates at their destination. Hence, a trade-off between overcrowding and presence of conspecifics likely determines the choice of a vehicle especially when destination sites are distant, ephemeral and unique. Here, we investigate whether a trade-off between the presence of conspecifics versus overcrowding by conspecifics or heterospecifics on a vehicle affects hitchhiker choice. We also investigate the sensory modality responsible for this choice. We experimentally examine these questions using a phoretic nematode community (containing plant- and animal-parasitic taxa) obligately associated with a brood-site pollination mutualism. In this model system, nematodes co-travel with conspecifics and heterospecifics on pollinators as vehicles, between ephemeral plant brood sites to complete their developmental life cycle. In this system, hitchhiker overcrowding has proven negative impacts on vehicle and plant fitness. We expected nematodes to respond to conspecifics and heterospecific density on offered vehicles when making their choice. We found that animal-parasitic nematodes preferred vehicles containing some conspecifics within a certain density range. However, plant-parasitic nematodes preferentially boarded vehicles that were devoid of conspecifics or had few conspecifics. Plant parasites that preferred empty vehicles likely hitchhiked in pairs. Both nematode types employed volatile cues to discriminate between vehicles with different conspecific nematode densities. Our results suggest that vehicle overcrowding by conspecifics, most likely, guaranteed access to mates at the destination determined hitchhiker choice. Surprisingly, and contrary to our expectations, plant- and animal-parasitic nematodes did not respond to heterospecific crowding on vehicles and did not discriminate between vehicles with different heterospecific nematode densities. The reason for this lack of response to heterospecific presence is unknown. This study not only shows that phoretic organisms use different strategies while choosing a vehicle but also confirms that density-dependent effects can ensure the stability and persistence of phoretic interactions in a mutualism by balancing overcrowding against reproductive assurance.

Ultrastructural plasticity in the plant-parasitic nematode, Bursaphelenchus xylophilus

Phenotypic plasticity is one of the most important strategies used by organisms with low mobility to survive in fluctuating environments. Phenotypic plasticity plays a vital role in nematodes because they have small bodies and lack wings or legs and thus, cannot move far by themselves. Bursaphelenchus xylophilus, the pathogenic nematode species that causes pine wilt disease, experiences fluctuating conditions throughout their life history; i.e., in both the phytophagous and mycetophagous phases. However, whether the functional morphology changes between the life phases of B. xylophilus remains unknown. Our study revealed differences in the ultrastructure of B. xylophilus between the two phases. Well-developed lateral alae and atrophied intestinal microvilli were observed in the phytophagous phase compared with the mycetophagous phase. The ultrastructure in the phytophagous phase was morphologically similar to that at the dauer stage, which enables the larvae to survive in harsh environments. It suggests that the living tree represents a harsh environment for B. xylophilus, and ultrastructural phenotypic plasticity is a key strategy for B. xylophilus to survive in a living tree. In addition, ultrastructural observations of obligate plant-parasitic species closely related to B. xylophilus revealed that B. xylophilus may be in the process of adapting to feed on plant cells.

Description of Basilaphelenchus brevicaudatus n. sp. (Aphelenchoidea: Tylaphelenchinae) from a dead forest tree in northern Iran

Basilaphelenchus brevicaudatus n. sp., the third species of this apparently rare genus, is described and illustrated. It was recovered from wood and bark samples from a dead forest tree in the Golestan province of northern Iran. It is typologically characterised by female body length (448 (365-492) μm), three lines in the lateral fields, raised cephalic region having a sclerotised vestibule and cephalic framework, stylet thin with delicate conus and thicker shaft, both parts lacking a visible lumen, and with three elongate, backwardly directed knobs, small, spherical to spade-shaped metacorpus with small, posteriorly located valve (at 72 (58-74)% of metacorpus length), simple vulva without flap at 72.5 (69-78)% of body length, post-vulval uterine sac 32.4 (29.0-37.0) μm long, functional rectum and anus, female tail conical, short (c′ = 2.6 (1.9-3.3) in female, and 2.5 (2.3-2.8) in male), dorsally convex and ventrally concave with blunt end or having a small mucron, both forms with a hyaline-like tip. Males common, with well-curved 9.2 (9.0-10.5) μm long spicules measured along the mid-line, three pairs of small caudal papillae (lacking the single P1 ventral papilla) and no bursa at tail tip, but with hyaline region, similar to females. Basilaphelenchus brevicaudatus n. sp. is compared with the two currently known species of the genus, the type species, B. persicus, and B. grosmannae. Molecular phylogenetic inferences using partial sequences of small and large subunit ribosomal RNA genes (SSU and LSU) from different isolates of the new species revealed that it belongs to the Tylaphelenchinae clade.

Field studies reveal a close relative of C. elegans thrives in the fresh figs of Ficus septica and disperses on its Ceratosolen pollinating wasps

BACKGROUND

Biotic interactions are ubiquitous and require information from ecology, evolutionary biology, and functional genetics in order to be understood. However, study systems that are amenable to investigations across such disparate fields are rare. Figs and fig wasps are a classic system for ecology and evolutionary biology with poor functional genetics; Caenorhabditis elegans is a classic system for functional genetics with poor ecology. In order to help bridge these disciplines, here we describe the natural history of a close relative of C. elegans, Caenorhabditis inopinata, that is associated with the fig Ficus septica and its pollinating Ceratosolen wasps.

RESULTS

To understand the natural context of fig-associated Caenorhabditis, fresh F. septica figs from four Okinawan islands were sampled, dissected, and observed under microscopy. C. inopinata was found in all islands where F. septica figs were found. C.i nopinata was routinely found in the fig interior and almost never observed on the outside surface. C. inopinata was only found in pollinated figs, and C. inopinata was more likely to be observed in figs with more foundress pollinating wasps. Actively reproducing C. inopinata dominated early phase figs, whereas late phase figs with emerging wasp progeny harbored C. inopinata dauer larvae. Additionally, C. inopinata was observed dismounting from Ceratosolen pollinating wasps that were placed on agar plates. C. inopinata was not found on non-pollinating, parasitic Philotrypesis wasps. Finally, C. inopinata was only observed in F. septica figs among five Okinawan Ficus species sampled.

CONCLUSION

These are the first detailed field observations of C. inopinata, and they suggest a natural history where this species proliferates in early phase F. septica figs and disperses from late phase figs on Ceratosolen pollinating fig wasps. While consistent with other examples of nematode diversification in the fig microcosm, the fig and wasp host specificity of C. inopinata is highly divergent from the life histories of its close relatives and frames hypotheses for future investigations. This natural co-occurrence of the fig/fig wasp and C. inopinata study systems sets the stage for an integrated research program that can help to explain the evolution of interspecific interactions.

On the morphology and phylogeny of Robustodorus Andrássy, 2007 and two ‘Aphelenchoides’ species (Nematoda: Aphelenchoidinae)

In a survey of nematode damage in groundnut (Arachis hypogaea) (Fabaceae) production areas in the Vaalharts Irrigation Scheme in the Northern Cape Province of South Africa, a nematode was recovered and initially believed to be a member of the genus Robustodorus, i.e., the species has a characteristic robust stylet with very well-developed teardrop-shaped (garlic bulb-like) basal swellings. The specimens were recovered in large numbers from damaged hulls and kernels of field-collected groundnuts and, after thorough morphological and molecular studies, were subsequently identified as Aphelenchoides arachidis. Molecular analysis based on near-full-length small subunit (SSU), internal transcribed spacer (ITS) and D2-D3 expansion segments of the large subunit (LSU) rRNA genes supported the monophyly of A. arachidis, A. subtenuis and R. megadorus within the subfamily Aphelenchoidinae. Based on the typological characters observed in the present study compared with descriptions in the literature, these three species are considered as congeneric, i.e., they share very well-developed basal swellings of the stylet. Accordingly, these two Aphelenchoides species are transferred to Robustodorus as R. arachidis n. comb. and R. subtenuis n. comb. In addition, the male tail characters of Robustodorus and Aphelenchoides are discussed.

Molecular and morphological characterisation of Aphelenchoides kheirii n. sp. (Nematoda: Aphelenchoididae) isolated from Pinus nigra in north-western Iran

Aphelenchoides kheirii n. sp. was isolated during a survey of nematodes associated with bark samples of pine trees (Pinus nigra) in West Azerbaijan province, north-western Iran. The new species has a body length of 500 (448-520) μm in the female and 442 (402-480) μm in the male. The cuticle is weakly annulated with four lateral lines and the lip region is offset. The stylet is 10.4 (10-11) μm long with small basal swellings and the excretory pore located immediately posterior to base of metacorpus; hemizonid invisible. The post-vulval uterine sac length 37.7 (28-45) μm. Spicules are relatively short (18-20 μm in dorsal limb) and the end of the dorsal limb clearly curved ventrally like a hook. The male tail has usual three pairs of caudal papillae (2 + 2 + 2) and a well-developed mucron. The female tail is conical, terminating in a complicated step-like projection, usually with many tiny nodular protuberances. The new species belongs to the Group 2 category of Aphelenchoides species sensu Shahina in which ten known species among Groups 2 and 4 sensu Shahina, namely: A. arcticus, A. blastophthorus, A. fuchsi, A. parasaprophilus, A. paraxui, A. xui, A. dactylocercus, A. gynotylurus, A. iranicus and A. saprophilus are the most similar species. Phylogenetic analysis based on small subunit (SSU) and partial large subunit (LSU) sequences of rRNA supported the morphological results.

A molecular phylogenetic approach for unravelling the taxonomic status of Basilaphelenchus persicus n. gen., n. sp. (Aphelenchoididae: Tylaphelenchinae)

Basilaphelenchus persicus n. gen., n. sp. is described and illustrated based on morphological and molecular phylogenetic studies. The new genus belongs to the family Aphelenchoididae and is characterised mainly by the small body size of females (297-393 μm) and males (304-331 μm), high cephalic region in both sexes, fine 5.5-7.8 μm long stylet that is barely visible in mounted specimens yet clear in fresh individuals, stylet with a linear conus and weak shaft ending in three elongate, posteriorly directed, knobs, small spherical metacorpus with posteriorly located (at 72-75% of metacorpus) weak but distinct valve, monodelphic-prodelphic reproductive system with a long post-vulval uterine sac containing large rounded sperm cells, a vulva lacking any flap apparatus, conical tail of female usually ventrally bent at tip and male tail ventrally bent as in the female, lacking the P1 supplement, but with three pairs of caudal papillae, and small arcuate spicules with rounded condylus and small pointed rostrum. The new genus is similar to both Tylaphelenchus and Pseudaphelenchus in the possession of a raised cephalic region and a small spherical metacorpus, placing it in the subfamily Tylaphelenchinae. It is also typologically similar to Aphelenchoides. Molecular phylogenetic studies using both SSU and LSU rRNA gene sequences (both partial) revealed that the new genus formed a robustly supported sister clade with Pseudaphelenchus spp. and had a basal placement to this clade and, probably, to all other aphelenchoidids. Tylaphelenchus grosmannae is transferred to the new genus as B. grosmannae n. comb. and A. christinae n. comb. (= T. christinae) is proposed. The taxonomic status of Tylaphelenchus is discussed and T. sinodendroni n. comb. (= A. sinodendroni) proposed.

Disparate gain and loss of parasitic abilities among nematode lineages

Plant parasitism has arisen time and again in multiple phyla, including bacteria, fungi, insects and nematodes. In most of these organismal groups, the overwhelming diversity hampers a robust reconstruction of the origins and diversification patterns of this trophic lifestyle. Being a moderately diversified phylum with ≈ 4,100 plant parasites (15% of total biodiversity) subdivided over four independent lineages, nematodes constitute a major organismal group for which the genesis of plant parasitism could be mapped. Since substantial crop losses worldwide have been attributed to less than 1% of these plant parasites, research efforts are severely biased towards this minority. With the first molecular characterisation of numerous basal and supposedly harmless plant parasites as well as their non-parasitic relatives, we were able to generate a comprehensive molecular framework that allows for the reconstruction of trophic diversification for a complete phylum. In each lineage plant parasites reside in a single taxonomic grouping (family or order), and by taking the coverage of the next lower taxonomic level as a measure for representation, 50, 67, 100 and 85% of the known diversity was included. We revealed distinct gain and loss patterns with regard to plant parasitism per se as well as host exploitation strategies between these lineages. Our map of parasitic nematode biodiversity also revealed an unanticipated time reversal in which the two most ancient lineages showed the lowest level of ecological diversification and vice versa.

Description of Aphelenchoides macrospica n. sp. (Nematoda: Aphelenchoididae) from Northwestern Iran

Aphelenchoides macrospica n. sp. is described and illustrated from the West Azerbayjan province, northwestern Iran. The new species is characterized by its body length of 807 to 963 μm (males) and 792 to 1,094 μm (females), offset cephalic region, lateral fields with four incisures, long stylet with 15 to 16 μm length, and excretory pore situated opposite or behind the nerve ring. Pharyngeal glands overlapping intestine dorsally and extending for 90 to 121 μm, tail terminus mucronate in both sexes. Vagina directed anteriad, and spicules are relatively large (27-32 μm) with well-developed broadly rounded apex and condylus. The new species comes close to seven known species of the genus namely A. arcticus, A. blastophthorus, A. haguei, A. huntensis, A. lucknowensis, A. parasaprophilus, and A. xui, but it differs from them by the body size, stylet length, size of spicules, and length of postvulval uterine sac. The results of phylogenetic analyses based on sequences of D2-D3 expansion region of 28S and 18S rDNA, confirmed its status as a new species.

Aphelenchoides eldaricus n. sp. (Nematoda: Aphelenchoididae) isolated from Pinus eldarica in western Iran

Aphelenchoides eldaricusn. sp. is described and illustrated from wood and bark samples of a dead Mondell pine in Kermanshah Province, western Iran. The new species has a body length of 597 (507-700) μm (females) and 662 (636-695) μm (males). The cuticle is weakly annulated with three lateral lines and the lip region is offset. The stylet is 9.6 (9-10) μm long with small basal swellings and the excretory pore is locatedcaone body diam. posterior to the metacorpus valve. The spicules are large with the dorsal limb 40 (38-42) μm long with a prominent rostrum and rounded apex. The female tail is conical, tapering gradually to an acute terminus with a simple ventral mucron. The male tail bears six (2 + 2 + 2) caudal papillae and a well-developed mucron. The new species belongs to the Group 2 category ofAphelenchoidesspecies and is close to four known species, namelyA. cibolensis,A. indicus,A. rutgersiandA. sacchari. Molecular analyses of the partial 18S and the D2-D3 expansion segments of the 28S rRNA gene confirmed its morphological status as a new species.

Four new species and five morphospecies of Ficophagus Davies & Bartholomaeus, 2015 (Nematoda: Aphelenchoididae) from Ficus subgenus Urostigma sect. Americana (Moraceae) in Central America

Four new species ofFicophaguswere recovered from the sycones ofFicusspp. from the SubgenusUrostigmasectionAmericanafrom Central America. The species are described here asFicophagus bulleneisp. n.,F. costaricanussp. n.,F. paraensissp. n. andF. kayaisp. n. The new species are differentiated from other species of the genus by a combination of morphological characters including body length, position of the excretory pore, spicule shape, stylet form, length of the post-uterine sac, tail shape, sequence data of the ribosomal DNA 18S, 28S D2-D3 and mitochondrial DNA cytochrome oxidase subunit I, biogeographical range, and host wasp andFicusspecies affiliations. In addition, five morphospecies are described fromFicus cahuitensis,F. citrifolia,F. dugandii,F. obtusifolia, andF. trigonata, respectively. The morphospecies are not formally named due to a lack of pertinent data/molecular sequences.

Aphelenchoidid nematodes associated with two dominant Ficus species in Aceh, Indonesia

Aphelenchoidid nematodes associated with the syconia of two dominant fig species,Ficus hispidaandF. racemosa, were surveyed in Banda Aceh, Indonesia. Nematodes were isolated from sycones and pollinating wasps of these two fig species from four localities in the area, and identified based on the molecular sequences of two genetic loci, D2-D3 expansion segments of large subunit ribosomal RNA (D2-D3 LSU) and mitochondrial cytochrome oxidase subunit I (mtCOI). Molecular sequences of D2-D3 LSU and mtCOI were successfully determined for 44 and 19 individual nematodes, respectively, and these sequences were separated into four clades,i.e., types A-D of D2-D3 LSU and types I-IV of mtCOI. Phylogenetic analysis of the DNA sequences deposited in the GenBank database showed that the DNA sequences corresponded to three species, namely,Martininema baculum(type B/II),Ficophagus fleckeri(types A/I, D/IV) andF. cf.centerae(type C/III). Within these species,F. fleckeriwas separated into two clades as suggested in previous studies and thus it may possibly reflect the existence of two different taxa,F. fleckeriand a cryptic species. The IndonesianF. cf.centeraewas monophyletic with, but clearly separated from, the Chinese population ofF. centeraeand thus the Indonesian population is potentially an undescribed species. Overall, the species composition of fig-associated aphelenchoidids in the Aceh region seemed intermediate between continental Chinese and Australian species. However, further material collections followed by detailed morphological analyses are necessary to characterise or describe these fig-associated aphelenchoidids in Indonesia.

Two new species and three morphospecies of Ficophagus Davies & Bartholomaeus, 2015 (Nematoda: Aphelenchoididae) from Ficus subgenus Pharmacosycea (Moraceae) in Central America

Aphelenchoidid nematodes were collected from the sycones ofFicussubgenusPharmacosyceafrom Central America. Two new species ofFicophaguswere recovered, and are described herein asF. maximasp. n. andF. yoponensissp. n. fromFicus maximaandF. yoponensis, respectively. They are differentiated from other species of the genus by a combination of morphological characters including having C-shaped females and spiral males, EP opening close to the lips, a short to long post-uterine sac, spicule characters, three pairs of subventral caudal papillae, DNA sequence data, biogeographical range, and host wasp andFicusspecies affiliation. The new species are differentiated from each other by spicule characters, length of the post-uterine sac, spermatheca shape, and female tail shape. In addition, three morphospecies were collected from sycones ofFicus glabrata,F. insipidaandF. tonduzii, respectively. Their morphological descriptions are presented but these taxa are not formally named as they currently lack molecular data.

Aphelenchoides salixae n. sp. (Nematoda: Aphelenchoididae) isolated from Salix alba in western Iran

Aphelenchoides salixaen. sp. was isolated from wood and bark samples of a dead willow in Kermanshah Province, western Iran. The nematodes were collected directly from wood samples and were successfully reared onBotrytis cinerea. The new species has a body length of 567 (507-620) μm (females) and 382 or 400 μm (males). The cuticle is weakly annulated with four lateral lines. Lip region offset. The stylet is 9.5 (9-10) μm long with small basal swellings. The excretory pore is locatedcaone body diam. posterior to the metacorpus valve. The spicules are short with the dorsal limb 14 or 15 μm long (n = 2), apex and rostrum rounded and only slight offset. The female tail is cylindrical with a broadly rounded terminus. The male tail is conical, bearing six (2 + 2 + 2) caudal papillae with a hamate mucron at terminus. The new species belongs to the Group 1 category ofAphelenchoidesspecies and is close to seven known species, namely:A. capsuloplanus,A. confusus,A. limberi,A. obtusicaudatus,A. obtusus,A. orientalisandA. rotundicaudatus. Molecular analyses of the partial 18S, D2-D3 expansion segments of the 28S rRNA genes and internal transcribed spacer (ITS) supported it as a new species and that the new species is closest toA.besseyi,A. fujianensisandA. ritzemabosiin dendrograms inferred using 18S and 28S D2-D3 genes.

Description of Pseudaphelenchus zhoushanensis n. sp. (Tylenchina: Aphelenchoididae) found in the wood of Pinus thunbergii at Zhoushan Islands, Zhejiang Province, China

Pseudaphelenchus zhoushanensis n. sp. was isolated from a dead Pinus thunbergii at Changgang Mountain, Zhoushan Islands, Zhejiang Province, China. It is characterised by the small to medium length body, cuticle slightly annulated, presence of three lateral lines, stylet 9.0-10.7 μm with small but conspicuous basal knobs, excretory pore located from same level as the metacorpus to slightly anterior to metacorpus, true bursa surrounding entire tail but inconspicuous, male tail conical with a single mucron, spicule with distinct condylus and rostrum strongly arcuate to a pointed end, female tail conical with annulation, strongly ventrally bent in distal part of tail, with terminus bluntly pointed or finely mucronate. Phylogenetic analyses using sequences of the18S and 28S D2-D3 regions of rDNA confirmed the status of P. zhoushanensis n. sp. as a new species. Combining the molecular phylogenetic analyses, morphology and biology of P. zhoushanensis n. sp. and Tylaphelenchus jiaae indicates that T. jiaae is a member of Pseudaphelenchus to which it is herein transferred as P. jiaae n. comb. (= T. jiaae).

Recharacterisation of three Parasitodiplogaster species based on morphological and molecular profiles

Three previously described Parasitodiplogaster spp., P. nymphanema, P. obtusinema and P. trigonema were re-isolated from their type locality, Barro Colorado Island Research Station, Smithsonian Tropical Research Institute, in Panama. The re-isolated materials were morphologically observed to compare with the original descriptions and molecularly characterised by DNA sequences of the near-full-length small subunit and D2-D3 expansion segments of the large subunit of the ribosomal RNA genes. Although the male tail characters, i.e., arrangement of genital papillae and spicule and gubernaculum morphologies, were close to the original descriptions, a compressed stoma with two (right subventral and dorsal) teeth was observed for the first time and confirmed in the newly re-isolated materials. The molecular phylogenetic analysis revealed that the three re-isolated species are close to P. laevigata, P. citrinema and P. popenema, forming the P. laevigata group in the genus, and this group was separated into three subgroups, P. citrinema + P. popenema (subgroup 1), P. nymphanema + P. obtusinema (subgroup 2) and P. laevigata + P. trigonema and three undescribed species (subgroup 3). The P. laevigata group is characterised by a relatively compressed stoma with two (right subventral and dorsal) teeth, arrangement of genital papillae (three or four precloacal and four postcloacal pairs), but distinguishable from each other by stomatal morphology, i.e., the shortest and most compressed being in subgroup 3, widest in subgroup 1, and intermediate in subgroup 2. Furthermore, a large and long spicule and gubernaculum were observed in subgroup 2 as its hypothesised apomorphy.

Aphelenchoides iranicus n. sp. (Nematoda: Aphelenchoididae) from West Azerbaijan province, Iran

Aphelenchoidesiranicusn. sp. is described and illustrated from bark samples of an oak tree (Quercussp.) in West Azerbaijan province, north-western Iran. The new species is characterised by body length of 350 (330-383) μm in females and 343 (323-370) μm in males, lip region set off from body contour, lateral fields with three lines, stylet 8 (7-9) μm long with small basal swellings, excretory pore 59 (56-62) μm from anterior end, hemizonid invisible, pharyngeal glands overlapping intestine dorsally and extending for 48 (41-54) μm, female tail subcylindrical with many tiny finger-like appendages at the tip, and male with aphelenchoid type spicules 17.6 (17-18) μm long. The new species comes close to nine known species of the genus namely:A. brevicaudatus,A. cibolensis,A. conimucronatus,A. editocaputis,A. montanus,A. pusillus,A. rarus,A. sphaerocephalusandA. vaughani, but differs from them by the number of incisures in the lateral field, shape of tail mucron, stylet length, size of spicules and length of post-vulval uterine sac. Additionally, this species is characterised molecularly and phylogenetically by sequences of the D2-D3 expansion segments of the 28S and partial 18S rRNA genes that are unique in relation to the sequences deposited in GenBank.

Description of Aphelenchoides huntensis sp. n. (Nematoda: Aphelenchoididae) isolated from Pinus sylvestris in western Iran

Aphelenchoides huntensissp. n. is described and illustrated from wood and bark samples of a dead scots pine in Kermanshah Province, western Iran. The new species has a body length of 507-673 μm (females) and 636-640 μm (males). The cuticle is weakly annulated with four lateral lines. Lip region offset. The stylet is 9.5 (9.0-10.0) μm long with small basal swellings. The excretory pore is locatedcaone body diam. posterior to the metacorpus valve. The spicules are large with the dorsal limb 37 or 38 μm long (n = 2), and have a prominent rostrum and rounded apex. The female tail is conical, the terminus having a complicated step-like projection, usually with many tiny nodular protuberances. The male tail bears six (2 + 2 + 2) caudal papillae and a well-developed mucron. The new species belongs to the Group 2 category ofAphelenchoidesspecies. Phylogenetic analysis based on the 18S and 28S D2-D3 regions of rDNA confirmed its status as a new species.