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.

Description of Ruehmaphelenchus kuroshioi n. sp. and R. interjectus n. sp. (Tylenchomorpha: Aphelenchoididae) isolated from ambrosia beetles, Euwallacea spp. (Scolytinae), from Japan

Two Ruehmaphelenchus species were isolated from the ambrosia beetles Euwallacea kuroshio and E. interjectus, collected from Okinawa and Kagoshima, Japan, respectively. Both nematodes were successfully cultured on a lawn of the grey mould Botrytis cinerea. Morphological observation and molecular characterisation revealed that both species are undescribed; therefore, the nematodes are described herein as R. kuroshioi n. sp. and R. interjectus n. sp. Phylogenetically, both species are closely related to R. formosanus, R. fujiensis, R. digitulus and R. asiaticus. Ruehmaphelenchus kuroshioi n. sp. is characterised by a conical male and female tail, which has a terminal projection (mucron), small male spicule with a weakly-developed triangular condylus, dorsal and ventral limbs that are connected to each other by three different tissues, and clearly separated distal pairs of genital papillae (P3 and P4). However, R. kuroshioi n. sp. can be distinguished from its close relatives by a combination of male and female tail characters and its distinctive phylogenetic status. Ruehmaphelenchus interjectus n. sp. is almost identical to R. formosanus, sharing characteristic lateral spikes of the spicule; they form a well-supported phylogenetic clade. However, R. interjectus n. sp. is distinguished from R. formosanus by morphometric values and ribosomal RNA, i.e., a 6-bp difference from the ca 1.7 kb molecular sequence of the 18S ribosomal RNA of R. formosanus, which warrants independent species status.

Description of Ruehmaphelenchus americanum n. sp. (Nematoda: Aphelenchoididae) found in Loblolly pine from the USA

Ruehmaphelenchus americanum n. sp., isolated from southern yellow pine (Pinus taedae L.) from the USA is described and figured. It is characterised by a relatively stout body (a = 30 for females and males), three lines in the lateral field, both oocytes and spermatocytes arranged in two rows, male spicules relatively small (14-18 μm) with weakly developed condylus and rostrum, short tail with a bluntly pointed tip, seven papilliform genital papillae present, female vulva positioned at ca 82% of body length, vulval lips slightly protruding, post-uterine branch extending two-thirds of vulva to anus distance, tail cylindrical, ca two anal body diam. long, terminus forming a spike-like projection or mucron, 7.6-12.2 μm long, with pointed tip. The new species can be separated from 11 known species (except R. thailandae) by male genital papillae arrangement (the second and third pair adjacent vs separated). Detailed phylogenetic analysis based on 18S and 28S D2-D3 region ribosomal RNA (rRNA) sequences has confirmed the status of this nematode as a new species.

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.  

A reference of identification keys to plant-parasitic nematodes (Nematoda: Tylenchida\ Tylenchomorpha)

The present review has documented a list of keys for identifying plant-parasitic nematodes at different taxonomic levels including superfamily, family, subfamily, genus, and species. It was compiled as a current source of information to assist students and professionals in the discipline of nematology for identification of this important group of soil nematodes.

A new aphelench nematode, Basilaphelenchus brevistylus n. sp. (Aphelenchoididae: Tylaphelenchinae) from Pinus massoniana in China

Basilaphelenchus brevistylus n. sp. was isolated from masson pine (Pinus massoniana) in Guangdong province, China. The new species is characterized by an offset lip region, short stylet (female stylet 4.5-5.5 μm and male stylet 4-5 μm long) with three elongate posteriorly directed knobs, posteriorly located metacorpal valve and lateral field composed of three lines. The female has an elongate postuterine sac and a short conical tail, uniformly narrowing toward a sharp tip, or tapering to a slightly offset mucronate tip in a few individuals. The male has a conical tail with a sharp terminal mucro, three pairs of caudal papillae, and small arcuate spicules with a bluntly rounded condylus and small pointed rostrum. B. brevistylus n. sp. can be distinguished from all described Basilaphelenchus nematodes by numerous morphological and morphometrical traits, especially the tail morphology of both sexes and stylet length. In addition, molecular phylogenetic trees inferred from rRNA small subunit and D2-D3 expansion domains of large subunit revealed that this nematode belongs to the Basilaphelenchus, and is clearly different from all the other Basilaphelsenchus species.

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.

Termites and Chinese agricultural system: applications and advances in integrated termite management and chemical control

Termites are eusocial arthropod decomposers, and improve soil fertility, crop yield, and also are used by humans for their benefits across the world. However, some species of termites are becoming a threat to the farming community as they are directly and indirectly causing major losses to the agricultural system. It is estimated that termites cost the global economy more than 40 billion USD annually, and considerable research has been done on their management. In this review, we present the available information related to sustainable and integrated termite management practices (ITM). Furthermore, we insist that the better management of this menace can be possible through: (i) improving traditional methods to keep termites away from crops; (ii) improving agricultural practices to maintain plants with more vigor and less susceptible to termite attack; and (iii) integration of available techniques to reduce termite infestation in crops and surroundings. The application of an effective combination of traditional practices with recently developed approaches is the best option for agricultural growers. Moreover, keeping in mind the beneficial nature of this pest, more innovative efforts for its management, particularly using rapidly emerging technology (e.g., RNA interference), are needed.

Nematode-free agricultural system of a fungus-growing termite

Fungus-growing termites forage dead plant materials from the field to cultivate symbiotic Termitomyces fungi in the nest. Termite foraging behavior and the entry of symbiotic arthropod inquilines may transfer nematodes into a nest and adversely affect fungus production. To test whether nematodes were transferred to fungus gardens by termites and inquilines, we examined the occurrence of nematodes in fungus gardens, five termite castes, and nine species of inquilines of a fungus-growing termite, Odontotermes formosanus. Our results revealed that nematodes were commonly carried by foraging termites and beetle inquilines. Numerous nematodes were found under the beetle elytra. No nematodes were found on termite larvae, eggs, and wingless inquilines. In addition, nematodes rarely occurred in the fungus garden. By observing the response of nematodes to three species of Termitomyces spp. and the fungus gardens, we confirmed that the fungus and fungus gardens are not actually toxic to nematodes. We suggest that nematodes were suppressed through grooming behavior and gut antimicrobial activity in termites, rather than through the antimicrobial activity of the fungus.

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.

Seinura caverna n. sp. (Tylenchomorpha: Aphelenchoididae), an androdioecious species isolated from bat guano in a calcareous cave

A new species of a predator aphelenchoidid, Seinura caverna n. sp., is described and illustrated. The new species was isolated from bat guano collected from a calcareous cave in Japan. The new species is characterised by its three-lined lateral field, secretory-excretory pore at the level of the posterior two-thirds of the metacorpus, a long post-uterine sac, hermaphrodite tail shape elongate conoid with a filiform tip, and an androdioecious reproductive mode. The new species is typologically and biologically close to S. steineri, but is distinguished by its longer post-uterine sac, slightly longer stylet and slightly larger median bulb. The comparisons with other morphologically similar species, i.e., S. chertkovi, S. tenuicaudata and S. steineri, are discussed. A molecular phylogenetic analysis based on two small and large subunit ribosomal RNA genes revealed that the new species is located at the basal position of clade 3 of the Aphelenchoididae, clearly separate from S. demani, its congener with unclear rectum and anus, which is located at the derived position, suggesting that further generic revision is necessary for the genus. Aphelenchoides lii n. comb. (= Seinura lii) is proposed.

Phoresy and Within-colony Transmission of Nematodes Associated with Alates of Subterranean Termites (Isoptera: Rhinotermitidae)

Termites and their nests are potential resources for a wide assemblage of taxa including nematodes. During dispersal flight events from termite colonies, co-occurring nematodes in the nest may have phoretic opportunities to use termite alates as transportation hosts. The two subterranean termite species Coptotermes gestroi (Wasmann) and Coptotermes formosanus Shiraki are both invasive and established in south Florida. Alates of both species (n = 245) were collected during dispersal flight events in 2015-2016 from six locations, of which 30 (12.2%) were associated with one or more species of nematodes. Species of Bunonema Jägerskiöld (Rhabditida: Bunonematidae), Halicephalobus Timm (Rhabditda: Panagrolaimidae), and Poikilolaimus regenfussi (Sudhaus) Sudhaus and Koch (Rhabditida: Rhabditidae) were isolated from 5.3, 4.9, and 0.4% of termite alates, respectively, and Bunonema and Halicephalobus were concomitant in 1.6% of alates. Additional C. formosanus alates were field-collected to establish laboratory colonies in sterilized rearing containers (SRC) to determine if alate-associated nematodes would colonize the newly established nest and/or brood. Among 1-yr-old termite colonies reared in SRCs, 26.9% of the colonies were positive for nematodes confirming that within-colony transmission of nematodes occurred. All three isolated nematode genera are free-living bacterivores capable of asexual reproduction. This suggests that these common co-occurring, termite-associated nematodes are opportunistic and facultative symbionts that receive increased opportunities of geographical dispersion through phoresy during termite dispersal flight events.

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.

Description of Ruehmaphelenchus quercophilus n. sp. (Nematoda: Aphelenchoididae) from dying oak, Quercus robur, in Poland

Ruehmaphelenchus quercophilus n. sp., isolated from a dying oak, Quercus robur, in the State Forests, Łopuchówko District, Poland, is described and figured. It is characterised by three lateral lines, relatively stout body, excretory pore posterior to nerve ring, five caudal papillae, spicules relatively small (12-14 μm) with weakly developed condylus and rostrum, bursa absent, vulva positioned at ca 78% of body length, vulval flap absent, post-uterine branch extending for slightly over half of vulva to anus distance, and conoid tail with a bend at the distal end forming a terminal projection 10-14 μm long. The new species is very similar to four other described species, namely R. formosanus, R. juliae, R. thailandae, and R. sirisus. Detailed phylogenetic analysis based on 18S, 28S D2-D3 and ITS sequences has confirmed the status of this nematode as a new species.

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).

Description of Ektaphelenchus berbericus n. sp. (Rhabditida: Ektaphelenchinae) from eastern Iran

Ektaphelenchus berbericus n. sp. was recovered from soil samples collected in eastern Iran and is described and illustrated based on morphological, morphometric and molecular data. The new species is characterised by having female body 512-691 μm long, lip region separated from rest of body by a shallow depression, lips separated and equally sized, 19-22 μm long stylet with wide lumen and lacking knobs or swellings at its base, cuticle with fine, but distinct transverse annuli and three lines in lateral field, excretory pore located at base of metacorpus (with slight variation in position), reproductive system monodelphic-prodelphic with spheroid and fine sperm cells inside spermatheca in some individuals and short post-vulval uterine sac (PUS), rectum and anus vestigial (invisible in few individuals), conical posterior body end (tail), narrowing at mid-point between anus and rounded tail tip, and males lacking. The new species is typologically similar to species belonging to four genera: Devibursaphelenchus, Ektaphelenchoides, Ektaphelenchus and Seinura, by a combination of morphological characters, e.g., gross morphology of stylet (lacking knobs or swellings at base), morphology of posterior body end (having short conical tail), PUS length, and having a vestigial anus and rectum in most individuals. In molecular phylogenetic analyses using sequences of the partial small subunit of the ribosomal RNA gene (SSU) and the D2-D3 expansion segments of the large subunit (LSU) ribosomal RNA gene, the new species is close to the Ektaphelenchoides/Cryptaphelenchus clade in an inferred SSU tree, and formed a clade with Ektaphelenchoides and Devibursaphelenchus spp. in a D2-D3 LSU tree. Further phylogenetic analyses using full length sequences of the internal transcribed spacer region (ITS) (= ITS1 + 5.8S + ITS2) corroborated results from the SSU and D2-D3 LSU trees, and the multilocus analyses using the combined SSU and LSU data placed the new species in a robustly supported clade with Ektaphelenchoides poinari and Devibursaphelenchus lini.

Description of Ruehmaphelenchus juliae n. sp. (Tylenchina: Aphelenchoididae) isolated from an ambrosia beetle, Xylosandrus crassiusculus (Motschulsky), from South Florida

During a survey of nematode associates of ambrosia beetles from dead and dying red bay and avocado trees affected by the laurel wilt epidemic in southern Florida, a Ruehmaphelenchus species was isolated from the non-native ambrosia beetle, Xylosandrus crassiusculus. The new species is characterised by its possession of an oral disc at the stoma opening, three lines in the lateral field, male spicule with clear dorsal and ventral limbs connected by elongated triangular cuticle, thin membrane-like tissue and cuticular bridge-like structure, conical tail with pointed tip of males and conical tail with digitate mucro of females. The new species is very similar to four previously described species: R. asiaticus, R. digitulus, R. thailandae and R. sirisus, and can be distinguished only by some minor morphological differences in male tail characters, i.e., spicule morphology, position of genital papillae and tail tip shape, and morphometric values. However, the new species is phylogenetically unique, i.e., it is the basal taxon of the Ruehmaphelenchus clade and close to Bursaphelenchus spp. Ruehmaphelenchus juliae n. sp. is therefore proposed based on its morphological diagnostic characters and molecular sequences of near-full-length of SSU, internal transcribed spacer region, D1, D2 and D3 expansion segments of LSU ribosomal RNA and partial mitochondrial COI genes.

Soil and litter nematode diversity of Mount Hamiguitan, the Philippines, with description of Bicirronema hamiguitanense n. sp. (Rhabditida: Bicirronematidae)

The nematode diversity in soil and litter was investigated on Mount Hamiguitan, the Philippines, along four eco-habitats from elevations of 75-1600 m a.s.l. A total of 155 and 467 nematodes were identified to 39 and 62 genera from litter and soil, respectively. The nematode assemblages and diversity did not show any relation to eco-habitat or elevation. Bacterivorous nematodes were the most common group (37.5%). Acrobeloides was most abundant from the soil and Aphelenchoides from the litter. Bicirronema hamiguitanense n. sp. is herein described based on morphology, morphometrics and molecular data. The new species has the following diagnostic features: a wide lateral field one-fifth of its body diam. with four incisures forming two ornamented ridges; gubernaculum with proximal thickening; spicules (35-38 μm) and gubernaculum (18-20 μm) longer than B. caledoniense; and with 37 molecular autapomorphies supporting its new species status. The phylogenetic position of the new species within Cephalobomorpha is discussed.