Parasitic Nematode Species Research Articles

Characterization of genetic homogeneity of an Indian population of cereal cyst nematode, Heterodera avenae using sequencing and PCR-RFLP of ribosomal DNA

The cereal cyst nematodes belonging to Heterodera avenae group is a complex species consisting of 12 valid species and overlapping morphological characters make them difficult to be distinguished from one another. The non coding internal transcribed spacer sequences, ITS1 and ITS2 including 5.8S region of ribosomal DNA (rDNA) has been very useful for the accurate identification of the species and characterization of molecular genetic variation within the species of plant parasitic nematodes. In the present study, sequencing and PCR-RFLP of rDNA has been used to confirm the species identity. Further it was used to determine the genetic homogeneity of an Indian population used for whole genome and transcriptome sequencing. The Sequence of ITS1 and ITS2 including 5.8S showed approximately 99% similarity with the existing sequences of H. avenae from different countries and confirmed the species identity. Secondary structure of ITS2 region shows that the isolates from India, China, Israel and Australian possess more stable conformational energy than the German strain. Further to characterize the genetic variation within the population, about 200 individual cysts or females were analyzed separately by PCR-RFLP of rDNA with five restriction enzymes that could distinguish H. avenae from other closely related species within the group. This analysis did not reveal any variation within the population indicating it is genetically homogeneous and suitable for next generation sequencing using Illumina platform.

Design and Evaluation of PCR Primers for Denaturing Gradient Gel Electrophoresis Analysis of Plant Parasitic and Fungivorous Nematode Communities

A PCR-DGGE primer pair, Tyl2F-Tyl4R, specific to plant parasitic and fungivorous nematodes was designed based on the 18S rRNA gene. The results of community analysis using the primers showed that they are specific to the order Tylenchida. This primer pair detected species belonging to Tylenchida with high sensitivity and high resolution. The number of detected species of plant parasitic and fungivorous nematodes and their band intensity were much improved compared with PCR-DGGE analysis using the SSU18A-SSU9R primer, which is commonly used for nematode community analysis. It was confirmed that using a group-specific primer was effective for nematode community analysis with PCR-DGGE.

Observations on nematodes from the Indonesian shortfin eel Anguilla bicolor bicolor McClelland in India, including a revalidation of Heliconema ahiri Karve, 1941 (Physalopteridae)

Two species of parasitic nematodes, Heliconema ahiri Karve, 1941 (Physalopteridae) and Procamallanus (Spirocamallanus) anguillae Moravec et al., 2006 (Camallanidae), were recorded from the Indonesian shortfin eel Anguilla bicolor bicolor Mc-Clelland in the Chalakkudi River and Veli Lake, respectively, both Kerala, India. The former species (H. ahiri), rediscovered from eels in India after 82 years from its original description, has been redescribed and revalidated based on its specific feature (presence of groups of minute denticles in the mouth) distinguishing it from other congeners; its finding in A. b. bicolor represents a new host record. The latter species (P. anguillae) has been recorded in India for the first time. SEM examination of its first-stage larvae from uterus has shown that P. anguillae is another species of Procamallanus whose larvae possess a crown of digit-like processes at the tail tip.

Nematodes associated with plant growth inhibition in the Wielkopolska region

Abstract The list of species of the plant parasitic nematodes presented in this paper (133 species belonging to 14 families) is based on the results of faunistic research conducted in the Wielkopolska region by Polish nematologists up until the year 2010, and the results obtained from the project “Elaboration of Innovative Methods for Rapid Identification of Nematodes Causing Damage to the Economy” managed by the Museum and Institute of Zoology of the Polish Academy of Sciences. During the two years of the project (2010-2011) we found 21 species of nematodes which had not yet been reported in the list of species from the Wielkopolska region. Two of them were reported for the first time in Poland.

Nematode diversity in banana rhizosphere from northern districts of Bangladesh

Context: Banana is one of the most important fruits crops among the different fruit crops in the agricultural and its intensively cultivated in all over the parts of Bangladesh especially in northern part. Many species of plant parasitic nematodes are association with banana root systems and are mainly responsible for controlling the banana productions to greater extend. Objective: Keeping in view of the disturbing nature of the nematode pest, the present study was undertaken to examine the biodiversity of plant parasitic nematodes associated with banana intensively grown in northern districts of Bangladesh. Materials and Methods: The collection of nematodes was conducted in the banana growing areas of Bogra, Natore, Rajshahi, Rangpur and Gaibandha districts. In each area, banana fields of different commercial cultivars were chosen for collection of soil and root samples. From each field 10 plants were selected randomly for sample collection. Each subsample consisted about 1 kg of soil and 20 g of fleshy roots taken from a single mat from a depth of 10-30 cm and from three equidistant points (40-50 cm) around the pseudostem Nematodes were extracted from soil by Cobb’s sieving technique and from root by Mechanical maceration technique, and processed by Seinhorst’s slow dehydration method. Fixing was done in boiling lactophenol cotton blue and finally by formalin glycerin solution. Dehydrated nematodes were kept in glycerol-ethanol solution and mounted permanently on glass slides. Identification was done up to species following the keys. Results: Among the plant parasitic nematodes ten species belonging to nine genera, six families of a single order, viz. Helicotylenchus dihystera, Rotylenchulus reniformis, Meloidogyne incognita, Hoplolaimus galeatus, Tylenchorhynchus mashhoodi, Tylenchorhynchus annulatus, Criconemoides sp., Hemicriconemoides cocophillus, Cephalenchus emarginatus and Aphelenchus avenae were encountered. Among the non-parasitic nematodes 15 genera belonging to seven families and three orders viz. Acrobeles, Acrobeloides, Aporcelaimus, Aporcelaimium, Aporcelaimellus, Cephalobus, Dorylaimus, Dorylaimoides, Discolaimus, Discolaimium, Discolaimoides, Indodorylaimus, Mylonchulus, Iotonchus, and Rhabditis were found to be associated with soils in banana field. It was found that species H. galeatus, C. emarginatus and M. incognita were present in all the surveyed areas. Four species of parasitic nematodes viz. C. emarginatus, H. cocophillus, Criconemoides sp. and A. avenae and 5 genera of non parasitic nematodes viz., Aporcelaimium, Aporcelaimellus, Discolaimium, Discolaimoides and Indodorylaimus are reported for the first time in Bangladesh. Conclusion: Present investigation have clearly indicated that the association of plant parasitic nematodes especially the most an important nematodes species like Hoplolaimus galeatus, Cephalenchus emarginatus and Meloidogyne incognita would cause severe economic yield loss to banana plantation in the study area. DOI: http://dx.doi.org/10.3329/jbs.v19i0.13003 J. bio-sci. 19 65-75, 2011

Nematode-Induced Low-Grade Chronic Inflammation of the Iris

There are thousands of parasitic nematode species that have been identified. Many have been documented to invade the eye and periorbital tissues. Whether adult or larvae, alive or dead, they can result in a wide range of ocular and systemic manifestations. Classification of the nematode can be helpful in the treatment planning for these patients. A 60-year-old Hispanic male presented without complaints. During routine examination, the presence of peripheral anterior synechiae, posterior synechiae, and focal cataract were linked to an immobile, partly degenerated 2 to 3 mm long coiled nematode in the anterior chamber. Results from DNA analysis were most consistent with a member of the Trichostrongylus or Metastrongylus genera, or a new nematode species.

A Novel Ascaroside Controls the Parasitic Life Cycle of the Entomopathogenic Nematode Heterorhabditis bacteriophora

Entomopathogenic nematodes survive in the soil as stress-resistant infective juveniles that seek out and infect insect hosts. Upon sensing internal host cues, the infective juveniles regurgitate bacterial pathogens from their gut that ultimately kill the host. Inside the host, the nematode develops into a reproductive adult and multiplies until unknown cues trigger the accumulation of infective juveniles. Here, we show that the entomopathogenic nematode Heterorhabditis bacteriophora uses a small-molecule pheromone to control infective juvenile development. The pheromone is structurally related to the dauer pheromone ascarosides that the free-living nematode Caenorhabditis elegans uses to control its development. However, none of the C. elegans ascarosides are effective in H. bacteriophora, suggesting that there is a high degree of species specificity. Our report is the first to show that ascarosides are important regulators of development in a parasitic nematode species. An understanding of chemical signaling in parasitic nematodes may enable the development of chemical tools to control these species.

New insights into sequence variation in the IGS region of 21 cyathostomin species and the implication for molecular identification

Cyathostomins comprise a group of 50 species of parasitic nematodes that infect equids. Ribosomal DNA sequences, in particular the intergenic spacer (IGS) region, have been utilized via several methodologies to identify pre-parasitic stages of the commonest species that affect horses. These methods rely on the availability of accurate sequence information for each species, as well as detailed knowledge of the levels of intra- and inter-specific variation. Here, the IGS DNA region was amplified and sequenced from 10 cyathostomin species for which sequence was not previously available. Also, additional IGS DNA sequences were generated from individual worms of 8 species already studied. Comparative analysis of these sequences revealed a greater range of intra-specific variation than previously reported (up to 23%); whilst the level of inter-specific variation (3-62%) was similar to that identified in earlier studies. The reverse line blot (RLB) method has been used to exploit the cyathostomin IGS DNA region for species identification. Here, we report validation of novel and existing DNA probes for identification of cyathostomins using this method and highlight their application in differentiating life-cycle stages such as third-stage larvae that cannot be identified to species by morphological means.

A molecular analysis of desiccation tolerance mechanisms in the anhydrobiotic nematode Panagrolaimus superbus using expressed sequenced tags

BackgroundSome organisms can survive extreme desiccation by entering into a state of suspended animation known as anhydrobiosis. Panagrolaimus superbus is a free-living anhydrobiotic nematode that can survive rapid environmental desiccation. The mechanisms that P. superbus uses to combat the potentially lethal effects of cellular dehydration may include the constitutive and inducible expression of protective molecules, along with behavioural and/or morphological adaptations that slow the rate of cellular water loss. In addition, inducible repair and revival programmes may also be required for successful rehydration and recovery from anhydrobiosis.ResultsTo identify constitutively expressed candidate anhydrobiotic genes we obtained 9,216 ESTs from an unstressed mixed stage population of P. superbus. We derived 4,009 unigenes from these ESTs. These unigene annotations and sequences can be accessed at http://www.nematodes.org/nembase4/species_info.php?species=PSC. We manually annotated a set of 187 constitutively expressed candidate anhydrobiotic genes from P. superbus. Notable among those is a putative lineage expansion of the lea (late embryogenesis abundant) gene family. The most abundantly expressed sequence was a member of the nematode specific sxp/ral-2 family that is highly expressed in parasitic nematodes and secreted onto the surface of the nematodes' cuticles. There were 2,059 novel unigenes (51.7% of the total), 149 of which are predicted to encode intrinsically disordered proteins lacking a fixed tertiary structure. One unigene may encode an exo-β-1,3-glucanase (GHF5 family), most similar to a sequence from Phytophthora infestans. GHF5 enzymes have been reported from several species of plant parasitic nematodes, with horizontal gene transfer (HGT) from bacteria proposed to explain their evolutionary origin. This P. superbus sequence represents another possible HGT event within the Nematoda. The expression of five of the 19 putative stress response genes tested was upregulated in response to desiccation. These were the antioxidants glutathione peroxidase, dj-1 and 1-Cys peroxiredoxin, an shsp sequence and an lea gene.ConclusionsP. superbus appears to utilise a strategy of combined constitutive and inducible gene expression in preparation for entry into anhydrobiosis. The apparent lineage expansion of lea genes, together with their constitutive and inducible expression, suggests that LEA3 proteins are important components of the anhydrobiotic protection repertoire of P. superbus.

Rhabdochona (Rhabdochona) keralaensis sp. nov. (Rhabdochonidae) and some other nematodes in the Indian mottled eel Anguilla bengalensis bengalensis from India

A new species of parasitic nematode, Rhabdochona (Rhabdochona) keralaensis sp. nov., is described based on specimens recovered from the intestine of Anguilla bengalensis bengalensis (Gray) collected from the freshwater bodies of Kerala State, southern India. It is characterized mainly by the presence of ten anterior prostomal teeth, absence of basal teeth, simple deirids, length of spicules, number and arrangement of preanal papillae and non-filamented eggs. Two species of camallanid nematodes, adults of Camallanus cotti Fujita, 1927 and a single Procamallanus (Spirocamallanus) sp. fourth-stage larva, were also recorded from A. bengalensis. Camallanus cotti, a pathogenic parasite of many species of wild and aquarium-reared fishes in many countries of South and East Asia, Europe, South and North America, West Indies and Australia, is reported for the first time from a representative of the fish family Anguillidae. Descriptions of R. (R.) keralaensis and Indian specimens of C. cotti, based on light and scanning electron microscopical examinations, are provided. Camallanus oxygasterae Gupta et Bakshi, 1983 is considered a junior synonym of C. cotti.

Collarinema eutriglae n. sp. (Nematoda: Cystidicolidae), a new gastric parasite of the scorpaeniform fish Eutrigla gurnardus (Osteichthyes: Triglidae) in the North Sea, with remarks on the systematic status of Collarinema Sey, 1970

A new species of parasitic nematode, Collarinema eutriglae n. sp. (Cystidicolidae), is described from the stomach of the marine scorpaeniform fish Eutrigla gurnardus (Linnaeus), the grey gurnard (Triglidae), collected in the North Sea in the vicinity of the Shetland Islands (61°12'N, 00°30'E) during March, 2011. The new species, studied using both light and scanning electron microscopy, is characterised mainly by the structure of the mouth (small pseudolabia with terminal projections, submedian labia and well-developed sublabia not exceeding the labia externally), very small simple deirids, the length of the spicules (405-423 and 117-135 μm) and non-filamented eggs. Collarinema Sey, 1970 is considered a valid genus and an amended diagnosis is provided. Ascarophis collaris Petter, 1970 is transferred to Collarinema as C. collaris (Petter, 1970) n. comb.

Molecular Diversity of Fungal Phylotypes Co-Amplified Alongside Nematodes from Coastal and Deep-Sea Marine Environments

Nematodes and fungi are both ubiquitous in marine environments, yet few studies have investigated relationships between these two groups. Microbial species share many well-documented interactions with both free-living and parasitic nematode species, and limited data from previous studies have suggested ecological associations between fungi and nematodes in benthic marine habitats. This study aimed to further document the taxonomy and distribution of fungal taxa often co-amplified from nematode specimens. A total of 15 fungal 18S rRNA phylotypes were isolated from nematode specimens representing both deep-sea and shallow water habitats; all fungal isolates displayed high pairwise sequence identities with published data in Genbank (99–100%) and unpublished high-throughput 454 environmental datasets (>95%). BLAST matches indicate marine fungal sequences amplified in this study broadly represent taxa within the phyla Ascomycota and Basidiomycota, and several phylotypes showed robust groupings with known taxa in phylogenetic topologies. In addition, some fungal phylotypes appeared to be present in disparate geographic habitats, suggesting cosmopolitan distributions or closely related species complexes in at least some marine fungi. The present study was only able to isolate fungal DNA from a restricted set of nematode taxa; further work is needed to fully investigate the taxonomic scope and function of nematode-fungal interactions.

Gene expression changes in a P-glycoprotein ( Tci-pgp-9) putatively associated with ivermectin resistance in Teladorsagia circumcincta

Anthelmintic resistance in parasitic nematodes of small ruminants is widespread and, in some parts of the world, threatens the sustainability of sheep production. The genetic changes underlying resistance to anthelmintics, particularly ivermectin (IVM), remain to be determined. The majority of studies to date have investigated target site mutations; relatively little attention has been paid to the role of changes in gene expression. In this study, we investigated the expression of putative drug transporter molecules, P-glycoproteins (Pgps), in Teladorsagia circumcincta, the predominant parasitic nematode species of sheep in the UK and the major anthelmintic resistant species. Utilising a degenerate PCR approach, 11 partial Pgp sequences were identified. Constitutive differences in gene expression between an IVM-susceptible (MTci2) and a multidrug-resistant (MTci5) isolate were determined for 10 of the Pgps using the ΔΔCt TaqMan® real-time PCR method. Gene expression differences were particularly marked in one of these genes, namely Tci-pgp-9. In the MTci5 isolate, statistically significant increases in Tci-pgp-9 expression, at the mRNA level, were observed across all life-cycle stages and most notably in eggs (55-fold increase). Comparison of the partial Tci-pgp-9 nucleotide sequences from MTci2 and MTci5 also identified high levels of polymorphism. This work has shown that constitutively increased expression in Tci-pgp-9, coupled with increased sequence polymorphism, could play a role in allowing multidrug-resistant T. circumcincta to survive IVM exposure. The genetic changes underpinning these gene expression changes remain to be elucidated and need to be investigated in other isolates. These changes could form the basis of an IVM resistance marker to monitor the spread of resistance and to evaluate management practices aimed at delaying its spread.

Discovery and initial analysis of novel viral genomes in the soybean cyst nematode

Nematodes are the most abundant multicellular animals on earth, yet little is known about their natural viral pathogens. To date, only two nematode virus genomes have been reported. Consequently, nematode viruses have been overlooked as important biotic factors in the study of nematode ecology. Here, we show that one plant parasitic nematode species, Heterodera glycines, the soybean cyst nematode (SCN), harbours four different RNA viruses. The nematode virus genomes were discovered in the SCN transcriptome after high-throughput sequencing and assembly. All four viruses have negative-sense RNA genomes, and are distantly related to nyaviruses and bornaviruses, rhabdoviruses, bunyaviruses and tenuiviruses. Some members of these families replicate in and are vectored by insects, and can cause significant diseases in animals and plants. The novel viral sequences were detected in both eggs and the second juvenile stage of SCN, suggesting that these viruses are transmitted vertically. While there was no evidence of integration of viral sequences into the nematode genome, we indeed detected transcripts from these viruses by using quantitative PCR. These data are the first finding of virus genomes in parasitic nematodes. This discovery highlights the need for further exploration for nematode viruses in all tropic groups of these diverse and abundant animals, to determine how the presence of these viruses affects the fitness of the nematode, strategies of viral transmission and mechanisms of viral pathogenesis.

GTP-Cyclohydrolase and development in Teladorsagia circumcincta and Dictyocaulus viviparus (Nematoda: Strongylida)

GTP-Cyclohydrolase (GTP-CH) is necessary for the production of tetrahydrobiopterin, a required cofactor for the three aromatic amino acid hydroxylases and nitric oxide synthases. The gene encoding GTP-CH is transcribed at high levels in infective third larval stages of a number of parasitic trichostrongylid nematodes. We explore the potential role of GTP-CH within the processes of nematode development and environmentally-induced hypobiosis. For two species of parasitic nematode that are of major economic and welfare importance to livestock in temperate regions, Teladorsagia circumcincta and Dictyocaulus viviparus, we have demonstrated that each of the pre-parasitic larval stages transcribe high mean levels of cat-4 (the gene encoding GTP-CH). Using quantitative real-time polymerase chain reaction analysis and two different isolates of D. viviparus, only one of which is capable of entering hypobiosis, we have shown that there were only minor differences between these isolates in mean cat-4 transcript levels, both during the parasitic stages and during the earlier environmental life cycle stages (L1–L3). Taken together, these data indicate that, although both species of nematode produce high levels of cat-4 transcript in pre-parasitic larval stages, GTP-CH levels are unlikely to be involved in the induction of parasite hypobiosis. Alternative roles for GTP-CH in larval development are discussed.

A Sensory Code for Host Seeking in Parasitic Nematodes

Parasitic nematode species often display highly specialized host-seeking behaviors that reflect their specific host preferences. Many such behaviors are triggered by host odors, but little is known about either the specific olfactory cues that trigger these behaviors or the underlying neural circuits. Heterorhabditis bacteriophora and Steinernema carpocapsae are phylogenetically distant insect-parasitic nematodes whose host-seeking and host-invasion behavior resembles that of some devastating human- and plant-parasitic nematodes. We compare the olfactory responses of Heterorhabditis and Steinernema infective juveniles (IJs) to those of Caenorhabditis elegans dauers, which are analogous life stages. The broad host range of these parasites results from their ability to respond to the universally produced signal carbon dioxide (CO(2)), as well as a wide array of odors, including host-specific odors that we identified using thermal desorption-gas chromatography-mass spectroscopy. We find that CO(2) is attractive for the parasitic IJs and C. elegans dauers despite being repulsive for C. elegans adults, and we identify a sensory neuron that mediates CO(2) response in both parasitic and free-living species, regardless of whether CO(2) is attractive or repulsive. The parasites' odor response profiles are more similar to each other than to that of C. elegans despite their greater phylogenetic distance, likely reflecting evolutionary convergence to insect parasitism.

A new species of Hysterothylacium (Ascaridoidea, Anisakidae) parasitic in Zenopsis conchifer (Zeiformes, Zeidae) from Argentinean waters

AbstractA new species of parasitic nematode, Hysterothylacium spirale sp. nov. (Ascaridoidea, Anisakidae), is described based on specimens collected from the intestine and pyloric caeca of the silvery john dory Zenopsis conchifer (Lowe) (Zeiformes, Zeidae), from the Argentinean Shelf (35°05′–40°46′S, 53°03′–58°07′W). Among the 66 valid species described so far in the genus, the new species most closely resembles H. zenis (Baylis, 1929). Both species, apparently specific for fishes of the family Zeidae, share the shape of the dorsal lip, the long expanded lateral alae originating from subventral interlabia and the ornamentation of the tail tip, as well as general morphometry. The combination of these shared features distinguishes both species from all congeners so far known. However, the new species is distinguishable from H. zenis by having shorter interlabia, and consequently the lateral alae originating more posteriorly, shorter spicules, a smaller number of postcloacal papillae and the presence of two pairs of double postcloacal papillae.

Observations on two nematode species parasitizing freshwater fishes in Thailand, including Spinitectus thaiensis sp. nov. (Cystidicolidae) from Pseudomystus siamensis (Bagridae)

AbstractOne new and one already known species of parasitic nematodes are described from the intestine of freshwater fishes in Chiang Mai Province, northern Thailand: Spinitectus thaiensis sp. nov. (Cystidicolidae) from the catfish Pseudomystus siamensis (Regan) (Bagridae, Siluriformes) in the Fang Brook, a tributary of the Kok River (the Mekong River basin), Fang District and Oceanicucullanus chitwoodae Le-Van-Hoa et Pham-Ngoc-Khue, 1971 (Cucullanidae) from the cyprinid Mystacoleucus marginatus (Valenciennes) (Cyprinidae, Cypriniformes) in the Ping River (the Chao Phraya River basin), Muang District. The new species, S. thaiensis, is very similar to S. petrowi Belous, 1965, differing from it, in addition to some biometrical differences, mainly in having simple cuticular spines (instead of transversely oriented peg-like spines with rounded ends) on the ventral surface of the female tail; the spicules are 156–171 and 66–72 μm long, the vulva is situated at 74% of female body length, and the entire oesophagus including the vestibule represents 14–15% of body length in the male and 12% in the female. The latter species, O. chitwoodae, was studied for the first time by scanning electron microscopy, which enabled to recognize some previously unrecorded morphological details in this species. The finding of O. chitwoodae in M. marginatus in Thailand represents new host and geographical records for this nematode.

Gastrointestinal Helminth Fauna of the Lesser Japanese Mole (Mogera imaizumii) in Kanagawa Prefecture, Japan, and Analyses on Infection Status of Two Parasitic Nematode Species of the Host

Sixty-two lesser Japanese moles (Mogera imaizumii) were captured on the Shonan Campus of Nihon University in Fujisawa City, Kanagawa Prefecture, from May 2002 to April 2004, and their gastrointestinal helminth fauna was surveyed. One species of cestodes, Hymenolepis mogerae, and 4 species of nematodes, Ascarops mogera, Protospirura pseudomuris, Parastrongyloides winchesi and Tricholinstowia talpae, were obtained. This is the first report on the helminth fauna of moles in Kanto District. Parasitism by 2 dominant nematode species, A. mogera and T. talpae showed intensive overdispersion with negative binomial distribution pattern. The factors, which affected the positive-negative infection status and abundance of the 2 dominant species were detected using a generalized linear model. In A. mogera, the main effect of host maturity was significant for the positive-negative infection status, whereas the main effect of host age and an interactive effect of host age and body weight were significant for the abundance in each optimal model. In T. talpae, the main effect of season of capture was only significant for both the positive-negative infection status and the abundance in each optimal model. These results were explained with some ecological features of the host animals, such as solitary habit and use of latrines, and the life cycle characteristics of helminths, such as use of intermediate hosts.

Constitutive and induced subterranean plant volatiles attract both entomopathogenic and plant parasitic nematodes

Summary 1. Indirect plant defences are well documented for the above‐ground constituents of plants. Although less investigated to date, below‐ground defences that mediate multitrophic interactions are equally important. Entomopathogenic nematodes (Steinernema diaprepesi) are attracted to herbivore‐induced volatiles from Swingle var. (Citrus paradisi×Poncirus trifoliata) when fed upon by root weevil, Diaprepes abbreviatus. 2. We examined the extent to which below‐ground volatiles modify behaviour of nematode species representing various foraging strategies (cruisers versus ambushers) and trophic levels (plant parasites versus entomopathogens). We compared attraction to volatiles of weevil‐infested and non‐infested roots from Swingle citrus rootstock and a parent line of the Swingle hybrid, Poncirus trifoliata (Pt). 3. Swingle weevil‐infested roots attracted more nematodes than non‐infested roots irrespective of nematode foraging strategy and trophic status. The parental line, Pt, attracted all nematode species irrespective of insect herbivory. 4. Dynamic in situ collection and GC–MS analysis of volatiles from soil revealed that Pt roots release attracting cues constitutively. A different non‐hybrid citrus species (sour orange, Citrus aurantium) released nematode attracting cues only in response to larval feeding, similar to responses found in Swingle. Volatile collections from above‐ and below‐ground portions of citrus plants revealed that above‐ground feeding by weevils does not induce production of nematode attracting cues analogous to that induced by root damage, nor does damage by larvae below‐ground induce a similar volatile above ground. 5. Synthesis. Our results suggest that release of nematode attractants by citrus roots occurs broadly and can be constant or herbivore‐induced. The major constituent of this indirect defence is produced by roots and not shoots and in response to below‐ground, but not above‐ground herbivory. Our findings suggest that this cue acts on nematode species broadly, attracting entomopathogenic nematodes that exhibit various foraging strategies. Unexpectedly, we also found that this cue attracts a plant parasitic nematode species. It appears, thus, that release of nematode attracting cues by citrus plants can cause ecological costs. The plants, however, appear to counteract against these costs, because constitutive release was found only in a cultivar that is resistant to phytopathogenic nematodes, while herbivore‐induced release occurred in lines susceptible to pathogenic nematode species.