Single Nematode Research Articles

Observations on mermithid parasitism (Nematoda: Mermithidae) in two species of Lasius ants (Hymenoptera: Formicidae)

The morphological effects of nematode parasitism by Pheromermis myrmecophila were investigated in two species of ants, Lasius flavus and Lasius niger, collected on Clare Island, Ireland. Infected males and queens were found for L. flavus but only infected queens in L. niger. The numbers of nematodes present in each infected specimen were counted and their lengths were measured. Head width, femur length and wing measurements were made for infected and non-infected individuals of both species. In queens, the length of the nematodes decreased as the number per ant increased. When single nematodes were present their mean lengths were significantly greater in L. flavus than in L. niger. In addition to the reduction in wing size for all parasitized specimens, head widths and femur lengths of the queens were significantly different in both species. A log–log graph of radial cell length versus width suggested a linear reduction of wing size.

New Insights into the Evolution of Wolbachia Infections in Filarial Nematodes Inferred from a Large Range of Screened Species

Background Wolbachia are intriguing symbiotic endobacteria with a peculiar host range that includes arthropods and a single nematode family, the Onchocercidae encompassing agents of filariases. This raises the question of the origin of infection in filariae. Wolbachia infect the female germline and the hypodermis. Some evidences lead to the theory that Wolbachia act as mutualist and coevolved with filariae from one infection event: their removal sterilizes female filariae; all the specimens of a positive species are infected; Wolbachia are vertically inherited; a few species lost the symbiont. However, most data on Wolbachia and filaria relationships derive from studies on few species of Onchocercinae and Dirofilariinae, from mammals.Methodology/Principal FindingsWe investigated the Wolbachia distribution testing 35 filarial species, including 28 species and 7 genera and/or subgenera newly screened, using PCR, immunohistochemical staining, whole mount fluorescent analysis, and cocladogenesis analysis. (i) Among the newly screened Onchocercinae from mammals eight species harbour Wolbachia but for some of them, bacteria are absent in the hypodermis, or in variable density. (ii) Wolbachia are not detected in the pathological model Monanema martini and in 8, upon 9, species of Cercopithifilaria. (iii) Supergroup F Wolbachia is identified in two newly screened Mansonella species and in Cercopithifilaria japonica. (iv) Type F Wolbachia infect the intestinal cells and somatic female genital tract. (v) Among Oswaldofilariinae, Waltonellinae and Splendidofilariinae, from saurian, anuran and bird respectively, Wolbachia are not detected.Conclusions/SignificanceThe absence of Wolbachia in 63% of onchocercids, notably in the ancestral Oswaldofilariinae estimated 140 mya old, the diverse tissues or specimens distribution, and a recent lateral transfer in supergroup F Wolbachia, modify the current view on the role and evolution of the endosymbiont and their hosts. Further genomic analyses on some of the newly sampled species are welcomed to decipher the open questions.

Comparison of whole-genome amplifications for microsatellite genotyping of Rotylenchulus reniformis

Currently, a large number of microsatellites are available for Rotylenchulus reniformis (reniform nematode); however, two barriers exist for genotyping samples from different geographical areas. The limited amount of nucleic acids obtained from single nematodes which would require their multiplication to obtain enough DNA for testing; and the strictly regulated transport of live samples and multiplication in greenhouse for being a plant pathogen. Whole-genome amplification (WGA) of samples consisting of one and five dead gravid females with their associated egg masses was successfully performed on disrupted tissue using three commercial kits. DNA yield after WGA ranged from 0.5 to 8 µg and was used to test 96 microsatellite markers we previously developed for the reniform nematode. The results were compared to those of fingerprinting the original population (MSRR03). Out of 96 markers tested, 71 had amplicons in MSRR03. Using WGA of single gravid females with their associated egg masses, 86-93% of the alleles found on MSRR03 were detected, and 87-88% of the alleles found on MSRR03 when using WGA of samples composed of five gravid females with their associated egg masses as template. Our results indicate that reniform nematode samples as small as a single gravid female with her associated egg mass can be used in WGA and direct testing with microsatellites, giving consistent results when compared to the original population.

Seasonal Dynamics of Skrjabinoptera phrynosoma (Nematoda) Infection in Horned Lizards From the Alvord Basin: Temporal Components of a Unique Life Cycle

The nematode Skrjabinoptera phrynosoma is a stomach parasite of horned lizards in the genus Phrynosoma. This nematode demonstrates a distinctive life cycle wherein entire gravid females harboring infective eggs exit with lizard feces. Pogonomyrmex spp. harvester ants collect these females and feed them to their larvae, which are the only stages of the intermediate host that can become infected. We hypothesized that the seasonal dynamics of nematode abundance within lizard hosts would be correlated with the seasonal availability of suitable intermediate hosts. To describe seasonal variation of nematode population variables and elucidate the timing of critical events in the parasite life cycle, nematodes were collected from both hosts across three collection periods in the ant-and-lizard activity season of 2008 in the Alvord Basin of southeastern Oregon. Among 3 collection periods, and across the activity season, nematodes were harvested from individual Phrynosoma platyrhinos , and the distribution of developmental categories and body lengths of nematodes was analyzed to determine the seasonal change in nematode population composition. Pogonomyrmex spp. ants were collected in pit-fall traps and dissected to determine infection prevalence. The abundance of non-gravid female and juvenile nematodes collected from lizards' stomachs decreased significantly between the early and late collection period, which was likely a consequence of the sequential conversion of these developmental categories to gravid females. The presence of gravid female nematodes peaked in cloacal and fecal collections during mid-season. The body lengths of male nematodes increased as the activity season progressed, perhaps due to growth, but their abundance remained the same. Smaller juvenile nematodes were present in late-season collections from lizards, possibly indicating new acquisitions from infected ants. We propose that once a set population of male nematodes establishes in lizards' stomachs, newly acquired juvenile nematodes develop into non-gravid females that mate, become gravid females, and exit the lizard mid-season. We additionally suggest that the exit of females may be timed with the peak foraging activity of ant intermediate hosts and access to larval ants in the nests. Infection prevalence in the intermediate host was low, with only 1 of 6,000 dissected harvester ants containing a single larval nematode. The temporal dynamics of S. phrynosoma populations within P. platyrhinos at this northern locale is most likely driven by the seasonal availability of harvester ant intermediate hosts.

Identification and localization of food-source microbial nucleic acids inside soil nematodes

Microorganisms (e.g., prokaryotes, fungi) are food sources for soil nematodes, but they can also be potential mutualists or pathogens. Understanding the linkages between microorganism and invertebrate diversity in soils requires the ability to distinguish between these microbial roles. We tested the potential of a taxon-specific fluorescent in situ hybridization (FISH) procedure for identifying and localizing microbial rRNA within the bodies of soil nematodes. Our objective was to determine whether the rate of digestion permitted detection and identification of food-source nucleic acids within the nematode digestive system (i.e., pharynges, intestines) before their breakdown. First, using laboratory cultures of Caenorhabditis elegans maintained on Escherichia coli, we were able to localize bacterial rRNA throughout the nematode pharynx with the universal bacterial-probe EUB338, although never in the intestines. Second, we applied the fungal rRNA probe FR1 to Aphelenchus avenae cultured on the fungus Rhizoctonia solani. We were unable to detect fungal rRNA within these nematodes, and it appears that this material may be digested rapidly. Next, we applied our technique to nematodes extracted directly from soils. We were able to localize bacterial rRNA within the pharynges of bacterial-feeding species of nematodes from desert soils. We also localized archaeal rRNA using the probe ARC344. Finally, application of EUB338 to desert soil nematodes revealed the presence of bacteria in the intestines of some nematodes and within the ovary of a single nematode. This technique has great potential for use in understanding the feeding behavior of bacterial-feeding soil nematodes and in studies of nematode:bacterial relationships.

Amplification of the Second Internal Transcribed Spacer Ribosomal DNA of Individual Trichostrongylid Nematode Larvae by Nested Polymerase Chain Reaction

The second internal transcribed spacer (ITS2) of ribosomal DNA (rDNA) is used as a genetic marker to identify trichostrongylid nematodes. However, it is often difficult to amplify by polymerase chain reaction (PCR) the ITS2 rDNA of a single trichostrongylid nematode larva or egg. A nested PCR (nPCR) assay was, therefore, developed to amplify the ITS2 from individual trichostrongylid nematode larvae. The results show that the ITS2 rDNA of a significantly greater proportion of individual larvae was amplified using nPCR compared with a standard PCR. There was also no need to column-purify the genomic DNA before nPCR, which is more time and cost effective for studies involving large sample sizes. The amplicons produced from the secondary phase of the nPCR were subjected to single-strand conformation polymorphism analyses and DNA sequencing to confirm the species identity of the larvae used in the current study as Ostertagia gruehneri. The nPCR assay was also used to amplify the ITS2 from individual trichostrongylid eggs. The ability to amplify the ITS2 rDNA from large numbers of individual nematode eggs and larvae has important implications for diagnostic testing and for conducting epidemiological studies on these parasites of veterinary importance.

Linking operational clustered taxonomic units (OCTUs) from parallel ultra sequencing (PUS) to nematode species

DNA-sequence-based approaches such as single nematode PCR and sequencing have been successfully used in nematode species diagnostics. Here, we use SSU rDNA sequences generated from an artificially-assembled community of nematodes of known identity and relative abundance to assess a relationship between nematode species and operationally clustered taxonomic units (OCTUs). OCTUs that formed at 95% similarity underestimated species richness by ca 30%, and all expected species were recovered only at 99% OCTU similarity. Although the number of OCTUs formed at 99% similarity was considerably higher than the actual number of nematode species, a pattern of the distribution of OCTUs within each species allowed an assignment of OCTUs to specific species. The pattern was highly predictable and helped to discern rather than obscure species recognition. The patterns and parameters that emerged from the control nematode dataset were then used to test our approach on environmental samples of nematodes obtained from a tropical rainforest in Costa Rica.

UNC-64 and RIC-4, the plasma membrane-associated SNAREs syntaxin and SNAP-25, regulate fat storage in nematode Caenorhabditis elegans

To investigate whether genes required for synaptogenesis and synaptic function are also involved in fat storage control in Caenorhabditis elegans. Fat storage was examined in mutants of genes affecting the synaptogenesis and synaptic function. In addition, the genetic interactions of SNAREs syntaxin/unc-64 and SNAP-25/ric-4 with daf-2, daf-7, nhr-49, sbp-1 and mdt-15 in regulating fat storage were further investigated. The tissue-specific activities of unc-64 and ric-4 were investigated to study the roles of unc-64 and ric-4 in regulating fat storage in the nervous system and/or the intestine. Mutations of genes required for the formation of presynaptic neurotransmission site did not obviously influence fat storage. However, among the genes required for synaptic function, the plasma membrane-associated SNAREs syntaxin/unc-64 and SNAP-25/ric-4 genes were involved in the fat storage control. Fat storage in the intestinal cells was dramatically increased in unc-64 and ric-4 mutants as revealed by Sudan Black and Nile Red strainings, although the fat droplet size was not significantly changed. Moreover, in both the nervous system and the intestine, expression of unc-64 significantly inhibited the increase in fat storage observed in unc-64 mutant. And expression of ric-4 in the nervous system completely restored fat storage in ric-4 mutant. Genetic interaction assay further indicated that both unc-64 and ric-4 regulated fat storage independently of daf-2 [encoding an insulin-like growth factor-I (IGF-I) receptor], daf-7 [encoding a transforming growth factor-beta (TGF-beta) ligand], and nhr-49 (encoding a nuclear hormone receptor). Besides, mutation of daf-16 did not obviously affect the phenotype of increased fat storage in unc-64 or ric-4 mutant. Furthermore, unc-64 and ric-4 regulated fat storage probably through the ARC105/mdt-15- and SREBP/sbp-1-mediated signaling pathways. In addition, fat storage in unc-64; ric-4 was higher than that in either unc-64 or ric-4 single mutant nematodes, suggesting that unc-64 functions in parallel with ric-4 in regulating fat storage. The plasma membrane-associated SNAREs syntaxin/unc-64 and SNAP-25/ric-4 function in parallel in regulating fat storage in C. elegans, probably through the ARC105/mdt-15- and SREBP/sbp-1-mediated signaling pathways.

A DNA extraction method with SDS from single nematodes for direct application to PCR amplification

Various methods for extracting DNA from single nematodes for PCR amplification have been developed by many authors. Such techniques generally do not include a purification step, and direct application of crude lysate to PCR amplification is usual. SDS is not used in DNA extraction methods for PCR amplification from single nematodes, although it is a common detergent used in DNA extraction. This is because SDS has an inhibitory effect on PCR (Gelfand, 1989). The author developed an SDS-based DNA extraction method from single nematodes, where the crude lysate can be applied directly to PCR amplification, and reports it here.

Species-specific polymerase chain reaction primers for simple detection of Bursaphelenchus fraudulentus (Nematoda: Parasitaphelenchidae)

Nematology , 2010, Vol. 12(1), 157-160 Short communication Species-specific polymerase chain reaction primers for simple detection of Bursaphelenchus fraudulentus (Nematoda: Parasitaphelenchidae) Anna F I L I P I A K 1 , ∗ , Agata J AKUBOW SKA 1 , 2 and Marek T OMALAK 1 Bursaphelenchus fraudulentus Ruhm, 1956 (Nema- toda: Parasitaphelenchidae) is a tree-inhabiting species frequently found in Europe (Ruhm, 1956; Schauer-Blume & Sturhan, 1989; Tomalak, 2004; Carletti et al ., 2005) and Asia (Braasch et al ., 2001). It is primarily found in dy- ing or dead deciduous trees (Ruhm, 1956; Schauer-Blume & Sturhan, 1989), although occasionally reported from conifers (Braasch et al ., 2001). Within the genus the spe- cific morphological characters (i.e. , vulval flap, shape of spicules, position of caudal papillae and presence of four incisures in the lateral fields) place B. fraudulentus into a distinct xylophilus -group which comprises eight other, morphologically similar, species, including the quarantine pest B. xylophilus (Gu et al ., 2008). Reliable methods of taxonomic identification of these species are therefore of particular interest to plant quarantine services. Several molecular techniques have been developed and used for identification of Bursaphelenchus spp. (Wang et al. , 1999; Matsunaga & Togashi, 2004; Burgermeister et al ., 2005; Castagnone et al. , 2005; Leal et al ., 2005, 2007) with ITS-RLFP analysis the most widely used in research and quarantine practice. An alternative method, based on a simple PCR amplification with primers specific for B. xylophilus and B. mucronatus (Matsunaga & Togashi, 2004), enables rapid and precise species identification, even from a single nematode (Filipiak et al ., 2007). Both native European species from the xylophilus - group, i.e. , B. mucronatus and B. fraudulentus , are rela- tively common and harmless to trees. They can be mor- phologically difficult to distinguish from each other and from the quarantine pest B. xylophilus. The provision of PCR primers specific for the DNA of B. fraudulentus , in addition to those already existing for B. xylophilus and B. 1 Department of Biological Pest Control and Quarantine, Institute of Plant Protection, Wladyslawa Wegorka 20, Poznan, 60-318, Poland 2 Department of Genetics, University of Valencia, Dr. Moliner 50, 46-100, Burjassot, Spain ∗ Corresponding author, e-mail: A.Filipiak@ior.poznan.pl Received: 22 October 2008; revised: 26 June 2009 Accepted for publication: 29 June 2009 Keywords: Bursaphelenchus xylophilus -group, diagnostics, molecular. mucronatus (Matsunaga & Togashi, 2004), enhances the utility of this method. The main objectives of our research were to sequence the ITS regions of the B. fraudulentus genome and to design specific primers for PCR amplifica- tion. Eight isolates of B. fraudulentus , two of B. mucrona- tus and one of B. xylophilus were examined. The Aus- trian (Osterreich), Russian (DE10w), German (Helmstedt and H26), and Hungarian (Ungarn) isolates of B. fraudu- lentus and the isolate of B. xylophilus (China) were ob- tained from the nematode collection of the Federal Re- search Centre for Cultivated Plants (formerly Federal Bi- ological Research Centre for Agriculture and Forestry – BBA), Braunschweig, Germany (Dr T. Schroder). All the remaining nematode populations were isolated from in- fested trees in Poland. The populations of B. fraudulentus originated from Poznan (PL-01 and PL-05) and Kornik (PL-04) and those of B. mucronatus from Nowy Tomysl (NTo-01) and Slawa Slaska (SlS-01). Their taxonomic identification was originally based on morphological and morphometric characteristics and subsequently confirmed by ITS-RLFP analysis according to the protocol described by Burgermeister et al. (2005). Prior to examination, all isolates were reared on Botrytis cinerea /malt agar (4.5%) at 25 ◦ C for ca 2 weeks. Propagated nematodes were col- lected by the Baermann funnel method and stored in 10 μ l H 2 O at − 20 ◦ C until use. Extraction of DNA was performed according to the method described by Iwahori et al. (1998), with mi- nor modifications to the composition of the lysis buffer: 100 mM Tris, pH 8.5, 100 mM NaCl, 50 mM EDTA, 1% SDS, 1% β -mercaptoethanol, 100 μ g ml − 1 proteinase K per 100 μ l buffer. Before incubation, the mixture was © Koninklijke Brill NV, Leiden, 2010 DOI:10.1163/138855409X12469543767319 Also available online - www.brill.nl/nemy 157

Ecotoxicological assessment of lanthanum with Caenorhabditis elegans in liquid medium

With their widespread applications in industry, agriculture and many other fields, more and more rare earth elements (REEs) are getting into the environment, especially the aquatic systems. Therefore, understanding the aquatic ecotoxicity of REEs has become more and more important. In the present work, Caenorhabditis elegans (C. elegans) was used as a test organism and life-cycle endpoints were chosen along with elemental assay to evaluate the aquatic toxicity of lanthanum (La), a representative of REEs. The results show La³+ had significant adverse effects on the growth and reproduction of worms above a concentration of 10 μmol L⁻¹. The elemental mapping by microbeam synchrotron radiation X-ray fluorescence (μ-SRXRF) illustrated how La treatment disturbed the metals distribution in the whole body of a single tiny nematode at lower levels. Our results suggested that the high-level REEs in some polluted water bodies would lead to an aquatic ecological crisis. The assessment we performed in the present work could be developed as a standardized test design for aquatic toxicological research.

Nucleotide excision repair genes are expressed at low levels and are not detectably inducible in Caenorhabditis elegans somatic tissues, but their function is required for normal adult life after UVC exposure

We performed experiments to characterize the inducibility of nucleotide excision repair (NER) in Caenorhabditis elegans, and to examine global gene expression in NER-deficient and -proficient strains as well as germline vs. somatic tissues, with and without genotoxic stress. We also carried out experiments to elucidate the importance of NER in the adult life of C. elegans under genotoxin-stressed and control conditions. Adult lifespan was not detectably different between wild-type and NER-deficient xpa- 1 nematodes under control conditions. However, exposure to 6 J/m 2/day of ultraviolet C radiation (UVC) decreased lifespan in xpa- 1 nematodes more than a dose of 100 J/m 2/day in wild-type. Similar differential sensitivities were observed for adult size and feeding. Remarkably, global gene expression was nearly identical in young adult wild-type and xpa- 1 nematodes, both in control conditions and 3 h after exposure to 50 J/m 2 UVC. Neither NER genes nor repair activity were detectably inducible in young adults that lacked germ cells and developing embryos ( glp- 1 strain). However, expression levels of dozens of NER and other DNA damage response genes were much (5–30-fold) lower in adults lacking germ cells and developing embryos, suggesting that somatic and post-mitotic cells have a much lower DNA repair ability. Finally, we describe a refinement of our DNA damage assay that allows damage measurement in single nematodes.

Evaluating high‐throughput sequencing as a method for metagenomic analysis of nematode diversity

Nematodes play an important role in ecosystem processes, yet the relevance of nematode species diversity to ecology is unknown. Because nematode identification of all individuals at the species level using standard techniques is difficult and time-consuming, nematode communities are not resolved down to the species level, leaving ecological analysis ambiguous. We assessed the suitability of massively parallel sequencing for analysis of nematode diversity from metagenomic samples. We set up four artificial metagenomic samples involving 41 diverse reference nematodes in known abundances. Two samples came from pooling polymerase chain reaction products amplified from single nematode species. Two additional metagenomic samples consisted of amplified products of DNA extracted from pooled nematode species. Amplified products involved two rapidly evolving ~400-bp sections coding for the small and large subunit of rRNA. The total number of reads ranged from 4159 to 14771 per metagenomic sample. Of these, 82% were > 199 bp in length. Among the reads > 199 bp, 86% matched the referenced species with less than three nucleotide differences from a reference sequence. Although neither rDNA section recovered all nematode species, the use of both loci improved the detection level of nematode species from 90 to 97%. Overall, results support the suitability of massively parallel sequencing for identification of nematodes. In contrast, the frequency of reads representing individual species did not correlate with the number of individuals in the metagenomic samples, suggesting that further methodological work is necessary before it will be justified for inferring the relative abundances of species within a nematode community.

A novel species-specific satellite DNA family in the invasive root-knot nematode Meloidogyne mayaguensis and its potential use for diagnostics

The root-knot nematode (RKN) Meloidogyne mayaguensis is considered as one of the most damaging RKN species because of its extremely wide host range. Recent surveys have shown the rapid spread of this parasite in agro-ecosytems, often making crop cultivation not viable in the heavily infested areas. Here, we report the identification, molecular cloning, genomic organisation and sequence analysis of a new satellite DNA (satDNA) family from M. mayaguensis (named pMmPet). It is comprised of two groups of A+T rich, tandemly repeated units of 174 and 180 bp, respectively. Using these sequences as targets, hybridisation and PCR experiments performed on a wide collection of 44 populations belonging to 15 RKN species showed that the pMmPet family could only be detected in the 16 M. mayaguensis populations tested. In addition, because of their repetitive nature, positive detection of pMmPet sequences was achieved in single individual nematodes. Therefore, the repeated sequence described here possesses features that make it an excellent candidate for use as a specific and extremely sensitive tool for the accurate detection and identification of this invasive pest on a routine basis. Clearly, monitoring the occurrence and spread of M. mayaguensis at the domestic and international levels are needed to avoid wholesale loss of agricultural resources in the infested regions.

Small Subunit rDNA-Based Phylogeny of the Tylenchida Sheds Light on Relationships Among Some High-Impact Plant-Parasitic Nematodes and the Evolution of Plant Feeding

Cyst (Heteroderidae), root knot (Meloidogyne spp.), and lesion (Pratylenchus spp.) nematodes all belong to a single nematode order, Tylenchida. However, the relationships between and within these economically highly relevant groups, and their relatedness to other parasitic Tylenchida is unclear. We constructed a phylogeny of 116 Tylenchida taxa based on full length small subunit ribosomal DNA (small subunit [SSU] rDNA) sequences. Ancestral state reconstruction points at a gradual development of simple to more complex forms of plant parasitism. Good resolution was observed in distal clades that include cyst, root knot, and lesion nematodes, and monophyly of most families was confirmed. Our data suggest that root knot nematodes have evolved from an ancestral member of the genus Pratylenchus, but it remains unclear which species is closest to this branching point. Contrary to the notoriously polyphagous distal representatives, basal members of the genus Meloidogyne (and probably, their common ancestor) have narrow host ranges. Our analysis also shows that mitotic parthenogeny has arisen at least two times independently among root knot nematodes. In many cases resolution till species was observed, suggesting that SSU rDNA sequences have a potential for DNA barcode-based species identification with, due to the overall conserved nature of this gene, limited intra-species variation.

Interactions among bacterial-feeding nematode species at different levels of food availability

Accurate prediction of the biodiversity–ecosystem functioning relationship requires adequate understanding of the interactions among species in a community. Effects of species diversity on ecosystem functioning are usually considered more pronounced with increasing functional dissimilarity, although species within functional groups may also perform non-identical functions and interact with each other. Here we present results of a laboratory experimental study aimed at elucidating whether interspecific interactions among species within a single nematode trophic group, bacterivores, (1) affect population development and community structure, and (2) depend on food availability. We studied the population growth of Rhabditis (Pellioditis) marina, a rhabditid nematode known to favour very high food densities when in monoculture, and of Diplolaimelloides meyli and D. oschei, congeneric Monhysteridae known to perform better in monocultures at intermediate food availability. Both Diplolaimelloides species showed significantly different patterns of food-density dependence in combination culture compared to monoculture. At very high food availability, the rhabditid nematode facilitated growth of both monhysterid species, probably as a result of down-regulation of bacterial density. At the lowest food availabilities, the presence of even low numbers of monhysterid nematodes lead to exclusion of the rhabditid, which at such low food availability has a very inefficient food uptake. At intermediate food availabilities, abundances of both Diplolaimelloides species were strongly depressed in the combination culture, as a result of food depletion by the rhabditid, indirect inhibitory interactions between the two congeneric species, or both. The complexity of the species interactions render predictions on the outcome and functional consequences of changes in within-trophic-group diversity highly problematic.

Molecular biological characterization of bursaphelenchus xylophilus and bursaphelenchus mucronatus in Korea

Pine wood nematode (PWN), Bursaphelenchus xylophilus, is a causal organism to induce pine wilt disease (PWD) in many varieties of pine trees. PWD was first introduced to Korea in 1988 but, the damage has been dramatically increased since 2000. Recently PWD is newly reported in Korean pine tree (Pinus koraien‐sis) and is considered one of the most important forest diseases in Korea. Fifteen isolates of B. xylophilus, 2 isolates of B. mucronatus, and 6 unidentified Bursaphelenchus spp. were collected from different geographical locations and hosts in Korea. All the isolates were cultured in fungal medium and nematodes were harvested for further experiment. First, all the isolates were characterized by both ITS and D2D3 rDNA sequence analysis. Template DNA was prepared by DNA extraction from single female nematode. ITS and D2D3 region were amplified by PCR and followed by cloning and sequence. As a result, all the sequences of ITS and D2D3 from B. xyophilus isolates were identical and there is no intraspecific variation. However, 2 genotypes of B. mucronatus were found, which one from P. thunbergii was East Asian type and the other one from P. koraiensis was European type. ITS‐RFLP phenotype was also proposed to discriminate different species and genotypes and 5 enzymes, Hinf I, Alu I, Msp I, Hae III, and Rsa I. were selectively treated.

Age- and sex-based variation in helminth infection of helmeted guineafowl (Numida meleagris) with comments on Swainson's spurfowl (Pternistis swainsonii) and Orange River francolin (Scleroptila levaillantoides)

Gastrointestinal tracts from 48 helmeted guineafowl (Numida meleagris), five Swainson's spurfowl (Pternistis swainsonii) and a single Orange River francolin (Scleroptila levaillantoides) were examined for helminth parasites. Twelve species of helminths were found in helmeted guineafowl, comprising six nematodes, five cestodes and a single acanthocephalan. Six species of nematodes were recovered from Swainson's spurfowl and a single nematode was recovered from the Orange River francolin. First-year guineafowl had more than twice the intensity of infection than did adult guineafowl, particularly regarding the acanthocephalan Mediorhynchus gallinarum, the caecal nematodes Subulura dentigera and S. suctoria, and the cestodes Octopetalum numida, Hymenolepis cantaniana and Numidella numida. Female guineafowl had significantly higher intensities of infection than males, especially concerning M. gallinarum, S. dentigera and N. numida and the nematode Gongylonema congolense. The recovery of the cestode Retinometra sp. from helmeted guineafowl constitutes a new host-parasite record.

Nematode resistance in bananas: screening results on some wild and cultivated accessions of Musa spp.

Bananas cultivated for export all belong to Cavendish cultivars and are all recognized as very susceptible to nematodes, particularly to the burrowing nematode Radopholus similis and the lesion nematode Pratylenchus coffeae. Even if there have been many changes in the management of banana nematodes in large commercial banana plantations, chemical control still remains most often the last resort method to manage the nematodes, although the number of registered products is definitely declining. Therefore, nematode control though genetic improvement is gaining new interest worldwide. In this study, 55 banana accessions mostly diploids from the Musa acuminata genome group (AA) but including some triploid accessions (AAA), some diploids of the Musa balbisiana genome group (BB) and some interspecific hybrids (AAB, AB) were evaluated for resistance to four nematode species R. similis, P. coffeae, Meloidogyne incognita and M. arenaria. These experiments were conducted in a growth chamber under controlled conditions. All banana accessions were susceptible to nematode species, although many different levels of susceptibility were detected. This study confirmed the good resistance status to R. similis of some cultivars from the Pisang jari buaya and Pisang batuau subgroups and the partial resistance of 17 diploid accessions significantly different from the susceptible reference cv. Grande Naine. This study also showed that 12 diploid accessions exhibited a partial resistance to P. coffeae, including some usual or potential genitors belonging to the wild diploids subspecies burmannica (cvs. Long Tavoy 1 and 2) and burmannicoides (cv. Calcutta 4). No source of resistance to Meloidogyne spp. was found. These screening results, combining for the first time four nematode species, are discussed within the scope of banana breeding in order to produce parental diploid lines with single or combined nematode resistances and further develop triploids that can substitute existing susceptible commercial cultivars.

First Report of the European Type of Bursaphelenchus mucronatus on Korean Pine (Pinus koraiensis) in Korea.

More than 70 species of Bursaphelenchus have been reported and they are morphologically very similar. The pine wood nematode (Bursaphelenchus xylophilus) is a causal agent of pine wilt and accurate identification is essential for diagnosis of the disease. However, many other saprophytic nematodes are found in dead trees and some of them have high morphological similarity to B. xylophilus. B. mucronatus is commonly found in dead pine trees and is distinguished from B. xylophilus only by the presence of a distinct mucro in the female tail (3). However, natural populations of B. xylophilus show variation in tail morphology and some of them have a small lump on the end of the tail that looks like a short mucro, which could lead to misidentification. B. mucronatus has been reported to have two genotypes known as the East Asian type and the European type (2). The European type has a more rounded tail with a mucro, which is much more similar to B. xylophilus than the East Asian type. Molecular identification by internal transcribed spacer restriction fragment length polymorphism (ITS-RFLP) can distinguish these two genotypes clearly by using five different restriction enzymes (2). In Korea, we collected wood samples from dead Pinus koraiensis located at Pocheon, Gyeonggi Province in April, 2007 and nematodes were extracted by a modified Baermann funnel method. After 24 h, nematodes were collected and morphology was observed under an inverted light microscope (Leica DE/DMI 3000B, Wetzlar, Germany). Morphology was characterized by a typical Aphelenchoid-type esophagus, head constriction, female vulva flap, post uterine sac, female tail with mucro, and males with arched-shaped spicules. The tail was rounded with a long mucro >4 μm. For molecular diagnosis, DNA was extracted from single individual nematodes by using a DNeasy Kit (Qiagen, Valencia, CA) and the ITS 1 and 2 and 5.8S regions in rDNA were amplified by PCR (US/PTC-0220; Bio-Rad, Hercules, CA). ITS-RFLP patterns were analyzed and nucleotide sequences were compared with sequences of B. mucronatus already reported in GenBank (Accession Nos. AM179514, BMU93554, and DQ841162). The ITS-RFLP pattern of individuals matched the European type of B. mucronatus and was differentiated from the East Asian type by RsaI and HaeIII digestion (2). The ITS DNA sequence of nematodes from Korean pines was >98% identical to B. mucronatus in GenBank. The European type of B. mucronatus was consistently isolated from dead trees, but the pathogenicity of the European type of B. mucronatus on Korean pine is not yet clear. To our knowledge, this is the first report of the European type of B. mucronatus species on P. koraiensis in Korea, but it is already distributed in certain locations of Japan (4), China, and Europe (1).