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PubMed2002

In vivo rearing of Thripinema nicklewoodi (Tylenchida: Allantonematidae) and prospects as a biological control agent of Frankliniella occidentalis (Thysanoptera: Thripidae).

Methods are described for the in vivo production of the nematode Thripinema nicklewoodi (Siddiqi), an obligate parasite and potential biological control agent of western flower thrips Frankliniella occidentalis (Pergande). Nematode infection is not lethal but causes sterilization of adult female hosts. Both fertilization and horizontal transmission of T. nicklewoodi is achieved in 1.5-ml microcentrifuge tubes (infection arenas), in the presence of 100% humidity, a temporary food source and preferably a damp substrate. Following exposure to infection arenas, F. occidentalis are reared on excised bean leaves Phaseolus vulgaris (L.) in polypropylene containers for 2 wk at 25 degrees C to allow the reproduction and development of a single generation of nematodes within infected hosts's abdominal cavity. To identify infected hosts after this incubation period, thrips are isolated in microcentrifuge tubes and monitored for free-living nematodes being released along with frass. Infected thrips are reintroduced back into infection arenas to inoculate further thrips to maintain the culture. We documented the output of the rearing procedure using a standard method and following simple manipulation of several individual parameters of the infection technique. The standard method was the most efficient, and resulted in an increased (output/input) ratio of infected thrips of approximately 2; i.e., the number of infected thrips approximately doubles each generation. Monitoring infected thrips revealed that nematodes were first released between 12-14 d postinfection and for an average of 7.9 d at 25 degrees C; highlighting the potential to reuse infective thrips between infection arenas. The possibility of using T. nicklewoodi as an inoculative agent against F. occidentalis infesting floricultural crops is discussed.

Animals↗
PubMedDate not supplied

[Paraiotonchium osiris (Iontonchiinae : Tylenchida), a new species of nematode of the zoophilic fly, Musca osiris Wd].

The description and figures are given to the nematode Paraiotonchium osiris sp. n. parasitic in the body cavity of Musca osiris and in the genital organs of the host females from Turkmenia. Two morphologically different generations of nematodes, gamagenetic and parthenogenetic ones, develop in the body cavity of the insects. Juvenile females of the gamagenetic generation: n=11; L=474.6 to 587.6; a=15.02 to 22.1; c=5.23 to 6.97; V=(71.5 to 77.7); St=13.0 to 16.1. Mature parasitic females of the gamagenetic generation: n=14; L=1028.3 to 2695.1; a=8.79 to 18.04; c=8.51 to 15.9; V=(76.2 to 84.6); St=21.0 to 27.0. Parasitic females of the parthenogenetic generation: n=7; L=813.6 to 1412.5; a=8.24 to 13.15; c=9.94 to 17.92; V=(88.2 to 91.9); St=14.0 to 16.5. Males: n=30; L=469.2 to 803.8; a=17.0 to 29.12; c=4.5 to 6.99; St=7.5 to 14.0; Sp (d)=18.4 to 23.0; Sp (pr)=34.5 to 41.4; T=(62.41 to 83.57). The new species differs from two other members of the genus Paraiotonchium in the structure of the spicules (a longer distal portion) and a larger bursa in males. A key to the species of the genus Paraiotonchium is given.

Animals↗
PubMedDate not supplied

[2 new species of nematodes of the family Dolichodoridae (Nematoda: Tylenchida) from the soil around cotton roots].

The description and figures of two new species of nematodes of the genus Tylenchorhynchus Cobb, 1913 are given. T. variannus sp. n. is characterized by an asymmetrical position and variation of the width of cuticular rings in the trophic, genital and caudal parts of the body. It differs from T. irregularis Wu, 1969 in the shape of the stylet and tail and in the number and width of the tail rings. T. chirchikensis sp. n. differs from allied species by the protrusion of the cuticle into the body around the vulva, length of the ovary, structure of the head capsule, stylet and tail and by the ratio between the tail length and body width of the anus.

Animals↗
PubMed2006

Characterization of a new beta-1,4-endoglucanase gene from the root-knot nematode Meloidogyne incognita and evolutionary scheme for phytonematode family 5 glycosyl hydrolases.

Cellulases from plant parasitic nematodes are encoded by multiple gene families and are thought to originate from horizontal gene transfer. Unraveling the evolution of these genes in the phylum will help understanding the evolution of plant parasitism in nematodes. Here we describe a new gene, named MI-eng-2, that encodes a family 5 glycosyl hydrolase (GHF5) with a predicted signal peptide and devoid of linker domain and cellulose-binding domain. The beta-1,4-endoglucanase activity of the protein MI-ENG-2 was confirmed in vitro and the transcription of the gene was localized in the secretory oesophageal glands of infective juveniles, suggesting that MI-ENG-2 is involved in plant cell wall degradation during parasitism. Phylogenetic and exon/intron structure analyses of beta-1,4-endoglucanase genes in the order Tylenchida strengthen the hypothesis that nematode GHF5 genes result from horizontal gene transfer of a bacterial gene with a cellulose-binding domain. GHF5 gene families in Tylenchida result from gene duplications associated with occasional loss of the cellulose-binding domain and the linker domain during their evolution.

Amino Acid Sequence↗
PubMed2002

Description and identification of four species of plant parasitic nematodes associated with grassland, fruit trees and maize in Romania.

Three species of plant parasitic nematodes present in two romanian soil samples were described and identified in the present study. The species belong to order tylenchida and to taxonomical families Tylenchidae (Basiria aberrans) and Belonolaimidae (Tylenchorhynchus georgiensis and Merlinius brevidens). The identification of the present specimens was based on the classical taxonomy, following morphological and morphometrical characters in the species specific identification keys.

Animals↗
PubMed2006

Application of the secondary structure model of rRNA for phylogeny: D2-D3 expansion segments of the LSU gene of plant-parasitic nematodes from the family Hoplolaimidae Filipjev, 1934.

Knowledge of rRNA structure is increasingly important to assist phylogenetic analysis through reconstructing optimal alignment, utilizing molecule features as an additional source of data and refining appropriate models of evolution of the molecule. We describe a procedure of optimization for alignment and a new coding method for nucleotide sequence data using secondary structure models of the D2 and D3 expansion fragments of the LSU-rRNA gene reconstructed for fifteen nematode species of the agriculturally important and diverse family Hoplolaimidae, order Tylenchida. Using secondary structure information we converted the original sequence data into twenty-eight symbol codes and submitted the transformed data to maximum parsimony analysis. We also applied the original sequence data set for Bayesian inference. This used the doublet model with sixteen states of nucleotide doublets for the stem region and the standard model of DNA substitution with four nucleotide states for loops and bulges. By this approach, we demonstrate that using structural information for phylogenetic analyses led to trees with lower resolved relationships between clades and likely eliminated some artefactual support for misinterpreted relationships, such as paraphyly of Helicotylenchus or Rotylenchus. This study as well as future phylogenetic analyses is herein supported by the development of an on-line database, NEMrRNA, for rRNA molecules in a structural format for nematodes. We also have developed a new computer program, RNAstat, for calculation of nucleotide statistics designed and proposed for phylogenetic studies.

Animals↗
PubMed2003

Associations between mycophagous Drosophila and their Howardula nematode parasites: a worldwide phylogenetic shuffle.

Little is known about what determines patterns of host association of horizontally transmitted parasites over evolutionary timescales. We examine the evolution of associations between mushroom-feeding Drosophila flies (Diptera: Drosophilidae), particularly in the quinaria and testacea species groups, and their horizontally transmitted Howardula nematode parasites (Tylenchida: Allantonematidae). Howardula species were identified by molecular characterization of nematodes collected from wild-caught flies. In addition, DNA sequence data is used to infer the phylogenetic relationships of both host Drosophila (mtDNA: COI, II, III) and their Howardula parasites (rDNA: 18S, ITS1; mtDNA: COI). Host and parasite phylogenies are not congruent, with patterns of host association resulting from frequent and sometimes rapid host colonizations. Drosophila-parasitic Howardula are not monophyletic, and host switches have occurred between Drosophila and distantly related mycophagous sphaerocerid flies. There is evidence for some phylogenetic association between parasites and hosts, with some nematode clades associated with certain host lineages. Overall, these host associations are highly dynamic, and appear to be driven by a combination of repeated opportunities for host colonization due to shared breeding sites and large potential host ranges of the nematodes.

Animals↗
PubMed2003

Analysis and functional classification of transcripts from the nematode Meloidogyne incognita.

BACKGROUND: Plant parasitic nematodes are major pathogens of most crops. Molecular characterization of these species as well as the development of new techniques for control can benefit from genomic approaches. As an entrée to characterizing plant parasitic nematode genomes, we analyzed 5,700 expressed sequence tags (ESTs) from second-stage larvae (L2) of the root-knot nematode Meloidogyne incognita. RESULTS: From these, 1,625 EST clusters were formed and classified by function using the Gene Ontology (GO) hierarchy and the Kyoto KEGG database. L2 larvae, which represent the infective stage of the life cycle before plant invasion, express a diverse array of ligand-binding proteins and abundant cytoskeletal proteins. L2 are structurally similar to Caenorhabditis elegans dauer larva and the presence of transcripts encoding glyoxylate pathway enzymes in the M. incognita clusters suggests that root-knot nematode larvae metabolize lipid stores while in search of a host. Homology to other species was observed in 79% of translated cluster sequences, with the C. elegans genome providing more information than any other source. In addition to identifying putative nematode-specific and Tylenchida-specific genes, sequencing revealed previously uncharacterized horizontal gene transfer candidates in Meloidogyne with high identity to rhizobacterial genes including homologs of nodL acetyltransferase and novel cellulases. CONCLUSIONS: With sequencing from plant parasitic nematodes accelerating, the approaches to transcript characterization described here can be applied to more extensive datasets and also provide a foundation for more complex genome analyses.

Animals↗
PubMed2006

Three-dimensional reconstruction of the nose epidermal cells in the microbial feeding nematode, Acrobeles complexus (Nematoda: Rhabditida).

The epidermis of the anterior end (nose) plays an important role in the evolution, development, and functional feeding morphology in nematodes, but information on this complex organ system is limited. Here, we produce a 3D model of 13 of the cells making up this organ system reconstructed from serial transmission electron micrographs of the microbial feeding nematode, Acrobeles complexus. Nose epidermal cells were found to be broadly similar to those of the distantly related model organism Caenorhabditis elegans in the number and arrangement of nuclei in these largely syncytial cells; this similarity demonstrates striking evolutionary conservation that allows for robust statements of homology between the taxa. Examining details of cell shape, however, revealed surprisingly complex subcellular specialization, which differed markedly from C. elegans in the number and arrangement of cell processes. Anterior toroid processes of the anterior arcade, posterior arcade, and HypB syncytia form a nested complex at the base of the labial probolae. Anterior toroid processes of HypC and the inner labial socket cells are associated with the base of the cephalic probolae and radial ridge processes. Extracellular filaments (tendon organs) and radiating cytoskeletal filaments of the posterior arcade syncytium form a connection between the body wall muscle cells and the pharynx. An epidermal cell with no known homolog in other nematodes is identified. Findings provide a basis to propose hypotheses related to the development and evolutionary origin of specialized feeding appendages (probolae) in the Cephalobinae (including Acrobeles), and hypotheses of homology are revised for epidermal cells in the nose of the closely related and primarily plant parasitic group, Tylenchida.

Anatomy, Comparative↗
PubMed1997

Phylogenetic analysis of nematodes of the genus Pratylenchus using nuclear 26S rDNA.

We used nucleotide sequences of the large subunit ribosomal genes (26S rDNA) to examine evolutionary relationships among species of the genus Pratylenchus (Order: Tylenchida, Family: Pratylenchidae), commonly known as root-lesion nematodes. Ten species of Pratylenchus were studied including, P. penetrans, P. crenatus, P. minyus, P. vulnus, P. thornei, P. musicola, P. coffeae, P. hexincisus, P. scribneri, and P. brachyurus. The species Hirschmanniella belli, Meloidogyne javanica, Heterorhabditis bacteriophora, Nacobbus aberrans, Radopholus similis, and Xiphinema index were used as outgroups. Based on parsimony analyses of approximately 307 aligned nucleotides of the D3 expansion region of the 26S rDNA, it is clear that species of Pratylenchus are a paraphyletic assemblage. The outgroup taxon H. belli shares a common ancestor with the clade that includes P. vulnus and P. crenatus while N. aberrans and R. similis share a common ancestor with 5 other species included in this study.

Animals↗
PubMed1998

Buccal capsule development as a consideration for phylogenetic analysis of Rhabditida (Nemata).

Bacterial feeding nematodes in the order Rhabditida including Zeldia punctata (Cephalobidae) and Caenorhabditis elegans (Rhabditidae) differ profoundly in the buccal capsule parts and associated cells. We carried out a range of tests to determine which buccal capsule parts and cells are evolutionarily homologous between the representative species of the two families. Tests included reconstruction of the buccal capsule and procorpus with transmission electron microscopy (TEM), nuclei position and morphology using 4, 6-diamidino-2-phenylindole (DAPI) staining, and cell lineage using four dimensional (4D) microscopy. The lining of the buccal capsule of Z. punctata and additional Cephalobidae includes four sets of muscular radial cells, ma, mb, mc and md, in contrast to C. elegans and additional Rhabditidae, which has two sets of epithelial cells (e1, e3) and two sets of muscle cells (m1, m2). Cell lineage of a nematode closely related to Z. punctata, Cephalobus cubaensis, supports the hypothesis that in cephalobids the e1 and e3 cells become hypodermal cells or are programmed to die. Our findings contradict all previous hypotheses of buccal capsule homology, and suggest instead that ma and mb in Z. punctata are homologous to m1 and m2 in C. elegans respectively. We also hypothesize that ma and mb could be homologous to primary and secondary sets of stylet-protractor muscle cells in the plant parasitic Tylenchida.

Animals↗
PubMed1991

Entomopathogens of phlebotomine sand flies: laboratory experiments and natural infections.

The susceptibility of different geographical strains of Phlebotomus papatasi to a cytoplasmic polyhedrosis virus (CPV) was determined experimentally by feeding polyhedra to larvae. Of the Indian P. papatasi, 15.6% became infected, whereas Egyptian P. papatasi were mostly refractory. Infection rates were not augmented in colony flies from the Jordan Valley, 23.8% of which were naturally infected with CPV. The infectivity of Serratia marcescens and Beauvaria bassiana to P. papatasi were determined experimentally. A suspension of B. bassiana spores or S. marcescens bacteria, ingested by P. papatasi in sucrose solution, did not significantly augment mortality rates or reduce the number of eggs oviposited. However, B. bassiana spores smeared on a filter paper constituting 1 or 5% of the surface area available to flies induced 100% mortality of P. papatasi on days 5 and 4, respectively. Mortality in Lutzomyia longipalpis reached 100% on day 4. There were markedly lower mortality rates in the control groups and more eggs were produced by these females (P. papatasi: control = 48.5; experimental = 0.9-1.6 eggs/female; L. longipalpis; control = 17.1; experimental = 0 eggs/female). From wild-caught Colombian Lutzomyia spp., a nonfluorescent pseudomonas, an Entomophthorales fungus, and a Trypanosomatid protozoon (probably Leptomonas) were isolated in culture media. Gregarines (Ascogregarina saraviae) and nematodes (Tylenchida and Spirurida) were also recorded. In laboratory-reared flies, an ectoparasitic fungus was associated with high mortality rates of first instar Lutzomyia spp. larvae. Opportunistic ectoparasitic aggregates of bacteria, yeast, and fungi on the tarsi of colonized L. longipalpis and P. papatasi hindered their mobility and were associated with reduced colony vigor. Aspergillus flavus, B. bassiana, and S. marcescens were isolated from laboratory-bred P. papatasi adults.

Animals↗
PubMed1998

A new AluI satellite DNA in the root-knot nematode Meloidogyne fallax: relationships with satellites from the sympatric species M. hapla and M. chitwoodi.

A highly abundant satellite DNA comprising 20% of the Meloidogyne fallax (Nematoda, Tylenchida) genome was cloned and sequenced. The satellite monomer is 173 bp long and has a high A + T content of 72.3%, with frequent runs of A's and T's. The sequence variability of the monomers is 2.7%, mainly due to random distribution of single-point mutations. A search for evidence of internal repeated subunits in the monomer sequence revealed a 6-bp motif (AAATTT) for which five degenerated repeats, differing by just a single base pair, could be identified. Pairwise comparison of the M. fallax satellite with those from the sympatric species Meloidogyne chitwoodi and Meloidogyne hapla revealed a high sequence similarity (68.39%) with one satellite DNA subfamily in M. chitwoodi, which indicated an unexpected close relationship between them. Given the high copy number and the extreme sequence homogeneity among monomeric units, it may be assumed that the satellite DNA of M. fallax could have evolved through some recent and extensive amplification burst in the nematode genome. In this case, its relatively short life would not yet have allowed the accumulation of random mutations in independent amplified repeats. Considering the morphological resemblance between the two species and their ability to produce interspecific fertile hybrids under controlled conditions, these results indicate that M. fallax may share a common ancestor with M. chitwoodi, from which it could have diverged recently. All these data suggest that M. fallax could be the result of a recent speciation process and show that Meloidogyne satellite DNAs may be of interest to resolve phylogenetic relationships among closely related species from this genus.

Animals↗