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Abstract

Entomopathogenic nematodes of the family Steinernematidae may significantly reduce insect populations. They inhabit most terrestrial habitats and their prevalence can be influenced by biotic factors. Some sawfly species, the geometrid and noctuid moth complexes, and bibionid and sciarid flies characteristically aggregate as diapausing or hibernating larvae in the soil. A survey for entomopathogenic nematodes from habitats characterized by these aggregations was performed in the Czech Republic by collecting soil samples and utilizing Galleria traps in the laboratory. Steinernematids were recovered from 61 of 87 (70.1%) sampled localities. Seven Steinernema species, S. kraussei, S. feltiae, S. affine, S. intermedium, S. bicornutum and two designated as species B and F were identified. Among these, S. kraussei was prevalent in sawfly localities (77.8%) while, in winter moth localities, S. feltiae (55.6%) dominated and S. kraussei (22.2%) and S. affine (25.9%) were common. Soil-dwelling insect aggregations seem to provide an opportunity for entomopathogenic nematode multiplication.Les nématodes entomopathogènes de la famille des Steinernematidae peuvent réduire significativement les populations d'insectes. Ils occupent la plupart des habitats terrestres et leur prévalence peut être influencée par des facteurs biotiques. Quelques espèces de tenthrèdes move, des Géométrides et des aleurodes Noctuides, de même que les mouches Sciarides et Bibionides forment des aggrégats caractéristiques lorsque leurs larves sont en diapause ou hivernent dans le sol. Une enquête sur ces nématodes entomopathogènes dans des habitats caractérisés par ces aggrégations d'insectes a été réalisée en République tchèque en collectant des échantillons de sol et en utilisant au laboratoire des pièges à Galleria. Des Steinernematides ont été trouvés dans 61 des 87 (70,1%) des localités échantillonnées. Cinq espèces connues de Steinernema (S. kraussei, S. feltiae, S. affine, S. intermedium, S. bicornutum) et deux espèces désignées comme espèces B et F ont été identifiées. S. kraussei était prévalent dans les localités à tenthrèdes (77,8%) tandis que S. feltiae dominait dans les localités à arpenteuse tardive (55,6%) ou S. kraussei (22,2%) et S. affine (25,9%) apparaissaient communs. Les aggrégats d'insectes terricoles semblent ainsi offrir une situation propice à la multiplication des nématodes entomopathogènes.

In: Nematology

Abstract

Steinernema silvaticum sp. n. is described from woodland soil near Berlin, Germany. The species is quite common in European woodlands, being found in forest soil all over Germany, in Belgium, the Czech Republic, The Netherlands, Sweden and the UK. It was previously reported as Steinernema sp. 'B' in Germany and the Czech Republic, and as Steinernema sp. 'B3' in UK, Belgian and Dutch surveys. Third-stage infective juveniles are mainly characterised by a straight body of medium length (means = 700–900 μm), lateral fields with eight equal ridges (with appearance of nine parallel, equally spaced lines under light microscope), rather broad, flatly rounded and continuous cephalic region, excretory pore at level of mid-pharynx and average hyaline tail portion constituting ca half total tail length; males with mucronate tail, yellowish spicules of ca 50 μm length and wide manubria; females with short conoid tail with pointed non-mucronate tip. According to the ITS rDNA sequences, S. silvaticum sp. n. belongs to the 'feltiae-kraussei-oregonense' group of Steinernema species, although it is closest to S. kraussei. The new species shows a high level of nucleotide differences in ITS rDNA sequences from other steinernematid species and can be easily distinguished from S. kraussei, S. feltiae, S. oregonense, S. weiseri and S. jollieti by morphological characters of the infective juveniles and males.

In: Nematology

A new nematode species belonging to the family Alloionematidae was originally isolated by Dr Marie Anne Félix on 16 December 2007 from a rotting coconut at the boat boarding point in Estuary island resort, Poovar, Kerala, India. Both morphologically and molecularly, the new isolate resembles Neoalloionema tricaudatum but, unlike N. tricaudatum this species has no phasmidial ‘horns’ in the juvenile stage, even though prominent structures in the mid-tail of dauer juveniles were observed. Females are characterised by a body length of 947 (869-1030) μm, vulva in the mid-body region, long, and tapering tail with a minute post-anal swelling. Males are 678 (606-757) μm long with a long tapering tail that is very thick at base. They are further characterised by seven pairs of genital papillae and a single genital papilla. Dauer juveniles are only 391 (364-434) μm long, thin and almost straight when heat-killed. Large, prominent phasmids are located laterally at the mid-tail region and lateral fields consisting of a single ridge are present. Several morphological and molecular differences encouraged us to describe the nematode as N. indicum n. sp. The ecology of the newly described species is unknown, but it is probably a saprophytic bacteriophagous nematode preferring rotting organic material.

In: Nematology

A new nematode species belonging to the family Rhabditidae, genus Phasmarhabditis, was isolated in the city of Bari (strain BAR) and near the village Gravina (strain GRA) in Apulia, Italy, and is described herein as Phasmarhabditis apuliae n. sp. The original hosts were Milax sowerbyi and M. gagates. Females are 2623 (2262-2848) μm long with a long tapering tail. Prominent papilla-like phasmids are present. Males are 2096 (1898-2363) μm long. They have a peloderan bursa with nine pairs of rays arranged as 1 + 1 + 1 + 2 + 1 + 3. Each ray bears a single papilla. A non-paired papilla is located near the ventral appendage anterior to the cloacal aperture. Prominent papilla-like phasmids are situated close to the tail tip. Dauer juveniles have lateral fields formed from two prominent wide ridges and have three incisures. Phasmarhabditis apuliae n. sp. seems to be a facultative mollusc-parasitic nematode that is capable, in a similar manner to P. hermaphrodita, of long-term survival in the saprophytic phase on decaying organic matter. Ecology, morphology and phylogenetic relationships of Phasmarhabditis nematodes are discussed.

In: Nematology

Abstract

Morphometrics of four Canadian, three US and two European isolates representing distinct geographic populations of Steinernema kraussei (Steiner, 1923) were compared and analysed by multivariate analysis. A total of 540 individuals (270 males and 270 third-stage infective juveniles) representing the nine populations was measured. Fourteen morphometric variables were selected and subjected to principal component and canonical analyses. Results from both analyses indicate that there are morphological differences among the studied isolates, and that these differences are congruent with their geographic origin. The European isolates were shown to be distinctly different from the North American isolates. Within the North American isolates, the western isolates were distinguished from the eastern one (Parishville). No significant differences were observed between the two European isolates studied. Ont été comparées et étudiées par analyse multivariable les caractéristiques morphométriques de quatre isolats canadiens, trois isolats américains et deux isolats européens représentant des populations géographiques distinctes de Steinernema kraussei. Un total de 540 individus (270 mâles et 270 juvéniles infestants de troisième stade) représentant les neuf populations a été mesuré. Quatorze variables morphométriques ont été sélectionnées et soumises à des analyses en composantes principales et canonique. Les résultats des deux analyses montrent qu’il existe des différences morphologiques entre les isolats étudiés et que ces différences sont congruentes avec leur origine géographique. Les isolats européens sont apparus comme étant nettement différents des isolats nordaméricains. Dans le groupe des isolats nord-américains, les isolats de l’ouest ont été différenciés de celui de l’est (Parishville). Aucune différence significative n’a été observé entre les deux isolats européens étudiés.

In: Nematology

Alloionema appendiculatum is a common juvenile parasite of many terrestrial molluscs. Its third-stage juveniles (dauers) invade the foot muscle of snails and slugs and develop into fourth-stage juveniles, which then leave the host. Later they mature and reproduce in the soil. A population of A. appendiculatum was isolated from infected individuals of the invasive slug Arion vulgaris (= A. lusitanicus), collected in the city of České Budějovice, Czech Republic, and was designated as the AL strain. This nematode is also able to reproduce on pig kidney in laboratory culture. Our isolate was compared primarily with the description published by Mengert (1953) and in some aspects with the original description published by Schneider (1859). Insufficient morphology, morphometrics, phylogeny and an absence of pictorial material encouraged us to re-describe this frequent slug parasite and to add some new information on its life-cycle. The species is characterised by the absence, in adults, of ridges in the lateral fields. At this life stage the stoma is short, narrow and approximately twice as long as it is broad. Fourth-stage female juveniles produce a mucus-like substance from the phasmids. Males possess six pairs of papillae and a single inconspicuous papilla. The nematode has both parasitic and saprophytic life-cycles. Parasitic adults are bigger than the saprophytes and have a thick, digitate tail, whereas the smaller saprophytic generation has a filiform tail. The species is amphimictic, displaying a higher proportion of females, but males are frequent.

In: Nematology

Summary

The mucron in male steinernematid nematodes may be missing or present either in the first or second generation, or missing in both generations, with variable shape. However, for many species, the information on mucron morphology is incomplete and its taxonomic significance and distribution remain unclear. The present study assessed mucron morphology in males of 26 species using LM and SEM microscopy. For other species we summarised the published data. Furthermore, ancestral character state reconstruction analysis was performed to assess the distribution of mucron morphology within steinernematid phylogeny. In most species, papilla/spine-like or filamentous mucrons occur at least in the second generation. The species gathered in single phylogenetic groups have a similar mucron morphology. Generally, species with a prominent filamentous mucron belong to the ‘kraussei/feltiae’ and ‘carpocapsae’ groups, whereas mostly non-mucronated species occur in ‘glaseri’ and ‘riobrave’ groups. For future descriptions a precise mucron characterisation in both generations of the male is recommended.

In: Nematology

Phasmarhabditis bohemica n. sp. is described and illustrated from the body of Deroceras reticulatum from the village of Chelčice, the Czech Republic. Morphological and molecular data showed that the new isolate is close to other species of Phasmarhabditis, particularly P. californica and P. papillosa. Females are characterised by a body length of 2079 (1777-2222) μm and a long tapering tail with prominent papilliform phasmids located laterally in the mid-tail region. Males are 1683 (1515-1818) μm long. They have a peloderan bursa, with nine pairs of rays, 1/1/1/2/1/3, and a reflexed testis 495 (434-555) μm long. Dauer juveniles are thin, 553 (474-636) μm long, with prominent lateral fields consisting of two prominent ridges and three incisures. Small subunit (18S), ITS, and D2-D3 expansion segments of the large subunit of ribosomal DNA were used to analyse the phylogenetic relationships of sequenced species in Phasmarhabditis and other closely related species. Our preliminary observations suggest that the newly described species may be a facultative mollusc-parasitic nematode that is able to survive permanently in the saprobic phase on decaying organic matter. The ecology, morphology, and phylogenetic positions of P. bohemica n. sp. are discussed.

In: Nematology