Anhydrobiosis in Nematodes II: Carbohydrate and Lipid Analysis in Undesiccated and Desiccate Nematodes

Glycogen, trehalose, glucose, and total lipid contents of six nematode species were studied. Anhydrobiotic Anguina tritici and Ditylencbus dipsaci stored trehalose in preference to glycogen and only small amounts of glucose were detected. Glycogen content was also reduced in anhydrobiotic Aphelenchus avenae. Conversely, Panagrellus redivivus and Turbatrix aceti contained large amounts of glycogen, appreciable amounts of glucose, and minimal amounts of trehalose. Ditylenchus myceliophagous "curds" contained low amounts of glycogen and very little trehalose; total lipid was 60% of that in fresh samples. The lipid contents of fresh samples of P. redivivus, T. aceti, and A. avenae were high (23.1, 21.9, and 36.7% dry weight, respectively), but in anhydrobiotic A. avenae larvae the level was reduced by over 60%. In contrast, lipid levels remained high in anhydrobiotic A. tritici and D. dipsaci larvae (40.6 and 38.3%, respectively). Analysis of lipid composition in anhydrobiotic A. tritici and A. avenae did not indicate any specific metabolic adaptations to desiccation survival.     

Accumulation and metabolism of aldicarb by the free-living nematodes Aphelenchus avenae and Panagrellus redivivus

The accumulation and metabolism of aldicarb has been compared in two species of free-living soil nematodes, Aphelenchus avenae and Panagrellus redivivus, which differ considerably in their sensitivity to this and other pesticides. Similar levels of aldicarb were found to accumulate in the two species. The results showed that although the rate of uptake of aldicarb was greater in P. redivivus, so also was the rate of metabolism and elimination. Levels of toxic metabolites of aldicarb were two to three times higher in the more susceptible species A. avenae after 24 h incubation than in the less susceptible P. redivivus. The toxicological significance of these findings is discussed in relation to previous work with the organophosphorus pesticide phorate and its effects on the same two nematode species.     

Fluorescent and Ferritin Labelling of Cuticle Surface Carbohydrates of Caenorhabditis elegans and Panagrellus redivivus

Caenorhabditis elegans and Panagrellus redivivus were investigated for surface carbohydrates using fluorescent-labelled and ferritin-labelled lectins. Rhodamine-labelled Concanavalin A was specifically located in the cephalic region of both species. Rhodamine-labelled wheat germ agglutinin was located over the entire cuticle of P. redivivus but was absent on C. elegans. Rhodamine-labelled peanut agglutinin and Limax flavus agglutinin did not label nematodes of either species. Galactose and sialic acid were not detected on either species, whereas mannose-glucose residues were specifically localized in the head areas of both species. No detectable N-acetylglucosamine occurred on C. elegans, but it was evenly distributed over the cuticle surface of P. redivivus.     

Nematicidal metabolites from the fungusPleurotus ferulae Lenzi

Pleurotus ferulae Lenzi, a species of edible fungus, was found to have nematicidal activity in experiments searching for nematicidal fungi. Three nematicidal metabolities cheimonophyllon E (compound 1), 5α,8α-epidioxyergosta-6,22-dien-3β-ol (compound 2) and 5-hydroxymethyl-furancarbaldehyde (compound 3) were isolated based on bioassay-guided fractionation from the extracts of the fungusP. ferulae. Their structures were determined by spectroscopic data. All of them showed activities against nematodesBursaphelenchus xylophilus (Steiner et Buhrer) Nickle andPanagrellus redivivus (Linn.) Goodey. The median lethal concentrations (LC₅₀) of compounds 1, 2 and 3 at 72 h were 70.8, 174.6, and 54.7 mg L^?1 respectively againstB. xylophilus and were 125.6, 128.1, and 82.8 mg L^?1 respectively againstP. redivivus. The three compounds were obtained fromP. ferulae for the first time.     

Postembryonic nongonadal cell lineages of the nematode Panagrellus redivivus: Description and comparison with those of Caenorhabditis elegans

The postembryonic nongonadal cell lineages of the nematode Panagrellus redivivus are described and compared with those of Caenorhabditis elegans. The newly hatched larvae of P. redivivus females and males and C. elegans hermaphrodites and males are very similar. An almost identical set of blast cells divides postembryonically in P. redivivus and C. elegans to produce similar changes in the neuronal, muscular, hypodermal, and digestive systems. Most of these cell lineages are invariant; however, there is substantial variability in the number of cell divisions in the relatively extensive lineages of the lateral hypodermis of P. redivivus. Typically, in P. redivivus females, 55 blast cells generate 635 surviving progeny and 29 cell deaths; in P. redivivus males, 59 blast cells generate 758 surviving progeny and 35 cell deaths. The lineages generating the cells of the male tails of P. redivivus and C. elegans are almost identical; thus, the grossly different characteristics of these structures must reflect differences in the morphogenesis of cells equivalent in lineage history. Laser ablation experiments demonstrate that the gonad induces vulva development and that cell-cell interactions are important in specifying the fates of hypodermal precursor cells. The lateral hypodermal lineages provide striking examples of the apparent construction of complex lineages from modular sublineages; one simple pattern of cell divisions and cell fates occurs 70 times in the P. redivivus female. The differences in cell lineage between P. redivivus and C. elegans are relatively minor, and many appear to have involved two types of evolutionary change: the replacement of sublineages, and the modification of sublineages by the four classes of lineage transformations previously proposed based on a comparison of P. redivivus and C. elegans gonadal cell lineages (Sternberg and Horvitz, 1981). These types of differences suggest that the genetic programming of cell lineage includes instructions specifying where and when a particular sublineage is utilized, and other instructions specifying the nature of that sublineage.     

Coprinus comatus Damages Nematode Cuticles Mechanically with Spiny Balls and Produces Potent Toxins To Immobilize Nematodes

We reported recently a unique fungal structure, called the spiny ball, on the vegetative hyphae of Coprinus comatus (O. F. Müll.:Fr.) Pers. Although some observations regarding the role of this structure were presented, its function remained largely unknown. In this study, we showed that purified (isolated and washed) spiny balls could immobilize and kill the free-living nematode Panagrellus redivivus Goodey highly efficiently. Scanning electron microscopy studies illustrated that the spiny structure damaged the nematode cuticle, suggesting the presence of a mechanical force during the process of nematode immobilization. Severe injuries on nematode cuticles caused the leakage of inner materials of the nematodes. When these structures were ground in liquid nitrogen, their killing efficacy against nematodes was lost, indicating that the shape and the complete structure of the spiny balls are indispensable for their function. However, extraction with organic solvents never lowered their activity against P. redivivus, and the extracts showed no obvious effect on the nematode. We also investigated whether C. comatus was able to produce toxins which would aid in the immobilization of nematodes. In total, we identified seven toxins from C. comatus that showed activity to immobilize the nematodes P. redivivus and Meloidogyne incognita (Kofoid et White) Chitwood. The chemical structures of these toxins were identified with nuclear magnetic resonance, mass spectrometry, infrared, and UV spectrum analysis. Two compounds were found to be novel. The toxins found in C. comatus are O-containing heterocyclic compounds.     

Interactions between Heterodera avenae and Pratylenchus neglectus on Wheat

In a long-term field experiment, differential population densities of Heterodera avenae were produced by frequent cropping with resistant (cv. Panema) or susceptible (cv. Peniarth) oat. The two oat cultivars were equally good hosts of Pratylenchus neglectus in a glass house experiment with field soil. On wheat crops grown after oats in field experiments, P. neglectus population densities in roots were higher in plots where H. avenae had been controlled than in plots with moderate infestations (40 H. avenae eggs/g soil). The field observations indicated that the reduction in population densities of P. neglectus coincided with the development in roots of sedentary stages of the cyst nematode. Evidence for an indirect effect of H. avenae on P. neglectus was found in vitro in a split-root experiment. In the same field, grain yields of two wheat cultivars susceptible or resistant to H. avenae, but both susceptible to P. neglectus, was not reduced by P. neglectus. Alternation of H. avenae resistant and susceptible cultivars is a possible way of exploiting the inverse relationship between these nematodes, whilst controlling cyst nematode -populations in intensive cereal production systems.     

Partial characterisation of and the effect of insect growth hormones on the ribosomes and polyribosomes of the nematode, Panagrellus redivivus

An investigation of some of the properties of the ribosomes and polyribosomes of Panagrellus redivivus revealed that: the polyribosomal RNA was resolvable into eight species, four of which possessed typical S-values and M.W.s and closely resembled those of Aphelenchus avenae; the estimated S-value of the ribosomes was 92; the polyribosomes were mainly free and not membrane-bound: and, the polyribosomes showed a low level of activity in in vitro amino-acid incorporation. The polysomes (double-labelled or unlabelled) revealed no effect of synthetic juvenile hormone or ß-ecdysone (1 × 10^?5M) on their polyribosomal profile, at intervals up to and including 19 h of incubation.     

Nematicidal activity of <Emphasis Type="Italic">Paecilomyces</Emphasis> spp. and isolation of a novel active compound

Many species of Paecilomyces are entomogenous fungi and several are efficacious toward nematodes. To study the potential of Paecilomyces species in controlling nematodes, fungal extracts of 40 Paecilomyces spp. were evaluated for their nematicidal activity against Bursaphelenchus xylophilus and Panagrellus redivivus. The extracts of six Paecilomyces spp. exhibited the nematicidal activity against P. redivivus, and 11 species exhibited the nematicidal activity against B. xylophilus. The methanol extract of strain 1.01761 incubating on Czapek solid medium killed more than 95% P. redivivus in 24 h at 5 mg/ml, and the filtrate of strain 1.01788 cultured in Sabouraud’s broth medium resulted in 90% mortality of B. xylophilus in 24 h at 5 mg/ml. A novel nematicidal compound 4-(4′-carboxy-2′-ethyl-hydroxypentyl)-5,6-dihydro-6-methylcyclobuta[b]pyridine-3,6-dicarboxylic acid, was isolated from Paecilomyces sp. YMF1.01761. The LD₅₀ value of the compound within 24 h against P. redivivus was 50.86 mg/L, against Meloidogyne incognita was 47.1 mg/L, and against B. xylophilus was 167.7 mg/L.     

FMRFamide-like Immunoactivity in Heterodera glycines (Nemata: Tylenchida)

Material antigenically related to the neuromodulatory peptide FMRFamide was detected and examined in preparations of the soybean cyst nematode, Heterodera glycines, and in the free-living nematodes Caenorhabditis elegans and Panagrellus redivivus. FMRFamide-related peptides were quantified by an enzyme-linked immunosorbent assay. Specific activities were remarkably similar among all of the vermiform members of the three species. FMRFamide-related peptide immunoactivity was present in both sexes and all stages of H. glycines examined. The highest specific activity was present in second-stage juveniles and in males, and the lowest in white and yellow females. Total FMRFamide-related peptide level per individual was highest in brown females, with 90% of the activity associated with the eggs. Peptide levels in these eggs and in second-stage juveniles were comparable and increased in adults, especially in females. Chromatographic analysis of FMRFamide-related peptide preparations from H. glycines juveniles, C. elegans, and P. redivivus revealed distinct qualitative differences between the infective plant parasite and the free-living nematodes.     

Regulation of nematode behavior by physical means

Application of microwave radiation, laser microbeam irradiation, and short pulses of electric current stimulates changes in normal swimming behavior of the free-living nematode Panagrellus silusiae. The altered behavior, termed activated behavior, involves increased movement of the ends of the nematode, rapid changes in orientation, and an increase in the proportion of the swimming time that the nematode is curved such that the ends are pointing in the same direction. Laser microbeam studies indicate that the receptor for mating attraction is situated on the spicule. Panagrellvs silusiae shows mating attraction with two strains of P. redivivus, but the P. redivivus strains only attract P. silusiae or the other P. redivivus strain. Experiments with pulses of electric current indicate that the nematodes can be conditioned and that this conditioning requires RNA and protein synthesis.     

Interaction of nematodes with nematophagus fungi: induction of trap formation, attraction and detection of attractants

Induction of trap formation in Arthrobotrys oligospora, A. conoides and Monacrosporium cystosporum was studied during a 24 h period in the presence of the free-living nematodes Panagrellus redivivus on various nutrient media. A definite pattern of trap formation was observed in these fungi. Low nutrient mineral salt medium had the most pronounced effect on trap formation. Attraction and repulsion of P. redivivus towards these three nematophagous and three non-nematophagous fungi was studied. The nematodes were attracted towards three nematophagous and one non-nematophagous fungi, the other two repelled them. Attractants of the nematophagous fungi were determined by thin-layer chromatography. In the case of A. oligospora and M. cystosporum, four spots were traced, whereas in A. conoides, five spots were detected.     

Taxonomic Notes on Four Species of Panagrellus Thorne (Nematoda: Cephalobidae)

Four populations of Panagrellus redivivus (Linnaeus, 1767) Goodey, 1945, and syntypes of P. dubius Sanwal, 1960, P. redivivoides (Goodey, 1943) Goodey, 1945, P. pycnus Thorne, 1938, P. zymosiphilus (Brunold, 1950) Brunold, 1954, and P. leucocephalus Steiner, 1936 were examined. Additional information on the morphology of spicules and stoma is presented. P. zymosiphilus is synonymized with P. redivivoides and Rühm''s synonymization of P. silusiae and P. leucocephalus with P. redivivus is supported. Lectolypes for P. pycnus and P. redivivoides are designated.     

Precision and accuracy of radioimmunoassay in the analysis of endogenous 3-indoleacetic acid from needles of scots pine

The precision and accuracy of a radioimmunoassay (RIA) for 3-indoleacetic acid (IAA) were assessed when applied to the analysis of extracts from Pinus sylvestris seedlings. It was found that extracts contained contaminants that adversely affected both the precision and accuracy of quantitative estimates of IAA. When samples were subjected to purification procedures prior to RIA, accurate and more precise estimates were obtained. Parallel analysis with high performance liquid chromatography using a fluorescence detector (HPLC-FL) indicated that HPLC-FL provided accurate estimates of the IAA content of Pinus extracts at the same stage of purification as RIA. The precision of HPLC-FL estimates was similar to that obtained with RIA.     

Acanthocytes of Stropharia rugosoannulata Function as a Nematode-Attacking Device

Efficient killing of nematodes by Stropharia rugosoannulata Farlow ex Murrill cultures was observed. This fungus showed the ability to immobilize the free-living nematode Panagrellus redivivus Goodey within minutes and to immobilize the pine wilt nematode Bursaphelenchus xylophilus (Steiner & Buhrer) Nickle within hours on agar plates. Moreover, P. redivivus worms were completely degraded by the fungus within 24 to 48 h. The cultures of S. rugosoannulata studied shared the characteristic of abundantly producing cells with finger-like projections called acanthocytes. We showed that the nematode-attacking activity of this fungus is carried out by these spiny acanthocytes and that mechanical force is an important factor in the process. Furthermore, the growth and nematode-attacking activity of the fungus in soil were also determined, and our results suggest that acanthocytes are functional in soil.     

Gonadal cell lineages of the nematode Panagrellus redivivus and implications for evolution by the modification of cell lineage

To explore the nature of cell lineage modifications that have occurred during evolution, the gonadal cell lineages of the nematode Panagrellus redivivus have been determined and compared to the known gonadal lineages of Caenorhabditis elegans (J. Kimble and D. Hirsh, 1979, Develop. Biol.70, 396–417). Essentially invariant lineages generate the 143 somatic cells of the male gonad and at least 326 somatic cells of the female gonad of P. redivivus. The basic program of gonadogenesis is strikingly similar among both sexes of both species. For example, the early division patterns of the somatic gonad precursors Z1 and Z4 are almost identical. Later division patterns are more divergent and, in a few cases, generate structures that are species specific. In general, similar cell types are produced after similar patterns of cell divisions. Differences among the Z1 and Z4 cell lineages appear to reflect phylogenetic modifications of a common developmental program. The nature of these differences suggests that the evolution of cell lineages involves four distinct classes of alterations: switches in the fate of a cell to that normally associated with another cell; reversals in the polarity of the lineage generated by a blast cell; alterations in the number of rounds of cell division; and an “altered segregation” of developmental potential, so that a potential normally associated with one cell instead becomes associated with its sister. A number of cell deaths occur during gonadogenesis in P. redivivus. The death of Z4.pp, a cell that controls the development of the posterior ovary in C. elegans, probably prevents the development of a posterior ovary in P. redivivus and hence is responsible for the gross difference in the morphologies of the gonads of the P. redivivus female and the C. elegans hermaphrodite. As exemplified by the death of Z4.pp, an alteration in the fate of a “regulatory cell” could facilitate rapid and/or discontinuous evolutionary change.     

Effect of three isolates of Pandora neoaphidis from a single population of Sitobion avenae on mortality,speed of kill and fecundity of S. avenae and Rhopalosiphum padi at different temperatures

We studied the effect of three Pandora neoaphidis isolates from one Sitobion avenae population, three temperatures, and two aphid species namely S. avenae and Rhopalosiphum padi on (i) aphid mortality, (ii) time needed to kill aphids, and (iii) aphid average daily and lifetime fecundity. A total of 38% of S. avenae and 7% of R. padi died and supported fungus sporulation. S. avenae was killed 30% faster than R. padi. Average daily fecundity was negatively affected only in S. avenae inoculated with, but not killed by, P. neoaphidis. Nevertheless, lifetime fecundity of both aphid species inoculated and sporulating with P. neoaphidis was halved compared to lifetime fecundity of surviving aphids in the control. Increased temperature resulted in higher mortality rates but did not consistently affect lethal time or fecundity. Results suggest that (i) temperature effects on virulence differ between isolates, even when obtained within the same host population, and (ii) even though an isolate does not kill a host it may reduce its fecundity. Our findings are important for the understanding of P. neoaphidis epizootiology and for use in pest-natural enemy modelling.     

Impact of intercropping aphid-resistant wheat cultivars withoilseed rape on wheat aphid (Sitobion avenae) and its natural enemies

The effects of intercropping of wheat cultivars and oilseed rape on the densities of wheat aphid, Sitobion avenae, and their arthropod natural enemies were evaluated. Three winter wheat cultivars with different resistant levels to S. avenae were used: ‘KOK’ (high resistance), ‘Xiaobaidongmai’ (low resistance) and ‘Hongmanghong’ (susceptible). The results showed that the densities of S. avenae were significantly higher on the monoculture pattern than on either the 8-2 intercropping pattern (eight rows of wheat with two rows of oilseed rape) or the 8-4 intercropping pattern (eight rows of wheat with four rows of oilseed rape). The mean number of predators and the mummy rates of S. avenae were significantly higher in two intercropping patterns than those in the monoculture pattern. The densities of S. avenae, ladybeetles, and mummy rate of S. avenae were significantly different among different wheat cultivars. The highest densities of S. avenae and ladybeetles were found on wheat cultivar Hongmanghong. The lowest densities of S. avenae associated with high mummy rate of S. avenae were found on wheat cultivar Xiaobaidongmai. The results showed that wheat-oilseed rape intercropping conserved more predators and parasitoids than in wheat monoculture fields, and partial resistance of wheat cultivar Xiaobaidongmai had complementary or even synergistic effects on parasitoid of S. avenae.