Nematode Panagrellus Redivivus Research Articles

Two highly reiterated nucleotide sequences in the low C-value genome of Panagrellus redivivus

Two families of highly reiterated satellite nucleotide (nt) sequences have been found in the genome of the sexually separated nematode Panagrellus redivivus. The repeats are arranged in tandem arrays but the different satellites are not intermingled. Monomeric lengths are of 155 bp for one kind and 167 bp for the other; they were named E155 and E167. The A + T content is elevated in both families (i.e., 59.5% and 65.3, respectively). No similarity was found between the two satellites nor to other known highly repetitive elements. Furthermore, nt methylation as well as transcriptional activity were negative. An internal subrepeating unit, about 30 bp long, was observed in E167, implying that it could have evolved from a shorter sequence. Reiteration frequencies are approx. 30 000 and 40 000 copies per haploid genome, for E155 and E167, respectively, constituting together about 17% of the total DNA. This figure is astonishingly high, considering a C-value of 70 000 kb in P. redivivus, which is thought to be the lower limit for metazoans. Hence, the genome complexity is approx. 58 000 kb. In contrast to the nematodes Ascaris lumbricoides and Parascaris equorum, however, P. redivivus does not seem to eliminate large blocks of satellite DNA in the presomatic cells during early development.

Assessing toxicity of Lake Diefenbaker (Saskatchewan, Canada) sediments using algal and nematode bioassays

Lake Diefenbaker, on the South Saskatchewan River, Saskatchewan, Canada, receives, on average, 90% of its inflow from snowmelt and rainfall in the Rocky Mountains. The inflowing rivers also receive irrigation return flows and municipal and industrial effluents which may result in the contamination of lake sediments. The sediments were assessed by nematode and algal bioassays. The toxicity of five chemical fractions of the sediment was determined using the nematode Panagrellus redivivus as the test organisms. The results suggest that the sediment chemical fractions frequently inhibit growth and maturation, while lethality was observed at 4 of 12 sites. Samples from 3 of these sites were further evaluated using conventional elutriate Algal Fractionation Bioassays (AFB) with both natural Lake Diefenbaker phytoplankton and a mixed laboratory grown algal culture. The natural phytoplankton showed inhibition at sediment: water ratios of 10: 1; whereas the algal cultures showed both enhancement and inhibition. Evidently, the sediments are frequently toxic to the species tested except for the algal culture. The AFB assesses the mitigative and synergistic effects of contaminants and nutrients and being a conventional elutriate, is more realistic and potentially more acceptable than the chemical fractionation/nematode bioassay technique which essentially considers potential trace organic contaminant effects.

Glutathione transferase in the free-living nematode Panagrellus redivivus

The free-living nematode Panagrellus redivivus was found to have relatively high cytosolic glutathione transferase activity. Chromatofocusing indicated that at least four GSH transferase forms were present in the nematode cytosol. An endogenous molecular factor interfered with the binding of the cytosolic GSH transferases to a glutathione affinity matrix and binding only occurred after a partial purification step. The major resolved GSH transferase form B was a basic enzyme that showed no biochemical homology to the three mammalian multigene GSH transferase families and appeared to interact with plant phenols, possible natural substrates. A minor GSH transferase form AT showed a biochemical relationship to the mammalian α family including catalytic activity with a model lipid hydroperoxide substrate.

The possible absence of cytochrome P-450 linked xenobiotic metabolism in helminths

The distribution of cytochrome P-450, b 5 and associated oxidations, aniline hydroxylase, 7-ethoxycoumarin O-deethylase and 4-nitroanisole O-demethylase were studied in the parasitic nematode Heligmosomoides polygyrus, its mammalian host, Mus musculus and the free-living nematode Panagrellus redivivus. Cytochrome P-450, its associated oxidations and cytochrome b 5 could not be detected in whole homogenates or subcellular fractions (mitochondrial, microsomal and soluble fractions) of either nematode under a variety of assay conditions which included attempted induction with sodium phenobarbital. P. redivivus was able to reduce 1,2-dimethyl-4-(4-carboxyphenylazo)-5-hydroxybenzene and azobenzene, but activity was localised in the soluble fraction unlike the mammalian cytochrome P-450 linked reduction of azobenzene, which is predominantly microsomal. The implications of these results in terms of chemotherapy are discussed.

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.

Isolation and characterization of a nematode transposable element from Panagrellus redivivus.

We have isolated a transposable element, designated PAT-1, from the free-living nematode Panagrellus redivivus. P. redivivus strain C15 was found to have a high spontaneous mutation frequency compared to the standard Caenorhabditis elegans laboratory strain N2. To characterize the genetic lesions occurring in spontaneous C15 mutants, we molecularly cloned the homolog of the C. elegans unc-22 gene from wild-type P. redivivus and two strains carrying spontaneous mutations in this gene. One of these mutations resulted from the insertion of a 4.8-kilobase segment of repetitive DNA. This repetitive element (PAT-1) varies in copy number (10-50 copies) and location in different P. redivivus strains and is absent from C. elegans. The element could be useful as a transformation vector for C. elegans. Our approach is a general one that could be used to isolate additional nematode transposons from other species.

24-Methyl-23-dehydrocholesterol: A new sterol intermediate in C-24 demethylation from the nematodes Panagrellus redivivus and Caenorhabditis elegans?

Panagrellus redivivus produced 24-methyl-23-dehydrocholesterol as 4.0% of the 4-desmethylsterols when propagated in a medium containing campesterol as the dietary sterol. The re-examination of previous data revealed that Caenorhabditis elegans produced 1.8% 24-methyl-23-dehydrocholesterol when propagated in medium containing campesterol. 24-Methyl-23-dehydrocholesterol was not detected when the nematodes were propagated in medium containing 22-dihydrobrassicasterol or 24-methylenecholesterol. This may be a result of the greater efficiency of dealkylation of the latter two sterols. This is the first report of the natural occurrence of this sterol in a non-photosynthetic organism, and the first report in organisms that dealkylate 24-alkylsterols.

A fungal lectin and its apparent receptors on a nematode surface

A lectin was isolated from the nematode-trapping fungus Arthrobotrys oligospora. This carbohydrate-binding protein was developmentally regulated and was found only on trap-bearing mycelia. The lectin receptor on the surface of the nematode Panagrellus redivivus has, furthermore, been investigated using homogenates from whole nematodes or nematode cuticle. The ability of macromolecules from nematodes, fractionated according to Mr and lectin affinities, to inhibit the capture of nematodes by A. oligospora was tested using an inhibition assay, based on a simple dialysis membrane technique. One major lectin-binding glycoprotein, with apparent Mr of 65 000, was isolated from the nematode cuticle.

Growth and survival of Culicoides melleus larvae (Diptera: Ceratopogonidae) on four prey organisms.

Growth of the predatory larvae of Culicoides melleus on 4 prey organisms was compared by measurement of daily changes in larval body length and dry weight. The prey organisms were Brachionus plicatilis (a haline rotifer), the nematode Panagrellus redivivus (the largest nematode species used), and 2 unnamed nematodes designated species N (intermediate in size) and n (the smallest species). Food organisms were provided in excess throughout larval development and all rearing was done in nutrient agar at 27 °C. Survival of 1st-instar larvae fed P. redivivus was slightly but significantly reduced compared to larvae fed the other 2 nematode species. Growth was rapid and very similar in larvae fed P. redivivus and species N. However, larvae provided with the smallest nematode, species n, showed progressively retarded development after day 9 of the experiment. Nematode n was apparently too small to support optimal larval growth once larvae had reached the 3rd instar. The rotifer B. plicatilis was provided to larvae only after day 8, the larvae having been fed P. redivivus until this time. Larvae so treated continued to develop quite rapidly to pupation, but their growth was somewhat slower than that of larvae fed P. redivivus and species N nematodes. Withholding vitamins and other supplementary trace nutrients from the rearing medium resulted in considerable asynchrony and retardation in development. The importance of the results in defining suitable diets for rearing predatory ceratopogonid larvae is discussed.

DNA stability in the anabiotic fourth‐stage juveniles of Ditylenchus dipsaci (Nematoda)

SUMMARYWater plays an important role in DNA structure and desiccation of microorganisms has been correlated with breaks in their DNA.The fourth‐stage juveniles of the anabiotic nematode Ditylenchus dipsaci can lose up to 90% of their body water and survive in a dehydrated state for long periods of time; however, there was no increase in the frequency of breaks in DNA isolated from anabiotic as opposed to hydrated juveniles. Desiccation of the non‐anabiotic nematode Panagrellus redivivus similarly did not lead to an increased frequency of DNA breaks, nor did the polyol glycerol significantly effect DNA stability.The stability of DNA during tissue desiccation, like the stability of proteins, seems to be a general feature of biological material and not a unique property of anabiotic organisms.

Polyploid tissues in the nematode Caenorhabditis elegans

During larval development, the number of somatic nuclei in C. elegans hermaphrodites increases from 558 to 959 (J. E. Sulston and H. R. Horvitz, Dev. Biol. 56, 110–156, 1977; J. E. Sulston et al., Dev. Biol. 100, 64–119, 1983). At the same time, the animals increase about 60-fold in volume. We have measured the DNA contents of several classes of nuclei by quantitating the fluorescence of Hoescht 33258 stained DNA (D. G. Albertson et al., Dev. Biol. 63, 165–178, 1978). Probably all embryonic nuclei, including those of neurons, muscles, hypodermis, and intestine, are diploid at hatching. Neurons, muscles, and nondividing hypodermal nuclei remain diploid throughout larval development. The DNA content of the intestinal nuclei doubles at the end of each larval stage, reaching 32C by the adult stage. New hypodermal cells, generated by division of seam cells in the larval stages, undergo an additional round of DNA replication before fusing with the major syncytium (hyp7, Sulston et al., 1983). Thus the larval hyp7 syncytium comprises a fixed number of diploid embryonic nuclei plus an increasing number of tetraploid postembryonic nuclei. Some of the endoreduplications that occur in the intestinal and hypodermal lineages of C. elegans may correspond to nuclear or cellular divisions in another nematode Panagrellus redivivus (P. W. Sternberg and H. R. Horvitz, Dev. Biol. 93, 181–205, 1982).

Measuring minimal concentrations of attractants detected by the nematodePanagrellus redivivus

A simple method for the experimental determination of minimal concentrations of attractants detected by the nematodePanagrellus redivivus is described. The lowest concentrations of methyl, ethyl, propyl, butyl, and amyl acetate as well as the minimal differences in concentrations of these attractants detectable byPanagrellus redivivus are presented.

Anaerobic Metabolism in the Free-Living Nematode Panagrellus redivivus

Under anaerobic conditions, the free-living nematode Panagrellus redivivus produces a range of acidic and neutral end products. The main acidic end product was lactate with lesser amounts of alanine, acetate, and propionate; the major neutral end product was ethanol with smaller amounts of glycerol and traces of acetoin. Apart from carbon dioxide, no other end products could be detected. During recovery from anaerobiosis, P. redivivus was found to be able to remetabolize the accumulated end products. The coproduction of ethanol and glycerol may provide a mechanism for reoxidizing mitochondrial NADH during anaerobiosis.

Acetaldehyde formation by mitochondria from the free-living nematode Panagrellus redivivus.

The mitochondrial fraction from the free-living nematode Panagrellus redivivus decarboxylates pyruvate to produce significant amounts of acetaldehyde. Acetaldehyde formation is stimulated by thiamin pyrophosphate, shows a sharp optimum at pH 6.8 and is greater under anaerobic than aerobic conditions. The pyruvate decarboxylase activity cofractionates with, and is probably a partial reaction of, the pyruvate dehydrogenase complex. Acetaldehyde production is modulated by NAD+, ATP and acetyl-CoA and is greatly stimulated by lipoic acid. The pyruvate decarboxylase system is extremely sensitive to thiol-group inhibitors and is inhibited by oxygen in the presence of pyruvate.

Life cycle of the endoparasitic nematophagous fungus Meria coniospora: a light and electron microscopic study.

The obligate endoparasitic fungus Meria coniospora lives its entire vegetative life within infected nematodes. Conidia of M. coniospora infect the nematode Panagrellus redivivus mainly in the mouth region. The infection, starting with adhesion of conidia to the nematode surface, growth of trophic hyphae, production of conidiophores and conidia, was followed using light, scanning and transmission electron microscopy.

Estimation of mutation rates induced by large doses of gamma, proton and neutron irradiation of the X-chromosome of the nematode Panagrellus redivivus

The radiation-resistant free-living nematode Panagrellus redivivus was used to study mutation rates in oocytes, following gamma, proton and neutron irradiation in the dose range 45–225 grays. γ-Radiation produced approximately 0.001 lethal X-chromosomes per gray over the range tested. Proton or neutron irradiation produced approximately 0.003 lethal X-chromosomes per gray at lower doses, with the mutation rate dropping to 0.001 lethal X-chromosome per gray at the higher doses. These results suggest a dose-dependent mutation-repair system. Cell lethality was also examined. γ-Radiation produced the greatest amount of cell lethality at all doses, while neutron irradiation had no cell lethal effect at any of the doses examined.

Effect of dose-rate on the frequency of X-linked lethal mutation in the nematode Panagrellus redivivus

A total X-ray dose of 50 Gy was applied to the nematode Panagrellus redivivus using dose-rates ranging from 0.23 Gy/min to 10.49 Gy/min, and the frequency of lethal X-chromosomes was determined. This frequency ranged from approximately 1.6% at the lower dose-rate to 4.3% at the highest dose-rate, indicating a dose-rate dependency of mutation frequency in the spermatogonia and oogonia of this organism.

SURVIVAL, METAMORPHOSIS AND GROWTH OF PENAEID SHRIMP LARVAE REARED ON A VARIETY OF ALGAL AND ANIMAL FOODS

ABSTRACTExperiments conducted with Penaeus aztecus, P. setiferus and P. vannamei compared survival, metamorphosis and dry weight growth of larvae fed a variety of algal and animal food regimes. The major objectives were: (a) comparison of the nematode Panagrellus redivivus and the brine shrimp Artemia as animal food sources and (b) comparison of effects of feeding diatoms (Skeletonema costatum and Chaetoceros gracilis) vs phytoflagellates (Isochrysis sp. and Tetraselmis chuii) with nematodes or brine shrimp nauplii added to the diet starting at the protozoea‐two or mysis‐one substage.Specific feeding regimes were identified for each shrimp species tested which would allow for total or partial replacement of Artemia as the animal food source, without reducing production results. However, Panagrellus redivivus was found to be less versatile than Artemia nauplii in terms of overall nutritional value to the shrimp larvae. The superiority of using two diatom species vs two phytoflagellate species as an algal food source for penaeid shrimp larvae demonstrated in earlier experiments was confirmed.The results strongly suggest that evaluation of rearing regimes used for production of penaeid postlarvae should include growth in terms of dry weight, as well as survival and rate of metamorphosis.

Involvement of Sialic Acid in Nematode Chemotaxis and Infection by an Endoparasitic Nematophagous Fungus

SUMMARY: Conidia of the endoparasitic nematophagous fungus Meria coniospora adhere to the sensory organs of the nematode Panagrellus redivivus leading to a complete loss of the nematode's ability to be attracted to fungi. Sialic acids located on the head region of the nematode seem to be involved in this interaction. Treatment of the nematode with sialidase reduced attraction towards fungi, and treatment with the sialic acid-specific lectin, limulin, reduced both nematode attraction and conidial adhesion. Other lectins tested (WGA, SBL, HPL, Con A) gave no effect on either attraction or adhesion. Treatment of conidia with trypsin or glutaraldehyde reduced conidial adhesion, indicating the presence of a fungal sialic acid-specific carbohydrate-binding protein. The results show the importance of sialic acids in nematode chemotaxis and also in adhesion of conidia of M. coniospora. Sialic acid, therefore, seems to be a link between attraction and adhesion in this system.

The Endoparasitic Nematophagous Fungus Meria coniospora Infects Nematodes Specifically at the Chemosensory Organs

SUMMARY: Conidia of the endoparasitic fungus Meria coniospora infected the bacterial-feeding nematode Panagrellus redivivus at specific sites, namely the mouth region and in male nematodes also in the tail. Plant-parasitic nematodes were also infected in other parts of the body. The specific infection sites in P. redivivus were the sensory organs, which are the sites of chemoreception. Blocking of chemoreceptors by adhered conidia of M. coniospora caused a complete loss of the ability of nematodes to be attracted to different sources of attractants. Inhibition of conidial adhesion by means of sugar haptens suggested a lectin-carbohydrate interaction. Out of 21 sugars only N-acetylneuraminic acid inhibited the adhesion, indicating the importance of sialic acids in the infection process. Reduction of conidial adhesion by treatment of nematodes with neuraminidase further supported this view.