Free-living Nematode Panagrellus Redivivus Research Articles

Bacillus toyonensis biovar Thuringiensis: A novel entomopathogen with insecticidal activity against lepidopteran and coleopteran pests

The Bacillus cereus group includes eight species: Bacillus anthracis, B. cereus, Bacillus cytotoxicus, Bacillus mycoides, Bacillus pseudomycoides, Bacillus thuringiensis, Bacillus weihenstephanensis and Bacillus toyonensis, which are highly related at the phylogenetic level. In this work, we performed the isolation and characterization of a novel Bacillus sp. strain exhibiting parasporal crystals with insecticidal activity that was initially classified as a Bacillus thuringiensis strain. Its genome encoded three genes showing homology to known pesticidal proteins from B. thuringiensis and Lysinibacillus sphaericus proteins: Cry7Ga1 (a crystal protein), a Mpp2Aa3 (ETX/Mtx2 family) homolog and a mosquitocidal-like protein (NPP1). However, since its genome sequence shared > 98% ANI with several Bacillus toyonensis genomes, the strain has subsequently been renamed as Bacillus toyonensis biovar Thuringiensis and designated Bto-UNVM_94. Bioassays demonstrated that this novel strain exhibited toxicity against Cydia pomonella (Lepidoptera: Tortricidae) and Anthonomus grandis (Coleoptera: Curculionidae), a low toxicity against Aedes aegypti (Diptera: Culicidae) and Alphitobius diaperinus (Coleoptera: Tenebrionidae) whereas no toxicity was shown to the free-living nematode Panagrellus redivivus (Rhabditida: Panagrolaimidae).

Taxonomic and biological characterization and predatory activity of four nematophagous fungi isolates of Arthrobotrys species from Tapachula, Chiapas, Mexico

ABSTRACT A batch of nematophagous fungi (NF), isolated from soil and animal faeces at Tapachula, Chiapas, Mexico, was identified through morphological methods and molecular tools. Additionally, the fungi were biologically characterised through their in vitro predatory capability against the free-living nematode Panagrellus redivivus. Molecular identification of nine isolates was achieved by amplifying the 18S, 5.8S and 28S regions using ITS5 and ITS4 oligonucleotides, followed by sequencing and aligning through BLAST. Only species of Arthrobotrys genus: A. oligospora, A. conoides, A. arthrobotryoides and A. musiformis were found. The in vitro bioassay revealed a large variability in the predatory capabilities of the different isolates. The isolate Z1-1-2 of A. arthrobotryoides showed the highest nematode reduction (NR) from 822.8 (± 169.5) to only 51.4 (± 35.2) = 93.7% NR; in contrast A. oligospora (isolate Z3-2-2) showed the lowest NR from 548.5 (± 66.6) to 234.2 (± 123.6) = 57.2% Genotyping analysis corroborated the morphological identification. The comparison of sequences with the NCBI sequences showed a close phylogenetic relationship. A phylogenetic tree was generated to compare its phylogenetic relationship with other strains reported in the NCBI. The NF isolated could be potential candidates for future studies on the biological control of nematodes.

Butlerius butleri (Nematoda: Diplogasteridae) Feeds on Haemonchus contortus (Nematoda: Trichostrongylidae) Infective Larvae and Free-Living Nematodes in Sheep Faecal Cultures Under Laboratory Conditions: Preliminary Report.

This study assessed the feeding activity of the predatory nematode Butlerius butleri on the infective larvae of the sheep parasitic nematode Haemonchus contortus (Hc-L3) and on two free-living nematodes Panagrellus redivivus (Pr) and Rhabditis sp. (R) in sterile sheep faecal cultures. A bioassay was carried out in sheep faecal cultures, where predatory and prey nematodes were put together to assess the predatory behaviour on the different nematodes. Faecal cultures (n = 9) were set up in different treatments as follows: Treatments 1, 2 and 3 contained 20 specimens of B. butleri and 2000 Hc-L3, Pr and R, respectively; treatments 4, 5 and 6, contained only 2000 Hc-L3, Pr and R, respectively, as control groups. Treatment 7 contained 20 B. butleri as control. All treatments were incubated at room temperature for 30days. The average number of nematodes recovered from each treatment was obtained and the reduction rate with respect to their corresponding control was estimated. Data were analysed using an ANOVA test using a completely randomised design in the SAS programme. Butlerius butleri reduced the Hc-L3, population by 91.8%, whereas its population increased 131.6 times. The interactions between B. butleri and Pr and R resulted in 80.9% and 62.5% nematode reduction and B. butleri increased its populations 268.3 and 82.7 times, respectively. This experiment was performed only once, so this can be considered a preliminary report at this time. This study provides evidence for the first time that B. butleri feeds on one of the most economically important nematodes of small ruminants, Hc-L3.

Effects of Zinc Oxide Nanoparticles on Panagrellus redivivus (Nematoda) and Folsomia candida (Collembola) in Various Test Media

The toxic effects of zinc oxide (ZnO) nano- and non-nanoparticles on two species of soil organisms, the free-living nematode Panagrellus redivivus and the springtail Folsomia candida, were investigated. The toxicity of ZnO particles (with 15 and 140 nm average particle size) and ZnCl2 (used as a positive control for zinc ion dissolution) was tested in two different kinds of test media. Milli-Q water vs. soil solution was used for the tests involving P. redivivus, and plaster of paris vs. artificial soil for F. candida. For P. redivivus, application of the soil solution decreased the toxic effect. It is considered that this may be due to the less dissolved zinc ions, the organic matter content and ZnO aggregation. Furthermore, all of the compounds caused concentration-dependent mortality to the tested nematode species. In the tests with F. candida, the toxic effects of both ZnO and ZnCl2 were significantly lower in the tests involving plaster of paris. This could have resulted from the avoidance of the contaminated foods by the springtails. A decreasing effect on reproduction was observed only in the tests using artificial soil. Additionally, the ZnO particles of 140 nm significantly increased mortality in the soil solution test with P. redivivus and in the artificial soil in the tests with F. candida. Possibly, this is a consequence of a greater aggregation of the nanoparticle-sized ZnO at the end of the experiment, which resulted in a lower level of toxicity.

Hirsutella thompsonii and Pochonia chlamydosporia (Syn. Verticillium chlamydosporium) Mycelia Growth and Predation on Panagrellus redivivus

This research aimed to evaluate the nematophagous ability of 4077-Verticillium chlamydosporium var. chlamydosporium and 4466-Hirsutella thompsonii isolates and relate mycelia growth to the influence provoked by movement of nematodes. Each fungus grew in PDA (potato, dextrose, agar) medium end up to pure colonization. Then, ten mycelia plugs of 8 mm diameter were removed from colony borders and transferred to the center of ten Petri plates containing water-agar 2% medium. These plates were previously divided into four quadrants that received a number of 25 individuals of free-living nematodes (Panagrellus redivivus), composing a total of 100 nematodes per plate. Evaluations started after 24 hours of interaction, considering predation percentage and mycelia growth as stimuli of nematodes presence. Results showed growing predation performance to both isolates, being higher for V. chlamydosporium var. chlamydosporium since from first evaluation time, controlling more than 50% of nematode population initially added. Its predation potential was 39.2%, 38.4% and 48.35% higher than H. thompsonii at first, second and third evaluation day, respectively. Generally, nematodes did not stimulate mycelia growth, unless for H. thompsonii at 72 hours of interaction compared to control plates (without nematodes). Stress resulting from isolates transference from PDA to water-agar 2% resulted in sparse mycelia growth and it could have affected the predation performance of H. thompsonii that controlled nematodes in low levels throughout experiment. Independently of predation level, pictures revealed that both isolates has ability to control P. redivivus through hyphae penetration.

Effects of catechin polyphenols and preparations from the plant–parasitic nematode Heterodera glycines on protease activity and behaviour in three nematode species

Protease activities in preparations from the plant-parasitic nematodes Heterodera glycines and Meloidogyne incognita and the free-living nematode Panagrellus redivivus were inhibited by exposure to a series of eight catechin polyphenol analogues, (+)-catechin, (-)-epicatechin (EC), (-)-gallocatechin (GC), (-)-epigallocatechin (EGC), (-)-catechin gallate (CG), (-)-gallocatechin gallate (GCG), (-)-epicatechin gallate (ECG) and (-)-epigallocatechin gallate (EGCG) (1 mm each), and by a preparation from H. glycines cysts. General protease activity detected with the FRET-peptide substrate QXL520-KSAYMRF-K(5-FAM)a and proteasome chymotrypsin-like (CTL) activity detected with succinyl-LLVY-AMC were each inhibited significantly more (P < 0.05) by the gallated form of the polyphenol than by the corresponding non-gallated form. Species differences in response to inhibition across all analogues were revealed with the CTL substrate, but CG was a consistently potent inhibitor across all three species and with each substrate. A heat-stable component (CE) from H. glycines cysts inhibited M. incognita CTL activity by 92.07 ± 0.68%, significantly less (P < 0.05) in H. glycines (52.86 ± 2.77%), and by only 17.24 ± 0.55% (P < 0.05) in P. redivivus preparations. CTL activity was, however, inhibited more than 60% in all preparations by the proteasome-specific inhibitor MG-132. Hatching of M. incognita infective juveniles exposed to 1 mm CG, ECG, GCG or EGCG was reduced by 83.88 ± 4.26%, 69.98 ± 9.14%, 94.93 ± 1.71% and 87.93 ± 2.89%, respectively, while hatching of H. glycines was reduced less than 25% by each analogue. CE had no effect on nematode hatch, but did cause a 60% reduction in mobility of H. glycines infective juveniles exposed overnight to CE in vitro, which was more (P < 0.05) than the reduction of M. incognita infective juvenile mobility (20%).

Uso de productos derivados de bacillus thuringiensis como alternativa de control en nematodos de importancia veterinaria. revisión

Bacillus thuringiensis is an entomopathogenic bacterium that produces crystal-proteins with cytotoxic activity against insects and nematodes. B. thuringiensis toxicity on agriculture pests is widely recognized, however, there is little information about the lethal action of B. thuringiensis against nematodes. Recently, the nematicide activity of B. thuringiensis proteins was showed against Haemonchus, Teladorsagia, Nippostrongylus, and Ancylostoma genera of mammals, and against the plant parasitic nematodes, Globodera and Meloidogyne. From a list of B. thuringiensis strains with nematicide effect, selected proteins from the IB-16 isolate showed 50 to 100 % nematocidal efficacy against different developing stages of H. contortus. Additionally the in vitro assay showed evidence about the lethal activity of this strain against the free-living nematodes Panagrellus redivivus and Caenorhabditis elegans. The Cry5B protein of B. thuringiesis caused tissue damage on the C. elegans mid-gut and its action probably involves specific gut-receptor, similar to reporte with nematodes of importance in agriculture. Also, Cry5B protein-receptors link appears to involve carbohydrate moieties on intestinal cells, and cause tissue damage and nematodes death. Through these studies, selected B. thuringiensis proteins could be considered in future trials as potential alternative tools of control against parasitic nematodes of domestic animals, such as ruminants and other pathogens of mammals and even from agriculture crops.

Digestion of invertebrate neuropeptides by preparations from the free-living nematodePanagrellus redivivus

Proteases in the soluble fraction of homogenates prepared from the free-living nematode Panagrellus redivivus hydrolysed the amidated invertebrate neuropeptides FMRFa and FLRFa, and nematode FMRFa-like peptides (FLPs) KPNFLRFa (FLP-1-H), APKPKFIRFa (FLP-5-A), KNEFIRFa (FLP-8), KPSFVRFa (FLP-9), RNKFEFIRFa (FLP-12) and KHEYLRFa (FLP-14) in vitro. Results were assessed by analysing reaction components with RP-HPLC, UV detection at 210 nm and peak integration. Based upon substrate peak size, more than 90% of most of the peptide substrates was consumed after 1 h at 27 degrees C, but digestion was not complete even with a crude protease mixture. Two peptides, FLP-12 and FLP-14, were significantly less susceptible to digestion than the others. FLP-12 was the least susceptible of all sequences (71% loss; P < 0.0001), while FLP-14 was digested less (84% loss; P < 0.0004) than all but FLP-12. Product peak digestion patterns of FLP-12, a second nonapeptide (FLP-5-A), and FMRFa, incubated with aminopeptidase (amastatin) and serine endoprotease (AEBSF) inhibitors, demonstrated highly specific behaviours of each sequence to protease cleavage. Amastatin significantly (P < 0.03) reduced digestion of FLP-12 (54% loss) and FMRFa (61% loss; P < 0.0005), but had no effect on FLP-5-A. AEBSF had no protective effect on FMRFa but significantly decreased hydrolysis of FLP-5-A (77% loss; P < 0.0001) and FLP-12 (59% loss; P < 0.03). The combination of both inhibitors had additive effects only for FMRFa (34% loss; P < 0.0005). Further analysis of FMRFa digestion using peptides with D-amino acid substitutions demonstrated nearly complete protection of FdMRFa (2% loss; P < 0.0001) from all proteolytic digestion, whereas digestion of FMRdFa was complete. Results suggest that in addition to aminopeptidase and serine proteases, both deamidase and aminopeptidase P participate in neuropeptide metabolism in P. redivivus.

Evaluation and identification of potential organic nematicidal volatiles from soil bacteria

Naturally occurring volatile compounds with nematicidal activities (NAs) are of significant economical importance in agriculture and forestry. In this study, volatile organic compounds (VOCs) produced by 200 isolates of soil bacterial were evaluated in in vitro experiments. Our results identified that among the 200 bacterial isolates, 149 (74.5%) and 165 (82.5%) exhibited a greater than 20% NA against the free-living nematode Panagrellus redivivus and the pinewood nematode Bursaphelenchus xylophilus, respectively. Among them, 22 isolates showed 100% NA against P. redivivus and seven isolates showed 100% NA against B. xylophilus. When exposed to nematicidal volatiles, nematodes gradually reduced their movements within 1–12 h after treatment, and most stopped moving completely after 24 h. Our analysis indicated significant variation in nematicidal capability of the VOCs not only among bacterial species but also among isolates of the same species. Volatiles of representative isolates were extracted using solid-phase micro-extraction (SPME) and their structures identified using gas chromatography–mass spectrometry (GC–MS). The detected so volatile compounds included alcohols, aldehydes, ketones, alkenes and ethers. Of the 20 VOCs with strong NA (⩾80%), nine (phenol, 2-octanol, benzaldehyde, benzeneacetaldehyde, decanal, 2-nonanone, 2-undecanone, cyclohexene and dimethyl disulfide) displayed 100% NA to both model nematodes. Furthermore, five compounds (terpineol, benzeneethanol, propanone, phenyl ethanone and nonane) showed different NA to B. xylophilus (75–100%) and P. redivivus (17.02–100%).

Digestion and Assimilation of the Free-living Nematode Panagrellus redivivus Fed to First Feeding Coregonid Larvae: Evidence from Histological and Isotopic Studies

The free-living nematode Panagrellus redivivus is a potential source of live food for first feeding fish. The digestion and assimilation of nematodes by larval fish were investigated with the aid of a histological and stable isotope approach. Larvae of whitefish Coregonus lavaretus were reared for 8 d with nematodes and compared with an unfed control. Nematodes were readily ingested by 3-d-old larvae. Different stages of nematode digestion could be observed in transverse sections of fish larvae sampled on Day 6 at regular intervals after feeding. Nematodes were produced on corn medium. In this way nematodes with a stable carbon isotope signature clearly different from the isotopic pattern of the fish larvae could be obtained. Stable carbon isotope signatures for lipids and lipid-free matter of fish larvae sampled on Days 2 and 8 after first feeding were clearly influenced by the stable isotopic pattern of the nematodes. The high acceptance of the nematodes by Coregonus lavaretus larvae and the early onset of digestion and nutrient retention positively confirm the potential of PanagreUus redivivus as a live food for first feeding fish larvae.

Cloning and characterization of an extracellular serine protease from the nematode-trapping fungus Arthrobotrys conoides

An extracellular serine protease (Ac1) with a molecular mass of 35 kDa was purified from the nematode-trapping fungus Arthrobotrys conoides. The optimum activity of Ac1 is at pH 7.0 and 53.2 degrees C (over 20 min). Ac1 can degrade a broad range of substrates including casein, gelatin, bovine serum albumin, collagen, and nematode cuticles. Moreover, the enzyme can immobilize the free-living nematode Panagrellus redivivus and the pine wood nematode Bursaphelenchus xylophilus, indicating Ac1 may be involved in infection against nematodes. The encoding gene of Ac1 contains one intron of 60-bp and two exons encoding a polypeptide of 411 amino acid residues. The deduced polypeptide sequence of Ac1 showed a high degree of similarity to two previously reported serine proteases PII and Mlx from other nematode-trapping fungi (81% aa sequence identity). However, three proteases Ac1, Aoz1 and Mlx showed optimum temperatures at 53.2, 45 and 65 degrees C, respectively. Compared to PII, Ac1 appears to have a significantly higher activity against gelatin, bovine serum albumin, and non-denatured collagen. Moreover, our bioassay experiments showed that Ac1 is more effective at immobilizing P. redivivus than B. xylophilus.

Purification and cloning of a novel serine protease from the nematode-trapping fungus Dactylellina varietas and its potential roles in infection against nematodes

From the culture filtrate of the fungus Dactylellina varietas (syn. Dactylella varietas), an extracellular protease (designed Dv1) was purified by cation exchange and hydrophobic interaction chromatography. The purified protease showed a molecular mass of approximately 30 kDa and displayed an optimal activity at pH 8 and 60.5 degrees C (more than 20 min). This protease could degrade a broad range of substrates including casein, gelatin, BSA (bovine serum albumin), and nematode cuticle. However, its proteolytic activity was highly sensitive to the serine protease inhibitor Phenylmethylphonylfuoride (1 mM), indicating that it belongs to the serine-type peptidase group. This protease could immobilize the free-living nematodes Panagrellus redivivus and Caenorhabditis elegans and hydrolyze the purified cuticle of P. redivivus, suggesting it may play a role in infection against nematodes. The encoding gene of Dv1 and its promoter sequence were cloned using degenerate primers and the DNA walking technology. Its open-reading frame contains 1,224 base pairs and without any intron. The deduced amino-acid sequence shared low identity to serine proteases from other nematode-trapping fungi. Our report identified a novel pathogenic protease from the nematode-trapping fungus D. varietas, and the three-dimensional structure of this protease was predicted using the Swiss-Prot method.

Panagrellus redivivus mass produced on solid media as live food for Litopenaeus vannamei larvae

The free-living soil nematode Panagrellus redivivus is well known to be an excellent food source for first feeding fish larvae. It represents an alternative to the highly expensive Artemia, which is commonly used. The lack of a proper method for mass production of P. redivivus has prevented its wider use in commercial hatcheries. A new cultivation method allows the production of a sufficient quantity of nematodes to deliver a standardized and permanently available live food of high quality, throughout the larval rearing period. In two experiments – carried out at the Centro de Investigacion en Alimentacion y Desarrollo, Mexico – several feeding regimes were established to prove the quality of the mass produced P. redivivus for larvae of Litopenaeus vannamei, the Pacific white shrimp. Two different nematode treatments were compared with a no-feed group and a control group that was fed with Artemia. All treatments had an additional algal co-feed and were run in five replicates. Panagrellus redivivus was cultured on two different media (wheat/corn flour and oat flour) to compare these for their suitability as high-quality live food for the larvae. Shrimp fed nematodes grown on wheat/corn medium reached the postlarval stage earlier than those from other treatments. The nematode treatments showed promising results; however, further research is needed on the development of improved culture media or enrichment methods to further increase the nutritional value of P. redivivus.

Morphological variability and molecular phylogeny of the nematophagous fungus Monacrosporium drechsleri

An isolate of the nematode-trapping fungus Monacrosporium drechsleri was collected from cultures of the root-knot nematode Meloidogyne arenaria that had been maintained on tomato roots in greenhouse pots in Beltsville, Maryland. The plant-parasitic nematodes Heterodera glycines, Meloidogyne incognita and Pratylenchus zeae and the free-living nematodes Caenorhabditis elegans and Panagrellus redivivus were placed on colonies of M. drechsleri grown in Petri dishes to study ability of the isolate to trap various nematode hosts. None of the nematodes placed near adhesive knobs were motile within 1 d. To determine where M. drechsleri fits within the existing phylogeny of nematode-trapping fungi, the ITS1-ITS2 regions of rDNA and the nuclear gene EF1-α were sequenced for the new isolate of M. drechsleri, for the species M. parvicolle and M. lysipagum, and for an isolate of M. ellipsosporum distinct from the one listed in GenBank. Parsimony trees were constructed showing the closest molecular relative of M. drechsleri to be the newly sequenced isolate of M. ellipsosporum; the latter had a highly divergent sequence from the sequence recorded in GenBank for a different isolate of M. ellipsosporum. Unique, consistent and discrete morphological characters are absent in these related taxa, so an independent molecular character should be considered essential for their accurate identification.

Molecular Characterization of the Actin Gene from Cyst Nematodes in Comparison with Those from Other Nematodes

Actin is an abundant, highly expressed, and much conserved protein belonging to the actin–heat shock protein70–sugarkinase superfamily. The full-length messenger RNAs encoding actin were cloned and characterized from the plant-parasitic cyst nematodes Heterodera glycines and Globodera rostochiensis and from the free-living nematode Panagrellus redivivus. The actins from the plant-parasitic nematodes showed highest amino acid sequence identity to filarial nematode homologues, whereas nucleotide sequence identity was much lower than that for many actins from very distant organisms, such as vertebrates, plants, or fungi. Analysis of base composition revealed a striking difference between the H. glycines actin gene and those of filarial nematodes in (G C) content and usage of particular codons. Analysis of genomic DNA revealed the presence of 7 introns in the H. glycines actin gene. The first was atypically long and started with a GC dinucleotide, and the fifth intron occupied a novel site in the catalogue of intron positions known thus far for actin genes. Analysis of the partial genomic DNA sequences obtained from 6 other Heterodera spp. suggested that features shown for the H. glycines actin gene are characteristic for a wide range of cyst nematodes.

Coprinus comatus: A Basidiomycete Fungus Forms Novel Spiny Structures and Infects Nematode

Nematophagous basidiomycete fungi kill nematodes by trapping, endoparasitizing and producing toxin. In our studies Coprinus comatus (O.F.Müll. : Fr.) Pers. is found to be a nematode-destroying fungus; this fungus immobilizes, kills and uses free-living nematode Panagrellus redivivus Goodey and root-knot nematode Meloidogyne arenaria Neal. C. comatus produces an unusual structure designated spiny ball. Set on a sporophore-like branch, the spiny ball is a burr-like structure assembled with a large number of tiny tubes. Purified spiny balls exhibit moderate nematicidal activity. Experiments show that spiny balls are not chlamydospores because of the absence of nuclei in the structures and quick formation within 3 d in a young colony. Nematodes added to C. comatus cultures on potato-dextrose agar (PDA) and cornmeal agar (CMA) become inactive in hours. Infection of nematodes by the fungus occurs only after the nematodes are immobilized (feeble or dead), probably by a toxin. Electron micrographs illustrate that C. comatus infect P. redivivus by producing penetration pegs with which hyphae colonize nematode bodies. An infected nematode is digested and consumed within days and hyphae grow out of the nematode.

Coprinus comatus: A basidiomycete fungus forms novel spiny structures and infects nematode

Nematophagous basidiomycete fungi kill nematodes by trapping, endoparasitizing and producing toxin. In our studies Coprinus comatus (O.F.Müll. : Fr.) Pers. is found to be a nematode-destroying fungus; this fungus immobilizes, kills and uses free-living nematode Panagrellus redivivus Goodey and root-knot nematode Meloidogyne arenaria Neal. C. comatus produces an unusual structure designated spiny ball. Set on a sporophore-like branch, the spiny ball is a burr-like structure assembled with a large number of tiny tubes. Purified spiny balls exhibit moderate nematicidal activity. Experiments show that spiny balls are not chlamydospores because of the absence of nuclei in the structures and quick formation within 3 d in a young colony. Nematodes added to C. comatus cultures on potato-dextrose agar (PDA) and cornmeal agar (CMA) become inactive in hours. Infection of nematodes by the fungus occurs only after the nematodes are immobilized (feeble or dead), probably by a toxin. Electron micrographs illustrate that C. comatus infect P. redivivus by producing penetration pegs with which hyphae colonize nematode bodies. An infected nematode is digested and consumed within days and hyphae grow out of the nematode.

The suitability of the free-living nematode Panagrellus redivivus as live food for first-feeding fish larvae

Summary The free-living nematode Panagrellus redivivus has been recommended as a suitable food source for first-feeding fish. A new technology for mass production of P. redivivus enables fish hatchery operators to rely on an inexpensive, standardized and permanently available live food for first-feeding fish larvae. The proximate composition, and the fatty acid and amino acid profiles of nematodes mass produced on oat-based and purified ingredient media were determined. The quality of nematodes was significantly influenced by the culture medium used. The lipid content and fatty acid composition of nematodes could be modified by using lipid-enriched media. Mass-produced nematodes were tested on first-feeding common carp (Cyprinus carpio L.) and whitefish (Coregonus lavaretus) larvae. Carp larvae, grown on nematodes cultured on oat medium enriched with sunflower oil, showed a higher survival rate (87.1%) than the control group fed frozen zooplankton (82.9%) at the end of the 1-week feeding experiment. Differences in larval mass between the treatments disappeared after subsequent feeding of a dry diet for 2 weeks. Whitefish larvae can be reared exclusively on a dry diet; here, the initial feeding of nematodes had no effect on final biomass and survival of larvae.

Mass produced nematodes Panagrellus redivivus as live food for rearing carp larvae: preliminary results

The free-living nematode Panagrellus redivivus was mass produced on a solid culture medium enriched with sunflower oil or fish oil by means of a new technology. Nematodes with different fatty acid compositions were obtained. A 7-day experiment was performed in order to compare the lipid enriched nematodes with Artemia as live food for first feeding common carp (Cyprinus carpio L.) larvae. Larvae fed nematodes doubled their body mass and had a mean survival rate higher than 80%. No significant differences could be observed between the two groups fed nematodes. Fish larvae fed with Artemia showed almost no mortality and had a final body mass five times higher than larvae fed nematodes. It is concluded that mass produced nematodes are a promising food source for first feeding common carp larvae. However, further research is needed on the development of improved culture media to increase the nutritional value of P. redivivus.

Incorporation and metabolism of fatty acids by desaturation and elongation in the nematode, Panagrellus redivivus

AbstractThe free-living nematode Panagrellus redivivus can be mass produced in monoxenic solid culture on Saccharomyces cerevisiae and therefore could be useful as a live food for marine fish or crustacean larvae in the rapidly expanding aquaculture industry. However, this will depend on their lipid and fatty acid composition and so this was investigated in mass produced P. redivivus grown on S. cerevisiae in three different media. Live nematodes were also incubated with [1-14C]-labelled fatty acids and the desaturation and elongation of the fatty acids were determined. The combined results from the growth trials on different media and the metabolic studies with labelled fatty acids indicated the presence of Δ9, Δ12, Δ6 and Δ5 fatty acid desaturase activities, and elongase activities active towards C18, C16 and shorter chain fatty acids. The presence of Δ15, and therefore the ability to produce n-3 polyunsaturated fatty acids, was suggested by the compositional data, but could not be conclusively established from metabolic studies.