Search Results (130)

Nematophagous fungi are important biological control agents that naturally reduce nematode populations through specialized predatory mechanisms. This study evaluated the viability and predatory capacity of the nematophagous fungus Duddingtonia flagrans (AC001) after fourteen years of refrigerated storage in sodium alginate pellets. Fungal viability was assessed by reactivating the pellets on Corn Meal Agar and Potato Dextrose Agar, with subsequent monitoring of mycelial growth and morphological confirmation by light microscopy. The predatory capacity was determined by means of in vitro assays using Panagrellus redivivus as a model organism. Plates previously colonized by the fungus received approximately 400 nematodes and were compared with fungus-free controls. Predatory activity was evaluated daily for five days by counting live nematodes in random microscopic fields. Final recovery of viable nematodes was performed using a modified Baermann technique. The data were analyzed using Student’s t-test (p < 0.05). Isolate AC001 exhibited successful reactivation, preserved morphological characteristics, and sustained high predatory activity, resulting in reductions in nematode populations ranging from 91% on the first day to 95% on subsequent days, with a final reduction of 67% in nematode recovery. These findings demonstrate that sodium alginate encapsulation combined with refrigeration enables the exceptionally long-term preservation of functional and predatory attributes of nematophagous fungi, supporting its applicability in biological control strategies. Full article

Rice intensification influences soil biodiversity and ecological functioning in paddy ecosystems; however, its effects on soil nematode communities across different rice production systems remain poorly understood in the Vietnamese Mekong Delta (MD). This study evaluated the effects of rice cropping practices in the MD on nematode community composition, trophic structure, functional guilds, diversity, plant-parasitic nematodes (PPN), and soil chemical properties. A total of 91 soil samples were collected from double-rice intensive (RR), triple-rice intensive (RRR), and rice–upland–rice rotational (RUR) systems. Thirty nematode genera were identified, with a total abundance showing high variability, but no significant differences among cropping systems. Community composition differed considerably among systems, with Chronogaster dominating across all systems, particularly under RRR, whereas RUR supported more dominant genera with higher abundances of Tyleptus, Mesodorylaimus, Cephalobus, and Calolaimus. RUR exhibited significantly greater genus richness, and higher abundances of fungivores, omnivores, and higher colonizer–persister groups (cp4–cp5), indicating greater soil food-web complexity and ecological stability. In contrast, RRR was characterized by bacterivore-dominated communities, and increased abundance of cp3 nematodes, suggesting simplified community structures associated with agricultural intensification. Plant-parasitic nematodes remained relatively stable across management systems, despite taxon-specific responses. Soil pH, organic matter, and nitrogen availability were strongly associated with nematode community variation. Therefore, crop diversification through rotational practices enhanced belowground biodiversity, and promoted more sustainable soil ecological functioning in intensive rice production systems. Full article

The rise in anthelmintic resistance in small ruminants has driven the search for sustainable control alternatives. Among these, entomopathogenic fungi such as Metarhizium robertsii stand out for their potential to reduce the free-living stages of gastrointestinal nematodes (GINs). This study evaluated the field efficacy of M. robertsii (LCM S15) under climatic conditions in the Recôncavo region of Bahia, Brazil. The experiment was conducted between November 2022 and July 2023 in a completely randomized design with four groups (n = 8): aqueous control, oil control, aqueous suspension, and oil formulation of M. robertsii. Egg counts per gram of feces (EPG) and L3 larval recovery were assessed by coproculture and the Baermann technique. Efficacy ranged from 15.23% to 27.34%, with the oil formulation showing higher performance. Haemonchus sp. and Trichostrongylus sp. were the most prevalent genera. These findings suggest the potential of M. robertsii (LCM S15) as a biological control agent under field conditions. Full article

Three new species of free-living marine nematodes, which were collected from Chinese marine waters, are herein described and illustrated. Metadesmolaimus pilosus sp. nov. is distinguished by a colourless body bearing numerous long somatic setae; cephalic setae measuring 13–17 µm in length; arcuate spicules with a cephalated proximal end and a conical, pointed distal end, approximately 1.6 cloacal body diameters long; a boat-shaped gubernaculum without apophyses; and a conico-cylindrical tail with three terminal setae. M. sinicus sp. nov. is distinguished by a relatively large amphideal fovea (53% of corresponding body diameter) in males; cephalic setae measuring 12 µm in length; slender, almost straight spicules, with a cephalated proximal end and a conical distal end, approximately 1.9 cloacal body diameters long; gubernaculum hooked distally without apophysis; and tail conico-cylindrical with two terminal setae. Steineria gracilis sp. nov. is distinguished by outer labial setae comparatively thick; eight groups of subcephalic setae, each comprising four unequal setae, 15–49 µm long; two sublateral pairs of cervical setae posterior to each amphid; circular amphideal fovea located about one head diameter from the anterior end; spicules slightly bent ventrally, approximately 1.2–1.3 cloacal body diameters long; gubernaculum sleeve-shaped with hooked dorso-caudal apophyses; and tails with two long terminal setae and two short terminal setae. Updated keys to all valid species of Metadesmolaimus and Steineria are provided. Full article

Rice straw mulching is a soil management practice that influences soil microbial communities. However, its effects on nematode communities under upland rice systems in salt-affected soils remain unclear. This study examined nematode community responses to rice straw mulching at rates of 0, 3.5, 7.0, and 10.5 t ha⁻¹ in paddy fields at two sites, Lieu Tu and Long Phu, in Soc Trang Province, Mekong Delta, Vietnam. A total of 37 and 35 nematode genera were identified in Lieu Tu and Long Phu, respectively. Bacterivores were the dominant group, followed by herbivores. Acrobeloides, Hirschmanniella, Chronogaster, Aporcelaimellus, and Prismatolaimus were prevalent in Long Phu, while Acrobeloides, Prismatolaimus, Hirschmanniella, and Alaimus dominated in Lieu Tu. The highest mulching rate (10.5 t ha⁻¹) increased total nematode abundance, particularly cp1 and cp2 groups in Long Phu, while the application of 7.0 t ha⁻¹ increased the proportion of omnivorous feeders in Lieu Tu. Mulching increased total nematode biomass and metabolic footprints, indicating improved soil fertility. At Long Phu, mulching also increased biodiversity, as reflected by the higher species richness and Shannon–Wiener indices. The highest mulching application rate (10.5 t ha⁻¹) increased the relative abundance of cp2 functional guilds at both sites. Mulching reduced the relative abundance of plant-parasitic nematodes at both sites, and increased cowpea yield from 5.1 to 13.9 t ha⁻¹ and 5.67 to 9.70 t ha⁻¹ at Lieu Tu and Long Phu, respectively. These findings suggest that the rice straw mulching at 10.5 t ha⁻¹ improves soil structure and nematode diversity, thereby supporting agricultural sustainability in salt-affected soils under climate change conditions. Full article

Four new species of Chromadorea (Nematoda) from marine benthic habitats in Chinese sea areas are described and illustrated. Halichoanolaimus parvulus sp. nov. is characterized by a comparatively smaller body; amphideal fovea comprising 4.5–5 turns; spicules arched, middle portion broad, progressively attenuating distally; gubernaculum slender, comprising two detached lateral elements becoming narrower toward the distal end; a short precloacal seta present; tail conico-cylindrical with three-fifths cylindrical portion in males. Cobbionema sinica sp. nov. is characterized by a pharynx with a distinct anterior bulb and an enlarged posterior portion; cephalic setae measuring 6 µm in length; amphideal fovea consisting of 4–4.5 turns; spicules 2.1–2.5 cloacal body diameters long, arrow-shaped; gubernaculum rod-like, parallel to the distal part of spicules, tail conico-cylindrical, terminating in an enlarged end and a distinct spinneret; precloacal supplement absent. Linhystera longispicula sp. nov. is characterized by cuticle with subtle transverse striations; six lateral labial sensory setae and four cephalic sensory setae are setiform, collectively forming a single circle; buccal cavity minute and slit-like, amphideal fovea circular far from the anterior end; curved, stout spicules reach a length exceeding two times the cloacal body diameter; gubernaculum is absent; conico-cylindrical tail without terminal setae. Linhystera nanhaiensis sp. nov. also has the common characteristics of the genus. It has relatively large body size with long conico-cylindrical tail; three terminal setae present; spicules resembling ox horns, reaching 1.2 times the cloacal body diameter, gubernaculum absent. This work contributes to the study of nematode diversity in China. Full article

Several species of saprophytic filamentous fungi are able of disrupting the life cycle of certain soil-born parasites that are of veterinary and agronomy importance, offering a promising sustainable control alternative. This study consisted of designing an experimental model, using catnip (Nepeta cataria) trays to simulate a vegetated environment for evaluating the parasiticidal activity of Mucor circinelloides, Trichoderma atrobrunneum, and Duddingtonia flagrans. Fungal spores were added to treated trays before adding feces with protozoan (Eimeria spp.), and gastrointestinal nematodes (roundworms, strongyles), and untreated-control water. No differences in plant growth or vigor, regardless of fungal presence, were observed, confirming the safety of these biological agents for vegetation. In the control trays, the viability of parasites ranged from 50% to 85%. In the treated trays, the viability of Eimeria and roundworms decreased by 40–100%, and the strongyle egg counts were reduced by 74% within 15 days. It is concluded that the vegetated tray model effectively simulates field conditions and provides a reliable platform for evaluating fungal efficacy against the free-living stages of parasites, offering a versatile tool for future research on soil-borne pathogens affecting animals and plants. Full article

The active constituents of essential plant oils (EOAIs), monoterpenoid carvacrol and monoterpene p-cymene, are widely distributed in many aromatic plants and their products. They differ in that carvacrol has a phenolic functional group. The numerous pharmacological effects of these two EOAIs are well known. In different doses/concentrations, they exhibit analgesic, neuroprotective, vasorelaxant, anti-inflammatory, antiviral, antibacterial and antiparasitic effects. The acute toxicity of carvacrol and p-cymene in rats and the free-living nematode Caenorhabditis elegans was investigated. Furthermore, the impact of subacute administration of these two terpenes on general health, CNS integration, i.e., motor coordination and balance of rats, as well as their effects on the movement of adult C. elegans, was also examined. The aim was to compare the effects and describe in more detail the selective toxicity of carvacrol and p-cymene. The calculated LD₅₀ value of carvacrol was 790.15 ± 1.15 mg/kg, while the LD₅₀ value of p-cymene is above 3000 mg/kg. Tested doses of carvacrol and p-cymene administered for 28 days (50, 100, and 200 mg/kg) did not exert any effect on the CNS of rats or cause any clinical disorders. LC₅₀ value of carvacrol for adult C. elegans was 184.13 ± 1.51 μM and for p-cymene 1268 ± 1.65 μM. In subacute testing, carvacrol showed negative effects on C. elegans reproduction, distance traveled, movement speed and rotational index at lower concentrations than p-cymene, indicating higher toxicity, which may be due to its phenolic structure. On the other hand, although less toxic to C. elegans, p-cymene exhibited a specific effect on worm motility, with more rolling which should be further investigated, and can be a consequence of cuticle damage or loss of orientation. Full article

Nematodes in the genus Oscheius (Rhabditidae) have traditionally been regarded as free-living bacteriophagous or necromenic associates of insects. Over the past two decades, however, multiple Oscheius species and isolates have been shown to express facultative pathogenicity toward insects and, in some cases, parasitism of mollusks. This has stimulated interest in Oscheius as a complementary group of biological control agents that may function under conditions limiting classical entomopathogenic nematodes (EPNs) of the genera Steinernema and Heterorhabditis. Here, we synthesize current knowledge on Oscheius taxonomy and diversity, life-history strategies, bacterial associations and virulence mechanisms, evidence for control of insect and mollusk pests, and recent advances in chemo-ecology relevant to host finding. We emphasize that Oscheius represents a continuum of ecological strategies, and we adopt conservative terminology in which “entomopathogenic” is reserved for Oscheius species/isolates that meet operational criteria of insect pathogenicity. Finally, we highlight key barriers to wider implementation—strain variability, bacterial partner instability, non-target and community effects, and production/quality control needs—and propose research priorities for the development of robust, field-reliable Oscheius-based biocontrol. Full article

Regenerative agriculture is oriented around restoring soil health through natural processes. In this context, soil biota plays a central role, and bioinoculation represents a potentially effective approach for targeted modification of microbial communities. Among beneficial microorganisms, Trichoderma atroviride is prominent for its biocontrol agent (BCA) activity against plant-parasitic nematodes (PPNs), whereas its effects on free-living nematodes (FLNs) under in vivo conditions remain insufficiently explored. The aim of this study was to assess the response of nematode communities to bioinoculation with T. atroviride as an indicator of soil functional status. A three-year field study was conducted in organic olive orchards at Vodnjan and Nadin on four autochthonous olive cultivars, applying two inoculum doses of T. atroviride: 1 × 10⁶ spores mL⁻¹ (LD) and 1 × 10⁸ spores mL⁻¹ (HD). Bioinoculation increased the diversity of the soil nematode communities at both locations. However, the responses differed between the two inoculum doses. Both doses were associated with an increased abundance of FLNs and a reduced abundance of herbivorous nematodes relative to the control, with LD showing a more consistent and ecologically favourable effect. In combination with biotic and abiotic factors, the LD dose was associated with greater trophic diversity and a more structured soil food web, whereas increasing the inoculum concentration (HD) did not result in additional functional improvement. Full article

The free-living infective juveniles of entomopathogenic nematodes (EPNs) are critical biological control agents against insect pests. The field efficacy of EPNs is largely determined by their tolerance to low-humidity stress, a trait closely linked to the mobilization of their energy reserves. This study aims to investigate how varying levels of humidity stress influence energy reserve dynamics in two EPNs, Steinernema kraussei 0657L and Heterorhabditis brevicaudis 0641TY, and their relationship with the survival rate and pathogenicity. The results demonstrated that lipids were the predominant energy reserve, followed by proteins and sugars. Notably, neutral lipid constituted approximately 3% of the total lipid content. Among sugars, soluble sugar levels were the highest, followed by glycogen and trehalose. Exposure to low-humidity stress resulted in increased levels of protein, total lipid, glycogen, and trehalose in nematodes. These increases were more pronounced in S. kraussei 0657L, a highly drought-resistant strain, compared to H. brevicaudis 0641TY. Furthermore, the accumulation of protein, total lipid, and trehalose was negatively correlated with survival rate and pathogenicity. However, positive correlations were observed between trehalose and both total lipids and soluble sugars. Furthermore, transcriptome analysis revealed that under low-humidity stress, S. kraussei 0657L exhibited an enrichment of differentially expressed genes (DEGs) involved in glycolysis/gluconeogenesis, fatty acid metabolism, and glycerophospholipid metabolism pathways. This indicates that S. kraussei 0657L regulated energy metabolism to adapt to low-humidity stress. These findings provide insights into the mechanisms underlying drought resistance in EPNs and offer an experimental basis for their application in arid environments. Full article

Three free-living marine nematode species of the family Desmodoridae are described and illustrated based on light and scanning electron microscopy. Pseudochromadora paraparva sp. nov. was collected from muddy sand sediments at Eulwangri Beach, Incheon, Korea, and P. capitata sp. nov. from sublittoral muddy sediments off Jindo Island, Korea. Metachromadora itoi Kito, 1978, is also recorded for the first time from Korean waters, based on specimens from sandy sediments off Jeju Island. Pseudochromadora paraparva sp. nov. is distinguished from P. parva Gagarin & Thanh, 2008 and related congeners by having a tripartite cephalic region consisting of a jar-shaped main capsule, an anterior transition zone with weaker cuticle bearing the cephalic setae, and a highly elevated hat-shaped labial region. It additionally shows a sexually dimorphic amphideal fovea, a unique arrangement of precloacal thorns, a gubernaculum with a dorsal apophysis, and ventral thorns lacking cuticular hillocks. Pseudochromadora capitata sp. nov. is characterized by a cephalic region composed of a rounded labial region and a thickly cuticularized main capsule, together with a sexually dimorphic amphideal fovea, arcuate spicules with a large hammer-shaped capitulum, a gubernaculum with a dorsal apophysis, and 3–8 precloacal and 3–5 postcloacal thorns arranged in a row. Molecular data (18S and 28S rRNA) were generated for both new species, and phylogenetic analyses support their placement within the genus Pseudochromadora and provide molecular evidence distinguishing them from closely related congeners. Scanning Electron Microscope (SEM) observations of M. itoi also revealed multiple configurations of the buccal cavity, providing additional morphological information useful for understanding structural variation within the genus. These findings refine the taxonomic framework within the Desmodoridae and expand current knowledge of morphological diversity in free-living marine nematodes. Full article

This paper reports two newly discovered species of Tricoma (Tricoma)—T. (T.) discrepans sp. nov. and T. (T.) parasetosa sp. nov.—obtained from the subtidal sediments at a depth of 13 m around Jindo Island, Korea. Tricoma (T.) discrepans sp. nov. differs from its congeners in possessing 40–41 main rings, an uncovered first main ring, large vesicular amphidial fovea, and a distinctly thickened tail cuticle that is densely covered with secretions and adhering particles. Somatic setae in males exhibit pronounced sexual dimorphism, with the subventral setae more than twice as thick as the subdorsal setae, a morphological feature documented here for the first time within the subgenus Tricoma (Tricoma). Tricoma (T.) parasetosa sp. nov. can be recognized by 31 (rarely 32) main rings, two pairs of long, thick posterior somatic setae inserted on massive peduncles, a vesicular amphidial fovea extending to the second main ring, and a gubernaculum proximal end gently curved ventrally. Although the labial region is indistinct, the species bears two conspicuous lateral labial projections and a prominent cephalic concretion. Together, these results broaden the current understanding of Tricoma diversity in the northwestern Pacific and emphasize additional morphological variation within Desmoscolecida based on detailed Differential Interference Contrast (DIC) and Scanning Electron Microscope (SEM) analyses. Full article

Two new species of free-living marine nematodes were collected in the Yellow Sea, China, and they are described herein as Actinonema sinica sp. nov. and Comesoma zhangi sp. nov. Actinonema sinica sp. nov. is characterized by short cephalic setae; lateral differentiation consisting of a row of longitudinal sclerotized bars and beginning at the level of anterior third of the pharyngeal region; horn-shaped telamons; a curved rod-shaped gubernaculum; and an elongate conical tail with a smooth, pointed tip. Comesoma zhangi sp. nov. is characterized by long, thick cephalic setae, reaching up to 28 µm in length; a cup-shaped buccal cavity lacking a tooth and narrowing posteriorly with small projections; an amphidial fovea with two turns; slender, arcuate spicules 2.6 times the cloacal body diameter in length, lacking a proximal capitulum; a plate-like gubernaculum without apophysis; and the absence of precloacal supplements. Updated keys to the valid species of the genus Actinonema and the genus Comesoma are provided. A comparative morphological table of all currently accepted species of Comesoma is also provided. Full article

Meiofaunal assemblages are crucial components of benthic ecosystems, significantly contributing to organic matter cycling and energy transfer. However, baseline quantitative data from some upwelling systems remain limited. This study characterizes the abundance, vertical distribution, and secondary production of meiofauna at a coastal upwelling station off southern Peru (14°16′ S) for July 2006 (Neutral conditions) and May 2007 (moderate La Niña, LN), using four-replicated sediment cores sectioned into 0–1, 1–2, 2–5, and 5–10 cm layers. While Nematoda (families Desmodoridae, Chromadoridae, Monhysteridae, Oxystominidae, Comesomatidae) dominated the community (>79% in all layers, both years), the total taxonomic richness did not differ substantially between study periods nor across the sediment column for 2006 or for 2007. Total density (0–10 cm) fluctuated between 3916 ± 2202 Ind 10 cm⁻² in 2006 and 4203 ± 2274 Ind 10 cm⁻² in 2007, with non-significant changes. Biomass (µgC 10 cm⁻²) in 2006 ranged from 80 ± 24 in the 5–10 cm section to 455 ± 134 in the 2–5 cm section. The uppermost 0–1 cm layer showed 238 ± 155, while the 1–2 cm section reached 302 ± 69. In 2007, biomass was consistently higher in the surface layers, with maximum values in the 1–2 cm section (500 ± 534), followed by the 0–1 cm section (376 ± 34). Hierarchical clustering produced depth-ordered groups with high within-depth similarity (>80–90%). SIMPER results identified Desmodora, Comesomatidae, and Chromadoridae among the top contributors to within-depth similarity and to the dissimilarity observed between surface and subsurface assemblages. A depth-related gradient of community composition was detected, suggesting vertical habitat heterogeneity modulated by several environmental factors; however, PERMANOVA analysis residuals (96.73%) indicate a high variation not explained by ENSO phase, sediment section, or their interaction, suggesting other unmeasured factors explaining meiofaunal community structure. Meiofauna’s production ranged from 2.836 ± 0.049 gC m⁻² y⁻¹ in 2006 to 3.106 ± 1.566 gC m⁻² y⁻¹ in 2007. These findings expand the limited knowledge on meiofaunal abundance and metabolic demands in this ocean region, fostering future efforts for comparative analyses across latitudes, depth gradients, and oceanographic regimes. Full article