Nematode Strains Research Articles

Comparison of silver nanoparticles and AgNO<sub>3</sub> toxic effects on <i>Caenorhabditis elegans</i> with a genetic disorder of copper metabolism

BACKGROUND: Silver nanoparticles are widely used in various types of industry, but their safety for humans has not been strictly proven. The experimental data currently available on the comparison of the toxic effect of silver nanoparticles and AgNO3 are contradictory and the question of the priority use of silver nanoparticles remains open, especially for organisms with impaired copper metabolism. AIM: The main aim of this study is to compare the effects of silver nanoparticles and AgNO3 on the nematode with normal and impaired copper metabolism and draw conclusions about their toxicity. MATERIALS AND METHODS: In this work, we determined the sublethal concentration (LC50) of AgNPs and AgNO3 for H828Q nematode strain. Using the results obtained, we performed the development assay, thrashing assay and lifespan analysis of the animals. RESULTS: It has been shown that LC50 of silver nanoparticles is lower than the one for AgNO3. Caenorhabditis elegans with impaired copper metabolism treated with silver nanoparticles have a statistically significant reduction in development, level of mobility and lifespan, comparing to animals treated with AgNO3. CONCLUSIONS: The results obtained allow us to conclude that the toxic effect of silver nanoparticles on C. elegans with a genetic defect in copper metabolism is higher comparing to ionic silver.

Ecological aspects of three strains of entomopathogenic nematodes from the department of Lambayeque-Peru

BackgroundEntomopathogenic nematodes (EPN) are used as a biological control agent for different insect pests in agriculture. The genera Heterorhabditis and Steinernema are the most used commercially. For an EPN species to be used as a biological controller, it is necessary to know its ecological aspects, including reproductive potential, movement capacity, and mean lethal concentration (LC50). These aspects were evaluated in three EPN strains isolated in Galleria mellonella larvae collected in the Lambayeque-Peru region, to determine if they are promising as biological controllers. The strains of EPN studied are Heterorhabditis sp. (PC9 strain), H. bacteriophora Poinar (PM10 strain), and Steinernema diaprepesi Nguyen y Duncan (SV19 strain).ResultsHeterorhabditis sp. (PC9 strain) and H. bacteriophora (PM10 strain) had high production of infective juveniles (IJs): 217.750 and 186.800, respectively, while S. diaprepesi (SV19 strain) only reached 84.150 IJs. The movement capacity of Heterorhabditis sp. (PC9 strain) and H. bacteriophora (PM10 strain) reached a depth of 15 cm to parasitize G. mellonella larvae, while S. diaprepesi (SV19 strain) only reached 10 cm. In decreasing order, the LC50 value of S. diaprepesi (SV19 strain), Heterorhabditis sp. (PC9 strain) and H. bacteriophora (PM10 strain) were: 24.03, 13.74, and 8.19 IJs/ml, respectively.ConclusionsHeterorhabditis sp. PC9 and H. bacteriophora PM10 are promising a biological control agent because they present great production of IJs, great displacement capacity, and high pathogenicity against G. mellonella. Additionally, both strains present a mixed search strategy or seeker-hunter (seeker-browser).

ENTOMOPATHOGENIC NEMATODES ASSOCIATION WITH SOIL- DWELLING BACTERIA: THE CASE OF STEINERNEMA FELTIAE

The symbiosis of entomopathogenic nematodes (EPNs) with bacteria in the genera Photorhabdus and Xenorhabdus is well known. However, other soil-dwelling bacteria can occasionally be isolated from EPNs collected from diseased larvae. Accordingly, through several studies, we have detected the presence of diverse bacterial species including isolates of Pseudomonas protegens and Serratia spp., in the body of different strains of the entomopathogenic nematode Steinernema feltiae. After documenting the presence of such bacteria inside the nematodes, both nematodes and EPN-associated bacteria were cultured, and bioassays were conducted to determine their potential against different insect targets. An isolate of P. protegens caused over 60% and 90% mortality of house fly and corn earworm larvae, respectively. These insecticidal effects were dose-dependent. The presence of the bacterium confers virulence to the nematode. According to our studies, it appears that these non-core bacteria can establish occasional or stable associations with S. feltiae. Key Words: Biological control, EPN, bacteria, symbiosis, Pseudomonas, soil, bioinsecticide.

New wild-type isolates of the nematode genera <i>Oscheius, Alloionema</i>, and a different rhabditid genus (Nematoda: Rhabditida) found in forests of Vietnam

In this report, we describe the isolation and determination of four new free-living nematode (FLN) strains of three species in different nematode genera (Oscheius, Alloionema, and another rhabditid genus) from Cat Tien and Cuc Phuong National Parks, Vietnam using the isolation protocol for Caenorhabditis nematodes. Of the four strains, three strains were similar to the previous determinants and one strain may be a new rhabditid species that was first found in Vietnam. They can grow well on the E. coli OP50 – seeded media (New Cheap Media No. 18 (NcM18) and Nematode Growth Media (NGM)). Compared with the isolation of the Caenorhabditis nematodes in the same scenario, the frequencies of finding these three genera were low because of the inappropriate isolation method employed by the Caenorhabditis nematodes. This data supports knowledge of the FLN diversity and implies that FLNs that stay uncovered in forestry ecosystems should be uncovered using different isolation methods for the nematode order Rhabditida, i.e. entomopathogenic nematodes (EPNs), helminths, and the superfamily Rhabditidae.

Interaction between Steinernema feltiae SC125 and Metarhizium anisopliae sensu lato 9236 for control of the Guatemalan potato moth

ABSTRACT The Guatemalan potato moth (Tecia solanivora) is one of the most destructive pests affecting potatoes in Colombia. Our objective was to evaluate the susceptibility of T. solanivora to a combination of entomopathogenic nematodes and entomopathogenic fungi, to study the interactions of these two agents under laboratory conditions. We evaluated the mortality of fourth instar larvae against 200 Infective Juveniles (IJs) per larva of ten strains of entomopathogenic nematodes, and 104–108 conidia per larva of Beauveria bassiana sensu lato Bb9205 and Metarhizium anisopliae sensu lato Ma9236. We found that Steinernema feltiae SC125 caused a mortality rate of 98.2% with an LC50 of 33 IJs/larva. M. anisopliae sensu lato Ma9236 achieved a mortality rate of 88.8% with an LC50 of 6.9 × 105 conidia/larva. We selected these strains for the interaction tests. We determined that the interaction test results were statistically additive regardless of any difference in application times of the entomopathogens and despite the observation of signs of infection in the hosts from both the nematode and the fungus. Despite not having found synergistic interactions between the evaluated control agents, these laboratory tests suggest a possible strategy of combining entomopathogenic nematode and fungi for biological management of the guatemalan moth T. solanivora in potato crops.

Characterisation and toxins analysis of symbiotic bacteria Photorhabdus luminescens isolated from Heterorhabditis indica ICRI-18 strain

Entomopathogenic nematodes are proven alternatives to pesticides in crop protection as they belong to the Heterorhabditidae and Steinernematidae families. The role of entomopathogenic nematodes has expanded considerably in the recent past for their efficacy as biopesticide which is influenced by nematode species and strain. Members of the genus Heterorhabditis have been found to harbor a symbiotic bacteria Photorhabdus sp. When the nematode is ingested by the insect, Photorhabdus sp. is released into the host haemocoel where they multiply rapidly and kill the insect. The main objective of our research was to examine the insect killing toxin property of symbiotic bacteria isolated from the entomopathogenic nematodes Heterorhabditis indica. The antagonistic potential of insecticidal toxin from Photorhabdus sp. was investigated. The results prove that toxic components produced by these bacteria could kill pests either through ingestion or injection. The broad-spectrum antimicrobial property produced by Photorhabdus sp. was analysed by conducting both antibiogram and antibiosis studies.

Analysis of Protection and Immune Response against Teladorsagia circumcincta in Goats Immunised with Thiol-Binding Proteins from Adult Worms.

In view of the increasing occurrence of anthelmintic-resistant strains of gastrointestinal nematodes in ruminants, various alternative control strategies have been investigated, such as those based on the induction of protective immune responses by immunisation with parasite antigens. In this study, the protective activity of somatic antigens from adult worms of Teladorsagia circumcincta purified by affinity chromatography on thiol-sepharose was analysed in goats. After challenge, the enriched products induced a slight reduction in the cumulative faecal egg counts (21%) and in the number of worms (23.3%), with a greater effect on female worms, which also showed a reduction in parameters related to their fertility. These parasitological findings were associated with a Th2 immune response, with a prominent local humoral response and an eosinophilic infiltrate in the gastric mucosa (negatively associated with the fertility of female worms and the number of worms, respectively), as well as an infiltration of MCHII+, CD4+, IgG+ and IgA+ cells. However, several analyses showed an increase in CD8+ cells in the mucosa, as well as IL-2 expression in the gastric lymph nodes, which may have been associated with inhibition of protective responses or with the development of mixed Th1/Th2 responses, a finding that should be analysed in future studies.

The biocontrol nematode Phasmarhabditis hermaphrodita infects and increases mortality of Monadenia fidelis, a non-target terrestrial gastropod species endemic to the Pacific Northwest of North America, in laboratory conditions.

Inundative biological control (biocontrol) efforts in pest management lead to the mass distribution of commercialized biocontrol agents. Many 'biocontrol gone awry' incidents have resulted in disastrous biodiversity impacts, leading to increased scrutiny of biocontrol efforts. The nematode Phasmarhabditis hermaphrodita is sold as a biocontrol agent on three continents and targets pest gastropods such as Deroceras reticulatum, the Grey Field Slug; P. hermaphrodita is not presently approved for use in the United States. Investigations into the potential for P. hermaphrodita to infect non-target gastropod species of conservation relevance, however, are limited. We examined the effects of three strains of P. hermaphrodita on mortality in Monadenia fidelis, the Pacific Sideband, a snail species endemic to the Pacific Northwest of North America, in laboratory conditions. Across a 71-day laboratory infectivity assay, snails exposed to each of the three nematode strains, each analyzed at two doses, experienced a mean 50% mortality by days 20-42. All nematode-treated snails were dead by the end of the study. By contrast, 30/30 water-control snails experienced no mortality. Nematodes killed smaller, juvenile-stage snails significantly faster than those in larger and more developmentally advanced hosts. Our results provide direct evidence that the biocontrol nematode P. hermaphrodita infects and kills M. fidelis, a non-target gastropod species endemic to the Pacific Northwest, in laboratory conditions. This study suggests that introduction of P. hermaphrodita to new ecosystems might negatively impact endemic gastropod biodiversity and advocates for further investigation of non-target effects, including in conditions closer to the natural environments of non-target species.

Geographical distribution and phoretic associations of the viviparous nematode Tokorhabditis atripennis with Onthophagus dung beetles in Japan.

Viviparity is generally considered to be rare in animals. In nematodes, only six species of Rhabditida are viviparous. Five of these species have been identified in association with Onthophagus dung beetles, with Tokorhabditis atripennis being repeatedly isolated from the dung beetle Onthophagus atripennis in Japan. T. atripennis is easy to culture in a laboratory setting, and its host, O. atripennis, is distributed all over Japan. Therefore, T. atripennis is an ideal candidate for ecological and evolutionary studies on viviparity. However, the extent of their distribution and relationship with dung beetles, as well as habitats, remain unclear. In the present study, we conducted field surveys and successfully isolated 27 strains of viviparous nematodes associated with tunneler dung beetles from various regions of Japan, all of which were identified as T. atripennis. T. atripennis exhibited a strong association with Onthophagus dung beetles, especially O. apicetinctus and O. atripennis. And it was predominantly found in specific anatomical locations on the beetle bodies, such as the 'groove between pronotum and elytron' and the 'back of the wings'. Our findings suggest that Onthophagus species are the primary hosts for T. atripennis, and T. atripennis exhibits a close relationship with the living environments of tunneler beetles. This association may play a significant role in the evolution of viviparity in nematodes.

Anthelmintic efficacy evaluation and mechanism of N-methylbenzo[d]oxazol-2-amine

Parasitic roundworms cause significant sickness and mortality in animals and humans. In livestock, these nematodes have severe economic impact and result in losses in food production on a global scale. None of the currently available drugs ideally suit all treatment circumstances, and the development of drug-resistant nematode strains has become a challenge to control the infection. There is an urgent need to develop novel anthelmintic compounds. According to our previous report, N-methylbenzo[d]oxazol-2-amine (1) showed anthelmintic activity and lowest cytotoxicity. In this study, in vivo anthelmintic properties were evaluated using Trichinella spiralis infected mice. Toxicity was evaluated using the rats and mode of action using molecular docking and metabolomics approaches. The in vivo results demonstrate that a dose of 250 mg/kg reduced the T. spiralis abundance in the digestive tract by 49%. The 250 mg/kg Albendazole was served as control. The relatively low acute toxicity was categorized into chemical category 5, with an LD50 greater than 2000 mg/kg body. Molecular docking analysis showed the T. spiralis tubulin beta chain and glutamate-gated channels might not be the main targets of compound 1. Metabolomics analysis was used to explain the effects of compound 1 on the T. spiralis adult worm. The results demonstrated that compound 1 significantly up-regulated the metabolism of purine, pyrimidine and down-regulated sphingolipid metabolism. In conclusion, compound 1 could be a potential molecule for anthelmintic development. The bioavailability, pharmacokinetics, and absorption of this compound should be studied further to provide information for its future efficacy improvement.

Biocontrol potential of entomopathogenic nematode, Heterorhabditis indica against pink bollworm, Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae)

BackgroundThe emergence of pink bollworm (PBW), Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae), in cotton due to Bt resistance and concealed feeding habit has created a need for alternative, eco-friendly, and cost-effective control methods. This study aimed to evaluate the bio-efficacy and reproductive potential of two native strains of entomopathogenic nematodes (EPNs), Heterorhabditis indica, namely CICR-HI-CL and CICR-HI-MN, against PBW larvae and pupae under in-vitro conditions.ResultsThe larval assay revealed that strain CICR-HI-CL exhibited higher potency than strain CICR-HI-MN against 2nd, 3rd, and 4th instar larvae, with median lethal dose (LD50) values of 5.45, 4.45, and 4.60 infective juveniles (IJs) per larva, respectively. In case of pupal bioassay, both EPN strains demonstrated greater virulence when applied directly (LD50 values: 29.65 and 73.88 IJs per pupa for strains CICR-HI-CL and CICR-HI-MN, respectively) compared to soil application (147.84 and 272.38 IJs per pupa). Both EPN strains successfully penetrated and reproduced on 4th instar larvae, resulting in maximum production of 19.28 and 20.85 lakh IJs per larva in the next generation when inoculated at 30 IJs per larva.ConclusionThe present study has generated useful information on the virulence and reproductive potential of two strains of EPN H. indica (CICR-HI-CL and CICR-HI-MN) against PBW, a dreaded pest of cotton. Higher virulence and reproductive potential of EPN strains demonstrated their ability to multiply, sustain and perpetuate on larval and pupal stages of PBW. The knowledge generated will help formulate effective management strategies for PBW with the inclusion of EPN as a potential biological control candidate. The soil-dwelling life stages viz., last instar hibernating larvae and pupae of PBW can be the ideal weak links to make a successful use of H. indica for sustainable management of PBW in the cotton ecosystem. However, before taking these EPN strains to field for managing PBW, detailed studies investigating their biocontrol potential against PBW under field conditions are needed.

The nematode fauna of the digestive tract of goats in the Moscow region

The purpose of the research is to study the fauna of gastrointestinal nematodes of goats in the Moscow region. Materials and methods. The studies were carried out from December 2022 to April 2023. The object for the studies was the contents of the digestive tracts of 10 goats from small farms in the Moscow region, which were collected and fixed according to the method of K. I. Skryabin (1928). The species of detected nematodes were identified according to V. M. Ivashkin et al. (1989). A study of fecal samples was carried out, the genus of infective larvae was determined by the method of P. A. Polyakov (1953). Results and discussion. Three species of nematodes were detected: Haemonchus contortus, Trichostrongylus colubriformis and Teladorsagia circumcincta according to the results of helminthological necropsies of goats. The highest rate of infection was noted for H. contortus and the highest intensity of infection was noted for T. colubriformis. The nematode T. circumcincta was found only in one of 10 studied goats, in the amount of 13 worms. The larvae of Trichostrongylus, Oesophagostomum and Chabertia genera were identified according to their morphology in the examined feces samples in one of the seven farms. Many larvae of the first two genera were found, and Сhabertia larvae were single. The low species diversity noted in this study may be due to the presence of anthelmintic-resistant nematode strains.

What Is More Important to Host-Seeking Entomopathogenic Nematodes, Innate or Learned Preference?

Entomopathogenic nematodes (EPNs), small soil-dwelling non-segmented roundworms, are obligate parasites of insects and commonly used in agriculture for biological control of insect pests. For successful reproduction, EPNs must identify, move towards, and successfully infect a suitable insect host in a chemically complex soil environment. EPNs can have innate host insect preferences and can be attracted to semiochemicals associated with that host. They can also develop strong learned preferences for chemical signals associated with the presence of a host, such as herbivory-induced volatiles. We hypothesized that simultaneous manipulation of innate and learned preferences could result in increased biological control services of EPNs in agriculture. Separate cohorts of the EPN Steinernema diaprepesi were raised on two insect hosts, Galleria mellonella and Tenebrio molitor, for multiple generations until the nematodes in a dual-choice olfactometer exhibited preference for the host they were reared on. Subsequently, the two strains of nematodes were imprinted on three plant-produced terpenoids of agricultural significance: pregeijerene, β-caryophyllene, and α-pinene. After exposure to one of the plant compounds, the behavior of the EPNs was assayed in an olfactometer where the two host insects were presented with and without the plant compounds. We found that plant volatile exposure increased the infection rate of the nematodes, and some host–compound combinations proved to be attractive, but other combinations appeared to become repellent. These results indicate that learned preference is neither subordinate nor superior to innate preference, and that infection efficiency can vary with compound exposure and insect host.

Pathogenicity of native Strains of Entomopathogenic Nematodes against Aphids and Pseudostem Weevil

The pathogenicity of three native strains of entomopathogenic nematodes isolated from different locations of Kerala were evaluated against aphids, Aphis craccivora Koch and 4th instar grubs of banana pseudostem weevil, Odoiporous longicollis Olivier under laboratory condition. Based on the morphological characters and morphometric measurements, they were identified as Steinernema sp., Metarhabditis sp. and Rhabditis sp. Metarhabditis sp. @ 100 IJs (infective juveniles) recorded 100% mortality of aphids at 48 HAT (hours after treatment) and it was statistically on par with dimethoate 30EC. Metarhabditis sp.@ 100 and 200 IJs/ insect showed 47.49 and 62.66% mortality of pseudostem weevil grubs at 72 HAT. Molecular characterization of the most potent isolate effective against both the pests was done and it was identified as Metarhabditis rainai.

Effectiveness of botanical insecticides on larval stage of red palm weevil Rhynchophorous ferrugineus and survival of entomopathogenic nematodes

Botanical oils are considered ecofriendly compounds with insecticidal characteristics. In this study, the effects of basil (Ocimum basilicum), camphor (Cinnamomum camphora), cinnamon (Cinnamomum verum), lemon (Citrus limon), clove (Syzygium aromaticum), ginger (Zingiber officinale), black pepper (Piper nigrum), and orange (Citrus sinensis var balady) oil extracts on the survival of four entomopathogenic nematode strains belonging to the Steinernema and Heterorhabditis genera, as well as their impacts on Rhynchophorus ferrugineus egg hatching and larvae, were assessed. The results for the camphor, lemon, black pepper, and orange oils were promising as 50 μL/mL of each resulted in 0%, 0%, 16%, and 0% hatchability for the R. ferrugineus eggs, respectively. Furthermore, the mortality of R. ferrugineus larvae was up to 95% with the similar concentrations and an exposure time of 48 h, for the other investigated oils. Various morphohistopathological alterations were found in the cuticle; outer cuticle folds swelling or shrinkage and subcuticular muscle degeneration, as well as midgut; fat globules in the epithelial lining with marked degeneration and/or necrosis, of the R. ferrugineus larvae when compared with those of controls replicates. Mortality percentage of infective juveniles (IJs) of Steinernema carpocapsae (S2) was significantly lower than Heterorhabditis marelatus (D1), Steinernema riobravae (Sr) and Steinernema carpocapsae (All) when using camphor oil compared to the other oils (50%). From the obtained observations on oils lethal effects, the target of developing integral biocontrol product formulated from combinations of essential oils and nematode with insecticidal properties against R. ferrugineus (not nematode survival) is possible; a sustainable and ecofriendly product for pest management.

Isolation of Native Strains of Entomopathogenic Nematodes against Fall armyworm, Spodoptera frugiperda (Smith.) in Maize

Entomopathogenic Nematodes (EPNs) found in a variety of soil types, geographical regions, and hosts, which belong to the genera Steinernematidae and Heterorhabditidae, have the potential to act as biocontrol agents. In comparison to chemical and microbial pesticides, they performed better. A total of 87 soil samples were taken from regions where maize was grown in Tuticorin district, Tamil Nadu, India and they were examined for the presence of EPN in 2022–2023. By using the Corcyra baiting approach, a total of 9 samples (10.33%) showed EPN-positive sites. A total of 8 Steinernema sp. (13.33%) and 1 Heterorhabditis sp. (5.00%) were isolated from that population. EPN is identified at a generic level using the cadaver’s colour. Heterorhabditis displays brick red, while Steinernema exhibits creamy white. At a dose of 100–600 IJs/larva for the third and fifth instar, the isolated efficient native EPN strain (Kayathar strain) demonstrated mortality of 95.00–100.00% and 94.50–99.80%. According to the study, EPN showed considerable potent against Spodoptera frugiperda. So, EPNs may be used as a promising bio-control agent to battle pests of the maize crop.

Compatibility of Egyptian strains of entomopathogenic nematodes (Nematoda: Rhabditida) with insecticides and their activity against Spodoptera frugiperda (Lepidoptera: Noctuidae) under laboratory conditions.

Compatibility of Egyptian strains of entomopathogenic nematodes (Nematoda: Rhabditida) with insecticides and their activity against Spodoptera frugiperda (Lepidoptera: Noctuidae) under laboratory conditions.

Popillia japonica - Italian outbreak management.

Popillia japonica, a priority pest for the EU, was first detected in Northern Italy in 2014. Since its discovery, the outbreak extended over an area of more than 16,000 square kilometers in Northern Italy and Southern Switzerland. In this review, we summarize the state-of-the-art of research conducted in Italy on both the spreading capacity and control measures of P. japonica. Chemical, physical, and biological control measures deployed since its detection are presented, by highlighting their strengths and weaknesses. An in-depth study of the ecosystems invaded by P. japonica disclosed the presence and pathogenicity of natural strains of entomopathogenic fungi and nematodes, some of which have shown to be particularly aggressive towards the larvae of this pest under laboratory conditions. The Plant Health authorities of the Lombardy and Piedmont regions, with the support of several research institutions, played a crucial role in the initial eradication attempt and subsequently in containing the spread of P. japonica. Control measures were performed in the infested area to suppress adult populations of P. japonica by installing several traps (e.g., for mass trapping, for auto-dissemination of the fungus Metarhizium anisopliae, and "attract & kill"). For larval control, the infested fields were treated with commercial strains of the entomopathogenic fungus M. anisopliae and nematode Heterorhabditis bacteriophora. Future studies will aim at integrating phenological and spread models developed with the most effective control measures, within an ecologically sustainable approach.

Evaluation of Indigenous Strains of Entomopathogenic Nematodes, in Combination with Low-Toxicity Insecticides for Control of Fall Armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera, Noctuidae)

A study was conducted during November, 2021 to evaluate the efficacy of local strains of Steinernema feltiae and Heterorhabditis bacteriophora in combination with low-toxicity insecticides at low and high dosages to control fifth-instar larvae in under laboratory condition. The experimental location in Department of Entomology, Nematology Laboratory, Dr. Yashwant Singh Parmar University of Horticulture and Forestry, Solan, Himachal Pradesh, India. The use of S. feltiae+Spinosad or chlorantraniliprole caused larvae mortality of over 90% at 96 h and H. bacteriophora+Spinosad or Chlorantraniliprole mortality caused of over 95% mortality at 96 h after treatment at the high dose and may be considered as a least toxic strategy to control fall armyworm. Our results showed that these strains of H. bacteriophora have high pathogenicity against S. frugiperda and have potential for biological control in integrated approaches causing even combination with low-toxicity insecticides at low and high dosages may be considered 90% mortality fifth instar larval of S. frugiperda at 96 h at the high dose as a least toxic strategy to control fall armyworm. The use of S. feltiae+Spinosad or chlorantraniliprole and H. bacteriophora+Spinosad or chlorantraniliprole caused larvae mortality of over 90% high dose and should be included as a least toxic strategy to control fall armyworm. Native strains of entomopathogenic nematodes are active against S. frugiperda shows potential alternative to the severe use of chemical insecticides to control fall armyworm population in corn plantations.

Automated recognition and analysis of body bending behavior in C. elegans

BackgroundLocomotion behaviors of Caenorhabditis elegans play an important role in drug activity screening, anti-aging research, and toxicological assessment. Previous studies have provided important insights into drug activity screening, anti-aging, and toxicological research by manually counting the number of body bends. However, manual counting is often low-throughput and takes a lot of time and manpower. And it is easy to cause artificial bias and error in counting results.ResultsIn this paper, an algorithm is proposed for automatic counting and analysis of the body bending behavior of nematodes. First of all, the numerical coordinate regression method with convolutional neural network is used to obtain the head and tail coordinates. Next, curvature-based feature point extraction algorithm is used to calculate the feature points of the nematode centerline. Then the maximum distance between the peak point and the straight line between the pharynx and the tail is calculated. The number of body bends is counted according to the change in the maximum distance per frame.ConclusionExperiments are performed to prove the effectiveness of the proposed algorithm. The accuracy of head coordinate prediction is 0.993, and the accuracy of tail coordinate prediction is 0.990. The Pearson correlation coefficient between the results of the automatic count and manual count of the number of body bends is 0.998 and the mean absolute error is 1.931. Different strains of nematodes are selected to analyze differences in body bending behavior, demonstrating a relationship between nematode vitality and lifespan. The code is freely available at https://github.com/hthana/Body-Bend-Count.