The Caenorhabditis elegans DEG-3/DES-2 Channel Is a Betaine-Gated Receptor Insensitive to Monepantel

Natural plant compounds, such as betaine, are described to have nematocidal properties. Betaine also acts as a neurotransmitter in the free-living model nematode Caenorhabditis elegans, where it is required for normal motility. Worm motility is mediated by nicotinic acetylcholine receptors (nAChRs), including subunits from the nematode-specific DEG-3 group. Not all types of nAChRs in this group are associated with motility, and one of these is the DEG-3/DES-2 channel from C. elegans, which is involved in nociception and possibly chemotaxis. Interestingly, the activity of DEG-3/DES-2 channel from the parasitic nematode of ruminants, Haemonchus contortus, is modulated by monepantel and its sulfone metabolite, which belong to the amino-acetonitrile derivative anthelmintic drug class. Here, our aim was to advance the pharmacological knowledge of the DEG-3/DES-2 channel from C. elegans by functionally expressing the DEG-3/DES-2 channel in Xenopus laevis oocytes and using two-electrode voltage-clamp electrophysiology. We found that the DEG-3/DES-2 channel was more sensitive to betaine than ACh and choline, but insensitive to monepantel and monepantel sulfone when used as direct agonists and as allosteric modulators in co-application with betaine. These findings provide important insight into the pharmacology of DEG-3/DES-2 from C. elegans and highlight the pharmacological differences between non-parasitic and parasitic nematode species.

Feeding selectivity of Aphelenchoides besseyi and A. pseudogoodeyi on fungi associated with Florida strawberry

Aphelenchoides besseyi and A. pseudogoodeyi are foliar nematodes associated with commercial strawberry production in Florida, USA. The reproductive and feeding habits of these two nematode species were assessed on Florida isolates of the fungi Botrytis cinerea, Colletotrichum gloeosporioides, Macrophomina phaseolina, and Neopestalotiopsis spp. pathogenic to strawberry, and the non-pathogenic isolates of Fusarium oxysporum and Monilinia fructicola grown on PDA in petri dishes. Each culture was inoculated with six specimens with mix life stages of either A. besseyi and A. pseudogoodeyi and incubated at 24°C under axenic and non-axenic conditions 23 and 31 days after inoculation, respectively. Aphelenchoides besseyi reproduction rates were significantly higher on strawberry pathogenic isolates of B. cinerea, C. gloeosporioides, and Neopestalotiopsis rosae than on the non-pathogenic isolates of F. oxysporum and M. fructicola. In contrast, reproductive rates of A. pseudogoodeyi did not significantly vary across the fungi cultures. For both nematode species, Macrophomina phaseolina was a poor host because it did not produce mycelium on the media used. Our findings indicate that A. besseyi is more selective in its fungal-feeding preference than A. pseudogoodeyi. Additionally, A. pseudogoodeyi eggs and juveniles were significantly higher than adults. Yet, for A. besseyi, adult stages were more common. Fungi aid in the maintenance of soil-dwelling populations of these two nematode species. Removing fungi-infected strawberry plant residues is both a desirable and effective management practice to limit A. besseyi in central Florida commercial strawberry fields.

Meta-analysis of the field efficacy of seed- and soil-applied nematicides on Meloidogyne incognita and Rotylenchulus reniformis across the U. S. Cotton Belt

Meta-analysis was used to compare yield protection and nematode suppression provided by two, seed- and two, soil-applied nematicides against Meloidogyne incognita and Rotylenchulus reniformis on cotton across three years and several trial locations in the United States Cotton Belt. Nematicides consisted of thiodicarb- and fluopyram-treated seed, aldicarb and fluopyram applied in-furrow and combinations of the seed treatments and soil-applied fluopyram. The nematicides had no effect on nematode reproduction or root infection but had a significant impact on seed cotton yield response (¯D) with an average increase of 176 and 197 kg/ha relative to the nontreated control in M. incognita and R. reniformis infested fields, respectively. However, because of significant variation in yield protection and nematode suppression by nematicides, five or six moderator variables [cultivar resistance (M. incognita only), nematode infestation level, nematicide treatment, application method, trial location, and growing season] were used depending on nematode species. In M. incognita infested fields, greater yield protection was observed with nematicides applied in-furrow and seed-applied + in-furrow than solo seed-applied nematicide applications. Most notably of these in-furrow nematicides were aldicarb and fluopyram (>131 g/ha) with or without a seed-applied nematicide compared to thiodicarb. In R. reniformis infested fields, moderator variables provided no further explanation of the variation in yield response by nematicides. Furthermore, moderator variables provided little explanation of the variation in nematode suppression by nematicides in M. incognita and R. reniformis infested fields. The limited explanation by the moderator variables on the field efficacy of nematicides in M. incognita and R. reniformis infested fields demonstrates the difficulty of managing these pathogens with nonfumigant nematicides across the U. S. Cotton Belt.

The Predation Behaviour of Fictor composticola on Parasitic Nematodes of Button Mushroom, Agaricus bisporus

In this study, the predation behaviour of male and female predatory nematode, Fictor composticola, was studied on five prey nematode species, Aphelenchus avenae, Aphelenchoides swarupi, Ditylenchus myceliophagus, Bursilla sp. and Panagrolaimus sp., found in the white button mushroom compost. The period of the study is of six months. The data recorded on number of encounters, part of the body of prey attacked, stage of the prey attacked, duration of feeding etc. The strike rate and prey susceptibility were calculated. The average number of encounters on all the five preys done by female F. composticola was 3.0 and that of the male was 6.0. Male F. composticola had more number of encounters on the prey nematode species than the females. Both the sexes preferred juvenile stages over adults as prey. The most attacked part by both females and males predator, was the posterior part of the prey body. In 80% of cases, female predators fed on the first encountered prey while males attacked the first encountered prey in 30% of cases only. The strike rate of female F. composticola was more (78.6%) than the male (48.2%). Mycophagous nematodes were more susceptible to predator’s attack than the microbivorous nematodes. The strike rate of the predator on different prey nematode species was found more on mycophagous nematodes than on microbivorous nematodes and minimum on Panagrolaimus sp. The average feeding duration of female F. composticola was 8 min and 31 sec and in the case of males it was 4 min and 11 sec.

Phytonematodes as a limiting biotic factor of agricultural production in the world (review)

Purpose. To analyze domestic and foreign scientific literature on the species composition and harmfulness of the world's most dangerous parasitic species of phytonematodes in crops. Results. Today, according to the available literature, the most dangerous species of phytonematodes include: gall nematode (Meloidogyne spp.), cyst-forming nematode (Heterodera spp. and Globodera spp.), root lesion nematode (Pratylenchus spp.), banana drill nematode (Radoholus similis), stem nematode (Ditylenchus dipsaci), pine stem nematode (Bursaphelenchus xylophilus), reniform nematode (Rotylenchulus reniformis), xiphinema index (Xiphinema index), false head nematode (Nacobbus aberrans), and rice leaf nematode (Aphelenchoides besseyi). Conclusions. The results of research on the prevalence and harmfulness of parasitic nematode species in crops convince us of the need for a more detailed study of this group of microorganisms. Due to the rapid development of molecular genetic methods in the last decade, scientists have been able to expand and improve their knowledge of identifying species, races and pathotypes of phytonematodes, their biological and environmental characteristics, and most importantly, to discover and understand extremely complex mechanisms of parasite and host plants. Nematologists are confident that further research in these and other areas in the future will create a basis for developing a new strategy for long-term and environmentally safe control of these dangerous plant parasites.

Report of Dirofilaria immitis infection with acute cardiopulmonary complications in a cat from Northeastern Brazil

Dirofilariasis is a zoonotic disease caused by Dirofilaria immitis, a nematode found mainly in the pulmonary artery and right chambers of the heart, lungs, and large vessels of dogs. This parasitism also occasionally occurs in cats, causing an amicrofilaremic and asymptomatic infection, resulting in severe illness and rapid death. In this case report, it was described acute clinical signs and histopathological alterations in a domestic cat with heartworm disease from the city of Mossoró, the Rio Grande do Norte, Brazil. The nematode species, D. immitis, was confirmed by morphological and molecular analyses. This is the first documented and full report of feline heartworm disease in northeastern Brazil.

Database of glutamate gated chloride (GluCl) subunits across 125 nematode species: patterns of gene accretion and sequence diversification

Glutamate Gated Chloride (GluCl) channels belong to the Cys-loop receptor superfamily. GluCl channels are activated by glutamate (Glu) and form substrates for the anti-parasitic drugs from the avermectin family. GluCl channels are pentameric, and each subunit contains an N-terminal extracellular domain that binds Glu and four helical transmembrane domains (TMs), which contain binding sites for avermectin drugs. In order to provide more insight into phylum-wide patterns of GluCl subunit gene expansion and sequence diversity across nematodes, we have developed a database of predicted GluCl subunit genes from 125 nematode species. Our analysis into this dataset described assorted patterns of species-specific GluCl gene counts across different nematodes as well as sequence diversity in key residues thought to be involved in avermectin binding.

Assessment of Biodegradation and Eco-Toxic Properties of Novel Starch and Gelatine Blend Bioplastics

To combat the release of petroleum-derived plastics into the environment the European Commission has adopted the EU plastics strategy, which aims for a complete ban on single-use plastics by 2030. Environmentally friendly and sustainable packaging like bioplastic is being up taken at significant levels by companies and consumers. In this study, the environmental impact of novel gelatine–starch blend bioplastics is investigated. The assessments included ecotoxicology with different species that can be found in marine and soil environments to simulate natural conditions. Microalgae, plant, and nematode species were chosen as these are representative of their habitats and are known for their sensitivity to pollutants. Degradation rates of these novel bioplastics were assessed as well as microbiome analysis of the soil before and after bioplastic degradation. The main findings of this study are that (i) the bioplastic generated can be fully biodegraded in soil environments at moderate conditions (20 °C) leaving no physical traces; (ii) bioplastic did not exhibit significantly adverse effects on any organisms assessed in this study; (iii) microbiome analysis of the soil after biodegradation showed a decrease in alpha diversity and a significant increase of Actinobacteria and Firmicutes phyla, which were dominative in the soil.