Parasitylenchus myiophagus n. sp. (Nematoda: Parasitylenchidae), a tylenchid nematode parasite of long-legged flies (Diptera: Dolichopodidae)

A tylenchid nematode parasite of a male long-legged fly, Tachytrechus sanus Osten Sacken (Diptera: Dolichopodidae) from Montana, USA is described as Parasitylenchus myiophagus n. sp. (Nematoda: Parasitylenchidae). The new species is characterized by the presence of an extremely long first generation female and numerous short and wide second generation males and females produced in “enclosed” clusters in the host’s body cavity. Both generation female nematodes are ovoviviparous, with short stylets lacking knobs and simple tails lacking spikes, palps or mucrons. The second generation males have paired, separate spicules, short stylets, and a bursa but no visible gubernaculum. The fly host shows evidence of demasculinization, which is attributed to nematode parasitism. The gonads of the second generation adults are infected with a microsporidium (Microsporidia), which is a new host record for tylenchid nematodes. A tylenchid-infected Baltic amber dolichopodid shows that associations between these two organisms extend back at least to the Eocene.

Canalization and developmental stability of the yellow-necked mouse (Apodemus flavicollis) mandible and cranium related to age and nematode parasitism

Background Mammalian mandible and cranium are well-established model systems for studying canalization and developmental stability (DS) as two elements of developmental homeostasis. Nematode infections are usually acquired in early life and increase in intensity with age, while canalization and DS of rodent skulls could vary through late postnatal ontogeny. We aimed to estimate magnitudes and describe patterns of mandibular and cranial canalization and DS related to age and parasite intensity (diversity) in adult yellow-necked mice (Apodemus flavicollis). Results We found the absence of age-related changes in the levels of canalization for mandibular and cranial size and DS for mandibular size. However, individual measures of mandibular and cranial shape variance increased, while individual measures of mandibular shape fluctuating asymmetry (FA) decreased with age. We detected mandibular and cranial shape changes during postnatal ontogeny, but revealed no age-related dynamics of their covariance structure among and within individuals. Categories regarding parasitism differed in the level of canalization for cranial size and the level of DS for cranial shape. We observed differences in age-related dynamics of the level of canalization between non-parasitized and parasitized animals, as well as between yellow-necked mice parasitized by different number of nematode species. Likewise, individual measures of mandibular and cranial shape FA decreased with age for the mandible in the less parasitized category and increased for the cranium in the most parasitized category. Conclusions Our age-related results partly agree with previous findings. However, no rodent study so far has explored age-related changes in the magnitude of FA for mandibular size or mandibular and cranial FA covariance structure. This is the first study dealing with the nematode parasitism-related canalization and DS in rodents. We showed that nematode parasitism does not affect mandibular and cranial shape variation and covariance structure among and within individuals. However, parasite intensity (diversity) is related to ontogenetic dynamics of the levels of canalization and DS. Overall, additional studies on animals from natural populations are required before drawing some general conclusions.

Mixed Grazing and Dietary Supplementation Improve the Response to Gastrointestinal Nematode Parasitism and Production Performances of Goats

Small ruminants are very affected by gastrointestinal nematode (GIN) parasitism worldwide. The improvement of the host protective response and the reduction of the probability of contact between hosts and parasites appear as very promising strategies. The objective of this study was to evaluate the effect of a combination of two components of these two strategies on natural GIN infection and production performances of Creole goat kids: dietary supplementation and a rotational mixed grazing system. One hundred and twenty weaned Creole kids and six Creole heifers were divided into four experimental batches: Splus (supplemented) vs. Szero (non-supplemented) × Mixed grazing (kids associated with heifers) vs. Control (kids alone), and grazing plots of forage grasses were balanced for live weight (LW) in both species. The feed intake, blood, and parasitological parameters and production performances between 3 and 11 months of age were monitored. The fecal egg count (FEC) was significantly lower and the packed cell volume (PCV) significantly higher in the Mixed grazing groups. No effect of supplementation was observed for FEC. In contrast, PCV, body condition score, and live weight were significantly higher in supplemented animals whatever the groups. Mixed grazing system and supplementation had significant effects on the slaughter parameters (P < 0.05), but there was no significant interaction. Our results suggested that the advantage driven either by mixed grazing or dietary supplementation on kids' performances would be equivalent, and the combination of both would improve the animal performances.

Meloidogyne enterolobii, a threat to crop production with particular reference to sub-Saharan Africa: an extensive, critical and updated review

Summary Crop damage inflicted by Meloidogyne enterolobii justifies an updated literature review focusing on recent discoveries about its identification, biology and management. Since its description in 1983, M. enterolobii has become a pest of great concern, particularly due to its virulence, which renders controlling this nematode pest a challenge. The global distribution of M. enteroblii is summarised, with emphasis placed on limited research done for the species in sub-Saharan Africa where food production and security is threatened by root-knot nematode parasitism. Novel advances in methods used to detect M. enterolobii are touched upon, especially the improvement in advanced molecular techniques that complements shortcomings in morphology and morphometic approaches. Despite these exciting developments, the employment of effective management strategies to combat the species remains problematic. Future research on various aspects of M. enterolobii is crucial, with focus to be placed on the use of available resources to contain damage caused by this species.

The root-knot nematode: importance and impact on coffee in Brazil.

Coffee (Coffea spp.) is a crop of significant importance for Brazilian agribusiness, which in 2019 generated a gross revenue of US$3.73 billion. As a perennial crop, coffee stays in the field for many years, subjected to nematode parasitism from the seedling stage throughout the economic life of the plantation. In Brazil, it is a challenge for growers to produce coffee in the presence of the root-knot nematodes (RKN). Meloidogyne paranaensis and M. incognita are the most destructive species and their spread has expanded in recent years. This chapter discusses the economic importance, geographical distribution, host range, damage symptoms, biology and life cycle, interactions with other nematodes and pathogens, recommended integrated management, and management optimization of Meloidogyne paranaensis and M. incognita infesting coffee in Brazil.

Identification and Characterization of a Novel Protein Disulfide Isomerase Gene (MgPDI2) from Meloidogyne graminicola

Protein disulfide isomerase (PDI) is a multifunctional enzyme that catalyzes rate-limiting reactions such as disulfide bond formation, isomerization, and reduction. There is some evidence that indicates that PDI is also involved in host-pathogen interactions in plants. In this study, we show that the rice root-knot nematode, Meloidogyne graminicola, has evolved a secreted effector, MgPDI2, which is expressed in the subventral esophageal glands and up-regulated during the early parasitic stage of M. graminicola. Purified recombinant MgPDI2 functions as an insulin disulfide reductase and protects plasmid DNA from nicking. As an effector, MgPDI2 contributes to nematode parasitism. Silencing of MgPDI2 by RNA interference in the pre-parasitic second-stage juveniles (J2s) reduced M. graminicola multiplication and also increased M. graminicola mortality under H2O2 stress. In addition, an Agrobacterium-mediated transient expression assay found that MgPDI2 caused noticeable cell death in Nicotiana benthamiana. An intact C-terminal region containing the first catalytic domain (a) with an active motif (Cys-Gly-His-Cys, CGHC) and the two non-active domains (b and b′) is required for cell death induction in N. benthamiana. This research may provide a promising target for the development of new strategies to combat M. graminicola infections.