Journal of invertebrate pathology最新文献

The ovicidal effect of entomopathogenic fungi and the mechanisms involved are still debated. The hypothesis that the metabolic activity of germinating conidia can cause insect embryos to become unviable without physical penetration has been proposed. Here, we demonstrated that Metarhizium anisopliae and Metarhizium pingshaense, differently from Beauveria bassiana, reduced the percentage of nymphs hatching to less than 3%. They caused degradation of the egg wall due to the growth and penetration. The visualization of lipids being directed from the eggs towards the interior of the hyphae suggests that the lipid reserve was used as a source of nutrients for the development of these fungi.

This study investigates the prevalence and characteristics of disseminated neoplasia (DN) in Mytilus chilensis in the Los Lagos Region of southern Chile. DN is a malignant proliferative disease that has been described in several species of the genus Mytilus. More than 4.000 adult mussels, both cultured and natural, collected between 2016 and 2022 in different geographical areas (Calbuco-Hueihue, Castro, Quellón) and seasons (winter-spring, summer-autumn) were histologically analysed. The prevalence was assessed and three levels of severity of DN were defined, based on number of neoplastic cells and organs invaded. Morphology and morphometry of neoplastic cells and hemocytes were evaluated. Cell and nucleus diameters and the nucleus/cytoplasm ratio of granulocytes and hyalinocytes were analysed in healthy and neoplastic individuals. The size of neoplastic cells was significantly larger in stage 3 of neoplasia than in stage 1. The overall mean prevalence of DN in M. chilensis was 3.4%, significant differences were found between sites, being higher in Calbuco-Hueihue (5.59%) than in Castro (3.78%) and Quellón (1.40%). The prevalence was significantly higher in the winter-spring season (7.79%) than in the summer-autumn season (3.95%) in Calbuco-Hueihue. The sex, gametogenic stage, and Adipogranular (ADG) cells status were recorded for each mussel, and related to the severity stages of DN. For stages 1 and 2 of DN, females and males could be recognized, but in stage 3 almost no evidence of sex remained. The same trend was identified for the gonadal status, the advanced stages of DN were associated with castration of the mussels. The ADG cells status was highest at stage 1 of DN, declining in number and staining till stage 3. The sex ratio of healthy mussels was 53.5% female, 43.7% male, 1.6% hermaphrodite, and 1.3% indeterminate, for mussels with DN it was 34.1% female, 16% male, 2.2% hermaphrodite and 47.8% indeterminate. Occurrence of DN was higher in females, but the severity stages affected equally female and male mussels. Although the overall prevalence is low, there are some potential risks that warrant continued monitoring and further study of disseminated neoplasia in M. chilensis. This study provides important data on the epidemiology of DN in M. chilensis, which will inform future research and management strategies in aquaculture.

Pomacea canaliculata is a highly successful invasive snail that shapes freshwater communities in both native and invaded habitats. We studied its digenean parasites from three freshwater bodies in its native distribution area in Buenos Aires Province, Argentina. An integrated approach was used to determine and describe the larval stages of digenean, including morphological, molecular, and histopathology analyses. We provide the first record of P. canaliculata as the first intermediate host of Stomylotrema vicarium (Stomylotrematidae), two species of the family Phaneropsolidae, and one species of the family Cyclocoelidae. This is also the first record of a species of the family Cyclocoelidae parasitizing snails of the genus Pomacea, with the apple snail acting as both the first and second intermediate host. The digestive gland was identified as the target organ of infection for all species. Stomylotrema vicarium and Phaneropsolidae gen. et sp. 2 alter the structure of the gonads, causing indirect parasitic castration, and, through mechanical compression, destroying also the digestive gland. Adequate knowledge of the identity and dynamics of the parasites affecting P. canaliculata in its native range and the damage they cause is key to explaining the success of this invasive species. The lack of parasite records in invaded areas supports the "enemy release" hypothesis, which could explain the apple snail's success in these environments. Parasitic castration reduces the reproductive potential of hosts, limiting the expansion and competition of invasive species, making it crucial to understand these impacts for their conservation and control.

Plants employ various defense mechanisms to protect themselves from invaders such as microorganisms and herbivores. By recognizing these threats, plants can trigger a cascade of responses throughout their tissues, effectively priming their defenses and enhancing their resistance to future attacks. In this study, we examined the indirect effects of the entomopathogenic fungi Beauveria bassiana strain GHA and Metarhizium anisopliae strain F01 on tomato growth, expression of selected plant genes, production of secondary metabolites, and preference and performance of the tomato leafminer (Tuta absoluta). Both B. bassiana and M. anisopliae colonized tomato endophytically. Plants treated with B. bassiana had greater biomass than the untreated control and M. anisopliae treated plants. Oviposition was lower on plants treated with B. bassiana and M. anisopliae than on untreated controls in both choice and no-choice studies, and both endophytic EPF also affected the development of leafminer larvae. Gene expression analysis of tomato leaves inoculated with endophytic EPF provided evidence of triggering plant immune response genes, and of priming genes for herbivore attack, making plants more resistant to herbivory. These findings provide important insights into the mechanisms by which B. bassiana and M. anisopliae promote tomato plant growth and rapidly respond to T. absoluta infestation by priming the immune system. This knowledge could improve the development of entomopathogenic fungi for use in plant-protection strategies.

Captive, pelagic red crabs (Pleuroncodes planipes) had shortened lifespans and cutaneous black spots. Histologically, epidermal and mesenchymal cells had 3-5 µm diameter intranuclear inclusions, necrosis, vacuolation, and/or hyperplasia. The remaining organs were histologically unremarkable. Ultrastructurally, nuclei contained rod-shaped, 70-100nmx250-350 nm virions with a double membrane. PCR on 32 animals was negative for WSSV, and suggestive of a novel virus. The genomic sequence of the virus could not be retrieved due to the low amount of DNA obtained from the paraffin embedded tissue. This is consistent with a novel viral infection, and is the first description of a viral disease in pelagic red crabs.

The insect mass-rearing industry to produce feed and food is expanding rapidly. Insects in production frequently encounter multiple pathogens and environmental stressors simultaneously, which can lead to significant economic losses. Our understanding of the interactions between different stressors remains limited, and existing methods primarily focus on determining overall patterns of additivity, synergism, or antagonism. However, the interactions between different stressors may exhibit more intricate response patterns, such as time or dose dependency. With the expanding industry of insect production, it becomes vital to conduct comprehensive risk assessment of diseases, using approaches that can detect both lethal and sublethal effects. Here, we assessed the risk of co-exposure to a fungal (Metarhizium brunneum) and a bacterial (Bacillus thuringiensis) pathogen in the yellow mealworm (Tenebrio molitor) at ambient and elevated carbon dioxide (CO₂) concentrations. We assessed total larval biomass per treatment group, survival, and individual weight gain 14 and 20 days after pathogen exposure. To analyse the data, we used a mixture toxicity (MIXTox) model, which identifies dose ratio or dose level dependency in addition to overall antagonism or synergism. The interactions between the two pathogens were mostly antagonistic or additive at both CO₂ concentrations and time points, indicating that the observed effects during co-exposure did not exceed the expected combined effects of the individual exposure. We did not find evidence that the interactions between the pathogens substantially change at elevated CO₂. The antagonistic interactions measured in the bioassays are likely to be indirect via the insect host, as we did not detect direct inhibition between the two pathogens in in vitro experiments. Here we show that using the MIXTox model is a powerful tool to assess the effects of co-exposure to pathogens and quantify risk of disease in mass-reared insects.

During a field survey of parasitic ciliates diversity in South Korea, a scuticociliate was found in a water sample collected during scuba diving. At first glance, the species looks similar to members of the genus Paranophrys especially P. magna but they differ mainly in the body size and the number of somatic kineties. Thus, integrative taxonomic approaches (i.e., silver impregnations, scanning electron microscopy, and molecular phylogeny) were applied and confirmed that the isolate is a new species. Detailed comparison between the new species and the three members of the genus Paranophrys revealed that the new species is similar to P. magna in having membranelle 1 slightly shorter than membranelle 2 and the monokinetids are randomly scattered between dikinetids within each somatic kinety. On the other hand, membranelle 1 in both P. marina (type species) and P. thompsoni is about three times longer than membranelle 2 and their ciliary rows invariably consist of dikinetids anteriorly and monokinetids posteriorly. Observations on the feeding behavior and habitat suggest that the new species is facultative histophagous. Phylogenetic analyses based on 18S rRNA gene indicate that the new species and P. magna belong to the newly established genus Anteparanophrys n. gen. i.e., Anteparanophrys koreana n. sp. and Anteparanophrys magna (Borror, 1972) n. comb.

The Pacific white shrimp (Penaeus vannamei), one of the world's most economically important aquatic species, is highly susceptible to Ecytonucleospora hepatopenaei (EHP), a pathogen that infects the hepatopancreas and causes hepatopancreatic microsporidiosis (HPM), leading to stunted growth and substantial economic losses in shrimp farming. Currently, no effective treatments for EHP exist, making rapid on-site detection and preventive measures essential for disease control. While nucleic acid-based detection methods are commonly employed, they require specialized equipment, controlled environments, and trained personnel, which increase costs. To address this limitation, we developed a colloidal gold immunochromatographic assay (GICA) strip for rapid on-site detection of EHP in shrimp farms. Using LC-MS/MS, 15 high-abundance EHP proteins were identified, with EhSWP3 ranked highest and selected as the optimal antigen detection target. Recombinant EhSWP3 was used to immunize mice, resulting in the development of monoclonal antibodies. The optimal capture and labeled antibody combination (1B6, 3A6) was identified and incorporated into the GICA strip. Testing with common shrimp pathogens and various microsporidia samples demonstrated the high specificity of the EHP test strip. The strip exhibited a sensitivity of 1.81 × 10³ copies of the EHP-SSU rRNA gene for detecting EHP-infected shrimp and 1 × 10⁴ purified EHP spores, indicating its strong sensitivity in practical applications. To facilitate on-site use, a simple GICA workflow was established using disposable pestles, Buffer A, and Buffer B, enabling detection within 15 min. Testing of 110 shrimp samples revealed a 90.0 % concordance between the GICA strip and qPCR results. This study marks the first development and application of an EHP antigen detection strip, offering a practical tool for rapid, on-site disease monitoring in shrimp farming.

The small hive beetle (SHB), Aethina tumida Murray is an invasive pest of the honey bee. This beetle feeds not only on bee resources within the hive such as honey and pollen, but also on bee brood and dead bees. The impact of this beetle's intimate parasitic association with the honey bee on virus transmission is poorly understood. We aimed to characterize the virome of SHB to identify SHB viruses with potential for use in biological control of this pest. We characterized the virome of SHB by sequencing the transcriptomes and small RNAs of SHB collected from multiple geographical regions: Adult and larval SHB were collected from midwestern- (Illinois, Ohio) and southern- (Florida, Texas) states of the USA, and from South Africa. Small RNAs were sequenced for adult beetles from Florida and Ohio, for larvae from Florida, and for an SHB-derived cell line (BCIRL-AtumEN-1129). Assembled transcripts were annotated by BLASTx. In field-caught adult beetles and adults and larvae from South Africa, the near-complete sequences for all three genomic segments of a putative novel phasmavirus (order: Elliovirales, formerly Bunyavirales) were identified. In addition, transcripts from a partial glycoprotein sequence from a different phasmavirus integrated into the genome of SHB were detected in all samples, including the SHB-derived cell line. Apparent PIWI-interacting RNAs derived from the integrated glycoprotein sequence were also detected. Whether the putative extant phasmavirus replicates in SHB remains to be determined.

Corpse-mediated pathogen transmission is a viable route through which naïve hosts can become infected, but its likelihood for honey bee-associated viruses is largely unknown. While these viruses can be easily detected in deceased bees, it remains unclear if they stay infectious within postmortem hosts or if enough viral RNA degradation-and subsequently virus inactivation-occurs post-host death to render these viruses inviable. This knowledge gap has important implications for how researchers perform honey bee virus studies and for our general understanding of honey bee virus transmission. To better understand the resiliency of honey bee-associated viruses within deceased hosts, we first tested the hypothesis that postmortem specimens, stored in colony-normal temperature and humidity conditions, can be reliably used to quantify virus abundance. To determine this, we experimentally-infected adult honey bees with Israeli acute paralysis virus (IAPV) and then measured the virus levels of individuals sampled live or at different postmortem time points (4, 12, 24, and 48 hours post-death) using RT-qPCR and a standard curve absolute quantification method. We found no significant differences based on when bees were sampled, indicating that postmortem honey bees are statistically comparable to using live-sampled bees and can be reliably used to quantify absolute IAPV abundance. We then performed a follow-up experiment that determined whether or not the IAPV detected in postmortem bees remained infectious over time. We found that IAPV extracted from postmortem bees remained highly infectious for at least 48 hours post-death, indicating that any viral RNA degradation that may have occurred during the postmortem interval did not adversely affect IAPV's overall infectivity. The results from this study suggest that IAPV is more resilient to degradation than previously assumed, support the use of postmortem bees for downstream IAPV analyses, and indicate that postmortem hosts can act as sources of IAPV infection for susceptible individuals.