Brachylaima spp. (Trematoda) parasitizing Cornu aspersum (Gastropoda) in France with potential risk of human consumption

Evidence of predation pressure on sensitive species by raccoons based on parasitological studies

To demonstrate predation and potential impacts of raccoons on various species, a total of 108 raccoons from aquatic-associated nature reserves and natural areas in three federal states of Germany, Hesse (n = 36), Saxony-Anhalt (n = 36) and Brandenburg (n = 36), were investigated from a dietary ecological perspective in the present study. Fecal analyses and stomach content examinations were conducted for this purpose. Additionally, as a supplementary method for analyzing the dietary spectrum of raccoons, the parasite fauna was considered, as metazoan parasites, in particular, can serve as indicators for the species and origin of food organisms. While stomach content analyses allow for a detailed recording of trophic relationships solely at the time of sampling, parasitological examinations enable inferences about more distant interaction processes. With their different developmental stages and heteroxenous life cycles involving specific, sometimes obligate, intermediate hosts, they utilize the food web to reach their definitive host. The results of this study clearly demonstrate that spawning areas of amphibians and reptiles were predominantly utilized as food resources by raccoons in the study areas. Thus, common toad (Bufo bufo), common newt (Lissotriton vulgaris), grass frog (Rana temporaria), and grass snake (Natrix natrix) were identified as food organisms for raccoons. The detection of the parasite species Euryhelmis squamula, Isthmiophora melis, and Physocephalus sexalatus with partially high infestation rates also suggests that both amphibians and reptiles belong to the established dietary components of raccoons from an ecological perspective, as amphibians and reptiles are obligate intermediate hosts in the respective parasitic life cycles of the detected parasites. The study clearly demonstrates that raccoons have a significant impact on occurrence-sensitive animal species in certain areas and, as an invasive species, can exert a negative influence on native species and ecosystems.

Gut microbiota in parasite-transmitting gastropods

BACKGROUND

Gastropoda, the largest class within the phylum Mollusca, houses diverse gut microbiota, and some gastropods serve as intermediate hosts for parasites. Studies have revealed that gut bacteria in gastropods are associated with various biological aspects, such as growth, immunity and host-parasite interactions. Here, we summarize our current knowledge of gastropod gut microbiomes and highlight future research priorities and perspectives.

METHODS

A literature search was undertaken using PubMed, Web of Science and CNKI for the articles on the gut microbiota of gastropods until December 31, 2022. We retrieved a total of 166 articles and identified 73 eligible articles for inclusion in this review based on the inclusion and exclusion criteria.

RESULTS

Our analysis encompassed freshwater, seawater and land snails, with a specific focus on parasite-transmitting gastropods. We found that most studies on gastropod gut microbiota have primarily utilized 16S rRNA gene sequencing to analyze microbial composition, rather than employing metagenomic, metatranscriptomic, or metabolomic approaches. This comprehensive review provided an overview of the parasites carried by snail species in the context of gut microbiota studies. We presented the gut microbial trends, a comprehensive summary of the diversity and composition, influencing factors, and potential functions of gastropod gut microbiota. Additionally, we discussed the potential applications, research gaps and future perspectives of gut microbiomes in parasite-transmitting gastropods. Furthermore, several strategies for enhancing our comprehension of gut microbiomes in snails were also discussed.

CONCLUSIONS

This review comprehensively summarizes the current knowledge on the composition, potential function, influencing factors, potential applications, limitations, and challenges of gut microbiomes in gastropods, with a specific emphasis on parasite-transmitting gastropods. These findings provide important insights for future studies aiming to understand the potential role of gastropod gut microbiota in controlling snail populations and snail-borne diseases.

Potential of 3-octanone as a lure and kill agent for control of the Brown Garden Snail

The brown garden snail (Cornu aspersum) is a major agricultural pest, causing damage to a wide range of economically important crops. Withdrawal or restricted use of pollutant molluscicides like metaldehyde has prompted a search for more benign control products. This study investigated the response of snails to 3-octanone; a volatile organic compound (VOCs) produced by the insect pathogenic fungus Metarhizium brunneum. Concentrations of 1 - 1000 ppm of 3-octanone were first assessed in laboratory choice assays to determine behavioural response. Repellent activity was found at 1000 ppm whereas attractance was found for the lower concentrations of 1, 10 and 100 ppm. These three concentrations 3-octanone were carried forward in field evaluations to assess potential for use in "lure and kill" strategies. The highest concentration (100 ppm) was the most attractive to the snails but also the most lethal. Even at the lowest concentration this compound proved toxic making 3-octanone an excellent candidate for the development as a snail attractant and molluscicide.

Land snails can trap trematode cercariae in their shell: Encapsulation as a general response against parasites?

Terrestrial gastropods are hosts of a wide variety of metazoan parasites and can respond to parasite exposure in various ways. One of these defence mechanisms, the ability to trap parasites in the host shell, was previously thought to apply only against nematodes. During a field survey along an urbanisation gradient, we found that the shell of Cornu aspersum and Cepaea nemoralis can contain encapsulated trematode cercariae, with prevalences of 7% and 1%, respectively over the entire sample, and up to 47% at the local population level. To our knowledge, this is the first case study unambiguously showing that land snails can trap non-nematode parasites in their shell at non-negligible prevalences. Shell-encapsulation could be a more general defence mechanism than previously described, and more studies are needed to understand its importance and variability.

Raccoons contraband - The metazoan parasite fauna of free-ranging raccoons in central Europe

The invasive raccoon (Procyon lotor) is an abundant carnivore and considered as an important potential vector of infectious diseases and parasites in Europe. Raccoons show a broad, opportunistic, omnivorous food spectrum. Food supply and habitat quality in urban areas are very attractive for the generalist raccoon. This inevitably leads to increased interaction with humans, domestic animals and livestock, making the raccoon a potentially suitable zoonosis vector. In its autochthonous range, especially in the Eastern and Midwestern United States, the raccoon has been studied very intensively since the beginning of the 20th century. Whereas, basic field biology and parasitology studies in Germany and Europe are lacking and have only been conducted sporadically, regionally and on small sample sizes. In the presented study 234 raccoons from central Germany were comprehensively examined for their metazoan parasite fauna. The present study shows for the first time an extremely diverse parasite fauna in raccoons outside their native range and proves their essential role as intermediate hosts and hosts for ecto- and endoparasites. A total of 23 different parasite species were identified, five of which are human pathogens, 14 of which are new for the parasite fauna of raccoons in Europe. The human pathogenic raccoon roundworm Baylisascaris procyonis is the most common parasite species in this study, with a prevalence of up to 95%. The digenetic trematode Plagiorchis muris, another human pathogenic parasite species, was detected for the first time in raccoons. The ongoing spread of invasive carnivores and the associated spread and transmission of their parasites and other pathogens increases the potential health risk of wild and farmed animals as well as humans. An increase in parasitic diseases in humans (e.g. raccoon roundworm) is to be expected, especially in urban areas, where raccoons are becoming more and more abundant.

First record of the genus Xeropicta Monterosato, 1892 (Gastropoda: Eupulmonata: Geomitridae) in Serbia

Xeropicta Monterosato is a pulmonate xerophilous snail genus of the family Geomitridae. It is distributed in the eastern Mediterranean and the Black Sea region and also in Asia Minor, Ukraine, the Caucasus, the Middle East and Iran. No species of this genus was known from Serbia until now. Here, we present the first record of Xeropicta from Serbia. Morphological, anatomical and ecological characteristics of the species as well as its variation are discussed. Because of the wide shell variation, the analysed specimens were identified based on anatomy, and correspond to X. krynickii. However, in their shell morphology, some specimens resemble X. derbentina. Therefore, here they are treated as X. cf. krynickii. Further studies should shed more light on their identity.

Nematodes and trematodes associated with terrestrial gastropods in Nottingham, England

A parasitological survey of terrestrial slugs and snails was conducted at popular dog walking locations across the city of Nottingham, with the intensions of finding gastropods infected with parasites of medical (or veterinary) importance such as lungworm (metastrongyloid nematodes) and trematodes. A total of 800 gastropods were collected from 16 sites over a 225 km2 area. The extracted nematodes and trematodes were identified by molecular barcoding. Of the 800 gastropods collected, 227 were infected (172 had nematode infections, 37 had trematode infections and 18 had both nematode and trematode infections). Of the nematode infected gastropods genotyped, seven species were identified, Agfa flexilis, Angiostoma gandavense, Angiostoma margaretae, Cosmocerca longicauda, Phasmarhabditis hermaphrodita, Phasmarhabditis neopapillosa and an unknown Cosmocercidae species. Of the trematode infected gastropods genotyped, four species were identified, Brachylaima arcuate, Brachylaima fuscata, Brachylaima mesostoma and an unknown Plagiorchioidea species. No lungworm species were found within the city of Nottingham. To our knowledge, this study represents the first survey of gastropod-associated nematodes and trematodes in the East midlands of the United Kingdom.

The draft genome sequence of the grove snail Cepaea nemoralis

Studies on the shell color and banding polymorphism of the grove snail Cepaea nemoralis and the sister taxon Cepaea hortensis have provided compelling evidence for the fundamental role of natural selection in promoting and maintaining intraspecific variation. More recently, Cepaea has been the focus of citizen science projects on shell color evolution in relation to climate change and urbanization. C. nemoralis is particularly useful for studies on the genetics of shell polymorphism and the evolution of "supergenes," as well as evo-devo studies of shell biomineralization, because it is relatively easily maintained in captivity. However, an absence of genomic resources for C. nemoralis has generally hindered detailed genetic and molecular investigations. We therefore generated ∼23× coverage long-read data for the ∼3.5 Gb genome, and produced a draft assembly composed of 28,537 contigs with the N50 length of 333 kb. Genome completeness, estimated by BUSCO using the metazoa dataset, was 91%. Repetitive regions cover over 77% of the genome. A total of 43,519 protein-coding genes were predicted in the assembled genome, and 97.3% of these were functionally annotated from either sequence homology or protein signature searches. This first assembled and annotated genome sequence for a helicoid snail, a large group that includes edible species, agricultural pests, and parasite hosts, will be a core resource for identifying the loci that determine the shell polymorphism, as well as in a wide range of analyses in evolutionary and developmental biology, and snail biology in general.