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Shallow benthic invertebrate communities in relation to substrate types in coastal environments of the sub-Antarctic Crozet archipelago.
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"The European weatherfish Misgurnus fossilis, once widespread across Eurasia, is now critically endangered in Flanders (Belgium), prompting the establishment of a captive breeding programme as part of conservation efforts. During rearing, juvenile weatherfish suffered heavy infections from the ectoparasitic flatworm Gyrodactylus fossilis, leading to mortality events. Although G. fossilis is a natural parasite of M. fossilis, high host densities in hatchery conditions facilitated pathological infection intensities, while adult fish maintained at lower densities showed no visible pathology. This suggests that husbandry practices strongly modulate dynamics of this host–parasite system in captivity. To place these observations in a historical context, we screened both captive-bred fish and archival material (1881–1973, i.e. prior to the anthropogenic introduction of Asian congeners in Misgurnus) for ectoparasites. Morphological and molecular characterisation revealed infections of three monopisthocotylan flatworms: G. fossilis, Gyrodactylus misgurni (Gyrodactylidae), and Actinocleidus cruciatus (Dactylogyridae). All represent new records for Belgium, with G. misgurni and A. cruciatus considered native due to their occurrence in historical material. Notably, these parasites’ abundance has declined compared to historical collections, raising concerns about their own conservation status. Since parasites contribute substantially to species-richness, ecosystem functioning, and even the health of their host individuals and populations (e.g., their immunological development and resilience) their co-decline alongside endangered hosts represents a hidden and meaningful dimension of biodiversity loss. Our findings highlight both risks and opportunities associated with parasite conservation in ex situ programmes focused on fishes or other vertebrate hosts. High juvenile stocking densities increased parasite burdens and mortality, while improved husbandry practices allowed stable co-existence of host and parasite populations. This indicates that carefully managed captive breeding facilities may act as refugia not only for M. fossilis but also for its specialist parasites, maintaining ecological interactions and genetic diversity that would otherwise be lost. While parasites are often overlooked or actively eliminated in wildlife management, they play essential roles in ecosystems and represent species of conservation concern in their own right. These results emphasise the possibility of including parasites in conservation planning. For the weatherfish and its parasites, ex situ conservation thus provides an experimental framework for developing integrated strategies that safeguard both host and parasite persistence. Future reintroduction initiatives should therefore consider whether to also re-establish native parasite populations, a decision that requires informed discussion among conservation stakeholders. By demonstrating the feasibility of host–parasite co-conservation, this study advances the idea that conservation programmes can optimise resource allocation while preserving the evolutionary and ecological relationships of multiple species simultaneously.
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RBINS Staff Publications 2025
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Systematics and phylogeny of Chalcinotrematinae (Digenea: Haploporidae): Erection of a new genus and description of two new species from South America through integrated analyses
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The subfamily Chalcinotrematinae (Haploporidae) comprises an understudied group of digenean parasites infecting freshwater and brackish water fishes across the Americas, Africa, and Asia. Its systematics have rarely been investigated using molecular data, with DNA sequences available for only a few species representing two of the six recognised genera. We collected chalcinotrematine trematodes from freshwater fishes in the Jari River, Amazon Basin, Brazil, and in Misiones, Argentina. Specimens from Brazil were characterised through an integrative approach combining morphological examination with molecular data (partial 28S and ITS2 rDNA sequences), whereas those from Argentina were analysed morphologically. As a result, we describe two new species from Brazil: Chalcinotrema arleneae sp. nov. from Leporinus friderici and Laemolyta proxima, and Unicoelium gerardoi sp. nov. from Hypostomus plecostomus. This study provides the first molecular data for both Chalcinotrema and Unicoelium, expanding the phylogenetic framework of Chalcinotrematinae. Paralecithobotrys brasiliensis is recorded from Argentina in Megaleporinus obtusidens, extending its geographical range. We reassessed the generic limits of Saccocoelioides, the most species-rich genus within the subfamily. Based on combined morphological, molecular, host, and distributional evidence, we propose taxonomic revisions, establishing Neosaccocoelioides gen. nov. for several South American species formerly assigned to Saccocoelioides: N. antonioi comb. nov., N. bacilliformis comb. nov., N. elongatus comb. nov., N. magnus comb. nov., N. miguelmontesi comb. nov. (type species), and N. szidati comb. nov. Additionally, N. platense comb. nov., previously placed in Chalcinotrema, is transferred to the new genus. Saccocoelioides chilkaensis and S. lizae are considered species inquirendae; and S. guaporense is considered incertae sedis. These findings refine Chalcinotrematinae relationships and highlight the need for expanded molecular datasets to resolve systematic and biogeographical uncertainties.
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Reduced-representation sequencing detects trans-Arctic connectivity and local adaptation in polar cod (Boreogadus saida)
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Information on connectivity and genetic structure of marine organisms remains sparse in frontier ecosystems such as the Arctic Ocean. Filling these knowledge gaps becomes increasingly urgent, as the Arctic is undergoing rapid physical, ecological, and socio-economic changes. The abundant and widely distributed polar cod (Boreogadus saida) is highly adapted to Arctic waters, and its larvae and juveniles live in close association with sea ice. Through a reduced-representation sequencing approach, this study explored the spatial genetic structure of polar cod at a circum-Arctic scale. Genomic variation was partitioned into neutral and adaptive components to respectively investigate genetic connectivity and local adaptation. Based on 922 high-quality single nucleotide polymorphism (SNP) markers genotyped in 611 polar cod, broad-scale differentiation was detected among three groups: (i) Beaufort-Chukchi seas, (ii) all regions connected by the Transpolar Drift, ranging from the Laptev Sea to Iceland, including the European Arctic, and (iii) West Greenland. Patterns of neutral genetic structure suggested broadscale oceanographic and sea ice drift features (i.e. Beaufort Gyre and Transpolar Drift) as important drivers of connectivity. Genomic variation at 35 outlier loci indicated adaptive divergence of the West Greenland, and the Beaufort-Chukchi Seas populations, possibly driven by environmental conditions. Sea ice decline and changing ocean currents can alter or disrupt connectivity between polar cod from the three genetic groups, potentially undermining their resilience to climate change, even in putative refugia, such as the Central Arctic Ocean and the Arctic Archipelago.
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RBINS Staff Publications 2025
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Exploring hidden parasite diversity with environmental DNA metabarcoding during a ParasiteBlitz across a coastal habitat gradient
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Environmental DNA (eDNA) metabarcoding has lagged in parasite biodiversity assessments. We implemented this method to examine parasite diversity in sediment and water from 4 physically connected aquatic habitats in coastal South Carolina, USA, as part of a ParasiteBlitz in April 2023. Sediment was collected using a syringe corer, and water was sampled using active filtration and passive collection. Five amplicon libraries, using primers targeting portions of the mitochondrial COI of platyhelminths and 18S ribosomal RNA genes of nematodes, myxozoans, microsporidians, and protists, successfully yielded parasite sequences. Out of >5.8 million sequences, we identified >1,000 parasite amplicon sequence variants (ASVs) corresponding to ~600 parasite operational taxonomic units, from 6 parasite groups. Most diversity was observed among the microsporidians, whose assay demonstrated the highest fidelity. Actively-filtered water samples captured ASVs of all 6 groups, whereas sediment captured only 4, despite yielding 3× as many ASVs. Low DNA yields from passive water samples resulted in fewer, but some unique, ASVs representing 3 parasite groups. The most efficient sampling method varied with respect to parasite group across habitats, and the parasite communities from each habitat were distinct regardless of sampling method. We detected ASVs of 9 named species, 4 of which may represent introductions to the US. The abundance of our results demonstrates the effectiveness and efficiency of eDNA metabarcoding for assessing parasite diversity during short, intensive surveys, and highlights the critical need for more comprehensive sequence databases and the development of primers for those parasite taxa that elude detection using eDNA methods.
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RBINS Staff Publications 2025
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Divergent feeding habits of sister species of the Antarctic amphipod genus Charcotia
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Climate change and resource exploitation in the Southern Ocean are important anthropogenic pressures on Antarctic food webs. Understanding the eco-functional roles of Antarctic communities is essential for ecosystem management and conservation. Amphipods are among the most dominant and ecologically important benthic taxa in the Southern Ocean. The amphipod genus Charcotia is part of the scavenger guild playing a dominant role in nutrient recycling. To study the trophic habits of two sister species C. amundseni and C. obesa, stable isotope ratios of carbon and nitrogen were measured along geographical and bathymetrical gradients. Charcotia obesa belongs to the fourth and C. amundseni to the fifth trophic level, based on significant differences in δ15N values. Both benthic and pelagic primary producers dominate the diet in both species as derived from their low δ13C values. Charcotia obesa, the species with the narrowest depth range of the two studied species, did not show a depth-related pattern in isotopic ratios. An increasing geographic gradient of both δ15N and δ13C values was observed for C. obesa, ranging from the northern most tip of the Western Antarctic Peninsula to the southwestern most part in the Bellingshausen Sea. This might be linked to nutrient rich glacial meltwater in the latter part of the Southern Ocean. Nitrogen stable isotope ratios of C. amundseni showed a significant difference between Crown Bay and the other locations; this might be explained by the close location of the Filchner Area to nutrient rich upwelling in the Weddell Sea Gyre. Our study provides evidence for niche differentiation between two closely related amphipod species. Incorporation of additional samples from other locations and depth ranges in combination with isotope analysis and DNA-based prey identification might clarify the trophic position of benthic amphipods.
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RBINS Staff Publications 2025
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Going Dutch: Invasion pathways and current European distribution of non-native land flatworm species belonging to Geoplaninae and Bipaliinae with focus on the Netherlands
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Non-native land flatworms can have a negative impact on local ecosystems, due to their voracious appetites for earthworms or snails. Accurate knowledge on the distribution of non-native populations of land flatworms is necessary to design effective policy to control their spread across Europe. The aim of this study is to address the spatiotemporal distribution of selected species of non-native land flatworms (Geoplaninae and Bipaliinae) in the Netherlands, and provide their current distribution and introduction pathways in a pan-European perspective. Specimens of Obama spp., Bipalium kewense and Diversibipalium multilineatum were reported across selected Dutch gardens, greenhouses, plant nurseries or garden centers. European distribution of these planarians species was reconstructed using previously published datasets and from records available on GBIF. Morphological species identification was supported by DNA barcoding using a portion of the 28S rDNA marker. Introduction pathways were addressed via haplotype networks based on COI mtDNA. In total, 27 specimens of non-native land flatworms were collected in the Netherlands. Their different spatiotemporal distribution pattern indicates differences in tolerance to environmental conditions in Northern Europe between B. kewense restricted to greenhouses and D. multilineatum found in gardens. Generally, an increasing trend in the number of records of Obama nungara is observed in the Netherlands and in Europe, with the highest number of records per country reported in France (1.428) followed by the Netherlands (149) and Italy (64). The high numbers of France are, however, artificial and originate from communication towards the public, which has not been as pronounced in other European countries. Genetic analyses suggest multiple introductions of O. nungara in Europe. The combination of morphological and molecular species identification revealed the presence of Obama anthropophila being the first record of this species outside its native range in Brazil. Our results further support the established status of these species in Europe and highlight the importance of citizen scientists in non-native species research.
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Scanning Electron Microscopy Reveals New Ultrastructural Features in Metacercariae of Clinostomum cutaneum (Digenea: Clinostomidae) Infecting Oreochromis niloticus (Actinopterygii: Cichlidae) in Kenya
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Clinostomum is a genus of parasitic trematodes found worldwide, infecting a wide range of hosts, including freshwater fishes, snails, birds and occasionally humans. In this study, clinostomid metacercariae were collected from Nile tilapia raised in fish farms in the Upper Tana River region, Kenya. The prevalence of infection was 17.2%, with metacercariae infecting the skin, gills and buccal cavity of the fish. Using light microscopy, scanning electron microscopy (SEM) and molecular methods targeting both nuclear ribosomal (ITS1, 5.8S, ITS2) and mitochondrial (COI) regions, the metacercariae were identified as C. cutaneum, C. phalacrocoracis, C. tilapiae and Euclinostomum heterostomum. The three species of Clinostomum have previously been reported to infect fish or piscivorous birds in Kenya, while this is the first report of E. heterostomum in this country. SEM analysis revealed new ultrastructural features of C. cutaneum, including an excretory pore surrounded by minute spiny papillae, an everted cirrus and dome-shaped papillae on the tegumental area around the genital pore. The cirrus lacked basal papillae, showing morphological variation between the adult and metacercarial stages. Our study, therefore, provides new insights into the phenotypic identification of flukes that may be pathogenic to fishes and humans and, therefore, of scientific and practical importance.
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A Scanning Electron Microscopy method to visualise the copulatory organ morphology of microturbellarian flatworms: Trigonostomum Schmidt, 1852 as a case study
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Traditional methods for studying the morphology of microturbellarian flatworms rely on light microscopy, which often lacks the resolution necessary to capture fine structural details. Therefore, we present a protocol to improve the visualisation of structural morphological details in microturbellarians by means of scanning electron microscopy (SEM). We demonstrate this method by imaging the sclerotised copulatory organs of three species of Trigonostomum (Rhabdocoela, Trigonostomidae): T. venenosum, T. setigerum, and T. penicillatum. Additionally, we successfully visualise the bursal appendage of T. penicillatum. SEM imaging offered new morphological insights for the genus, and corrected earlier interpretations made with light microscopy. The method requires precision and careful handling, especially during the isolation of the hard parts. However, it is cost-effective and straightforward to carry out in any standard laboratory setting. Hence, our SEM protocol complements traditional light microscopy and opens new avenues for taxonomical research in microturbellarian taxa with hard parts.
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Growth and reproduction of the shrimp population in a lagoon system in southern Benin (West Africa)
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RBINS Staff Publications 2024
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Understanding late medieval farming practices: an interdisciplinary study on byre remains from the historical centre of Brussels (Belgium)
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During the preventive archaeological excavation in the cellar of the site of petite Rue des Bouchers in the historical centre of Brussels (Belgium), the waterlogged remains of a thirteenth century AD sunken byre (potstal) were discovered. The exceptional preservation instigated a multiproxy approach, including micro-archaeology, micromorphology, phytolith and endoparasite egg analysis on thin sections, palynology and the study of plant macroremains on the fill of the structure. Beyond permitting to detail the content and the multiple origins of the fill (including excremental waste and urines, fodder and bedding material, plaggen and/or soil sods, household and construction waste), this study also provides detailed insights into the foddering customs, hygienic conditions within the stable, and the health status of the animals kept. On a more general scale this study documented late medieval farming practices in Brussels, more specifically the need to collect substantial amounts of manure to add as fertilizer onto the cultivated poor sandy soils.
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