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Pteropods, holoplanktonic gastropods, play pivotal roles in marine ecosystems as integral components of food webs and carbon cycling. With global change threatening pelagic ecosystem equilibrium, conserving pteropod biodiversity is paramount. Here, we present the most extensive phylogenetic study of the order Pteropoda to date, utilizing a complete mitogenome phylogeny to support the suppression of Thecosomata, thus demonstrating the lack of relationship between Pseudothecosomata and Euthecosomata. Through multilocus Sanger-based taxon sampling with 411 specimens (92 newly sequenced), representing nearly 100 species (out of 163 valid) from various oceans, we elucidate robust support for higher taxonomic rankings. Despite strong support, relationships between the major groups Gymnosomata, Pseudothecosomata, and Euthecosomata remain contentious. Our study addresses unresolved taxonomic questions, identifying cryptic species complexes across vast biogeographic areas, and offering unprecedented insights into pteropod diversity. We shed light on several open questions in pteropod systematics, proposing the reclassification of L. antarctica stat. rest. and elucidating the position of Thliptodon, Heliconoididae, and Thieleidae. This systematic review enhances our understanding of pteropod diversity and underscores the urgency of conservation efforts in the face of changing oceanic conditions.

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The Miocene Climate Optimum (MCO, ~ 17-14 Ma) was a time of extraordinary marine biodiversity in the Circum-Mediterranean Region. This boom is best recorded in the deposits of the vanished Central Paratethys Sea, which covered large parts of central to southeastern Europe. This sea harbored an extraordinary tropical to subtropical biotic diversity. Here, we present a georeferenced dataset of 859 gastropod species and discuss geodynamics and climate as the main drivers to explain the changes in diversity. The tectonic reorganization around the Early/Middle Miocene boundary resulted in the formation of an archipelago-like landscape and favorable conditions of the MCO allowed the establishment of coral reefs. Both factors increased habitat heterogeneity, which boosted species richness. The subsequent cooling during the Middle Miocene Climate Transition (~ 14-13 Ma) caused a drastic decline in biodiversity of about 67%. Among the most severely hit groups were corallivorous gastropods, reflecting the loss of coral reefs. Deep-water faunas experienced a loss by 57% of the species due to changing patterns in circulation. The low sea level led to a biogeographic fragmentation reflected in higher turnover rates. The largest turnover occurred with the onset of the Sarmatian when bottom water dysoxia eradicated the deep-water fauna whilst surface waters-dwelling planktotrophic species underwent a crisis.

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Neuropeptides play essential roles in coordinating reproduction. Egg-laying hormone (ELH) is conserved in genetic sequence and behavioral function across molluscs, where neuronal clusters secrete ELH to modulate and induce egg-laying. Here we investigated ELH in the nudibranch mollusc, Berghia stephanieae. ELH preprohormone gene orthologs, which showed clade-specific differences at the C-terminus of the predicted bioactive peptide, were identified in brain transcriptomes across several nudipleuran species, including B. stephanieae. ELH shares deep homology with the corticotropin-releasing hormone gene family, which has roles broadly in stress response. Injection of synthesized B. stephanieae ELH peptide into mature individuals induced egg-laying. ELH gene expression in the brain and body was mapped using in-situ hybridization chain reaction. Across the adult brain, 300-400 neurons expressed ELH. Twenty-one different cell types were identified in adults, three of which were located unilaterally on the right side, which corresponds to the location of the reproductive organs. Ten cell types were present in pre-reproductive juvenile stages. An asymmetric cluster of approximately 100 small neurons appeared in the right pedal ganglion of late-stage juveniles. Additional neurons in the pleural and pedal ganglia expressed ELH only in adults that were actively laying eggs and sub-adults that were on the verge of doing so, implicating their direct role in reproduction. Outside the brain, ELH was expressed on sensory appendages, including in presumptive sensory neurons. Its widespread expression in the nudibranch B. stephanieae suggests that ELH plays a role beyond reproduction in gastropod molluscs.

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Repeated sequences, especially transposable elements (TEs), are known to be abundant in some members of the important invertebrate class Gastropoda. TEs that do not have long terminal repeated sequences (non-LTR TEs) are frequently the most abundant type but have not been well characterised in any gastropod. Despite this, sequences in draft gastropod genomes are often described as non-LTR TEs, but without identification to family type. This study was conducted to characterise non-LTR TEs in neritimorph snails, using genomic skimming surveys of three species and the recently published draft genome of Theodoxus fluviatilis. Multiple families of non-LTR TEs from the I, Jockey, L1, R2 and RTE superfamilies were found, although there were notably few representatives of the first of these, which is nevertheless abundant in other Gastropoda. Phylogenetic analyses of amino acid sequences of the reverse transcriptase domain from the elements ORF2 regions found considerable interspersion of representatives of the four neritimorph taxa within non-LTR families and sub-families. In contrast, phylogenetic analyses of sequences from the elements' ORF1 region resolved the representatives from individual species as monophyletic. However, using either region, members of the two species of the Neritidae were closely related, suggesting their potential for investigation of phyletic evolution at the family level.

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We investigated the therapeutic effects of EDTA application for 14 and 28 days on cadmium (Cd) induced pond snail Lymnaea stagnalis (Linnaeus, 1758). The sublethal concentration of cadmium (63.4 mg/l Cd) caused tissue damages to the snail after an exposure for 28 days.In the groups treated with EDTA, the concentration of Cd in the foot, mantle and hepatopancreas tissues showed significantly decreased during the recovery period. The curative effects of EDTA on Cd-induced damage were assessed using a scoring system. Cadmium exposure led to histopathological changes including increased mucositis, pigment and protein cells, foot epithelium desquamation, muscle fibril damage, connective tissue cell atrophy, and increased lipid vacuoles in the mantle and hepatopancreas. However, these changes were less severe in snails treated with EDTA (2.00 mL/L for 28 day), indicating that EDTA reduces their susceptibility to heavy metal toxicity.

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BACKGROUND: Snail-borne trematodes afflict humans, livestock, and wildlife. Recognizing their zoonotic potential and possible hybridization, a One Health approach is essential for effective control. Given the dearth of knowledge on African trematodes, this study aimed to map snail and trematode diversity, focusing on (i) characterizing gastropod snail species and their trematode parasites, (ii) determining infection rates of snail species as intermediate hosts for medically, veterinary, and ecologically significant trematodes, and (iii) comparing their diversity across endemic regions. METHODS: A cross-sectional study conducted in 2021 in Chiredzi and Wedza districts in Zimbabwe, known for high human schistosomiasis prevalence, involved malacological surveys at 56 sites. Trematode infections in snails were detected through shedding experiments and multiplex rapid diagnostic polymerase chain reactions (RD-PCRs). Morphological and molecular analyses were employed to identify snail and trematode species. RESULTS: Among 3209 collected snail specimens, 11 species were identified, including schistosome and fasciolid competent snail species. We report for the first time the invasive exotic snail Tarebia granifera in Zimbabwe, which was highly abundant, mainly in Chiredzi, occurring at 29 out of 35 sites. Shedding experiments on 1303 snails revealed a 2.24% infection rate, with 15 trematode species identified through molecular genotyping. Five species were exclusive to Chiredzi: Bolbophorus sp., Schistosoma mansoni, Schistosoma mattheei, Calicophoron sp., and Uvulifer sp. Eight were exclusive to Wedza, including Trichobilharzia sp., Stephanoprora amurensis, Spirorchid sp., and Echinostoma sp. as well as an unidentified species of the Plagiorchioidea superfamily. One species, Tylodelphys mashonensis, was common to both regions. The RD-PCR screening of 976 non-shedding snails indicated a 35.7% trematode infection rate, including the presence of schistosomes (1.1%) Fasciola nyanzae (0.6%). In Chiredzi, Radix natalensis had the highest trematode infection prevalence (33.3%), while in Wedza, R. natalensis (55.4%) and Bulinus tropicus (53.2%) had the highest infection prevalence. CONCLUSIONS: Our xenomonitoring approach unveiled 15 trematode species, including nine new records in Zimbabwe. Schistosoma mansoni persists in the study region despite six mass deworming rounds. The high snail and parasite diversity, including the presence of exotic snail species that can impact endemic species and biomedically important trematodes, underscores the need for increased monitoring.

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The monospecific genus Tartessiberus was described in the year 2021 including a single species (T.cilbanus). However, its description relied solely on morphological and anatomical data. In the present work, we use a fraction of the mitochondrial DNA cytochrome oxidase subunit I (COI), 16S ribosomal RNA (16S rRNA) and the nuclear large ribosomal subunit (LSU) to clarify its validity through phylogenetic positioning. Knowledge of the distribution of this species is also improved by citing new locations and expanding the geographical range to approximately 200 km2. Additionally, a morphometric analysis of 259 shells is presented for comparisons with shells of the Iberusmarmoratus complex and testing the power of conchological features as a tool for specimen identification. The relatively high conchological variability found for T.cilbanus, together with the discovery of populations with intermediate conchological features between T.cilbanus and other closely related taxa, suggest that the determination of this species should be based on genetic criteria. Our molecular analyses demonstrate that T.cilbanus belongs to the Iberus genus, and thus, we proceed to update its taxonomic status to Iberuscilbanuscomb. nov., and, thus, to consider Tartessiberus from now on as a junior synonym of Iberus.

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Background: Arionvulgaris Moquin-Tandon, 1855 is amongst the fastest-spreading terrestrial slugs Europe-wide. In recent years, it has been recorded in Canada, Mexico and continues to expand eastwards into Eurasia. Renowned for its high invasiveness, combatting its swift spread creates significant challenges in organising effective preventative measures. New information: This study presents the first record of Arionvulgaris from Armenia, which is the second record of this species' invasion of the Caucasus. In 2022, a substantial population of A.vulgaris was observed close to the City of Stepanavan, which is also the first record in Armenia of the family Arionidae. How the species was introduced to Armenia remains unknown. Identification of Arionvulgaris was conducted, based on external and genital morphology and mitochondrial CO1 (cytochrome c oxidase subunit 1) gene sequencing, revealing notable similarities with Central European clades. Our results confirm the introduction and distribution of A.vulgaris to Armenia. Invasion of such species into Armenia will require additional monitoring and would be aided by further research on Armenia's mollusc fauna in the future.

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Background: Culuccia is a small peninsula of about 3 km2 placed in north-western Sardinia (Italy) at the margin of the Maddalena Archipelago. The marine area surrounding this Peninsula is a Special Area of Conservation, included in the European Natura 2000 Ecological Network of protected areas, but until now, no information on biodiversity of this area is available. In 2021, a research project to study both terrestrial and marine biodiversity of Culuccia has started in order to fill this gap of knowledge. New information: This work provides the first inventory of the marine malacofauna of the coast of Culuccia. Fifteen sites were sampled seasonally for one-year by using different sampling methods and the present study shows the results from approximately 50 scientific SCUBA and free dive surveys, carried out in all main marine habitats of the studied area. In total, 259 species of molluscs were recorded along the coasts of the Culuccia Peninsula (0-25 m depth), belonging to the classes Bivalvia, Gastropoda, Polyplacophora and Scaphopoda. Amongst the four classes recorded, gastropods were the most represented (66.90%; 173 species), followed by bivalves (28.10%; 73 species), polyplacophorans (4.60%; 12 species) and scapophods (0.40%; 1 species). Notes about distribution, conservation status and ecology for some valuable species are provided, together with images of representative species, consisting mainly of in situ photographs. Additionally, the present investigation recorded the presence of four alien species, whose Mediterranean distribution was extended to north-western Sardinia.

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The freshwater amphibious snail Orientogalba viridis commonly occurs in eastern Asia, on certain Pacific islands and more importantly has recently dispersed into Europe. Since this snail is now considered an invasive species, its distribution is of growing parasitological interest as an alien intermediate host for various trematodes, particularly liver flukes. As part of ongoing surveillance for snail-borne diseases in Malawi, a population of O. viridis was first observed in May 2023, alongside an alarming presence of a human schistosome cercaria. This snail population later underwent detailed morphological characterisation with both snail and parasite identities confirmed upon DNA barcoding. This seminal observation triggered more extensive local snail surveys, finding 3 further populations in separated rice paddies, with further field-caught snails (n = 465) screened for infection and a selection used for repeated experimental challenges with miracidia from Schistosoma haematobium and Schistosoma mattheei. Although no field-caught (and experimentally exposed) snail was seen to shed schistosome cercariae, molecular xenomonitoring for schistosomiasis provided tangible evidence of putative transmission potential. Our first report of O. viridis here in Malawi, and more broadly in Africa, flags a need for increased vigilance for this invasive species alongside local clarification(s) of its transmission potential for trematodiases of either medical and/or veterinary importance.

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Wet meadows harbor rich biodiversity, making them pivotal ecosystems worldwide. These habitats are commonly used for grazing or hay production for livestock. However, regular mowing can influence these habitats, potentially leading to significant repercussions for the animals residing within them. In order to investigate the effects of land management practices, we conducted an experimental study to compare snail communities in mowed and unmowed wet meadows in northern Hungary. We found that overall, mowing decreases snail populations, as well as species richness and diversity. Thus, our results suggest that routine mowing of wet meadows is deleterious to their snail communities. Based on these results, we suggest that designated patches of meadows that are regularly managed should be left uncultivated in their natural state. These patches can serve as potential colonization sites, facilitating the restoration of the entire meadow's ecological balance.

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Consistent species identification is foundational to biological research and requires coordination among a diversity of researchers and institutions. However, such consistency may be hindered for rare organisms where specimens, identification resources, and taxonomic experts are few. This is often the case for deep-sea taxonomic groups. For example, the deep-sea gastropod genus Provanna Dall, 1918 is common at chemosynthetic sites throughout the world's oceans, yet no formal guide to these species has yet been produced. Recent exploration has recovered new specimens of Provanna from hydrocarbon seeps off the Pacific Costa Rica Margin. The current work assesses the species identity of these specimens using shell morphology, radular morphology, and genetic barcoding (mitochondrial CO1 and nuclear H3). Records of occurrence for P.laevis Warén & Ponder, 1991, P.ios Warén & Bouchet, 1986, and P.pacifica Warén & Bouchet, 1986 are herein presented from the Costa Rica Margin. A critical taxonomic review of the 29 extant species within this genus was conducted and their genetic, morphological, and biogeographical distinction assessed. In this review, genetic and morphological support was found for nearly all current species delineations except for P.glabraOkutani et al., 1992, syn. nov. and P.laevis, syn. nov., which are herein synonymized to P.laevis, and for P.ios, syn. nov. and P.goniata Warén & Bouchet, 1986, syn. nov., which are synonymized to P.ios. Finally, the first species identification key for the extant species in this genus is presented. This work clarifies the taxonomy and systematics of this deep-sea gastropod genus and contributes a novel polytomous key for use in future research.

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This is a critical review of what we know so far about the evolution of metallothioneins (MTs) in Gastropoda (snails, whelks, limpets and slugs), an important class of molluscs with over 90,000 known species. Particular attention will be paid to the evolution of snail MTs in relation to the role of some metallic trace elements (cadmium, zinc and copper) and their interaction with MTs, also compared to MTs from other animal phyla. The article also highlights the important distinction, yet close relationship, between the structural and metal-selective binding properties of gastropod MTs and their physiological functionality in the living organism. It appears that in the course of the evolution of Gastropoda, the trace metal cadmium (Cd) must have played an essential role in the development of Cd-selective MT variants. It is shown how the structures and Cd-selective binding properties in the basal gastropod clades have evolved by testing and optimizing different combinations of ancestral and novel MT domains, and how some of these domains have become established in modern and recent gastropod clades. In this context, the question of how adaptation to new habitats and lifestyles has affected the original MT traits in different gastropod lineages will also be addressed. The 3D structures and their metal binding preferences will be highlighted exemplarily in MTs of modern littorinid and helicid snails. Finally, the importance of the different metal requirements and pathways in snail tissues and cells for the shaping and functionality of the respective MT isoforms will be shown.

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This study introduces a comprehensive method for quantifying mass mortality events in freshwater wildlife, exemplified by the ecological disaster in the Odra River in 2022. Our approach integrates field observations, statistical analysis, and ecological assessment to measure the impact of such events on various aquatic species. Key steps include systematic counting of deceased organisms, assessing population declines, and evaluating the ecological repercussions of invasive species. Utilizing the R programming language, we developed a framework that is adaptable to similar ecological crises in different aquatic environments. This methodology facilitates a detailed understanding of the scale and implications of mass mortality events, thereby contributing to effective environmental management and conservation efforts. •The analysis and modeling methods of the disaster are presented in the R programming language.•Exclusively open-source software was used for the analysis.•The analysis includes detailed data on the disaster's impact on various species.

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BACKGROUND: How novel phenotypes originate from conserved genes, processes, and tissues remains a major question in biology. Research that sets out to answer this question often focuses on the conserved genes and processes involved, an approach that explicitly excludes the impact of genetic elements that may be classified as clade-specific, even though many of these genes are known to be important for many novel, or clade-restricted, phenotypes. This is especially true for understudied phyla such as mollusks, where limited genomic and functional biology resources for members of this phylum have long hindered assessments of genetic homology and function. To address this gap, we constructed a chromosome-level genome for the gastropod Berghia stephanieae (Valdés, 2005) to investigate the expression of clade-specific genes across both novel and conserved tissue types in this species. RESULTS: The final assembled and filtered Berghia genome is comparable to other high-quality mollusk genomes in terms of size (1.05 Gb) and number of predicted genes (24,960 genes) and is highly contiguous. The proportion of upregulated, clade-specific genes varied across tissues, but with no clear trend between the proportion of clade-specific genes and the novelty of the tissue. However, more complex tissue like the brain had the highest total number of upregulated, clade-specific genes, though the ratio of upregulated clade-specific genes to the total number of upregulated genes was low. CONCLUSIONS: Our results, when combined with previous research on the impact of novel genes on phenotypic evolution, highlight the fact that the complexity of the novel tissue or behavior, the type of novelty, and the developmental timing of evolutionary modifications will all influence how novel and conserved genes interact to generate diversity.

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Goniodorididae is a family of small dorid nudibranchs distributed worldwide that feed on entoprocts, ascidians, and bryozoans. The evolutionary relationships between its taxa have been uncertain due to the limited taxa available for phylogenetic analyses; some genera being paraphyletic. The family includes a remarkable number of synonymized genera in which the species richness is unequally distributed, while some genera have dozens of species others are monospecific. Some clades are very uniform morphologically while others are considered highly variable. To increase backbone phylogenetic resolution a target enrichment approach of ultra-conserved elements was aimed at representative Goniodorididae species for the first time. Additionally, we increase species representation by including mitochondrial markers cytochrome c oxidase subunit I and ribosomal RNA 16S as well as nuclear Histone 3 and ribosomal RNA 18S from 109 Goniodorididae species, out of approximately 160 currently valid species. Maximum likelihood and Bayesian inference analyses were performed to infer the phylogeny of the family. As a result, two subfamilies and eleven genera were elucidated. The synonymized genera Bermudella, Cargoa, and Ceratodoris are here resurrected and a new genus, Naisdoris gen. nov., is described. The clades included taxa with shared prey preference, showing that trophic behavior could have driven species evolution and morphological uniqueness within the family Goniodorididae.

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Chemoreception is critical for the survival and reproduction of animals. Except for a reduced group of insects and chelicerates, the molecular identity of chemosensory proteins is poorly understood in invertebrates. Gastropoda is the extant mollusk class with the greatest species richness, including marine, freshwater, and terrestrial lineages, and likely, highly diverse chemoreception systems. Here, we performed a comprehensive comparative genome analysis taking advantage of the chromosome-level information of two Gastropoda species, one of which belongs to a lineage that underwent a whole genome duplication event. We identified thousands of previously uncharacterized chemosensory-related genes, the majority of them encoding G protein-coupled receptors (GPCR), mostly organized into clusters distributed across all chromosomes. We also detected gene families encoding degenerin epithelial sodium channels (DEG-ENaC), ionotropic receptors (IR), sensory neuron membrane proteins (SNMP), Niemann-Pick type C2 (NPC2) proteins, and lipocalins, although with a lower number of members. Our phylogenetic analysis of the GPCR gene family across protostomes revealed: (i) remarkable gene family expansions in Gastropoda; (ii) clades including members from all protostomes; and (iii) species-specific clades with a substantial number of receptors. For the first time, we provide new and valuable knowledge into the evolution of the chemosensory gene families in invertebrates other than arthropods.

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In response to the significant ecological disaster in the Odra River during the summer of 2022, a comprehensive data collection process was initiated to quantify the extent of mortality among aquatic species. The dataset focuses on the downstream section of the river, identified as the area with the highest accumulation of deceased organisms. The data collection involved systematic sampling and counting of dead organisms, including fish, bivalves , and aquatic snails. Special attention was given to specific species such as Unionidae mussels, Anodonta anatina, Sinanodonta woodiana, and Viviparus viviparus. Additionally, transects were designated for focused data collection on fish mortality. The dataset provides detailed mortality figures, biomass estimates, and percentage reductions for each species. This comprehensive dataset holds significant potential for reuse by researchers studying the effects of toxins on freshwater ecosystems, the impact of invasive species on native populations, and conservationists aiming to restore the affected areas.

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How novel phenotypes originate from conserved genes, processes, and tissues remains a major question in biology. Research that sets out to answer this question often focuses on the conserved genes and processes involved, an approach that explicitly excludes the impact of genetic elements that may be classified as clade-specific, even though many of these genes are known to be important for many novel, or clade-restricted, phenotypes. This is especially true for understudied phyla such as mollusks, where limited genomic and functional biology resources for members of this phylum has long hindered assessments of genetic homology and function. To address this gap, we constructed a chromosome-level genome for the gastropod Berghia stephanieae (Valdés, 2005) to investigate the expression of clade-specific genes across both novel and conserved tissue types in this species. The final assembled and filtered Berghia genome is comparable to other high quality mollusk genomes in terms of size (1.05 Gb) and number of predicted genes (24,960 genes), and is highly contiguous. The proportion of upregulated, clade-specific genes varied across tissues, but with no clear trend between the proportion of clade-specific genes and the novelty of the tissue. However, more complex tissue like the brain had the highest total number of upregulated, clade-specific genes, though the ratio of upregulated clade-specific genes to the total number of upregulated genes was low. Our results, when combined with previous research on the impact of novel genes on phenotypic evolution, highlight the fact that the complexity of the novel tissue or behavior, the type of novelty, and the developmental timing of evolutionary modifications will all influence how novel and conserved genes interact to generate diversity.