The molecular phylogeny of Caenogastropoda (Mollusca, Gastropoda) based on mitochondrial genomes and nuclear genes

Comprising about 60 % of gastropod diversity, caenogastropods display almost all kinds of shell forms and include many commercially important marine groups. Although the monophyly of Caenogastropoda has been widely accepted, thier internal phylogenetic relationships remain unclear. In the present study, a total of 27 caenogastropods belonging to eight superfamilies were sequenced and used for phylogenetic reconstruction. All newly sequenced mitogenomes adhered to the consensus gene order of caenogastropods, except for those of Vanikoroidea, Vermetoidea and Cerithioidea, which involved protein-coding genes. The reconstructed mitogenomic phylogeny suggested the monophylies of Architaenioglossa, Sorbeoconcha, Hypsogastropoda and the siphonate clade. The present study also identified a close affinity among Cypraeoidea, Ficoidea, Tonnoidea, and Neogastropoda, supported by the presence of a pleurembolic proboscis. The monophyly of Neogastropoda was not supported, as Cancellariidae was found to be sister to the limpet-shaped group Calyptraeoidea, and (Tonooidea + Ficoidea) were sister to the remaining neogastropods. This study provides important information for better understanding the evolution of caenogastropods, as well as for the protection and utilization of these diverse and economically significant marine resources.

Increased microgastropoda sampling give new insights into the phylogenetic relationships of Littorinoidea (Littorinimorpha)

Littorinoidea is one of the most diverse radiations and the most successful group that evolutionary transitions from marine to terrestrial within Littorinimorpha. With such an unmatched diversity, few phylogenetic investigations have attempted to understand their evolutionary relationships, and existing research has primarily focused on typical intertidal species. To address this gap, we conducted the first phylogenomic analysis of the Littorinoidea, leveraging 35 transcriptomes to investigate their internal relationships. Our analyses revealed significant revisions necessary within the Littorinoidea: 1) Pomatias appears distantly related to Littorinidae, suggesting a potential ancestral origin outside of Littorinoidea, challenging traditional classification. The homology of penial innervation within Littorinoidea warrants reevaluation. 2) Lacuna's placement indicates a close relationship with Naticidae, prompting consideration for its removal from Littorinidae. 3) Based on the current phylogenetic research, Peasiella may belong to a distinct family separate from Littorinidae. 4) Our findings support revising the placement of Pteropods within the Littorinimorpha, which is situated phylogenetically between the families Littorinoidea and Naticoidea. Additionally, we highlight the impact of site heterogeneity and evolutionary rate variation on phylogenetic inference. Our study provides a robust phylogenomic framework for the Littorinoidea, emphasizing the importance of including microgastropoda taxa in molecular phylogenetic reconstructions of gastropod subgroups.

Phylogenomics of Neogastropoda: The Backbone Hidden in the Bush

The molluskan order Neogastropoda encompasses over 15,000 almost exclusively marine species playing important roles in benthic communities and in the economies of coastal countries. Neogastropoda underwent intensive cladogenesis in the early stages of diversification, generating a "bush" at the base of their evolutionary tree, which has been hard to resolve even with high throughput molecular data. In the present study to resolve the bush, we use a variety of phylogenetic inference methods and a comprehensive exon capture dataset of 1817 loci (79.6% data occupancy) comprising 112 taxa of 48 out of 60 Neogastropoda families. Our results show consistent topologies and high support in all analyses at (super)family level, supporting monophyly of Muricoidea, Mitroidea, Conoidea, and, with some reservations, Olivoidea and Buccinoidea. Volutoidea and Turbinelloidea as currently circumscribed are clearly paraphyletic. Despite our analyses consistently resolving most backbone nodes, 3 prove problematic: First, the uncertain placement of Cancellariidae, as the sister group to either a Ficoidea-Tonnoidea clade or to the rest of Neogastropoda, leaves monophyly of Neogastropoda unresolved. Second, relationships are contradictory at the base of the major "core Neogastropoda" grouping. Third, coalescence-based analyses reject monophyly of the Buccinoidea in relation to Vasidae. We analyzed phylogenetic signal of targeted loci in relation to potential biases, and we propose the most probable resolutions in the latter 2 recalcitrant nodes. The uncertain placement of Cancellariidae may be explained by orthology violations due to differential paralog loss shortly after the whole genome duplication, which should be resolved with a curated set of longer loci.

Between sea angels and butterflies: A global phylogeny of pelagic pteropod molluscs

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.

Transcriptome data for an ancient 'living-fossil' mollusc, Entemnotrochus rumphii

The Pleurotomarioidea, commonly referred to as slit shells, constitute one of the most ancient and enduring lineages within the phylum Mollusca, with its fossil record tracing back to the Upper Cambrian epoch. Its rareness and evolutionary antiquity surpass even that of the nautilus. In this study, we conducted the first transcriptome sequencing and analyses of Entemnotrochus rumphii (Schepman, 1879), a representative species of Pleurotomarioidea. Full-length transcriptome sequencing of E. rumphii was performed using the PacBio Sequel II platform with SMRT technology. A total of 64.38 gigabytes of data and 964,550 polymerase reads were generated, resulting in 28,068,998 subreads after data filtering. After de-duplication, correction, and clustering, we identified 19,273 genes. Additionally, next-generation sequencing was performed on 11 tissues of E. rumphii. This investigation provides a detailed portrayal and analytical scrutiny of its transcriptomic landscape.

The Characterization of the Mitochondrial Genome of Fulgoraria rupestris and Phylogenetic Considerations within the Neogastropoda

Fulgoraria rupestris is a predatory marine gastropod belonging to Neogastropoda and possessing considerable taxonomic significance. However, research on this species remains limited. We acquired the complete mitochondrial genome of F. rupestris through second-generation sequencing and conducted an analysis of its genome structural features. The mitochondrial genome of F. rupestris spans a total length of 16,223 bp and encompasses 37 genes (13 protein-coding genes (PCGs), 22 transfer RNAs, and 2 ribosomal RNAs). Notably, most tRNAs exhibit the typical cloverleaf structure, but there is an absence of the Dihydrouridine (DHU) arm in the trnS1 and trnS2 genes. The A + T content is 68.67%, indicating a pronounced AT bias. Additionally, we conducted a selection pressure analysis on the mitochondrial genomes of four species within Volutidae, revealing that all PCGs are subjected to purifying selection. In comparison to other species within Neogastropoda, F. rupestris shares an identical gene arrangement. Additionally, based on mitochondrial genome sequences of the 13 PCGs from 50 species within Neogastropoda, we constructed a phylogenetic tree. The phylogenetic tree indicates F. rupestris forms a clade with species within the family Volutidae (Cymbium olla, Neptuneopsis gilchristi, and Melo melo). This study serves as a valuable reference for future research on F. rupestris, offering insights for the upcoming phylogenetic and taxonomic classification within Neogastropoda. Furthermore, the findings provide valuable information for the development of genetic resources in this context.

Ocean Species Discoveries 1-12 - A primer for accelerating marine invertebrate taxonomy

Background

Discoveries of new species often depend on one or a few specimens, leading to delays as researchers wait for additional context, sometimes for decades. There is currently little professional incentive for a single expert to publish a stand-alone species description. Additionally, while many journals accept taxonomic descriptions, even specialist journals expect insights beyond the descriptive work itself. The combination of these factors exacerbates the issue that only a small fraction of marine species are known and new discoveries are described at a slow pace, while they face increasing threats from accelerating global change. To tackle this challenge, this first compilation of Ocean Species Discoveries (OSD) presents a new collaborative framework to accelerate the description and naming of marine invertebrate taxa that can be extended across all phyla. Through a mode of publication that can be speedy, taxonomy-focused and generate higher citation rates, OSD aims to create an attractive home for single species descriptions. This Senckenberg Ocean Species Alliance (SOSA) approach emphasises thorough, but compact species descriptions and diagnoses, with supporting illustrations and with molecular data when available. Even basic species descriptions carry key data for distributions and ecological interactions (e.g., host-parasite relationships) besides universally valid species names; these are essential for downstream uses, such as conservation assessments and communicating biodiversity to the broader public.

New information

This paper presents thirteen marine invertebrate taxa, comprising one new genus, eleven new species and one re-description and reinstatement, covering wide taxonomic, geographic, bathymetric and ecological ranges. The taxa addressed herein span three phyla (Mollusca, Arthropoda, Echinodermata), five classes, eight orders and twelve families. Apart from the new genus, an updated generic diagnosis is provided for four other genera. The newly-described species of the phylum Mollusca are Placiphorellamethanophila Vončina, sp. nov. (Polyplacophora, Mopaliidae), Lepetodrilusmarianae Chen, Watanabe & Tsuda, sp. nov. (Gastropoda, Lepetodrilidae), Shinkailepasgigas Chen, Watanabe & Tsuda, sp. nov. (Gastropoda, Phenacolepadidae) and Lyonsiellaillaesa Machado & Sigwart, sp. nov. (Bivalvia, Lyonsiellidae). The new taxa of the phylum Arthropoda are all members of the subphylum Crustacea: Lepechinellanaces Lörz & Engel, sp. nov. (Amphipoda, Lepechinellidae), Cuniculomaeragrata Tandberg & Jażdżewska, gen. et sp. nov. (Amphipoda, Maeridae), Pseudionellapumulaensis Williams & Landschoff, sp. nov. (Isopoda, Bopyridae), Mastigoniscusminimus Wenz, Knauber & Riehl, sp. nov. (Isopoda, Haploniscidae), Macrostylispapandreas Jonannsen, Riehl & Brandt, sp. nov. (Isopoda, Macrostylidae), Austroniscusindobathyasellus Kaiser, Kniesz & Kihara, sp. nov. (Isopoda, Nannoniscidae) and Apseudopsisdaria Esquete & Tato, sp. nov. (Tanaidacea, Apseudidae). In the phylum Echinodermata, the reinstated species is Psychropotesbuglossa E. Perrier, 1886 (Holothuroidea, Psychropotidae).The study areas span the North and Central Atlantic Ocean, the Indian Ocean and the North, East and West Pacific Ocean and depths from 5.2 m to 7081 m. Specimens of eleven free-living and one parasite species were collected from habitats ranging from an estuary to deep-sea trenches. The species were illustrated with photographs, line drawings, micro-computed tomography, confocal laser scanning microscopy and scanning electron microscopy images. Molecular data are included for nine species and four species include a molecular diagnosis in addition to their morphological diagnosis.The five new geographic and bathymetric distribution records comprise Lepechinellanaces Lörz & Engel, sp. nov., Cuniculomaeragrata Tandberg & Jażdżewska, sp. nov., Pseudionellapumulaensis Williams & Landschoff, sp. nov., Austroniscusindobathyasellus Kaiser, Kniesz & Kihara, sp. nov. and Psychropotesbuglossa E. Perrier, 1886, with the novelty spanning from the species to the family level. The new parasite record is Pseudionellapumulaensis Williams & Landschoff, sp. nov., found in association with the hermit crab Pagurusfraserorum Landschoff & Komai, 2018.

Contributions on a small collection of the former Subulinidae Fischer & Crosse, 1877 (Eupulmonata, Achatinoidea) with catalogue of the Glessula and Rishetia species recorded from Myanmar

The taxonomy of subulinid snails in Myanmar has been evaluated, resulting in the recognition of 40 species and subspecies across nine genera: Allopeas, Bacillum, Curvella, Glessula, Opeas, Paropeas, Rishetia, Tortaxis, and Zootecus. Nine species are re-described based on recently collected specimens, and two new species, Glessulamandalayensis Man & Panha, sp. nov. from Mandalay Region and Tortaxiscylindropsis Man & Panha, sp. nov. from Shan State are introduced. The genitalia and radula of Zootecuspullus was studied for the first time. This study also presents a comprehensive list of all subulinid species recorded to date from Myanmar. The type specimens and authenticated museum specimens have been illustrated with accompanying taxonomic remarks and nine species formerly assigned in Glessula are now placed in Rishetia: R.akouktoungensis, R.baculina, R.basseinensis, R.burrailensismaxwelli, R.kentungensis, R.limborgi, R.nathiana, R.pertenuis, and R.pertenuismajor.

Staging of post-settlement growth in the nudibranch Hypselodoris festiva

Sea slugs of the family Chromodorididae (Nudibranchia, Gastropoda, Mollusca) have garnered attention by researchers and hobbyists alike for their bright and variable color patterns. However, the chromodorid life cycle has yet to be fully elucidated as there exist no reports of their rearing in the laboratory. Here, we report the rearing of Hypselodoris festiva from eggs to adults, where we categorized their post-settlement growth patterns from juvenile to adult stages. Body coloration appeared around 36 days, and organogenesis of vital adult organs began within 42 days after hatching. The anus of H. festiva was observed to change from a ventral to dorsal position during juvenile growth. Individuals reached sexual maturity after six months post-hatching, with successful mating and spawning observed ex situ. This study outlines comprehensive rearing methods and life cycle staging that could be applied to other chromodorid species. We propose H. festiva as a model organism for chromodorid research, with this research contributing to the progress of developmental and evolutionary research on sea slugs.

The distribution and evolutionary dynamics of dopaminergic neurons in molluscs

Dopamine is one of the most versatile neurotransmitters in invertebrates. It's distribution and plethora of functions is likely coupled to feeding ecology, especially in Euthyneura (the largest clade of molluscs), which presents the broadest spectrum of environmental adaptations. Still, the analyses of dopamine-mediated signaling were dominated by studies of grazers. Here, we characterize the distribution of dopaminergic neurons in representatives of two distinct ecological groups: the sea angel - obligate predatory pelagic mollusc Clione limacina (Pteropoda, Gymnosomata) and its prey - the sea devil Limacina helicina (Pteropoda, Thecosomata) as well as the plankton eater Melibe leonina (Nudipleura, Nudibranchia). By using tyrosine hydroxylase-immunoreactivity (TH-ir) as a reporter, we showed that the dopaminergic system is moderately conservative among euthyneurans. Across all studied species, small numbers of dopaminergic neurons in the central ganglia contrast to significant diversification of TH-ir neurons in the peripheral nervous system, primarily representing sensory-like cells, which predominantly concentrated in the chemotactic areas and projecting afferent axons to the central nervous system. Combined with α-tubulin immunoreactivity, this study illuminates the unprecedented complexity of peripheral neural systems in gastropod molluscs, with lineage-specific diversification of sensory and modulatory functions.

New records of non-indigenous species from the eastern Mediterranean Sea (Crustacea, Mollusca), with a revision of genus Isognomon (Mollusca: Bivalvia)

We report new data on non-indigenous invertebrates from the Mediterranean Sea (four ostracods and 20 molluscs), including five new records for the basin: the ostracods Neomonoceratina iniqua, Neomonoceratina aff. mediterranea, Neomonoceratina cf. entomon, Loxoconcha cf. gisellae (Arthropoda: Crustacea)-the first records of non-indigenous ostracods in the Mediterranean-and the bivalve Striarca aff. symmetrica (Mollusca). Additionally, we report for the first time Electroma vexillum from Israel, and Euthymella colzumensis, Joculator problematicus, Hemiliostraca clandestina, Pyrgulina nana, Pyrgulina microtuber, Turbonilla cangeyrani, Musculus aff. viridulus and Isognomon bicolor from Cyprus. We also report the second record of Fossarus sp. and of Cerithiopsis sp. cf. pulvis in the Mediterranean Sea, the first live collected specimens of Oscilla galilae from Cyprus and the northernmost record of Gari pallida in Israel (and the Mediterranean). Moreover, we report the earliest records of Rugalucina angela, Ervilia scaliola and Alveinus miliaceus in the Mediterranean Sea, backdating their first occurrence in the basin by 3, 5 and 7 years, respectively. We provide new data on the presence of Spondylus nicobaricus and Nudiscintilla aff. glabra in Israel. Finally, yet importantly, we use both morphological and molecular approaches to revise the systematics of the non-indigenous genus Isognomon in the Mediterranean Sea, showing that two species currently co-occur in the basin: the Caribbean I. bicolor, distributed in the central and eastern Mediterranean, and the Indo-Pacific I. aff. legumen, at present reported only from the eastern Mediterranean and whose identity requires a more in-depth taxonomic study. Our work shows the need of taxonomic expertise and investigation, the necessity to avoid the unfounded sense of confidence given by names in closed nomenclature when the NIS belong to taxa that have not enjoyed ample taxonomic work, and the necessity to continue collecting samples-rather than relying on visual censuses and bio-blitzes-to enable accurate detection of non-indigenous species.

Mitogenomes do not substantially improve phylogenetic resolution in a young non-model adaptive radiation of freshwater gastropods

BACKGROUND

Species flocks in ancient lakes, and particularly those arising from adaptive radiation, make up the bulk of overall taxonomic and morphological diversity in these insular ecosystems. For these mostly young species assemblages, classical mitochondrial barcoding markers have so far been key to disentangle interspecific relationships. However, with the rise and further development of next-generation sequencing (NGS) methods and mapping tools, genome-wide data have become an increasingly important source of information even for non-model groups.

RESULTS

Here, we provide, for the first time, a comprehensive mitogenome dataset of freshwater gastropods endemic to Sulawesi and thus of an ancient lake invertebrate species flock in general. We applied low-coverage whole-genome sequencing for a total of 78 individuals including 27 out of the 28 Tylomelania morphospecies from the Malili lake system as well as selected representatives from Lake Poso and adjacent catchments. Our aim was to assess whether mitogenomes considerably contribute to the phylogenetic resolution within this young species flock. Interestingly, we identified a high number of variable and parsimony-informative sites across the other 'non-traditional' mitochondrial loci. However, although the overall support was very high, the topology obtained was largely congruent with previously published single-locus phylogenies. Several clades remained unresolved and a large number of species was recovered polyphyletic, indicative of both rapid diversification and mitochondrial introgression.

CONCLUSIONS

This once again illustrates that, despite the higher number of characters available, mitogenomes behave like a single locus and thus can only make a limited contribution to resolving species boundaries, particularly when introgression events are involved.

Differentiation of Bulinus senegalensis and Bulinus forskalii Snails in West Africa Using Morphometric Analysis

PURPOSE

Accurate identification of medically important intermediate host and vector species is crucial for understanding disease transmission and control. Identifying Bulinus snails which act as intermediate host species for the transmission of schistosomiasis is typically undertaken using conchological and genital morphology as well as molecular methods.

METHODS

Here, a landmark-based morphometric analysis of shell morphology was undertaken to determine its utility to distinguish the closely related and morphologically similar sister species Bulinus senegalensis and Bulinus forskalii. The method was developed to increase the accuracy of conchological morphology methods to identify Bulinus species in the field. Both species are found in West Africa, but only B. senegalensis is implicated in the transmission of urogenital schistosomiasis.

RESULTS

We found when scaled down to the same length, 3-whorl and 4-whorl (juvenile) B. senegalensis shells had a longer spire, narrower body whorl and shorter aperture than B. forskalii. In contrast, 5-whorl (adult) B. senegalensis had a shorter spire, but still had a shorter aperture and narrower body whorl than B. forskalii. Canonical Variate Analysis (CVA) showed minimal overlap between B. senegalensis and B. forskalii for 3-whorl and 4-whorl shells, with a clear separation for 5-whorl shells. Overall, B. senegalensis had a consistently shorter aperture size and narrower body whorl than B. forskalii for all development stages. Spire length was variable depending on the stage of development, with 3-whorl and 4-whorl shells having the opposite trends of adult shells.

CONCLUSIONS

Our study demonstrates the applicability of landmark-based morphometrics in distinguishing the medically important, Bulinus senegalensis from its morphologically similar sister species, Bulinus forskalii. We recommend using measurements based on spire length, penultimate whorl length, body whorl width and aperture size to differentiate B. senegalensis and B. forskalii, when used with the appropriate information for each shell's development stage.

A combined phylogenetic strategy illuminates the evolution of Goniodorididae nudibranchs (Mollusca, Gastropoda, Heterobranchia)

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.

Comparative Mitogenome Analyses of Fifteen Ramshorn Snails and Insights into the Phylogeny of Planorbidae (Gastropoda: Hygrophila)

Ramshorn snails from the family Planorbidae are important freshwater snails due to their low trophic level, and some of them act as intermediate hosts for zoonotic trematodes. There are about 250 species from 40 genera of Planorbidae, but only 14 species from 5 genera (Anisus, Biomphalaria, Bulinus, Gyraulus, and Planorbella) have sequenced complete mitochondrial genomes (mitogenomes). In this study, we sequenced and assembled a high-quality mitogenome of a ramshorn snail, Polypylis sp. TS-2018, which represented the first mitogenome of the genus. The mitogenome of Polypylis sp. TS-2018 is 13,749 bp in length, which is shorter than that of most gastropods. It contains 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA) genes, and 2 ribosomal RNA (rRNA). We compared mitogenome characteristics, selection pressure, and gene rearrangement among all of the available mitogenomes of ramshorn snails. We found that the nonsynonymous and synonymous substitution rates (Ka/Ks) of most PCGs indicated purifying and negative selection, except for atp8 of Anisus, Biomphalaria, and Gyraulus, which indicated positive selection. We observed that transpositions and reverse transpositions occurred on 10 tRNAs and rrnS, which resulted in six gene arrangement types. We reconstructed the phylogenetic trees using the sequences of PCGs and rRNAs and strongly supported the monophyly of each genus, as well as three tribes in Planorbidae. Both the gene rearrangement and phylogenetic results suggested that Polypylis had a close relationship with Anisus and Gyraulus, while Bulinus was the sister group to all of the other genera. Our results provide useful data for further investigation of species identification, population genetics, and phylogenetics among ramshorn snails.

The fossil record of freshwater Gastropoda - a global review

Gastropoda are an exceptionally successful group with a rich and diverse fossil record. They have conquered land and freshwater habitats multiple times independently and have dispersed across the entire globe. Since they are important constituents of fossil assemblages, they are often used for palaeoecological reconstruction, biostratigraphic correlations, and as model groups to study morphological and taxonomic evolution. While marine faunas and their evolution have been a common subject of study, the freshwater component of the fossil record has attracted much less attention, and a global overview is lacking. Here, I review the fossil record of freshwater gastropods on a global scale, ranging from their origins in the late Palaeozoic to the Pleistocene. As compiled here, the global fossil record of freshwater Gastropoda includes 5182 species in 490 genera, 44 families, and 12 superfamilies over a total of ~340 million years. Following a slow and poorly known start in the late Palaeozoic, diversity slowly increased during the Mesozoic. Diversity culminated in an all-time high in the Neogene, relating to diversification in numerous long-lived (ancient) lakes in Europe. I summarise well-documented and hypothesised freshwater colonisation events and compare the patterns found in freshwater gastropods to those in land snails. Furthermore, I discuss potential preservation and sampling biases, as well as the main drivers underlying species diversification in fresh water on a larger scale. In that context, I particularly highlight the importance of long-lived lakes as islands and archives of evolution and expand a well-known concept in ecology and evolution to a broader spectrum: scale-independent ecological opportunity.

Rediscovery and systematics of the enigmatic genus Helicostoa reveals a new species of sessile freshwater snail with remarkable sexual dimorphism

Helicostoa sinensis E. Lamy, 1926 is a unique freshwater gastropod species with a sessile habit. This enigmatic species was first found cemented on river limestones from China about 120 years ago and described together with the genus. It was never collected again and has been considered monotypic. Here, we report the rediscovery of Helicostoa from several rivers in China, and describe a second species of this genus based on a comprehensive study. In addition to the unique sessile habit of both species, the new Helicostoa species presents one of the most remarkable cases of sexual dimorphism within molluscs. Only the adult female is sessile and the original aperture of the female is sealed by shell matter or rock, while an opening on the body whorl takes the function of the original aperture. The male is vagile, with a normal aperture. Our results confirm the recently suggested placement of Helicostoa within the family Bithyniidae. The sessility of Helicostoa species is considered as an adaption to the limestone habitat in large rivers. The extreme sexual dimorphism and secondary aperture of females are considered as adaptations to overcome the obstacles for mating and feeding that come with a sessile life style.

Underreported and taxonomically problematic: characterization of sanguinicolid larvae from freshwater limpets (Burnupiidae), with comments on the phylogeny and intermediate hosts of sanguinicolids

Blood flukes of freshwater fish are understudied worldwide. Consequently, genetic information and data on their intramolluscan stages are scarce. In the current study, freshwater limpets of the genus Burnupia (Burnupiidae) from South Africa were examined for digeneans. Of 1645 specimens, 3.10% were infected by Sanguinicolidae larvae. Four sanguinicolids were distinguished by body size, number of penetration glands, tegumental spines’ patterns and relative sizes of the finfolds on the body and furcae. Analyses of 28S, 18S and ITS rDNA sequences showed that the morphotypes were distinct from each other and from sanguinicolids whose genetic data are available. The present study is the first genetic characterization of sanguinicolids from Africa. Phylogenetic reconstruction revealed that the present species clustered with a sanguinicolid from Poland and were sister to Sanguinicola and Pseudosanguinicola from Russia and USA, respectively. The results indicate that the current species represent an unknown genus. What is more, blood fluke sequences from East Africa (presumed to be sanguinicolids), were distant from Sanguinicolidae and showed a closer relationship with acipensericolids from the USA. Freshwater fish blood flukes seem to be more diverse than previously recorded and use species of at least 13 gastropod families as intermediate hosts.

One-health approach on the future application of snails: a focus on snail-transmitted parasitic diseases

Snails are fascinating molluscs with unique morphological and physiological adaptive features to cope with various environments. They have traditionally been utilized as food and feed sources in many regions of the world. The future exploitation of alternative nutrient sources, like snails, is likely to increase further. Snails, however, also serve as an intermediate host for several zoonotic parasites. A category of parasitic infections, known as snail-transmitted parasitic diseases (STPDs), is harmful to humans and animals and is mainly driven by various trematodes, cestodes, and nematodes. The environment plays a crucial role in transmitting these parasites, as suitable habitats and conditions can facilitate their growth and proliferation in snails. In light of diverse environmental settings and biologically categorized snail species, this review evaluates the dynamics of significant STPDs of zoological importance. Additionally, possible diagnostic approaches for the prevention of STPDs are highlighted. One-health measures must be considered when employing snails as an alternative food or feed source to ensure the safety of snail-based products and prevent any adverse effects on humans, animals, and the environment.

Pocillopora damicornis-associated macroinvertebrate responses to spatial gradients in the southern Mexican Pacific

We explicitly tested for spatial changes in Pocillopora damicornis-associated invertebrates across several spatial scales in the southern Mexican Pacific. Sorting of invertebrates from 40 coral heads along 882 km of the coast yielded 325 taxa, 283% more than any other Pocillopora spp. coral host study to date, but estimators signals that richness might be 17-39% larger than the current number. Permutation, ordination, and regression analysis indicate that the composition and abundance of invertebrates vary in response to the spatial distance among coral heads: high similarity and variation occur among coral heads within localities (<500 m), probably related to faunal homogenization, but progressively modest reduction in similarity and variation as spatial distance increases suggesting a weak role for environmental sorting across southern Mexican Pacific coral reefs. Future studies should explicitly explore spatial, environmental, and historical biogeography processes that regulate and maintain community structure and biodiversity on eastern Pacific reefs.

The First Genome Survey of the Snail Provanna glabra Inhabiting Deep-Sea Hydrothermal Vents

The snail P. glabra is an endemic species in deep-sea chemosynthetic ecosystems of the Northwest Pacific Ocean. To obtain more genetic information on this species and provide the basis for subsequent whole-genome map construction, a genome survey was performed on this snail from the hydrothermal vent of Okinawa Trough. The genomic size of P. glabra was estimated to be 1.44 Gb, with a heterozygosity of 1.91% and a repeated sequence content of 69.80%. Based on the sequencing data, a draft genome of 1.32 Gb was assembled. Transposal elements (TEs) accounted for 40.17% of the entire genome, with DNA transposons taking the highest proportion. It was found that most TEs were inserted in the genome recently. In the simple sequence repeats, the dinucleotide motif was the most enriched microsatellite type, accounting for 53% of microsatellites. A complete mitochondrial genome of P. glabra with a total length of 16,268 bp was assembled from the sequencing data. After comparison with the published mitochondrial genome of Provanna sp. from a methane seep, 331 potential single nucleotide polymorphism (SNP) sites were identified in protein-coding genes (PCGs). Except for the cox1 gene, nad2, nad4, nad5, and cob genes are expected to be candidate markers for population genetic and phylogenetic studies of P. glabra and other deep-sea snails. Compared with shallow-water species, three mitochondrial genes of deep-sea gastropods exhibited a higher evolutionary rate, indicating strong selection operating on mitochondria of deep-sea species. This study provides insights into the genome characteristics of P. glabra and supplies genomic resources for further studies on the adaptive evolution of the snail in extreme deep-sea chemosynthetic environments.

Seven new genera and thirty-four new species of buccinoid gastropods (Neogastropoda: Buccinidae) from the Aleutian Islands, Alaska

Seven new genera and thirty-four new species of gastropods in the in the family Buccinidae, are described from the Aleutian Islands. The new taxa represent five subfamilies: Parancistrolepidinae Habe, 1972: Boreancistrolepis excelsus n. gen. & n. sp. Beringiinae Golikov & Starabogatov, 1975: Aleutijapelion mirandus n. gen. & n. sp.; Beringius nearensis n. sp., B. amliensis n. sp., B. bisulcatus n. sp., B. kiskensis n. sp., B. stanchfieldi n. sp., B. frausseni n. sp., B. aurulentus n. sp., B. maristempestus n. sp., B. undataformis n. sp.; Exiloberingius exiguus n. gen. & n. sp. Neptuneinae Stimpson, 1865: Aulacofusus canaliculatus n. sp., A. tanagaensis n. sp.; Neptunea aleutica n. sp., N. baxteri n. sp., N. dominator n. sp., N. petrelensis n. sp., N. quhmax n. sp., N. vesteraalen n. sp.; N. harrisoni n. sp., N. jewetti n. sp., Laevisipho galaxaios n. gen & n. sp., L. kessleri n. sp.; Volutopsiinae: Volutopsius nanus n. sp., Volutopsius gracilis n. sp.; Crebrivolutopsius labidentatus n. gen. & n. sp. Buccininae Rafinesque, 1815: Aleutibuccinum n. gen.; Castaneobuccinum orri n. gen. & n. sp., C. lauthi, n. sp., C. clinopsis n. sp., C. pagodaformis n. sp.; Sulcosinus carinatus n. sp.; Buccinum lanatum n. sp.; and Buccinum katharinae n. gen. & n. sp. The new genera and species are distinguished by the morphological characters of the shells and radulae.

Complete mitochondrial genomes of the slugs Deroceraslaeve (Agriolimacidae) and Ambigolimaxvalentianus (Limacidae) provide insights into the phylogeny of Stylommatophora (Mollusca, Gastropoda)

In this study, we sequenced two complete mitogenomes from Deroceraslaeve and Ambigolimaxvalentianus. The mitogenome of Ambigolimaxvalentianus represented the first such data from the family Limacidae. The lengths of the mitogenomes of Deroceraslaeve and Ambigolimaxvalentianus were 14,773 bp and 15,195 bp, respectively. The entire set of 37 mitochondrial genes were identified for both mitogenomes. Compared with the mitogenome of Achatinafulica, the trnP_trnA tRNA cluster was rearranged in both Deroceraslaeve and Ambigolimaxvalentianus. The secondary structures of tRNA and rRNA genes for the two species were predicted. Phylogenetic analyses based on amino acid sequences supported (1) monophyly of Stylommatophora, (2) division of Stylommatophora into the 'achatinoid' clade (i.e., the suborder Achatinina) and the 'non-achatinoid' clade (i.e., the suborder Helicina), (3) placement of the Orthurethra in the 'non-achatinoid' clade, and (4) monophyly of each of the superfamilies Helicoidea, Urocoptoidea, Succineoidea, Arionoidea, Pupilloidea and Limacoidea. The exemplars of Helicidae, Philomycidae and Achatinellidae displayed many more mitochondrial gene rearrangements than other species of Stylommatophora.

Molecular phylogeny of the Orthalicoidea land snails: Further support and surprises

The superfamily Orthalicoidea comprises approximately 2,000 species of terrestrial gastropods, mostly concentrated in the Neotropics but also present in southern Africa and Oceania. We provide a multi-marker molecular phylogeny of this superfamily, reassessing its family- and genus-level classification. We exclude two families from the group, Odontostomidae and Vidaliellidae, transferring them to Rhytidoidea based on their phylogenetic relationships as recovered herein. Two new families are recognized herein as members of Orthalicoidea, Tomogeridae and Cyclodontinidae fam. nov. The family Megaspiridae and the subfamily Prestonellinae are paraphyletic but are retained herein for taxonomic stability. The subfamily Placostylinae is synonymized with Bothriembryontinae. The new genera Alterorhinus gen. nov. and Sanniostracus gen. nov. containing some Brazilian species are described here to better reflect the phylogeny. The fossil record and paleobiogeographic history of the group is explored under the new phylogenetic framework.

Redescription and geographical distribution of Leiostracusobliquus (Reeve, 1849) (Mollusca, Gastropoda, Simpulopsidae)

Leiostracus Albers, 1850 was established to allocate land snails from Central America and Northern South America. Currently, approximately 19 species are considered valid. However, for most of them, the internal morphology is unknown. Leiostracusobliquus was described as a species of Bulimus from the state of Bahia based on shell characters. Until now, knowledge of this species has been scarce. The discovery of ethanol-preserved specimens from MZSP of this species allowed us to characterize, for the first time, the internal anatomy of this species and update its distribution. The shell of L.obliquus has seven to eight whorls and a wide pale-pink disrupted band all over the teleoconch. The rachidian tooth is small rectangular, symmetric, with round edges, and without differentiated cusps. After comparing the anatomy and radular characters between the shells of L.obliquus and L.carnavalescus, we found remarkable similarities in the morphology and color pattern.

The Lower Pliocene marine gastropods of Santa Maria Island, Azores: Taxonomy and palaeobiogeographic implications

In this work, all the Lower Pliocene gastropod assemblages of Santa Maria Island are revised. These all form part of the Touril Complex. Seventy-seven species are identified representing 61 genera. Two species are described as new: Bittium miradouroense nov. sp. and Erato mayeri nov. sp. The name Tritonium secans Bronn in Reiss 1862 is considered a junior subjective synonym of Monoplex comptus (A. Adams, 1855). Pleurotoma perturrita Bronn in Reiss 1862 is considered a junior subjective synonym of Crassopleura maravignae (Bivona, 1838). However, due to the difficulties in collecting from these deposits, this is likely to be a considerable underestimate of the original diversity of local Early Pliocene gastropod faunas. The assemblage reflects a fully tropical with mean annual sea surface temperatures (SSTs) estimated about 3.7°C to 6.3°C higher than the present-day 20.6°C, and with mean monthly SSTs ranging from 20°C to 28°C, with six months with mean SSTs over 24°C. The assemblages all represent relatively shallow water, fully saline marine environments. At genus level the assemblage is typical of that seen in the tropical Mediterranean-West African Palaeobiogeographical Province during the early Pliocene (MPPMU1; roughly equivalent to the Zanclean and earliest Piacenzian). At species level, 35% of the species taxa found in Santa Maria are also found in the Mediterranean during MPPMU1. There is a much weaker association with the northern warm temperate Pliocene Boreal-Celtic Province, with only 17% of species occurring in both. Moreover, most of those are ubiquitous European species with both wide geographic and stratigraphic distributions. The assemblage is relatively endemic (29%) suggesting that the Azorean subprovince/ecoregion, which is recognised today, was already in place in the Lower Pliocene. A small number of tonnoidean species found in Santa Maria are species known to have had an amphiatlantic distribution during the Pliocene, and for Distorsio mcgintyi Emerson & Puffer, 1953, a well-known and widely distributed tropical American Atlantic species from the Early Miocene to present-day, its presence in Santa Maria marks the most easterly range expansion for the species, as today is not found in the Azores.

Historical DNA solves century-old mystery on sessility in freshwater gastropods

Extinction rates are increasing unabatedly but resources available for conservation action are limited. Therefore, some conservationists are pushing for ecology- and evolution-based conservation choices, prioritizing taxa with phylogenetic and trait-based originality. Extinction of original taxa may result in a disproportionate loss of evolutionary innovations and potentially prevent transformative changes in living systems. Here, we generated historical DNA data from an almost 120-year-old syntype of the enigmatic sessile snail Helicostoa sinensis from the Three Gorges region of the Yangtze River (PR China), using a next-generation sequencing protocol developed for ancient DNA. In a broader phylogenetic context, we assessed the phylogenetic and trait-based originality of this enigmatic taxon to solve the century-old puzzle of sessility in freshwater gastropods. Our multi-locus data confirm the phylogenetic and trait-based originality of H. sinensis. It is an ultra-rare, subfamily-level taxon (Helicostoinae stat. nov.) within the family Bithyniidae, which exhibits the evolutionary innovation of sessility. While we conservatively classify H. sinensis as "Critically Endangered", there is mounting evidence of the biological annihilation of this endemic species. Although rapidly rising extinction rates in invertebrates are increasingly recognized, the potential loss of originality in these "little things that run the world" has received little attention. We therefore call for comprehensive surveys of originality in invertebrates, particularly from extreme environments such as rapids of large rivers, as a basis for urgently needed ecology- and evolution-based conservation decisions.

The lost vent gastropod species of Lothar A. Beck

Deep-sea hydrothermal vents host many endemic species adapted to these chemosynthesis-based ecosystems. The exploration of vent fields including those in the tropical Pacific is currently accelerating, due to the development of deep-sea mining for valuable minerals. Molecular evidence has shown that many vent endemic gastropod lineages include sibling species pairs in adjacent oceanic basins. While the fauna of the Manus Basin is relatively well described, many lineages in adjacent regions in North Fiji or Lau Basins are recognised as separate species, but unnamed. Valuable material from this fauna was studied by Lothar A. Beck in the 1990s, who fully drafted descriptions for these species, but did not publish them. Beck's manuscript names, prior to the present study, represented real species but nomina nuda without taxonomic validity. Here we present the descriptions of seven new species and one new genus, extracted from Beck's unpublished manuscript that was rediscovered after his death in 2020. The publication of these descriptions makes them taxonomically available and respects the scientific contributions of Beck. Providing valid descriptions of these species is critically important now to enable the recognition of species that may require conservation in the face of future environmental destruction. Symmetriapelta Beck, gen. nov. is described as new genus. Bathyacmaea nadinae Beck, sp. nov., Pyropelta ovalis Beck, sp. nov., Pseudorimula leisei Beck, sp. nov., Lepetodrilus fijiensis Beck, sp. nov., Shinkailepas conspira Beck, sp. nov., Symmetromphalus mcleani Beck, sp. nov. and Symmetriapelta wareni Beck, sp. nov. are introduced as new species.

Bioaccumulation and ecotoxicological impact of micro(nano)plastics in aquatic and land snails: Historical review, current research and emerging trends

Microplastics (MPs) and nanoplastics (NPs) are ubiquitous emerging pollutants in the environment. Although MPs/NPs' hazardous effects have been described at different trophic levels, little attention has been given to how they can affect gastropod communities. Thus, the current study aimed to summarize and critically address data available in the scientific literature about micro(nano)plastics' ecotoxicological impact on snails. The analyzed data has evidenced MP/NP bioaccumulation in 40 gastropod species collected in the field; 15 gastropod species were used to assess the potential toxicity of MPs/NPs. Asia accounted for the highest level of MPs/NPs bioaccumulated in gastropods; it was followed by the South American, European and Antarctic continents. MPs/NPs' toxicity depends on their composition, shape and size, as well as on differences in methodological approaches adopted by different studies. Results have shown that MPs/NPs induce several impairments - such as behavioral changes, developmental toxicity, dysbiosis, histopathological alterations, oxidative stress -, generate ecological impairments, as well as act as pollutant vector and increase chiral chemicals' toxicity. Research gaps and recommendations for future research were highlighted to help better understanding MPs/NPs' toxicity in gastropods, given the extremely important role played by them in studies focused on investigating how MPs/NPs can affect invertebrate communities living in terrestrial and aquatic environments.

Five times over: 42 new Angustopila species highlight Southeast Asia’s rich biodiversity (Gastropoda, Stylommatophora, Hypselostomatidae)

The Southeast Asian genus Angustopila, currently comprising 13 nominal species, encompasses the world’s tiniest land snails. This work shows that there are far more species than previously suspected, and that this genus is in fact, a very speciose group of tiny snails widely distributed in Southeast Asia. Angustopila is revised based on type material of known species as well as 211 samples newly collected in China, Laos, Myanmar, Thailand and Vietnam. Altogether, 53 species and one subspecies are recognised, of which 42 species and subspecies are new to science: A. akrodon Páll-Gergely & Hunyadi, sp. nov., A. apiaria Páll-Gergely & Hunyadi, sp. nov., A. apiostoma Páll-Gergely & Vermeulen, sp. nov., A. apokritodon Páll-Gergely & Hunyadi, sp. nov., A. antidomedon Páll-Gergely & Hunyadi, sp. nov., A. babel Páll-Gergely & Vermeulen, sp. nov., A. bathyodon Páll-Gergely & Hunyadi, sp. nov., A. bidentata Páll-Gergely & Jochum, sp. nov., A. cavicola Páll-Gergely & Dumrongrojwattana, sp. nov., A. cicatricosa Páll-Gergely & Vermeulen, sp. nov., A. coprologos uninodus Páll-Gergely & Grego, ssp. nov., A. erawanica Páll-Gergely & Dumrongrojwattana, sp. nov., A. fratermajor Páll-Gergely & Vermeulen, sp. nov., A. fraterminor Páll-Gergely & Vermeulen, sp. nov., A. gracilis Páll-Gergely & Hunyadi, sp. nov., A. halongensis Páll-Gergely & Vermeulen, sp. nov., A. hyron Páll-Gergely & Vermeulen, sp. nov., A. maasseni Páll-Gergely & Vermeulen, sp. nov., A. majuscula Páll-Gergely & Hunyadi, sp. nov., A. margaritarion Páll-Gergely & Hunyadi, sp. nov., A. megastoma Páll-Gergely & Vermeulen, sp. nov., A. occidentalis Páll-Gergely & Hunyadi, sp. nov., A. oostoma Páll-Gergely & Vermeulen, sp. nov., A. papaver Páll-Gergely & Hunyadi, sp. nov., A. parallela Páll-Gergely & Hunyadi, sp. nov., A. prolixa Páll-Gergely & Hunyadi, sp. nov., A. pusilla Páll-Gergely & Hunyadi, sp. nov., A. pustulata Páll-Gergely & Hunyadi, sp. nov., A. quadridens Páll-Gergely & Vermeulen, sp. nov., A. rara Páll-Gergely & Hunyadi, sp. nov., A. reticulata Páll-Gergely & Hunyadi, sp. nov., A. somsaki Páll-Gergely & Hunyadi, sp. nov., A. steffeki Páll-Gergely & Grego, sp. nov., A. tetradon Páll-Gergely & Hunyadi, sp. nov., A. thersites Páll-Gergely & Vermeulen, sp. nov., A. tonkinospiroides Páll-Gergely & Vermeulen, sp. nov., A. tridentata Páll-Gergely & Hunyadi, sp. nov., A. tweediei Páll-Gergely & Hunyadi, sp. nov., A. uvula Páll-Gergely & Hunyadi, sp. nov., A. vandevenderi Páll-Gergely & Jochum, sp. nov., A. vitrina Páll-Gergely & Hunyadi, sp. nov., A. vomer Páll-Gergely & Hunyadi, sp. nov., A. werneri Páll-Gergely & Hunyadi, sp. nov.

Angustopila subelevata Páll-Gergely & Hunyadi, 2015 is moved to the synonymy of Angustopila elevata (F. G. Thompson & Upatham, 1997), and A. singuladentis Inkhavilay & Panha, 2016 is a junior synonym of A. fabella Páll-Gergely & Hunyadi, 2015. Three species, namely A. elevata, A. fabella and A. szekeresi, are widespread over several hundred kilometres while some other species (A. huoyani, A. parallelasp. nov., A. cavicolasp. nov.) are known from just two sites a few hundred kilometres apart. All others are small range or single-site endemics. The reproductive anatomy of A. erawanicasp. nov. is described.

First Record of Corallivorous Nudibranch Pinufius (Gastropoda: Nudibranchia) in the South China Sea: A Suspected New Species of Pinufius

A corallivorous nudibranch from the South China Sea reproduced explosively and caused extensive damage to Porites in our aquarium. In this study, morphological and molecular analyses of the nudibranch were conducted and described. Morphologically, this nudibranch was nearly consistent with Pinufius rebus in its characteristics intermediate between arminids and aeolids. The only detected difference was that the hook-like denticles on the masticatory border of P. rebus were absent in this nudibranch. In a molecular analysis, phylogenetic results based on the cytochrome oxidase subunit-I, 16S rRNA, and histone H3 gene sequences showed that this nudibranch and P. rebus form a well-supported sister clade under the superfamily Fionoidea, with significant interspecific divergence (0.18). Thus, we presumed that this nudibranch is a new species of Pinufius. Our results extend the distribution of Pinufius to the South China Sea, support the current taxonomic status of Pinufius under the superfamily Fionoidea, and imply that the species composition of Pinufius is more complex than previous records. Moreover, as a corallivorous nudibranch, the potential threat of Pinufius to coral health cannot be neglected.

A histochemical and morphological study of the mucus producing pedal gland system in Latia neritoides (Mollusca; Gastropoda; Hygrophila)

The freshwater gastropod Latia neritoides is endemic to the streams of New Zealand's North Island. This species has evolved a unique defence system: it exudes a luminescent mucus thought to deter predators. While the bioluminescence itself has been investigated before, the underlying gland system has remained unstudied and relevant information to understand the defence system has been missing till now. For the release of the glowing mucus of L. neritoides two places of origin were assumed: the lateral foot area or the mantel cavity. In this study the focus was on the first suggestion. To gain insight into the defence system, morphological as well as histochemical analyses were performed involving all secretory gland types in the sub-epithelial foot layer. The results were compared with the foot gland system of Neritina sp., a snail living in a comparable habitat, but using a different survival strategy. The gland types of the two gastropods were compared and their mucus types were investigated. Seven subepithelial gland cell types can be distinguished in the foot region of L. neritoides. Neritina sp., in contrast, has six gland cell types of which three laterally located ones are epithelial. Both species show a pedal gland in the anterior foot region. A striking difference between the species are two prominent subepithelial gland cell types (L1l/L2l) in the lateral foot area of L. neritoides, which are missing in Neritina sp. These gland cells are distributed throughout the entire lateral foot area of L. neritoides and make up about 85% of the mucus gland cells in this area. Defence mucus and trail mucus of L. neritoides show different specificities in lectin staining, but are not equally represented in the gland cell types. Yet, based on the huge size and high density of L1l and L2L, we envision a role for these gland types in the defence system.

Systematic revision of the snorkel snail genus Rhiostoma Benson, 1860 (Gastropoda, Caenogastropoda, Cyclophoridae) with descriptions of new species

The snorkel snail genus Rhiostoma Benson, 1860 is comprised of terrestrial cyclophorid snails with wide-ranging species diversity and radiation in Southeast Asia. The typical characters of the genus are a depressed shell, a detached and descending portion of the last whorl with a distinctive peristomal breathing device attached, and a calcareous cup-shaped operculum. Herein, we have revised the systematics of extant species based on shell morphology combined with COI barcoding. From these thirty recognised species, twelve are described as new to science: R. ? amarapuraensesp. nov., R. anceyisp. nov., R. breviocollarsp. nov., R. ebenozosterasp. nov., R. cheliopegmasp. nov., R. furfurosumsp. nov., R. gnomus, sp. nov., R. lannaensesp. nov., R. laoensesp. nov., R. platymorphasp. nov., R. rhothonotaphrosasp. nov., and R. tigrinasp. nov. All conchological characters are provided via illustrations of type specimens and living snails, and descriptions of the shells and radulae. Phylogenetic analysis based on partial COI gene sequences strongly supports the designated morphospecies and a monophyletic Rhiostoma, confirming that all pterocyclinid snails with a calcareous, cup-shaped operculum belong to the same clade. A high intra-specific divergence was observed in R. jalorensis and R. housei populations from locations in close proximity, suggesting a lower dispersal and higher level of isolation. The low inter-specific divergence found in R. hainesi, R. samuiense, R. asiphon, and R. rhothonotaphrosasp. nov. supports their recent diversification and local adaptation, and is congruent with their marked morphological differences. Finally, nine formerly Rhiostoma-placed species were reclassified into either the genus Cyclotus or the genus Opisthoporus.

Diversity and abundance of terrestrial molluscs and their associated nematode fauna in urban kitchen gardens in the city of Rio de Janeiro, Brazil

Terrestrial molluscs can become agricultural pests and transmit parasites, playing an important role in different biological communities. In the present study, we evaluated the diversity and abundance of this group in two horticultural areas in Rio de Janeiro (Manguinhos and Jacarepaguá neighborhoods), as well the presence of parasitic nematodes associated with these molluscs. We collected specimens in the austral spring and summer, with four sites being sampled within each study area, including malabar spinach, sweet potato, chicory greens, and cassava plantations, and one site in an adjacent, non-cultivated area. We collected a total of 522 live mollusc specimens and identified 16 species from 10 different families. The greatest abundance of molluscs was recorded in summer (363) and at Jacarepaguá (309). Overall, 174 (57%) of the 303 specimens analyzed parasitologically were positive for nematodes. Larvae of superfamily Metastrongyloidea, which includes nematodes that are a concern for public health and veterinary medicine, were found parasitizing the slug Sarasinula linguaeformis, in Manguinhos. Our results contribute to understanding of the diversity of terrestrial molluscs occurring in kitchen gardens in the city of Rio de Janeiro, and provide important insights for generating subsidies for health education actions and control of parasitic diseases transmitted by them.

Neither slugs nor snails: a molecular reappraisal of the gastropod family Velutinidae

The systematics of the marine mollusc family Velutinidae has long been neglected by taxonomists, mainly because their often internal and fragile shells offer no morphological characters. Velutinids are usually undersampled owing to their cryptic mantle coloration on the solitary, social or colonial ascidians on which they feed and lay eggs. In this study, we address the worldwide diversity and phylogeny of Velutinidae based on the largest molecular dataset (313 specimens) to date, accounting for &gt; 50% of the currently accepted genera, coupled with morphological and ecological data. Velutinids emerge as a diverse group, encompassing four independent subfamily-level lineages, two of which are newly described herein: Marseniopsinae subfam. nov. and Hainotinae subfam. nov. High diversity was found at genus and species levels, with two newly described genera (Variolipallium gen. nov. and Pacifica gen. nov.) and ≥ 86 species in the assayed dataset, 58 of which are new to science (67%). Velutinidae show a remarkable morphological plasticity in shell morphology, mantle extension and chromatic patterns. This variability is likely to be the result of different selective forces, including habitat, depth and trophic interactions.

The complete mitochondrial genome of the terrestrial snail Monachacartusiana (O.F. Müller, 1774) (Gastropoda, Eupulmonata, Hygromiidae)

The mitochondrial genome of Monachacartusiana is the first complete mitochondrial sequence described for the pulmonate snail genus Monacha and for the family Hygromiidae. The identified mitogenome has a length of 13,894 bp and encodes 13 proteins, 22 tRNAs, and two rRNAs. A phylogenetic analysis of available mitogenomes from representatives of helicoid families shows a sister group relationship of Hygromiidae and Geomitridae, which have been recently recognised as separate families.

Molecular phylogeny of selected dorid nudibranchs based on complete mitochondrial genome

Dorid nudibranchs are a large group of mollusks with approximately 2,000 recorded species. Although agreement exists on the monophyletic nature of the dorid nudibranch group, the interfamily relationships of the suborder are subject to debate. Despite efforts to elucidate this issue using short molecular markers, the conclusiveness of the findings has been hindered by branching polytomy. Mitogenomes are known to be effective markers for use in phylogenetic investigations. In this study, eight mitogenomes of dorid nudibranchs were decoded and analyzed. Gene content and structure showed little change among species, reflecting the conserved mitogenomes of dorid nudibranchs. For most genes, the direction was typical for nudibranchs; nevertheless, tRNA^Cys had an inverse direction in Cadlinidae species. Phylogenetic trees based on nucleotide and amino acid datasets revealed a relatively consistent pattern of interfamily relationships with little difference for positions of Phyllidiidae and Cadlinidae. Species of Cadlinidae were clustered together and did not form a clade with Chromododidae. Additionally, Goniodorididae was sister to Aegiridae, whereas Discodoridae was sister to Dorididae. This finding was supported by tree topology test based on mitogenome data. The results of the present study indicate that complete mitogenomes are promising markers for investigating interfamily relationships among dorid nudibranchs.

Complete distribution of the genus Laevilitorina (Littorinimorpha, Littorinidae) in the Southern Hemisphere: remarks and natural history

Littorinid snails are present in most coastal areas globally, playing a significant role in the ecology of intertidal communities. Laevilitorina is a marine gastropod genus distributed exclusively in the Southern Hemisphere, with 21 species reported from South America, the sub-Antarctic islands, Antarctica, New Zealand, Australia and Tasmania. Here, an updated database of 21 species generated from a combination of sources is presented: 1) new field sampling data; 2) published records; 3) the Global Biodiversity Information Facility (GBIF) and The Atlas of Living Australia (ALA), to provide a comprehensive description of the known geographic distribution of the genus and detailed occurrences for each of the 21 species. The database includes 813 records (occurrences), 53 from field sampling, 174 from the literature, 128 from GBIF, and 458 from ALA. West Antarctica had the highest species richness (8 species), followed by sub-Antarctic islands of New Zealand (4 species) and the south-east shelf of Australia (4 species). The provinces of Magellan, New Zealand South Island, and sub-Antarctic Islands of the Indian Ocean include two species each. This study specifically highlights reports of L.pygmaea and L.venusta, species that have been almost unrecorded since their description. Recent advances in molecular studies of L.caliginosa showed that this species does not correspond to a widely distributed taxon, but to multiple divergent lineages distributed throughout the Southern Ocean. Ongoing molecular and taxonomic studies are necessary for a better understanding of the diversity and biogeography of this genus.

Molecular phylogeny of Columbellidae (Gastropoda: Neogastropoda)

The neogastropod family Columbellidae is a highly successful group of small, primarily epibenthic marine snails distributed worldwide and most abundant in the tropics. The great diversity of the group makes them attractive for studying evolutionary shifts in gastropod anatomy, morphology, ecology and diversity. The existing classification of the family has been based to a large degree on the morphology of the shell and radula. Indeed, membership in the family is traditionally confirmed using the unique morphology of the radula. To reconstruct columbellid phylogeny and assess monophyly of the group, we assembled a multilocus dataset including five mitochondrial and nuclear genes, for 70 species in 31 genera. Phylogenetic analyses using Bayesian inference and maximum likelihood are not well enough resolved to support a subfamilial classification, but do support the monophyly of the family and of several well-defined genera and supra-generic groupings. Two of the most diverse nominal genera, Mitrella and Anachis, are supported as highly polyphyletic. Overall, the resulting topologies indicate that the generic and subfamilial classification is in need of extensive revision but that phylogenomic data are needed to resolve columbellid relationships.

Dissecting an island radiation: systematic revision of endemic land snails on Lord Howe Island (Gastropoda: Stylommatophora: Microcystidae)

The Lord Howe Island Microcystidae currently comprise two endemic genera containing nine species. We revise their taxonomy comprehensively using comparative morphology and phylogenetic analyses of the mitochondrial genes COI and 16S and demonstrate that the Lord Howe Island microcystids probably represent a single radiation. Based on our findings, we recognize Melloconcha, Tribocystis and Annacharis as junior synonyms of Innesoconcha and provide a revised generic diagnosis of Innesoconcha and redescriptions for all species. In addition, we reinstate Innesoconcha segna from synonymy and describe Innesoconcha doppelganger sp. nov., bringing the total number of accepted species in the genus to 11. Most species are well differentiated, in terms of both morphological differences and basal branch lengths in the mitochondrial trees. However, members of the Innesoconcha catletti species complex reveal lower levels of genetic and morphological differentiation and are likely to represent examples of more recent, perhaps even ongoing, speciation which might be driven by reinforcement. We recommend conservation assessments of all species, particularly Innesoconcha aberrans and Innesoconcha grata, which are rare species that have declined in abundance over the past 50 years, and note that Innesoconcha rosacea and Innesoconcha delecta appear to have become geographically more restricted. Innesoconcha miranda and I. segna are probably extinct.

The molluscan assemblage of a pristine Posidonia oceanica meadow in the eastern Mediterranean

The seagrass Posidonia oceanica forms extensive meadows in the Mediterranean Sea. Studies on their associated highly diverse invertebrate assemblages are limited to the western Mediterranean. The eastern Mediterranean, however, is a basin undergoing rapid change due to the synergistic effects of climate warming, biological invasions and other human stressors that are driving native biodiversity to regional-scale collapses. We here surveyed the shelled molluscan assemblage of a Posidonia oceanica meadow in Plakias, south-western Crete, the first such study in the eastern Mediterranean Sea. This area has increased its yearly mean temperature by 1 °C in the last 20 years and is under heavy pressure by Lessepsian species. We sampled across a 5- to 20-m depth gradient, in two seasons to capture intra-annual variation and the leaf and rhizome strata separately. Against our expectations, the molluscan assemblage proved to be highly diverse, with species richness, dominant species and trophic guilds comparable to healthy western Mediterranean ones, and with a negligible non-indigenous component. The diversity of the native community (following the biotic resistance hypothesis) and oxygen supersaturation in the meadow may cause greater resistance to biological invasions and warming, respectively, suggesting that Posidonia oceanica meadows may act as a precious refugium for native biodiversity in the fast changing eastern Mediterranean Sea.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s12526-022-01292-2.

Integrative taxonomy of a new cocculinid limpet dominating the Aurora Vent Field in the central Arctic ocean

Deep-sea hydrothermal vents host lush chemosynthetic communities, dominated by endemic fauna that cannot live in other ecosystems. Despite over 500 active vents found worldwide, the Arctic has remained a little-studied piece of vent biogeography. Though located as early as 2001, the faunal communities of the Aurora Vent Field on the ultra-slow spreading Gakkel Ridge remained unsampled until recently, owing to difficulties with sampling on complex topography below permanent ice. Here, we report an unusual cocculinid limpet abundant on inactive chimneys in Aurora (3883-3884 m depth), describing it as Cocculina aurora n. sp. using an integrative approach combining traditional dissection, electron microscopy, molecular phylogeny, and three-dimensional anatomical reconstruction. Gross anatomy of the new species was typical for Cocculina, but it has a unique radula with broad, multi-cuspid rachidian where the outermost lateral is reduced compared to typical cocculinids. A phylogenetic reconstruction using the mitochondrial COI gene also confirmed its placement in Cocculina. Only the second cocculinid found at vents following the description of the Antarctic Cocculina enigmadonta, this is currently the sole cocculinid restricted to vents. Our discovery adds to the evidence that Arctic vents host animal communities closely associated with wood falls and distinct from other parts of the world.

Neogastropod (Mollusca, Gastropoda) phylogeny: A step forward with mitogenomes

The Neogastropoda (Mollusca, Gastropoda) encompass more than 15,000 described species of marine predators, including several model organisms in toxinology, embryology and physiology. However, their phylogenetic relationships remain mostly unresolved and their classification unstable. We took advantage of the many mitogenomes published in GenBank to produce a new molecular phylogeny of the neogastropods. We completed the taxon sampling by using an in-house bioinformatic pipeline to retrieve mitochondrial genes from 13 transcriptomes, corresponding to five families not represented in GenBank, for a final dataset of 113 taxa. Because mitogenomic data are prone to reconstruction artefacts, eight different evolutionary models were applied to reconstruct phylogenetic trees with IQTREE, RAxML and MrBayes. If the over-parametrization of some models produced trees with aberrant internal long branches, the global topology of the trees remained stable over models and softwares, and several relationships were revealed or found supported here for the first time. However, even if our dataset encompasses 60% of the valid families of neogastropods, some key taxa are missing and should be added in the future before proposing a revision of the classification of the neogastropods. Our study also demonstrates that even complex models struggle to satisfactorily handle the evolutionary history of mitogenomes, still leading to long-branch attractions in phylogenetic trees. Other approaches, such as reduced-genome strategies, must be envisaged to fully resolve the neogastropod phylogeny.

Annotated checklist of the operculated land snails from Thailand (Mollusca, Gastropoda, Caenogastropoda): the family Pupinidae, with descriptions of several new species and subspecies, and notes on classification of Pupina Vignard, 1829 and Pupinella Gray, 1850 from mainland Southeast Asia

Thailand is located at the crossroads of several biogeographical regions, and boasts a high level of biodiversity, especially among the malacofauna. The most recent checklist of land snail species in Thailand was compiled more than twenty years ago, and so this checklist needs revision and the addition of newly discovered taxa. This study updates the taxonomy and species list of the operculated land snail family Pupinidae from Thailand. This snail family is diverse and abundant, and can be found in various natural habitats in Southeast Asia. Although the taxonomy of some Southeast Asian pupinid genera has been reviewed, studies of Pupina Vignard, 1829, which contains the highest number of species, and a lesser-known genus Pupinella Gray, 1850 are still lacking. Herein we present an annotated checklist with an up-to-date systematic framework of the Pupinidae in Thailand based on both field investigations and literature surveys, and include the taxonomic treatment of all Pupina and Pupinella species from mainland Southeast Asia. This annotated checklist contains 30 nominal species and two subspecies from seven genera currently known to occur in Thailand. We describe two species of Pseudopomatias (P.doiangkhangensis Jirapatrasilp, sp. nov. and P.pallgergelyi Jirapatrasilp, sp. nov.), five species and one subspecies of Pupina (P.bensoni Jirapatrasilp, sp. nov., P.bilabiata Jirapatrasilp, sp. nov., P.godwinausteni Jirapatrasilp, sp. nov., P.latisulci Jirapatrasilp, sp. nov., P.stoliczkai Jirapatrasilp, sp. nov., and P.dorriisanensis Jirapatrasilp, ssp. nov.) as new to science. New records of Coptocheilussumatranus, Pupinellamansuyi, and Rhaphaulustonkinensis are also reported from Thailand. The mainland Southeast Asian Pupina species are classified into three species groups (Pupinaartata group, Pupinaarula group, and Pupinaaureola group) based on the distinction of shell teeth and canals, and operculum. Three species formerly in Pupina from Vietnam are allocated to Pupinella (P.illustris comb. nov., P.sonlaensis comb. nov., and P.thaitranbaii comb. nov.) due to the presence of a funnel-like anterior canal.

Additions to the genus Anthinus occurring in Minas Gerais and Goiás regions, Brazil, with description of five new species, one of them in the new related genus Catracca (Gastropoda, Eupulmonata, Strophocheilidae)

Four new species of the strophocheilid genus Anthinus are described from Brazil, being A. synchondrus from region of Unaí, Minas Gerais; A. vailanti from the region of Brasilândia de Minas, Minas Gerais; A. morenus from Paracatu region, Minas Gerais; and A. savanicus from Formosa region, Goiás. Another similar snail from Itacarambi, Minas Gerais, is described as a new genus and species: Catracca uhlei. All species are described conchologically and anatomically, with distinctions explored in almost all structures. For comparative purposes, a similar anatomical investigation on the Anthinus type species, A. multicolor, from Rio de Janeiro, is also performed. A detailed comparative analysis and discussion is provided, including taxonomic and initial phylogenetic inferences. The preliminary phylogenetic analysis is based on anatomically known species in the literature and in the presently study. A bulimulid, a simpulopsid and two dorcasiids are outgroups. The preliminary cladogram already shows a monophyletic Strophocheilidae (14 synapomorphies), divided into two also monophyletic subfamilies: Megalobuliminae (14 synapomorphies) and Strophocheilinae (5 synapomorphies). The new Catracca resulted as the most basal strophocheilid branch. Mirinaba and Anthinus were also supported as monophyletic (3 and 6 synapomorphies respectively. Register ZooBank: urn:lsid:zoobank.org:pub:FC4DD323-EF6A-404B-9755-F124F9DBB6D4.

A small slug from a tropical greenhouse reveals a new rathouisiid lineage with triaulic tritrematic genitalia (Gastropoda: Systellommatophora)

A small slug found in the tropical greenhouse of the Science Museum (MUSE) of Trento (Italy) turned out to be a species of the little-known systellommatophoran family Rathouisiidae. We undertook detailed comparative anatomical and molecular studies using specimens of the MUSE slug, Rathouisia sinensis, and sequences of other systellommatophoran species deposited in GenBank to conduct a systematic and phylogenetic assessment. Analysis of the genitalia of the MUSE slug and R. sinensis revealed an unusual triaulic tritrematic structure: two separate female ducts – one for egg release (oviduct), the other for intake of allosperm (vagina) – and a separate male duct for autosperm release. Analysis of the nucleotide sequences of several mitochondrial (COI, 16S rDNA) and nuclear (18S rDNA, ITS2 flanked by 5.8S and 28S rDNA fragments, H3) gene fragments supported assignation of the MUSE slug to Rathouisiidae, but also its distinction from the other rathouisiid genera Atopos, Granulilimax, Rathouisia and an undescribed genus from the Ryukyu Islands (Japan). Therefore, we decided to describe the MUSE slug as a new species in a new genus: Barkeriella museensis gen. et sp. nov. The species is certainly an alien introduced into the tropical greenhouse of MUSE, but its origin is unknown and calls for further investigation.

A phylogenomic backbone for gastropod molluscs

Gastropods have survived several mass extinctions during their evolutionary history resulting in extraordinary diversity in morphology, ecology, and developmental modes, which complicate the reconstruction of a robust phylogeny. Currently, gastropods are divided into six subclasses: Caenogastropoda, Heterobranchia, Neomphaliones, Neritimorpha, Patellogastropoda, and Vetigastropoda. Phylogenetic relationships among these taxa historically lack consensus, despite numerous efforts using morphological and molecular information. We generated sequence data for transcriptomes derived from twelve taxa belonging to clades with little or no prior representation in previous studies in order to infer the deeper cladogenetic events within Gastropoda and, for the first time, infer the position of the deep-sea Neomphaliones using a phylogenomic approach. We explored the impact of missing data, homoplasy, and compositional heterogeneity on the inferred phylogenetic hypotheses. We recovered a highly supported backbone for gastropod relationships that is congruent with morphological and mitogenomic evidence, in which Patellogastropoda, true limpets, are the sister lineage to all other gastropods (Orthogastropoda) which are divided into two main clades (i) Vetigastropoda s.l. (including Pleurotomariida + Neomphaliones) and (ii) Neritimorpha + (Caenogastropoda + Heterobranchia). As such, our results support the recognition of five subclasses (or infraclasses) in Gastropoda: Patellogastropoda, Vetigastropoda, Neritimorpha, Caenogastropoda and Heterobranchia.

Adapting mark-recapture methods to estimating accepted species-level diversity: a case study with terrestrial Gastropoda

We introduce a new method of estimating accepted species diversity by adapting mark-recapture methods to comparisons of taxonomic databases. A taxonomic database should become more complete over time, so the error bar on an estimate of its completeness and the known diversity of the taxon it treats will decrease. Independent databases can be correlated, so we use the time course of estimates comparing them to understand the effect of correlation. If a later estimate is significantly larger than an earlier one, the databases are positively correlated, if it is significantly smaller, they are negatively correlated, and if the estimate remains roughly constant, then the correlations have averaged out. We tested this method by estimating how complete MolluscaBase is for accepted names of terrestrial gastropods. Using random samples of names from an independent database, we determined whether each name led to a name accepted in MolluscaBase. A sample tested in August 2020 found that 16.7% of tested names were missing; one in July 2021 found 5.3% missing. MolluscaBase grew by almost 3,000 accepted species during this period, reaching 27,050 species. The estimates ranged from 28,409 ± 365 in 2021 to 29,063 ± 771 in 2020. All estimates had overlapping 95% confidence intervals, indicating that correlations between the databases did not cause significant problems. Uncertainty beyond sampling error added 475 ± 430 species, so our estimate for accepted terrestrial gastropods species at the end of 2021 is 28,895 ± 630 species. This estimate is more than 4,000 species higher than previous ones. The estimate does not account for ongoing flux of species into and out of synonymy, new discoveries, or changing taxonomic methods and concepts. The species naming curve for terrestrial gastropods is still far from reaching an asymptote, and combined with the additional uncertainties, this means that predicting how many more species might ultimately be recognized is presently not feasible. Our methods can be applied to estimate the total number of names of Recent mollusks (as opposed to names currently accepted), the known diversity of fossil mollusks, and known diversity in other phyla.