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Parasites exhibit high diversity in various ecosystems. Habitat selection has played an important role in the diversification of parasites by facilitating intra-host speciation and repeated shifts to a single host species by multiple parasite taxa. In this study, we investigated habitat selection in two gastropod species, Melanella cf. acicula and Peasistilifer nitidula (Caenogastropoda: Vanikoroidea: Eulimidae), that are parasitic on the black sea cucumber Holothuria atra in southwestern Japan. The number and position of parasites were observed for 335 hosts; in total, 89 individuals of M. cf. acicula and 194 of P. nitidula were found. Melanella cf. acicula exhibited strong habitat selection, with 70 individuals (78.7%) attached around the host's mouth, whereas P. nitidula had relatively low infection site specificity. This suggests that the two parasite species have different feeding habits. Molecular phylogenetic analysis verified their non-monophyletic relationship, indicating that they likely made independent host shifts to H. atra. The observed difference in habitat preference, as well as the abundance of suitable habitats, may have contributed to the repeated host shifts and sympatric distribution of M. cf. acicula and P. nitidula. Our phylogenetic analysis also revealed the non-monophyly of eulimids parasitising holothuroids, as in asteroid and ophiuroid parasitic taxa. [ABSTRACT FROM AUTHOR]

The fifth mass extinction event (MEE) at the Cretaceous–Palaeogene (K–Pg) boundary 66 million years ago (Ma) led to massive species loss but also triggered the diversification of higher taxa. Five models have been proposed depending on whether this diversification occurred before, during or after the K–Pg boundary and the rate of species accumulation. While the effects of the K–Pg MEE on vertebrate evolution are relatively well understood, the impact on invertebrates, particularly in freshwater ecosystems, remains controversial. One example is the hyperdiverse Hydrobiidae—the most species‐rich family of freshwater gastropods. Whereas some studies place its origin in the Jurassic or even Carboniferous, most fossil records postdate the K–Pg event. We therefore used robustly time‐calibrated multi‐locus phylogenies of >400 species representing >100 hydrobiid genera to unravel its evolutionary history and patterns of diversification. We found that the family started diversifying shortly after the K–Pg boundary (∼60 Ma; 95% highest posterior density 52–69 Ma). Lineage richness gradually increased to the present and phylogenetic diversity until ∼25 Ma. These findings suggest that diversification was not initially driven by ecological opportunity. Combining the two criteria of timing and rate of diversification, a soft‐explosive diversification model of aquatic vertebrates best fits the patterns observed. We also show that most higher hydrobiid taxa (i.e. subfamilies) diversified from the Middle Oligocene to Middle Miocene (i.e. 12–28 Ma). Two of the 15 major clades delimited are described here as new subfamilies (i.e. Bullaregiinae n. subfam. and Pontobelgrandiellinae n. subfam.), whose members are restricted to subterranean waters. Our results are an important contribution to understanding how the fifth MEE has shaped evolution and patterns of biodiversity in continental aquatic systems. Given the high extinction risks faced by many hydrobiids today, they also emphasise the need to study the biodiversity of vulnerable ecosystems. [ABSTRACT FROM AUTHOR]

Simple Summary: Lophiotoma leucotropis belongs to the Turridae and is a carnivorous snail that is widely distributed in shallow sea sand and intertidal zones around the world. Currently, the mitochondrial genome sequence of L. leucotropis has not been explored. And there is also great controversy over whether the order Neogastropoda to which L. leucotropis belongs is monophyletic. We sequenced the mitogenome of L. leucotropis and analyzed its basic gene characteristics. We found that it contains a total of 37 gene contents. Similar to species in the Turridae family, it has a higher content of AT bases and a preference for some codons. The selection pressure analysis results showed purification selection effects, and through comparison with other species in Turridae, it was found that the gene sequence of this species is conserved, which helps to deepen the understanding of the Turridae. We constructed a phylogenetic tree using the 13 protein coding genes of Neogastropoda and concluded that the order is monophyletic. This result is a supplement and validation to the research on the evolutionary status of Neogastropoda and also provides reference for the species classification and germplasm resource development of Neogastropoda. Neogastropoda is a group of marine organisms with an extremely wide distribution that is rich in species and economic and ornamental values, the classification of species in this order has been ongoing for a long time, but there is still a great controversy about whether this order is monophyletic. In this study, we obtained the complete mitogenome of Lophiotoma leucotropis by next-generation sequencing and analyzed the basic structural features of the genome, and we found that the number of genes was consistent with that of most of the Neogastropoda snails, containing 37 genes, including 13 protein-coding genes (PCGs), 2 rRNAs, and 22 tRNAs. Analyzing base content, amino acid content, codon usage preference, and tRNA structure, the mitogenomes of eight species of Turridae were selected for analysis of selection pressures, and it was found that the evolution of species in this family was affected by purifying selection. In addition, by analyzing the rearrangement characteristics, it was found that the sequence of L. leucotropis was consistent with the Conoidea consensus order, and four of the eight species involved in the analysis showed rearrangements. Finally, we constructed a phylogenetic tree by combining PCGs of 60 species within Caenogastropoda and found Neogastropoda to be a monophyletic group, validating the results of morphological classification. The results will provide more references for the classification and species evolution of Neogastropoda, as well as phylogenetic analysis. [ABSTRACT FROM AUTHOR]

Based both on published GenBank DNA sequences and newly produced sequences, I have assembled the largest multi‐loci sequence dataset of the Diplommatinidae to date to investigate their evolutionary history. The focus of this study is on the diverse genus Palaina, which is represented by new sequences of its type species as well as additional samples from Timor and the Solomon Islands. In addition, the type species of Palmatina from Norfolk Island is also included. A relaxed molecular clock hypothesis is presented that incorporates several calibration points based on fossils or on previously published age estimates for major clades. Accordingly, the Sundaland diplommatinids Plectostoma, Opisthostoma, Arinia and Diplommatina are of considerable evolutionary antiquity, each likely having originated during the Cretaceous or early Paleogene at the latest. The Palaina sensu lato main clade was found to be the sister of all other diplommatinids included in the tree and has also diverged during the late Cretaceous. Palaina as currently delineated is rendered non‐monophyletic by the radiations of Hungerfordia and Eupalaina, which are endemic to the archipelago of Palau, as well as Palmatina from Norfolk Island. [ABSTRACT FROM AUTHOR]

Among gastropods, the ability to swim has developed independently several times, mostly among Heterobranchia. Only a few species of Caenogastropoda are known to have swimming adults. Velutinidae Gray, 1840, is a family of caenogastropods with a fragile shell enclosed by the mantle. The adults of this family are benthic and ectoparasites of ascidians. Here, we present the first recorded instance of a swimming velutinid, Marsenia cf. gemma, filmed in New Caledonia. The swim propulsion method was based on the movement of the snail's foot, which followed a ∞-shaped curve. This first report changes our perspective on the biology of this family, unexpectedly placing it within the restricted group of swimming caenogastropods. [ABSTRACT FROM AUTHOR]

Previously, the main studies were focused on viruses that cause disease in commercial and farmed shellfish and cause damage to food enterprises (for example, Ostreavirusostreidmalaco1, Aurivirus haliotidmalaco1 and Aquabirnavirus tellinae). Advances in high-throughput sequencing technologies have extended the studies to natural populations of mollusks (and other invertebrates) as unexplored niches of viral diversity and possible sources of emerging diseases. These studies have revealed a huge diversity of mostly previously unknown viruses and filled gaps in the evolutionary history of viruses. In the present study, we estimated the viral diversity in samples of the Baikal endemic gastropod Benedictia baicalensis using metatranscriptomic analysis (total RNA-sequencing); we were able to identify a wide variety of RNA-containing viruses in four samples (pools) of mollusks collected at three stations of Lake Baikal. Most of the identified viral genomes (scaffolds) had only distant similarities to known viruses or (in most cases) to metagenome-assembled viral genomes from various natural samples (mollusks, crustaceans, insects and others) mainly from freshwater ecosystems. We were able to identify viruses similar to those previously identified in mollusks (in particular to the picornaviruses Biomphalaria virus 1 and Biomphalaria virus 3 from the freshwater gastropods); it is possible that picorna-like viruses (as well as a number of other identified viruses) are pathogenic for Baikal gastropods. Our results also suggested that Baikal mollusks, like other species, may bioaccumulate or serve as a reservoir for numerous viruses that infect a variety of organisms (including vertebrates). [ABSTRACT FROM AUTHOR]

The occurrence of Ocinebrellus inornatus and Rapana venosa, two exotic marine gastropods of the family Muricidae originating from the northwest Pacific, is reported in Spanish waters, specifically in the Galician waters (NW Spain) in 2023. Live specimens of O. inornatus were found on Illa de Arousa, in the Ría de Arousa, southern Galicia, where they are already established. Two new specimens of R. venosa are recorded in Galicia, one of them for the first time out of the Ría de Arousa, representing a range expansion for the species. The DNA barcoding analysis confirms the previous morphological identifications. It is suspected that both species may have been introduced through importation of clam spat and middle-sized oysters from countries such as France, the United Kingdom or Italy for subsequent culture, as has been the case with other exotic species that can currently be found in Galician waters. The continuous arrival of marine exotic species strongly supports the need to establish a monitoring program in Galician waters. [ABSTRACT FROM AUTHOR]

The Western Balkans hosts the richest subterranean aquatic gastropod fauna in the world. The main factors shaping intraspecies diversity are thought to be isolation and endemism. In the genus Belgrandiella, minute snails inhabiting subterranean waters and springs in Central Europe and Balkans, molecular studies have shown much fewer valid species than previously anticipated. The present study applies mitochondrial cytochrome c oxidase subunit I, histone 3, and RAPD analysis, to check the inter- and intraspecies genetic diversity in 36 Belgrandiella populations from caves, springs and interstitial aquifers. The level of gene flow is assessed to check if these snails form a widespread genetically uniform metapopulation or rather follow the highly endemic pattern. The studied populations have been assigned to six species. In the most widely distributed B. kusceri from 21 populations, 60 sequenced specimens represent 16 haplotypes. While the same haplotypes are present in distant populations, gene flow between the other populations is low. Nei distances for RAPD show no geographic pattern. The interspecies differences in COI evidently confirm the time of speciation in Pleistocene, before karstification, which rejects speciation within isolated caves. The pattern observed in Belgrandiella seems more similar to the one described in Montenegrospeum than in Kerkia. [ABSTRACT FROM AUTHOR]

Simple Summary: We sequenced the complete mitochondrial genomes of nine Tonnoidean species, and analyzed the genomic features including genome size, gene order, nucleotide composition and Ka/Ks ratio. The reconstructed phylogeny based on mitogenomic data supported the Tonnoidea classifications at family levels, but their internal relationships remained unclear. At the species level, the present study indicates that species diversity within Bursidae might be underestimated. The Tonnoidea Suter, 1913 (1825) is a moderately diverse group of large predatory gastropods, the systematics of which remain unclear. In the present study, the complete mitochondrial genomes of nine Tonnoidean species were sequenced. All newly sequenced mitogenomes contain 13 protein-coding genes (PCGs), 22 transfer RNA genes and two ribosomal RNA genes, showing similar patterns in genome size, gene order and nucleotide composition. The ratio of nonsynonymous to synonymous of PCGs indicated that NADH complex genes of Tonnoideans were experiencing a more relaxed purifying selection compared with the COX genes. The reconstructed phylogeny based on the combined amino acid sequences of 13 protein-coding genes and the nucleotide sequences of two rRNA genes supported that Ficidae Meek, 1864 (1840) is a sister to Tonnoidea. The monophylies of all Tonnoidean families were recovered and the internal phylogenetic relationships were consistent with the current classification. The phylogeny also revealed that Tutufa rebuta (Linnaeus, 1758) is composed of at least two different species, indicating that the species diversity within Bursidae Thiele, 1925 might be underestimated. The present study contributes to the understanding of the Tonnoidean systematics, and it could provide important information for the revision of Tonnoidean systematics in the future. [ABSTRACT FROM AUTHOR]

The terrestrial gastropod Ferussina petofiana Páll-Gergely sp. n. is described from uppermost Cretaceous (Maastrichtian) deposits from the Haţeg Basin, Romania. It represents the first properly diagnosed and described snail taxon from these deposits, despite numerous earlier reports of gastropod occurrences. This new species is characterized by a depressed, mostly smooth shell, three spiral carinae on the ventral side (inside the umbilicus), and an upward-turning aperture. The last feature characterizes two European fossil snail genera, the cyclophoroidean Ferussina, and the stylommatophoran Strophostomella. The new species is classified in the former group due to its nearly circular aperture, and the presence of conspicuous spiral carinae. In contrast, the aperture of most stylommatophoran genera (including Strophostomella) is semilunar, and if raised sculptural elements are present, they are mostly radially oriented. The identification of this new taxon in the uppermost Cretaceous of Romania represents an important range extension for the genus Ferussina, and adds it to the brief list of European clades that appear to have survived the mass extinction event at the Cretaceous-Paleogene boundary. [ABSTRACT FROM AUTHOR]

Cycloryx pemaledai Gittenberger et Sherub, 2022, which was described from northwestern Bhutan, is reported for the first time in Sikkim, India. That species differs from all its congeners by the short R3 (the region between the constriction and the peristome). The differences between the Bhutanese and Indian shells are minimal, therefore the Indian shells are identified as Cycloryx cf. pemaledai. Furthermore, Alycaeus himalayae sp. n. is described from Arunachal Pradesh. This is so far the only Alycaeus species inhabiting the Himalayas, and thus, its discovery is a surprise. [ABSTRACT FROM AUTHOR]

The Edwards and Edwards-Trinity Aquifers of Texas have diverse stygofauna, including fifteen species of snails found in phreatic and hyporheic habitats. These species have the hallmarks of adaptation to subterranean environments including extremely small body size and the loss of pigmentation and eyes. Here we use an integrative taxonomic approach, using shell, radula, and anatomical features as well as mitochondrial and nuclear DNA data, to circumscribe a new genus and two new cavesnail species from Central Texas. Vitropyrgus lillianae gen. et sp. nov. is described from Comal Springs (Comal County) and Fessenden Springs (Kerr County) and distinguished by a glassy, highly sculptured shell and distinctively simple, unornamented penial morphology. We also describe Phreatodrobia bulla sp. nov. from Hidden Springs (Bell County), and several other springs in Bell & Williamson Counties, Texas. This species has a smooth, unsculptured teleoconch, a reflected and flared lip, and deeply concave operculum. [ABSTRACT FROM AUTHOR]

The status of the indigenous Southeast Asian apple snails belonging to the genus Pila is of concern due to their fast rate of population decline, possibly as a result of multiple factors including habitat loss or disturbance and the introduction of globally-invasive apple snails, Pomacea spp. Conservation actions, including captive breeding of the native Pila species, have been suggested as urgent remedial practices, but the lack of knowledge regarding the fundamental reproductive biology of indigenous Pila spp. makes such practices difficult. In the present study, observations on the mating and egg-laying behaviour of an economic valuable apple snail native to Southeast Asia, P. virescens, were conducted using video recording to examine and describe their reproductive behaviour under a laboratory condition. A total of 15 types of mating and seven egg-laying behaviour were recorded. The mating sequence which subsequently resulted in egg laying was comprised of seven types of major sequential behaviour: mate probing, mounting, shell circling, positioning, insemination posture, sheath withdrawal and dismounting. Rejection of mating attempts by the female was frequently observed. Egg laying occurred during either day or night. A sequence of seven distinct types of behaviour were performed during oviposition: climbing, positioning, forming a temporary tube, mucous secreting, egg depositing, leaving and resting. Overall, these results provide an understanding of the egg-laying behavioural process and highlight its complexity in P. virescens. In addition, detailed ethograms of mating and egg-laying behaviour were derived. These will promote further systematic comparative studies of the reproductive behaviour of apple snails. [ABSTRACT FROM AUTHOR]

The gastropod Pachyoliva columellaris (formerly Olivella columellaris) is particularly common on many sandy beaches in North Peru. In the studied region north of Paita, Piura province, the species reaches densities of over 80,000 individuals per beach meter. The snails perform tidal migrations throughout the lunar cycle although tidal amplitudes differ four-fold between neap and spring tide. Not all animals complete their tidal migrations, and significant numbers remain above the water line at low tide. Throughout the tidal cycle, the proportion of small individuals is increased near the water line whereas large animals dominate in lower beach zones. I conclude that the sandy beaches north of Paita are well-suited for further studies of P. columellaris and the mechanisms underlying tidal migrations in invertebrates. [ABSTRACT FROM AUTHOR]

Apple snails of the genus Pomacea Perry, 1810 (Mollusca: Caenogastropoda: Ampullariidae) are native to the Neotropics and exhibit high species diversity, holding cultural and ecological significance as an important protein source in Peru. However, most genetic studies in Pomacea have focused mostly on invasive species, especially in Southeast Asia, where they are considered important pests. In this study, we assembled and annotated the mitochondrial genomes of two Pomacea species native to the Peruvian Amazon: Pomacea reevei Ampuero & Ramírez, 2023 and Pomacea aulanieri (Deville & Hupé, 1850). The mitogenomes of P. reevei and P. aulanieri comprise 15,660 and 16,096 bp, respectively, and contain the typical 37 genes of the animal mitochondria with a large control region of 292 bp in P. reevei and 524 bp in P. aulanieri—which fall within the range of what is currently known in Pomacea. Comparisons with previously published mitogenomes in Pomacea revealed differences in the overlapping of adjacent genes, the size of certain protein-coding genes (PCGs) and the secondary structure of some tRNAs that are consistent with the phylogenetic relationships between these species. These findings provide valuable insights into the systematics and genomics of the genus Pomacea. [ABSTRACT FROM AUTHOR]

Target‐capture approaches have facilitated a rapid growth in the field of phylogenomics but few probe sets exist for molluscs, an exceptionally rich phylum with unparalleled ecological and morphological diversity. We designed and tested the first universal probe set using Phyluce to capture ultraconserved elements (UCEs) and exon loci from the Subclass Caenogastropoda ‐ one of six major lineages of gastropods. The probe set consists of 29,441 probes designed to target 1142 UCE loci and 1933 exon loci (3075 total). In silico analyses of our probe set yielded an average of 2110 loci from genomes and 1389 loci from transcriptomes of diverse caenogastropods, from which an average of 1669 and 849 loci were retained respectively after screening to remove those that matched multiple contigs. Phylogenetic analyses of the loci extracted from transcriptomes produced well‐supported trees very similar to those published based on transcriptomic analyses. Phylogenetic relationships estimated from loci extracted from genomes recover similar phylogenetic relationships, and indicate that the loci targeted with this probe set are informative for resolving deep phylogenetic relationships. An in vitro analysis of the probe set with the Epitoniidae, a diverse caenogastropod family of uncertain affinity and with poorly resolved evolutionary relationships, recovered a total of 2850 loci. Although preliminary, the analysis of loci captured by our probe set for a small number of epitoniid taxa produced a well‐resolved tree indicating that this probe set is also able to resolve relationships at shallower hierarchical scales. Together, the in silico and in vitro analyses indicate that target‐capture enrichment with this probe set is a useful tool for reconstructing phylogenetic relationships across taxonomic levels and evolutionary time scales. [ABSTRACT FROM AUTHOR]

Muricidae is one of the most species‐rich and morphologically diverse families in Gastropoda, with a worldwide distribution. The classification of Muricidae has traditionally been based on shell and radular characteristics; however, the phylogenetic relationships within the family are debated due to morphological convergence and plasticity. In this study, to explore the phylogenetic relationships of Muricidae, we sequenced 11 muricid mitochondrial (mt) genomes and compared them with 13 previously reported complete muricid mt genomes. All muricid mt genomes shared the same gene arrangement and exhibited conserved genome size and nucleotide composition. Three‐nucleotide deletions in atp8 and nad4, and three‐nucleotide insertions in nad2 were detected in Rapaninae. Both maximum likelihood and Bayesian inference analyses supported the monophyly of each subfamily studied (Ocenebrinae, Muricinae, Rapaninae and Ergalataxinae). Ergalataxinae was recovered as the sister taxon of Rapaninae, refuting the traditional morphology‐based placement of Ergalataxinae within Rapaninae. In Rapaninae, Indothais was confirmed to be monophyletic and determined to be a valid genus. Similarly, Drupina was determined to be an independent genus rather than a subgenus of Drupa. Purpura was recovered as a paraphyletic group, with Purpura panama being sister to Reishia + Rapana + Indothais and clustering with Purpura bufo. [ABSTRACT FROM AUTHOR]

In desert environments, unique communities depend on groundwater from springs, including a diverse radiation of small (<5 mm) snails found in the desert across the southwestern United States. Nearly all springsnail species are considered critically imperiled with their existence depending on maintenance of spring-flows in regions of declining water availability. Extant, endemic springsnails in the Trans-Pecos region of Texas include one species of Pseudotryonia Hershler, 2001, five nominal Tryonia W. Stimpson, 1865 (Cochliopidae) and seven Pyrgulopsis Call & Pilsbry, 1886 (Hydrobiidae). Four of these are classified as endangered under the US Endangered Species Act. Surveys for springsnails were conducted at 128 sites, including 13 sites that were previously reported localities, and 115 previously unsampled spring sites were also searched for new springsnail populations. Sequences of the DNA barcoding region were used to establish a database of known sequences from the named species and confirm identifications of new populations encountered. We report eight new springsnail populations, including new records for T. metcalfi Hershler, Liu & Landye, 2011, T. cheatumi (Pilsbry, 1935), P. ignota Hershler, Liu & Lang, 2010, P. metcalfi (D.W. Taylor, 1987), and P. texana (Pilsbry, 1935). We were not able to recollect Juturnia brunei (D. W. Taylor, 1987), T. oasiensis Hershler, Liu & Landye, 2011, or P. davisi (D. W. Taylor, 1987). The DNA barcoding gap for Tryonia ranged from 1.56-4.47% and for Pyrgulopsis from 0.68-1.68%. [ABSTRACT FROM AUTHOR]

Cone snails, as a type of marine organism, have rich species diversity. Traditionally, classifications of cone snails were based mostly on radula, shell, and anatomical characters. Because of these phenotypic features' high population variability and propensity for local adaptation and convergence, identifying species can be difficult and occasionally inaccurate. In addition, mitochondrial genomes contain high phylogenetic information, so complete mitogenomes have been increasingly employed for inferring molecular phylogeny. To enrich the mitogenomic database of cone snails (Caenogastropoda: Conidae), mitogenomes of four Conus species, i.e., C. imperialis (15,505 bp), C. literatus (15,569 bp), C. virgo (15,594 bp), and C. marmoreus (15,579 bp), were characterized and compared. All 4 of these mitogenomes included 13 protein-coding genes, 2 ribosomal RNA genes, 22 tRNA genes, and non-coding regions. All the Protein Codon Genes (PCGs) of both newly sequenced mitogenomes used TAA or TAG as a terminal codon. Most PCGs used conventional start codon ATG, but an alternative initiation codon GTG was detected in a gene (NADH dehydrogenase subunit 4 (nad4)) of C. imperialis. In addition, the phylogenetic relationships were reconstructed among 20 Conus species on the basis of PCGs, COX1, and the complete mitogenome using both Bayesian Inference (BI) and Maximum Likelihood (ML). The phylogenetic results supported that C. litteratus, C. quercinus, and C. virgo were clustered together as a sister group (PP = 1, BS = 99), but they did not support the phylogenetic relation of C. imperialis and C. tribblei (PP = 0.79, BS = 50). In addition, our study established that PCGs and complete mitogenome are the two useful markers for phylogenetic inference of Conus species. These results enriched the data of the cone snail's mitochondrion in the South China Sea and provided a reliable basis for the interpretation of the phylogenetic relationship of the cone snail based on the mitochondrial genome. [ABSTRACT FROM AUTHOR]

The systematics and distribution of the family Pupinidae (Gastropoda: Cyclophoroidea) in Java is reviewed. The family is represented in Java by four species of the genus Pupina, P. bipalatalis, P. compacta, P. junghuhni, and P. treubi. The shells of the species are described and figured, and the distribution data of the species are summarized. We have synonymized Pupina verbeeki Möllendorff, 1897 with Pupina treubi Boettger, 1890. All of the species except P. treubi, which is also known from Sumatra, are endemic to Java. Most previous records of Pupina from Java were from the western part of the island. Our new records show that the Pupina species are also more widespread in the drier central and eastern parts of Java. Their conservation status is therefore Least Concern. [ABSTRACT FROM AUTHOR]

Microphytobenthos (MPB), typically comprised mainly of diatoms, is a key contributor to nearshore energy flow and nutrient cycles. Deposit‐feeding invertebrates are known to alter the structure and activity of MPB. The eastern mud snail Ilyanassa obsoleta can reach extremely high densities in estuaries of the northwestern Atlantic, and their deposit‐feeding and locomotion strongly influence other invertebrates and microbes. Our objective was to explore quantitative and qualitative effects of this keystone deposit‐feeder on diatoms of intertidal sediments. We gathered snails from mudflat and sandflat habitats and collected their fresh fecal pellets in the laboratory. DNA metabarcoding allowed us to characterize diatom assemblages of ingested sediments and feces. We noted selective feeding such that reduction in MPB biomass with gut passage was difficult to quantify. Diatom α‐diversity was reduced with gut passage in snails from both sedimentary regimes. Mudflat and sandflat diatom assemblages were distinct and differed markedly between feces and sediment in mud‐feeding snails, whereas the difference in sand‐feeding snails was minor. The sandy habitat was dominated by a mix of epipelic and epipsammic diatoms. In contrast, mudflat samples were dominated by epipelic and planktonic diatoms. Compositional differences between sediment and feces reflected preferential removal of planktonic taxa. Our results suggest the importance of phytodetritus to the mud snail diet, particularly in hydrodynamically quiescent environments. Due to the natural spatial patchiness of the snails and the capacity for rapid microbial recolonization, field experiments are recommended to determine whether MPB community changes attributed to gut passage are manifested at the landscape scale. [ABSTRACT FROM AUTHOR]

We analyse the distribution of the potamidid genus Terebralia Swainson, 1840 in the European fossil record (middle Eocene to Miocene). Extant Terebralia contains species restricted to mangroves and mudflats, rendering it a reliable element for detecting these coastal environments in the fossil record. Our contribution summarizes the European fossil record of this taxon and highlights the presence of this genus within coastal environments in the European realm. Distribution in the Cenozoic is interpreted based on ecological preferences, dispersal modes and climatic restrictions of recent species. Maximum geographical distribution is reached during the Early and Middle Miocene with two species being present from the southernmost parts of Europe and Anatolia to the North Sea Basin and the Paratethys. During the Late Miocene, the distribution of Terebralia lignitarum (Eichwald, 1830) is patchy and limited to the South of Europe. The Messinian Salinity Crisis coupled with a changing climate caused the disappearance of Terebralia in the Mediterranean first, and then marked the end of mangrove environments in this province. [ABSTRACT FROM AUTHOR]

The superfamily Buccinoidea is the most speciose group of Neogastropoda within the Antarctic Convergence, with ~70 species classified in 21 genera, but is still poorly represented in molecular phylogenies. The first molecular data on the group presented in the recent phylogeny of the Buccinoidea (Kantor et al. 2022) lacked many important lineages, thereby limiting inference of the relationships of Antarctic Buccinoidea. We revisited relationships of the Antarctic Buccinoidea, involving recently collected molecular-grade samples from the bathyal and abyssal depths of the Scotia Sea, the Weddel Sea and adjacent regions. Our data set includes 25 species (including six genera studied on a molecular basis for the first time), sequenced for five phylogenetic markers: the barcode fragment of cox 1 gene, fragments of ribosomal 12S , 16S rRNA and 28S and nuclear H3 genes. Based on phylogenetic reconstructions, we synonymise the genus Lussitromina with Falsitromina and reassign the latter from Cominellidae to Prosiphonidae. We confirm the placement of four further genera, Drepanodontus , Germonea , Parabuccinum and Spikebuccinum in Prosiphonidae. We detect a previously unrecognised deep lineage of the family Prosiphonidae and describe this as the new genus Scotiabuccinum. The genus Parabuccinum , previously recorded in the Magellanic province and off the eastern coast of Argentina was reported for the first time within the Antarctic Convergence. We discover four previously unrecognised species of Antarctic Prosiphonidae and these are the first Buccinoidea from Antarctic waters described based on molecular data. According to our data, all but two species of Antarctic Buccinoidea belong to the family Prosiphonidae. Seven of the nineteen Recent Antarctic Prosiphonidae genera (36%) cross the boundaries of the Convergence and eight Antarctic genera are monotypic (42%). Currently no Buccinoidea species are known to occur both within and outside the Antarctic Convergence. ZooBank: urn:lsid:zoobank.org:pub:DEEA1599-C951-414E-9098-563EAD10BD57 The superfamily Buccinoidea is the most speciose group of Neogastropoda within the Antarctic Convergence with ~70 species classified in 21 genera. We revisited the relationships of the Antarctic Buccinoidea based on published molecular phylogeny and recently collected samples. In total, 25 species attributed to 17 (out of 21) genera were sequenced for five phylogenetic markers. We synonymised the genus Lussitromina with Falsitromina and reassigned the latter to Prosiphonidae. The new genus Scotiabuccinum and four new species are described. Parabuccinum is reported within the Antarctic Convergence for the first time. All but two species of Antarctic Buccinoidea belong to Prosiphonidae. No Buccinoidea species are known to occur both within and outside the Convergence. [ABSTRACT FROM AUTHOR]

This work presents information about 19 taxa recorded from different habitats at depths between 0.2 and 508 m in the last two decades, which are new records or poorly known species along the Turkish coasts. Among the identified species, Epitonium vaillanti, Melanella cf. lubrica, Melanella monterosatoi, Pelseneeria minor, Setia amabilis, Kurtziella serga, Rissoella diaphana, Rissoella inflata, and Spirolaxis clenchi are new records for the Turkish mollusc fauna, Eatonina pumila is new report for the Turkish coast of the Aegean Sea, and Eatonina ochroleuca, Acirsa subdecussata, Lamellaria latens, Setia pulcherrima, Setia valvatoides, and Turbonilla cangeyrani are species with rare distribution which were sampled for one or a few times only. Viriola cf. bayani, Acirsa subdecussata, Melanella monterosatoi, Eatonina ochroleuca, E. pumila, Setia amabilis, Setia pulcherrima, Lamellaria latens, Rissoella diaphana, R. inflata, and Syrnola sp. were encountered along the Aegean Sea coast, whereas Epitonium vaillanti, Pelseneeria minor, Rissoidae sp., Kurtziella serga, Turbonilla cangeyrani, and Spirolaxis clenchi were recorded on the Levantine coast of Turkey, and Melanella cf. lubrica in the prebosphoric region of the Sea of Marmara. Setia valvatoides is the only species found on the Turkish Black Sea coast. On the other hand, Epitonium vaillanti and Viriola cf. bayani are species originated outside the Mediterranean basin. Most of the species were found at infralittoral and circalittoral depths, except for Kurtziella serga and Spirolaxis clenchi found at a depth of 508 m. The present study elucidates some ecological and distinguishing characteristics of the investigated species, along with their colour photographs and distribution along the Turkish coasts. [ABSTRACT FROM AUTHOR]

The benthic macrofauna of Arctic and subarctic seas is mainly represented by widespread species and is generally devoid of endemics. The exceptions are reduced habitats, such as cold seeps, hydrothermal areas, and wood falls, which include endemics of at least the species level. A detailed study and analysis of such endemics allows us to understand the mechanisms of colonization and to assess the age of the fauna of high-latitude marine regions. Here, the new species Provanna annae sp. nov. is described from the geothermal zone of the Piip volcano in the Bering Sea (subarctic Pacific) based on the morphological and molecular phylogenetic data. The new species appears to be the northernmost and one of the most shallow-water species among the known representatives of the family and is suggested to be endemic to the region. The new species is related to a group of Provanna species from reducing habitats off Japan. Composition of the gut content indicates that the new species bottom sediments. Bacteria are found on the gills of the mollusc and are probably symbionts that also provide nutrition. This type of mixotrophic feeding is rare in gastropods and may be a unique feature among Caenogastropoda. [ABSTRACT FROM AUTHOR]

The gastropod radula is highly diverse in structure in comparison with that of other mollusсs. The main radular types in the different phylogenetic groups of gastropods differ not only in the general morphology and configuration of the teeth but also in the mode of tooth synthesis and the ultrastructure of the formation zone. Previously, the formation and anlage of the radula in the ontogeny of radulae of all major phylogenetic gastropods groups have been studied, with the exception of the taenioglossan radula of Caenogastropoda. The data obtained in this study on the radular anlage and synthesis in one littorinimorph species Lacuna pallidula supplement the existing knowledge of diversity in gastropod radula formation. The radula is initially formed at the stage of the post-torsion veliger, with five teeth in each transverse row, and acquires the adult morphology before hatching from the egg mass. The larval radula is synthesized by a few morphologically uniform cells in the radular sac. Synthesis of the adult radula also occurs at the blind end of the radular sac, where groups of numerous odontoblasts each form one tooth, and membranoblasts, located on the ventral side, form the membrane. Characteristic features of the adult radular sac are an additional supporting cartilage-like structure at the radula curve in the middle of the radular sac, a well-defined proliferation zone in the zone of radula formation and the presence of an additional extracellular matrix around the teeth in the maturation zone. [ABSTRACT FROM AUTHOR]

The gastropod genus Litthabitella Boeters, 1970, type species L. chilodia Westerlund, 1886, inhabits mainly freshwater springs in the coastal regions of the Balkan Peninsula from Greece to Slovenia, southern Italy and the Ionian Islands. These snails are minute and show several synapomorphic character states, such as: broadly ovate osphradium, gonopore deep inside the mantle cavity, thickened circular oviduct, distal termination of the penis wide with a sharp and short lateral filament and two flat, cockscomb-like, four-folded lobes. These characters justify a family rank for the taxon. Three molecular loci – mitochondrial cytochrome oxidase subunit I, nuclear 18S and histone H3 – also confirm the distinctiveness of the Litthabitellidae fam. nov. Analysis of molecular data indicates an estimated time of origin in the Late Miocene (Tortonian) and supports its position as the sister clade of the Hydrobiidae. The shells, protoconchs, radulae, operculum, some histology, female reproductive organs and penis are herein illustrated and described. Molecular data presented for 10 studied populations, confirmed partly by morphological characters, indicate four distinct taxa of species rank. Three species are described: Litthabitella aquaadcrucem sp. nov., Litthabitella cetinensis sp. nov. and Litthabitella levkadensis sp. nov. [ABSTRACT FROM AUTHOR]

The snorkel snail genus Rhiostoma Benson, 1860 is comprised of terrestrial cyclophorid snails with wideranging 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. ? amarapuraense sp. nov., R. anceyi sp. nov., R. breviocollar sp. nov., R. ebenozostera sp. nov., R. cheliopegma sp. nov., R. furfurosum sp. nov., R. gnomus, sp. nov., R. lannaense sp. nov., R. laoense sp. nov., R. platymorpha sp. nov., R. rhothonotaphrosa sp. nov., and R. tigrina sp. 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. rhothonotaphrosa sp. 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. [ABSTRACT FROM AUTHOR]

Newly collected Early Badenian (Middle Miocene) Conorbidae and Conidae assemblages are presented from three localities in the Hungarian part of the Pannonian Basin. Ten species - among others Pseudonoduloconus wagneri (Boettger) - are recorded for the first time in the region, others show extended geographical distribution. A new species, Monteiroconus strauszi n. sp. is designated. With 67 figures and 1 table. [ABSTRACT FROM AUTHOR]

Background Genomes are powerful resources to understand the evolutionary mechanisms underpinning the origin and diversification of the venoms of cone snails (Conidae: Caenogastropoda) and could aid in the development of novel drugs. Findings Here, we used PacBio continuous long reads and Omni-C data to assemble the chromosome-level genome of Kalloconus canariensis , a vermivorous cone endemic to the Canary Islands. The final genome size was 2.87 Gb, with a N50 of 79.75 Mb and 91% of the reads located into the 35 largest scaffolds. Up to 55.80% of the genome was annotated as repetitive regions, being class I of transposable elements (16.65%) predominant. The annotation estimated 34,287 gene models. Comparative analysis of this genome with the 2 cone snail genomes released to date (Dendroconus betulinus and Lautoconus ventricosus) revealed similar genome sizes and organization, although chromosome sizes tended to be shorter in K. canariensis. Phylogenetic relationships within subclass Caenogastropoda were recovered with strong statistical support. The family Conidae was recovered as a clade, with K. canariensis plus L. ventricosus sister to D. betulinus. Conclusions Despite the great diversity of cone snails (>900 species) and their venoms (hundreds of peptides per species), only 2 recently reported genomes are available for the group. The high-quality chromosome-level assembly of K. canariensis will be a valuable reference for studying the origin and evolution of conotoxin genes as well as whole-genome duplication events during gastropod evolution. [ABSTRACT FROM AUTHOR]

Anaglyphula yanseni, new species, is described and illustrated based on specimens collected from Babi Island, off the west coast of Sumatra, Indonesia. The new species mostly differs from its congeners having similarly pitted surface sculpture by its small size. Additionally, Anaglyphula cancellata Rensch, 1932, the type species of the genus, is redescribed based on the type materials. The diagnostic features of Anaglyphula are also discussed in comparison with those of similar genera. [ABSTRACT FROM AUTHOR]

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 12 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 1) Vetigastropoda |$s.l.$| (including Pleurotomariida |$+$| Neomphaliones) and 2) Neritimorpha |$+$| (Caenogastropoda |$+$| Heterobranchia). As such, our results support the recognition of five subclasses (or infraclasses) in Gastropoda: Patellogastropoda, Vetigastropoda, Neritimorpha, Caenogastropoda, and Heterobranchia. [Compositional heterogeneity; fast-evolving; long-branch attraction; missing data; Mollusca; phylogenetics; systematic error.] [ABSTRACT FROM AUTHOR]

Olivella Swainson, 1831 is a genus of small marine benthic gastropods found worldwide, represented by 117 valid species in 17 subgenera usually defined by conchological features such as colouration, size, shape and shell sculpture. Despite some conchological research on species in the family Olividae Latreille, 1825, the soft anatomy of Olivella species is still poorly studied. The present study aims to describe and compare the morphology of the pallial cavity and its adjacent structures in three species of Olivella from the Brazilian coast: Olivella (Olivella) floralia (Duclos, 1844), Olivella (Olivella) nivea (Gmelin, 1791), and Olivella (Niteoliva) minuta (Link, 1807). We suggest that some conchological (e.g. reabsorption of the columella or not; presence or absence of the operculum) and soft anatomical (e.g. placement of the posterior mantle tentacle, morphology of osphradium and reproductive system) features are useful to better distinguish between the subgenera Olivella and Niteoliva. Such characters have a potential role in taxonomic decisions and hypotheses regarding subgenera and a better understanding of evolutionary relationships within Olivella. [ABSTRACT FROM AUTHOR]

This study was performed to obtain information on the basic reproductive ecology and biological resource management of Buccinum osagawai. Samples were collected from August 2018 to October 2019 with a drum-shaped net at a depth of 150–250 m along the continental shelf in Jumunjin, on the east coast of Korea. The species showed gonochorism and a lack of external sexual dimorphism. The overall sex ratio (F:M) was 1:1.2 (n = 549, F = 250, M = 299); as the size of the individuals increased, the proportion of males tended to decrease. The development pattern of the oocyte was synchronous, in which a dominant group of oocytes was identified within the same ovary. The size of the ripe oocyte was 82.3 (±22.6) × 125.5 (±22.0) μm. The spermatocyte development pattern was group-synchronous, in which multiple stages of germ cell populations were simultaneously identified within the same spermatogenic acinus. The gonad index (GI) for both males and females showed the highest value during June, after which it decreased sharply, and after August it was below 2.0. The main spawning season was from June to July, and the GI and stages of gonadal development did not show a pattern of seasonal changes. The main gonadal active season was from May to July, and both male and female gonadal development and maturation took place over a short period, whereas the recovery period after spawning was longer. At least 60.5% of the group, considering both males and females, showed maturity at 50.1 mm SH or more. Furthermore, the size of 50% group maturity was shown at approximately 50.0 mm SH. [ABSTRACT FROM AUTHOR]

Shell features are key factors for systematics and evolutionary biology studies of freshwater gastropods. Based mostly on shell morphology, 19 species of the springsnail genus Radomaniola (family Hydrobiidae) have been described. Although the scarce differentiation of various shell dimensions suggests morphological stasis, the evolutionary dynamics of shell and other anatomical structures have not yet been explored fully. By inferring a phylogeny and a time-calibrated species tree from mitochondrial (COI and 16S) and nuclear (28S) sequences of 15 recognized species, we initially examine the species diversity of the Radomaniola dataset and then, through phylogenetic comparative methods, assess the evolutionary correlation, pace and mode of 40 continuous shell and anatomical characters. By synthesizing the results of four species delimitation methods and through morphological examinations, we recognize 21 groups, for which taxonomy is discussed here. Seven new species are described. We reveal a high degree of correlated evolution between characters of the shell, which are constrained by a single morphological optimum, consistent with the morphological stasis model. Anatomical traits diverged rapidly in an unconstrained manner or toward multiple optima. These findings indicate that in order to understand the morphological evolution of springsnails, it is essential to examine different organs in detail. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

There have been few detailed studies on the associations between cnidarians and gastropod mollusks. Several hypotheses have been suggested to explain the origins of these symbioses. However, respective benefits for gastropod mollusks and cnidarians have generally not been well examined, as there are many understudied cnidarian taxa associated with gastropod mollusks, and in particular, species of the order Zoantharia in the family Epizoanthidae remain poorly studied. In this study, we examined family Epizoanthidae specimens associated with Granulifusus gastropods via morphological observations combined with molecular phylogenetic analyses. Based on our results, we formally describe a new Epizoanthus species from the northwest Pacific Ocean. Our phylogenetic analyses recovered at least two independent origins for associations with gastropod in Epizoanthidae. Furthermore, during the course of this work, we reconfirm the existence of the enigmatic species Paleozoanthus reticulatus, the only species of the genus Paleozoanthus, for the first time since its original description, and we add information on this species' morphological characteristics. This study provides a basis for evolutionary and behavioral studies of symbiotic associations between zoantharians and gastropods. Continued investigations examining the diversity of gastropod-associated zoantharians have the potential to greatly expand our overall comprehension of anthozoan-gastropod symbioses. [ABSTRACT FROM AUTHOR]

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. dorri isanensis Jirapatrasilp, ssp. nov.) as new to science. New records of Coptocheilus sumatranus, Pupinella mansuyi, and Rhaphaulus tonkinensis are also reported from Thailand. The mainland Southeast Asian Pupina species are classified into three species groups (Pupina artata group, Pupina arula group, and Pupina aureola 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. [ABSTRACT FROM AUTHOR]

Four new species of buccinoid gastropods from the continental shelf and slope are described. Neptunea flatteryensis Clark, n. sp. and Latisipho ritteri Clark, n. sp. from depths of 134-165 m off the Cape Flattery area of Washington State, Buccinum cascadiense Clark, n. sp. found at bathyal depths of 788-1203 m, off of the coasts of Washington and Oregon, and Golikovia fitchi Clark, n. sp. found at bathyal depths of 722-1240 m off of California. [ABSTRACT FROM AUTHOR]

Gastropods of the genus Mucronalia (Eulimidae) are known ectoparasites of brittle stars (Ophiuroidea). However, the identities of host species are only known for three of some ten described species in the genus. Here, we report associations of Mucronalia snails, including one new species, with ophiuroid hosts from Japan and New Caledonia: M. spp. aff. alba with Ophiomastix annulosa, Ophiomastix mixta, and Ophiocoma cynthiae; M. sp. cf. exquisita with Amphioplus (Amphioplus) sp.; Mucronalia ryukyuensis n. sp. with Ophionereis porrecta; and Mucronalia sp. with Amphiura velox. Mucronalia ryukyuensis n. sp. is described from Okinawa, southwestern Japan. The new species is characterized by its slender shell with a large body whorl and aperture compared with other species of the genus. Among Japanese congeners, the shell of the new species is most similar to that of M. exilis, but differs in having a teleoconch with less-convex whorls, regularly increasing in diameter. The present study corroborates Warén's (1983) general rule that eulimids in a single genus parasitize hosts of the same echinoderm class, and our records suggest that closely related species of Mucronalia tend to exploit hosts of a more restricted lineage. We also briefly discuss the divergence processes of Mucronalia snails, which likely involve host shifts and geographic isolation. [ABSTRACT FROM AUTHOR]

This survey reports the spatial distribution of gastropods belonging to Caenogastropoda, Architaenioglossa, Littorinimorpha, Cycloneritida and Hygrophila orders, and malacostracans from Amphipoda and Mysida orders in the lower sector of the Danube River, Romania, using DNA barcoding based on the cytochrome C oxidase I (COI) gene sequence. Sampling was performed for eight locations of Danube Delta branches and Bechet area during three consecutive years (2019–2021). Molecular identification of sixteen gastropods and twelve crustacean individuals was confirmed to the species level, providing the first molecular identification of gastropods from the Lower Danube sector. Phylogenetic analysis showed that species of gastropods and crustaceans clustered in monophyletic groups. Among gastropods, Microcolpia daudebartii acicularis, Viviparus viviparus, Bithynia tentaculata, Physa fontinalis, Ampullaceana lagotis and Planorbarius corneus were identified in Chilia and Sulina branches; and the Bechet area was populated by Holandriana holandrii, Theodoxus transversalis and Gyraulus parvus. The amphipods and mysids were present along the three main Danube branches. The calculated density of these species revealed an abundant community of crustacean Chelicorophium robustum on Sulina branch, and Dikerogammarus haemobaphes and D. villosus in extended areas of the Danube Delta. The presence of these invertebrates along Danube River was reported in relation to the sediment type and water depth. [ABSTRACT FROM AUTHOR]

Stenogyropsis is one of the few genera of Helicoidea having a high-spired shell. Here, we describe a new species (Stenogyropsis chorismenostoma n. sp.) that has a further remarkable trait: its last quarter whorl is detached from the penultimate whorl. We also show that a partly detached last whorl has evolved much more frequently in terrestrial Caenogastropoda than in Stylommatophora relative to the number of species within those groups. This may be due to the more superficial contact of the neighbouring whorls in the former group. [ABSTRACT FROM AUTHOR]

Considerable intraspecific variation has been known in the shell morphology of the freshwater snail genus Semisulcospira. However, sexual dimorphism and allometric growth have not been elucidated in the genus, although these factors contribute to generating intraspecific variation. We used a combination of geometric and traditional morphometrics methods (GMM and TMM) in a single population of Semisulcospira niponica to assess sex-related differences in shell size and shape at maturity. The results of a generalized Procrustes analysis of variance revealed significant differences in shell size and shape between males and females. A principal component analysis (PCA) showed allometric differences between males and females; Principal component (PC) 1 values and their overlap between the sexes decreased with size. PC1 explained 35.5% of the total variance, which corresponded to vertical elongation of the shell spire and aperture, and broadening of the shell. The results of a canonical variate analysis using the ten largest specimens of each sex showed that females have less elongate shells with rounder apertures and a broader body and penultimate whorls than males. TMM using nine morphological characters supported shell morphological differences between the sexes and correlations between shell size and shape associated with different growth stages. However, GMM was more sensitive for detecting shape differences than TMM. For example, TMM explained the observed increase in shell diameter primarily as a function of size, whereas GMM detected sex-related differences in shell diameter as shape differences between the sexes. Furthermore, dimorphism and allometry in shell sculpture traits could be explored only by TMM. For accurate evaluation of shell morphology in Semisulcospira , it is important to use larger specimens after separating males and females since the present results revealed intersex differences in size and shape, some of which become more evident with age. It is also essential to employ both GMM and TMM because the two methods capture different aspects of morphological variation in shell outline and sculpture. [ABSTRACT FROM AUTHOR]

The phylogenetic position of Haloceratidae, a little-known family of the subclass Caenogastropoda, is contested due to its extreme rarity in bathyal waters worldwide (c. 800–3,500 m deep). Haloceratids share several morphological and ecological traits with members of Vanikoroidea, Tonnoidea, Capuloidea and Velutinoidea, and were provisionally included in Vanikoroidea based on the absence of certain apomorphic features of the latter three taxa. Here, we first investigate the phylogenetic position of the family based on molecular data from both of the recognized genera, Haloceras and Zygoceras. Reconstruction based on three nuclear and three mitochondrial gene sequences suggests that the Haloceratidae constitute a sister clade to the Capulidae and that the two families collectively form the superfamily Capuloidea. This superfamily is united in a large, robust clade with Calyptraeoidea, Velutinoidea, Tonnoidea and Neogastropoda. The superfamily Cypraeoidea, as previously conceived, was found to be polyphyletic; we propose new concepts of Cypraeoidea (including Cypraeidae and Ovulidae) and Velutinoidea (including Velutinidae, Eratoidae and Triviidae). This topology also confirms the polyphyly of taxa with the 'echinospira' type of larvae (Echinospirida). The morphological resemblance of these polyphyletic taxa highlights parallel acquisition of traits in response to the same selective pressures. [ABSTRACT FROM AUTHOR]

Aim: The aim was to investigate the evolutionary origins of the striking biodiversity contrast between high‐ and low‐latitude regions in the present day. Is this a relatively recent phenomenon, causally linked in some way to the greenhouse–icehouse transition and onset of global cooling c. 34 Myr ago, or does it have deeper temporal roots and thus other potential causes? Location: Early Cenozoic fossil assemblages from two tropical and one polar region, and modern counterparts from various tropical localities and Antarctica. Time period: The Cretaceous–Palaeogene (K/Pg) mass extinction event, Early Cenozoic (Palaeocene–Eocene) and the present day. Major taxa studied: Shelf‐depth marine Mollusca; the four richest modern benthic clades: Imparidentia, Pteriomorphia, Neogastropoda and Littorinimorpha. Methods: The K/Pg mass extinction and subsequent recovery was compared between two tropical and one polar region at four distinct stratigraphic intervals. Taxa were identified to species level and assigned to principal families within the four largest benthic molluscan clades. Taxon counts were compared between the three regions at each level and also compared with standardized tropical and polar modern faunas. Results: The mass extinction was followed by a distinct 25 Myr phase of evolutionary radiation, during which the tropical–polar contrast in the taxonomic composition of all four clades was strongly enhanced; as the global molluscan fauna expanded, it differentiated into distinct low‐ and high‐latitude components. Main conclusions: A marked differentiation of tropical and polar molluscan faunas occurred in the immediate aftermath of the K/Pg mass extinction; it is likely that, at least for the two bivalve clades investigated, this differentiation was initiated well within the Mesozoic era. The greater antiquity of the tropical–polar split suggests that it was not the product of any single controlling factor during the Cenozoic. [ABSTRACT FROM AUTHOR]

Three new hairy snails (Caenogastropoda: Capulidae) are described from Alaskan waters, Turritropis cryptis n. sp., Ariadnaria willetti n. sp. from the Gulf of Alaska, and Ariadnaria exiguus n. sp. from the central and western Aleutian Islands. The new species are compared to similar species from the region. [ABSTRACT FROM AUTHOR]

The species of the Ponto-Caspian gastropod genus Clathrocaspia Lindholm, 1930 have been recorded so far from the Caspian Sea Basin only from marine waters, whereas they inhabit the estuarine areas as well as the purely freshwater environments in the Azov–Black Sea Basin. This genus has recently been assessed as putatively extinct in the Caspian Sea. A new purely freshwater species Clathrocaspia laevigata sp. n. from the water-flows of the Samur River delta in Dagestan, Russia, is described. A morphological comparison of the new species with C. brotzkajae (Starobogatov in Anistratenko & Prisjazhnjuk, 1992) from the Caspian Sea and C. knipowitschii (Makarov, 1938) inhabiting the Azov–Black Sea Basin shows their overall similarity. The major difference is that C. laevigata sp. n. almost completely lacks the reticulate teleoconch sculpture, whereas it is well-developed in all known Clathrocaspia species. The molecular data revealed probable sister relationships between the new species and C. knipowitschii. All Dagestan populations are ecologically and spatially isolated from the open sea and and are very locally restricted. We suggest to consider newly described snail species as retained in a pure freshwater refuge located in the coastal area of the Caspian Sea. The discovery of such a refuge sheds more light on the origin, current state and the future of the unique Ponto-Caspian aquatic biota under global change and increasing anthropogenic impact. [ABSTRACT FROM AUTHOR]

The superfamily Buccinoidea is distributed across the oceans of the world from the Arctic Ocean to the Antarctic and from intertidal to abyssal depths. It encompasses 3351 recent species in 337 genera. The latest taxonomic account recognized eight full families. For the first time, the monophyly of the superfamily and the relationships among the families are tested with molecular data supplemented by anatomical and radula data. Five genetic markers were used: fragments of mitochondrial COI , 16S rRNA, 12S rRNA and nuclear Histone 3 (H3) and 28S rRNA genes (for 225 species of 117 genera). Our analysis recovered Buccinoidea monophyletic in Bayesian analyses. The relationships between the formerly recognized families and subfamilies are drastically revised and a new classification of the superfamily is here proposed, now including 20 taxa of family rank and 23 subfamilies. Five new families (Chauvetiidae, Dolicholatiridae, Eosiphonidae, Prodotiidae and Retimohniidae) and one subfamily of Nassariidae (Tomliniinae) are described. Austrosiphonidae and Tudiclidae are resurrected from synonymy and employed in a new taxonomical extension. All but 40 recent genera are reclassified. Our results demonstrate that anatomy is rather uniform within the superfamily. With exceptions, the rather uniform radular morphology alone does not allow the allocation of genera to a particular family without additional molecular data. [ABSTRACT FROM AUTHOR]