Clausiliidae Research Articles

Pilsbrylia, a dextral-shelled door snail from South America (Gastropoda, Clausiliidae)

The land snail genusPilsbryliaHylton Scott, 1952 has been recently shown to not belong to the superfamily to which it was originally assigned (i.e., the Orthalicoidea), instead pointing out a relationship with the Clausilioidea. In this study, we included the type species of the genus in a multi-marker molecular phylogenetic framework to reassess its family-level classification. Our results show thatPilsbryliabelongs to family Clausiliidae (known as ‘door snails’) and more specifically, to subfamily Peruiniinae. This family is unique among stylommatophorans for consisting almost exclusively of animals with sinistral (left-handed) shells, whilstPilsbryliahas a “typical” dextral shell.

Modeling Current and Future Distribution of Cochlodina laminata in Eastern Europe under Climate Change

In this study, we focused on the eastern part of the Cochlodina laminata range. Although this door snail is widespread in Europe, even a widespread species may lose habitats if future climate change projections are realized. The range shift is one of the consequences of climate change. We applied SDM methods to model the current potential range of C. laminata and the range shift after 40 and after 80 years. We used climatic parameters as predictors. The annual mean temperature has the greatest impact on the modeling results (about 30–60% among models). The precipitation of the warmest quarter also had a high relative importance (about 15–40% among models). For future projections, we considered two shared socio-economic pathways (ssp245 and ssp585). We applied three algorithms: the generalized additive model (GAM), support vector machine (SVM) and multilayer perceptron (MLP) and ensemble prediction. Our projections showed a decrease in habitable area in the eastern part of the range of C. laminata in 40 and in 80 years. According to the forecast, the habitat suitable area will become more fragmented. The range shift with new suitable areas is expected toward the east direction.

Further notes on the taxonomy of the land snail family Clausiliidae Gray, 1855 (Stylommatophora, Helicina) from Myanmar with description of two new species.

This study presents a complete species list of the door snails inhabiting Myanmar, updated to now include 33 taxa, and provides taxonomic notes together with a re-description of the shell, radula, and genitalia for 13 species and subspecies, including Oospiraphilippiana, the type species of the genus Oospira. The snails previously treated as subspecies or synonyms of Oospiragracilior and Oospiramagna are reclassified and recognized as distinct species. The lectotype of Oospirainsignis has been clarified and an illustration of the original type specimen provided. A long-overlooked species, Oospiraandersoniana, has been collected and redescribed herein. Two new species from the limestone karsts in the Salween River Basin are introduced: Oospiraluneainopsis Man & Panha, sp. nov. and Oospirazediopsis Man & Panha, sp. nov. A synoptic view of all clausiliid taxa known from Myanmar is presented along with taxonomic information and distributional records. Photographs of the type materials for all taxa are provided for further comparison or, if unavailable, photographs of the examined specimens or the original figure from the literature.

Evidence that reduction of the apertural closing apparatus has no decisive effect on water loss in the land snail family Clausiliidae (Gastropoda: Stylommatophora)

Abstract Apertural barriers of land snails are thought to increase their shell’s effectiveness against dehydration and predation. The most complex apertural barrier among stylommatophoran snails is the clausiliar apparatus (CA) of Clausiliidae. Alopia is a unique genus in having a remarkably high proportion of taxa with a naturally reduced CA, representing at least five independent reduction events. We tested the prevailing hypothesis that the primary role of the CA within the door snail family is to help retain body moisture. In a laboratory experiment, we compared the water loss of two Alopia taxa with naturally reduced and two Alopia taxa with complete CAs. There was a detectable difference in the rate of water loss, but no relationship with the presence/absence of the CA could be shown. In another laboratory experiment, this time in Alinda biplicata, we did not detect significantly higher water loss in specimens from which the clausiliar plate was artificially removed compared to those left intact. These results suggest that the CA has no significant role in water retention but its actual function remains speculative. A possible explanation, which requires further work, could be that the CA provides protection against specific predators intruding through the aperture.

Brachylaima phaedusae n. sp. (Trematoda: Brachylaimidae) from door snails in Japan.

The metacercarial infections of door snails (Gastropoda: Clausiliidae) with unknown species of the genus Brachylaima (Trematoda: Brachylaimidae) have recently been reported in eastern Honshu and Kyushu, Japan. A large scale snail survey was carried out to clarify their taxonomic status. From the period of 2015 to 2020, a total of 1239 land snails (768 door snails and 471 others) were collected from 32 localities in Honshu, Shikoku, and Kyushu. The resulting trematode isolates were identified as Brachylaima sp. by mitochondrial DNA barcoding. The sporocysts were found only a few from Megalophaedusa sublunellata (Clausiliidae), Tauphaedusa subaculus (Clausiliidae), and Aegista trochula (Camaenidae), while the metacercariae were frequently detected from 14 species of Clausiliidae and 2 species of other families. Although Brachylaima sp. showed a broad range of intermediate hosts, door snails seem to be very important to drive the life cycle. The gravid adults of Brachylaima sp. was experimentally raised from metacercariae using immunosuppressed mice. Morphological, phylogenetical, and ecological considerations prompted us to propose Brachylaima phaedusae n. sp. for this unknown species. The definitive hosts of the new species are completely unknown. The wide geographic distribution and high genetic diversity of the new species suggest a possibility that the definitive host is ground-foraging birds, which prefer door snails.

Taxonomic study of a new green alga, Annulotesta cochlephila gen. et sp. nov. (Kornmanniaceae, Ulvales, Ulvophyceae), growing on the shells of door snails

Some algae are known to grow on shellfish shells. Most of these have been reported in aquatic environments. The species specificity for substrate shells varies, and some algae grow only on the shells of a certain species of shellfish, such as Pseudocladophora conchopheria (Cladophorales, Ulvophyceae) on Lunella coreensis (Trochida, Gastropoda). There are very few reports of algae that grow on land snails. In this study, we discovered green algae growing on the shells of six species of door snails (Clausiliidae) from nine localities in Japan. These green algae formed a green mat composed of thalli embedded in the extracellular matrix. The thallus was composed of aggregated oval cells and peripheral branched filaments. The cells possessed a single parietal chloroplast with a pyrenoid surrounded by two starch sheaths and transversed by a thylakoid. Oil droplets in the cell and ring-like structures on the cell wall surface were frequently observed. The 18S rDNA sequences of all shell-attached algae on different clausiliid species from different localities were almost identical and formed a new clade in the family Kornmanniaceae (Ulvales, Ulvophyceae). No other algae forming visible colonies on the clausiliid shell were found. These findings indicate the presence of specificity between the alga and clausiliid shells. Based on the results of morphological observation and molecular phylogenetic analysis, we propose a new genus and new species of shell-attached green alga, Annulotesta cochlephila.

Evolution of reproductive strategies in the species-rich land snail subfamily Phaedusinae (Stylommatophora: Clausiliidae)

Most of the present knowledge on animal reproductive mode evolution, and possible factors driving transitions between oviparity and viviparity is based on studies on vertebrates. The species rich door snail (Clausiliidae) subfamily Phaedusinae represents a suitable and unique model for further examining parity evolution, as three different strategies, oviparity, viviparity, and the intermediate mode of embryo-retention, occur in this group. The present study reconstructs the evolution of reproductive strategies in Phaedusinae based on time-calibrated molecular phylogenetics, reproductive mode examinations and ancestral state reconstruction. Our phylogenetic analysis employing multiple mitochondrial and nuclear markers identified a well-supported clade (including the tribes Phaedusini and Serrulinini) that contains species exhibiting various reproductive strategies. This clade evolved from an oviparous most recent common ancestor according to our reconstruction. All non-oviparous taxa are confined to a highly supported subclade, coinciding with the tribe Phaedusini. Both oviparity and viviparity occur frequently in different lineages of this subclade that are not closely related. During Phaedusini diversification, multiple transitions in reproductive strategy must have taken place, which could have been promoted by a high fitness of embryo-retaining species. The evolutionary success of this group might result from the maintenance of various strategies.

Repeated hybridization increased diversity in the door snail complex Charpentieria itala in the Southern Alps

The door snail species complex Charpentieria itala is widely distributed in the Southern Alps and subdivided into several morphologically differentiated subspecies. Thus, it can be used as a model group for understanding migration and differentiation processes in the Southern Alps. We generated genome-wide double digest Restriction Site Associated DNA (ddRAD) sequencing data for 166 specimens from 36 populations of the door snail Charpentieria itala and for 8 specimens of the other three Charpentieria species to reconstruct their evolutionary history and phylogeography. Phylogenetic and structure analyses based on the ddRAD data indicated that the repeated separation of the populations in western and eastern groups by the Garda glacier during the glacials was the process that most strongly shaped the population structure of C. itala. This process may also explain a similar phylogeographic boundary in many other southern Alpine animal and plant species. Our study revealed that some populations that resemble Charpentieria stenzii morphologically and ecologically, the ‘stenzioid’ subspecies, originated by a hybridization event with Charpentieria stenzii. A further hybridization event between stenzioid populations that survived the glacials in mountain refuges and non-stenzioid populations that probably came into contact with stenzioid populations as a result of climate warming during an interglacial resulted in the origin of a hybrid subspecies that is adapted to intermediate altitudes. Our study demonstrated that the origin of new differentiated taxa by hybridization, is more frequent than previously assumed.

New insights into and limitations of the molecular phylogeny in the taxon‐rich land snail genusMontenegrina(Mollusca: Gastropoda: Clausiliidae)

Rock-dwelling gastropods are usually patchily distributed in limestone habitats, presumably have low active and passive dispersal ability and often represent narrow-ranged endemic taxa. Their current taxonomy is predominantly shell morphology based, and it remains unknown whether the morphologically differentiated and geographically separated populations represent phylogenetic clades. In this study, we analysed the hyperdiverse, terrestrial door snail genus Montenegrina. Based on the current taxonomy defined by shell morphology, it contains 29 species and 106 subspecies distributed in the Balkan region. The constructed phylogenetic tree using three mitochondrial markers was used to test whether it agrees with the current taxonomy. In this comprehensive tree, about half of the species and subspecies are monophyletic. Some of the paraphylies could be reasonably resolved by taxonomic changes; that is, some subspecies should be reassigned or raised to species level. Other incongruencies probably arose due to introgression even between distant clades. The histone genes turned out to be unsuitable for elucidating the phylogeny of Montenegrina. In the species-delimitation tests, considerably more molecular operational taxonomic units were delimited than the number of presently described species. The present data indicate that (a) shell morphology-based taxonomy and taxon recognition can be problematic in such a large and morphologically highly variable genus; (b) the potential error due to incomplete sampling presents a problem in a genus as variable as Montenegrina; (c) multi-locus analyses should be conducted to arrive at a better basis for species delimitation; and (d) integrative approaches including genetic as well as morphological/anatomical data from a comprehensive geographic sample are necessary.

Cadmium Uptake, MT Gene Activation and Structure of Large-Sized Multi-Domain Metallothioneins in the Terrestrial Door Snail Alinda biplicata (Gastropoda, Clausiliidae).

Terrestrial snails (Gastropoda) possess Cd-selective metallothioneins (CdMTs) that inactivate Cd2+ with high affinity. Most of these MTs are small Cysteine-rich proteins that bind 6 Cd2+ equivalents within two distinct metal-binding domains, with a binding stoichiometry of 3 Cd2+ ions per domain. Recently, unusually large, so-called multi-domain MTs (md-MTs) were discovered in the terrestrial door snail Alinda biplicata (A.b.). The aim of this study is to evaluate the ability of A.b. to cope with Cd stress and the potential involvement of md-MTs in its detoxification. Snails were exposed to increasing Cd concentrations, and Cd-tissue concentrations were quantified. The gene structure of two md-MTs (9md-MT and 10md-MT) was characterized, and the impact of Cd exposure on MT gene transcription was quantified via qRT PCR. A.b. efficiently accumulates Cd at moderately elevated concentrations in the feed, but avoids food uptake at excessively high Cd levels. The structure and expression of the long md-MT genes of A.b. were characterized. Although both genes are intronless, they are still transcribed, being significantly upregulated upon Cd exposure. Overall, our results contribute new knowledge regarding the metal handling of Alinda biplicata in particular, and the potential role of md-MTs in Cd detoxification of terrestrial snails, in general.

New data on the genus PapilliferaW. Hartmann, 1842 (Gastropoda, Pulmonata, Clausiliidae) in Sicily (Italy)

Papillifera papillaris (O.F. Müller, 1774) is a door snail (Gastropoda, Pulmonata, Clausiliidae) with Graciliaria clausilial apparatus, autochthonous in southern Italy, Sicily and Maltese Islands, but that has been widespread in the western Mediterranean region. In Sicily, P. papillaris is widely distributed and relatively diverse and this led in the 1800s to the description of numerous taxa. Some of these taxa are considered valid subspecies, while other taxa have not been revised in recent times. In the present work the taxa described for the genus Papillifera W. Hartmann, 1842 in Sicily are re-examined and the distribution of the subspecies is redefined.

Ecological specialization resulting in restricted gene flow promotes differentiation in door snails

We tested the hypothesis that ecological specialization that affects dispersal promotes diversification by a comparison of the genetic structure of two sister species of door snails across their broadly overlapping ranges in the Crimean Mountains. The hypothesized effect of ecological specialization on diversification is supported by STRUCTURE analyses that showed that Mentissa gracilicosta that is restricted to limestone rocks, is subdivided into several distinct clusters, whereas all populations of the species adapted to more continuous habitat, the forests-dwelling Mentissa canalifera, were assigned to a single cluster. Furthermore, it is supported by AMOVAs that showed that a larger part of the genetic variation of M. gracilicosta is apportioned among populations than in M. canalifera. The stronger genetic differentiation of the M. gracilicosta populations corresponds to their more distinct morphological differentiation that resulted in the classification of M. gracilicosta into several geographical subspecies, whereas the more continuously distributed M. canalifera was not subdivided into subspecies. The stronger differentiation of populations of M. gracilicosta compared to M. canalifera can be ascribed to reduced gene flow between the isolated populations of M. gracilicosta and to founder events associated with the long distance dispersal events that are necessary for the colonization of isolated rocks by M. gracilicosta. In Central Europe, the Pleistocene climatic oscillations selected for species with high dispersal abilities, whereas the more stable climate in southern Europe facilitated the non-adaptive radiation of rock-dwelling door snails. Thus, the intrinsic ecological properties of these species groups contributed to the latitudinal diversity gradient.

High Fecundity, Rapid Development and Selfing Ability in Three Species of Viviparous Land Snails Phaedusinae (Gastropoda: Stylommatophora: Clausiliidae) from East Asia.

Anna Sulikowska-Drozd, Takahiro Hirano, Shu-Ping Wu, and Barna Páll-Gergely (2018) Life history traits are important yet understudied aspects of ecological diversification in land snail faunas. To acquire information for comparative analysis of gastropod life cycles, we conducted experimental breeding of three viviparous clausiliids from Japan and Taiwan. Under laboratory conditions, Tauphaedusa sheridani (Pfeiffer, 1866), T. tau (O. Boettger, 1877) and Stereophaedusa (Breviphaedusa) jacobiana (Pilsbry, 1902) featured similar times to complete shell growth (12-16 weeks), age of first reproduction (23-24 weeks) and annual fecundity (143- 173 neonates per pair of snails). The maximum number of eggs retained in genital tract reaches nine for T. sheridani, 11 for T. tau, and seven for S. jacobiana. The ratio between average shell height of neonate and adult varied between 13.5% for T. tau, 13.9% for T. sheridani, and 16.7% for S. jacobiana. All species were able to self-fertilize. Exposure to long drought affects intrauterine embryo development in all species; additionally, it results in parent and embryo mortality in S. jacobiana. Observed differences in the structure of the egg envelope among studied species point to greater than expected differentiation of developmental processes in viviparous Phaedusinae of East Asia.

High gene flow despite opposite chirality in hybrid zones between enantiomorphic door snails.

We studied differentiation and geneflow patterns between enantiomorphic door-snail species in two hybrid zones in the Bucegi Mountains (Romania) to investigate the effects of intrinsic barriers (complications in copulation) and extrinsic selection by environmental factors. A mitochondrial gene tree confirmed the historical separation of the examined populations into the dextral Alopia livida and the sinistral Alopia straminicollis in accordance with the morphological classification, but also indicated gene flow between the species. By contrast, a network based on amplified fragment length polymorphisms (AFLP) markers revealed local groups of populations as units independent of their species affiliation. Admixture analyses based on AFLP data showed that the genomes of most individuals in the hybrid zones are composed of parts of the genomes of both parental taxa. The introgression patterns of a notable fraction of the examined markers deviated from neutral introgression. However, the patterns of most non-neutral markers were not concordant between the two hybrid zones. There was also no concordance between non-neutral markers in the two genomic clines and markers that were correlated with environmental variables or markers that were correlated with the proportion of dextral individuals in the populations. Neither extrinsic selection by environmental factors nor intrinsic barriers resulting from positive frequency-dependent selection of the prevailing coiling direction were sufficient to maintain the distinctness of A.straminicollis and A.livida. Despite being historically separated units, we conclude that these taxa now merge where they come into contact.

First establishment of microsatellite markers in clausiliid snails (Mollusca: Gastropoda: Clausiliidae)

BackgroundClausiliidae (door snails) are gastropods with a very high diversity concerning shell morphology, especially of their complex closing apparatus, which provides the most important diagnostic traits for classification of taxa. Due to the high variability, a high number of taxa has been described, though their systematics and taxonomy is partially controversially discussed. Montenegrina is the second most speciose door snail genus in Europe. It is an obligate rock-dwelling land snail and has, compared to its complex systematics, a rather small distribution range in the western parts of the Balkan Peninsula. The different taxa themselves show a very narrow and patchy distribution range. As Montenegrina is comprehensively sampled over the whole distribution range, it is a perfect study system for general questions on speciation and morphological differentiation in land snails. To study the amount of gene flow between geographically close or co-occurring populations, highly polymorphic markers are needed.ResultsThirteen microsatellite loci with a tetranucleotid repeat were isolated and tested in three geographically close Montenegrina populations (two populations of M. dofleini prespaensis from the Prespa Lake, n = 35 and one population from M. stankovici from the Ohrid Lake, n = 20). The number of alleles per locus ranged from 2 to 27. No significant linkage disequilibria between the same two loci were found in all three tested populations. The deviation from Hardy–Weinberg equilibrium reveal only for two loci a significant deviation from HWE in more than one population (Mont_5483 and Mont_4477).ConclusionThe 13 newly established genetic markers will help to gain better insights to the population genetic structure of Montenegrina and might reveal new results about speciation processes in co-occurring taxa. Furthermore, these microsatellite loci could also be tested in other clausiliid species.

On the histology, ultrastructure and function of the spermoviduct and free oviduct in egg-retaining door snails (Pulmonata: Clausiliidae)

On the histology, ultrastructure and function of the spermoviduct and free oviduct in egg-retaining door snails (Pulmonata: Clausiliidae)

Checking Snails – pupils as snail watchers

Checking Snails – pupils as snail watchers

Presumable incipient hybrid speciation of door snails in previously glaciated areas in the Caucasus

Homoploid hybrid speciation, speciation by hybridization without a change in chromosome number, may be the result of an encounter of closely related species in a habitat that is different from that usually occupied by these species. In the northwestern Caucasus the land snail species Micropontica caucasica and M. circassica form two distinct entities with little admixture at low and intermediate altitudes. However, at higher altitudes in the Lagonaki plateau, which were repeatedly glaciated, Micropontica populations with intermediate characters occur. Admixture analyses based on AFLP data demonstrated that the populations from the Lagonaki plateau are homoploid hybrids that now form a cluster separate from the parental species. The Lagonaki populations are characterized by a mtDNA haplotype clade that has been found in the parental species only once. The fixation of this haplotype clade in most hybrid populations suggests that these haplotypes are better adapted to the cooler conditions in high altitude habitats and have replaced the haplotypes of the parental species in a selective sweep. The fixation of a presumably adaptive mitochondrial haplotype clade in the Lagonaki populations is an important step towards speciation under the differential fitness species concept.

Comparative Cytogenetic Study in Four Alopiinae Door Snails (Gastropoda, Clausiliidae)

A cytogenetic study was carried out by means of standard and NOR-FISH staining methods on the chromosomes of four Alopiinae door snails, two species of the Delimini tribe (Siciliaria paestana and Papillifera bidens) and two species of Medorini tribe (Leucostigma candidescens and Medora sp.). The two Delimini species and Medora sp. showed similar karyotypes, concerning the number of chromosomes, 2n = 62, and the first metacentric pair of chromosomes clearly bigger than the other pairs, but differed in the number of the telocentric pairs: none in P. bidens, four in S. paestana and, even, 21 in Medora sp. Leucostigma candidescens had 2n = 48, all biarmed chromosomes. Loci of NORs were on a single medium small chromosome pair in all the four studied species. The obtained results evidence a relevant degree of intergeneric karyotypic diversity in Alopiinae, concerning both chromosome number and/or shape. The data allow us to make a hypothesis on the evolutionary chromosome trends for this door snail subfamily.

Does the histological structure of spermoviduct and free oviduct correspond with the reproductive mode in Clausiliids (Gastropoda: Pulmonata: Baleinae)?

Spermoviduct and free oviduct of four species of Baleinae door snails of different reproductive strategy: Laciniaria plicata (oviparity), Vestia gulo (egg retention), Alinda biplicata and Vestia turgida (viviparity), were histologically examined. The spermoviduct contains three partly connected canals: autospermiduct, allospermiduct and oviduct. Their walls are built of pseudostratified epithelium which is composed of large, columnar cells and small, much thinner, supporting cells with the apical surface provided with cellular processes. The free oviduct includes two partly connected canals: oviduct and allospermiduct, with their walls also built of pseudostratified epithelium. Both morphology and secretory activity of epithelial cells are very similar in viviparous and oviparous forms. Key worDs: Clausiliidae, reproductive system, Alinda, Laciniaria, Vestia, land snails