Land Snail Research Articles

Monitoring arthropods under the scope of LIFE-SNAILS project: I - Santa Maria Island baseline data with implementation of the Index of Biotic Integrity.

The database we introduce is a pivotal component of the LIFE SNAILS project (Support and Naturalisation in Areas of Importance for Land Snails). This initiative is dedicated to safeguarding three endangered species of terrestrial molluscs, specifically, two snails (Oxychilusagostinhoi Martins 1981 and Leptaxisminor Backhuys, 1975) and a semi-slug (Plutoniaangulosa (Morelet, 1860)), all of which are single island endemics from Santa Maria Island and face significant threats towards their populations.In this study, we established a comprehensive database derived from a long-term arthropod monitoring campaign utilising SLAM (Sea, Land, Air, Malaise) traps. Although molluscs were not the primary focus, our findings serve as a credible proxy for evaluating the overall habitat quality for endemic invertebrates, with arthropods serving as principal indicators. From September to December of 2022, a total of 11 SLAM traps were installed and monitored monthly in eleven sites of mixed forests of Santa Maria Island. Based on the 33 available samples (11 sites x 3 sampling periods), we recorded a total of 118 taxa of arthropods (of which 94 were identified at species or subspecies level), belonging to three classes, 14 orders and 62 families. From the 94 identified taxa, a total of 21 species were endemic, 31 native non-endemic, 32 introduced and 10 indeterminate. We also provide additional information of the habitat quality (Index of Biotic Integrity), including general habitat and dominant species composition.We registered three new records to the Island, the native bug Piezodoruslituratus (Fabricius, 1794) (Hemiptera, Pentatomidae), the Azorean endemic beetle Phloeosinusgillerforsi Bright, 1987 (Coleoptera, Curculionidae) and the exotic ant Hypoponerapunctatissima (Roger, 1859) (Hymenoptera, Formicidae) and one new record for the Azores Archipelago, the native beetle Cephenniumvalidum Assing & Meybohm, 2021 (Coleoptera, Staphylinidae, Scydmaeninae).This publication not only contributes to the conservation of highly threatened endemic molluscs, through an assessment of habitat quality, based on arthropod communities and habitat description (e.g. native or exotic vegetation), but also provides an updated inventory of arthropods from Santa Maria Island.

Parasitic Fauna of Achatina Achatina in Otuoke Community, Ogbia Local Government Area, Bayelsa State

The Giant African land snail, Achatina achatina, is an invasive species recognized for being a serious agricultural pest and vector for diverse parasites that cause diseases in humans. This study assessed the prevalence of parasites harboured by the snails collected from bushes in the Otuoke community of Bayelsa State, Nigeria. The snail samples were collected and transported to the laboratory for examination using wet mouth preparation and teasing methods. Subsequently, they were classified by size into small, medium and large. The body organs were individually teased and examined under the microscope. 122 snail samples (32 small, 54 medium, 36 large) were randomly collected for this study and examined for the presence of eggs or larvae of parasites, out of which 108 (88.5%) were infected. The larvae of only two species of parasites, Angiostrongylus cantonensis (90.1%) and Strongyloides stercoralis (9.9%)) were recovered from the infected snails, with A. cantonensis being most prevalent, 737 (90.1%). The parasites were most prevalent in the medium snails (42.6%), followed by the small size (23.8%) and then, the large size snails with the least prevalence of infection. The slime, intestine and stomach were infected, with the parasites being more in the slime (88.5%) than any other body parts. Since the Giant African land snail serves as an intermediate host for several parasites, a thorough understanding of the snail parasites' lifecycles and modes of transmission to humans is important, for human health and welfare, sustainable snail farming, and for maintenance of snail biodiversity.

A description of a new species of the genus Brachydistomum (Trematode, Dicrocoeliidae) from the Eurasian Tree Sparrow Passer montanus (Linnaeus) (Passeriformes) in Japan, with a report on the first intermediate host.

The trematode Brachydistomum suzume n. sp. (Dicrocoeliidae) was detected in the Eurasian Tree Sparrow Passer montanus, and described as a new species in Japan. This new species can be distinguished from the other members of the genus on the basis of morphological characters of suckers and reproductive organs. A partial sequence of adult mitochondrial cytochrome c oxidase subunit 1 (COI) was used as a DNA barcode, and dicrocoeliid sporocysts and cercariae detected from four camaenid land snail species, Bradybaena pellucida, Brad. similaris, Acusta sieboldiana and Euhadra brandtii, were molecularly identified as the new species. Phylogenetic trees of nuclear 28S ribosomal DNA and COI also showed the new species to be distinct from the other trematode species, including Brachydistomum spp.

The land snail fauna of Batu Kudik, isolated limestone outcrop near Simunjan, Sarawak, Malaysian Borneo (Mollusca, Gastropoda).

The present study provides a checklist of land snails collected from Batu Kudik, a small and isolated limestone outcrop in Simunjan, Sarawak. A total of 24 species of land snails, representing 18 genera and 14 families were recorded, including one newly-described subspecies. The most species-rich of the families in Batu Kudik are Diplommatinidae (17%) and Chronidae (17%) with four recorded species from each of the families. Based on our analysis, Plectostomawallaceikudikense subsp. nov., Opisthostomajavanica and Georissapyrrhoderma were identified as the most abundant land snails at this isolated outcrop, whereas Diplommatinaonyx and Everettiaminuta were recorded as the least abundant. All of the land snails at Batu Kudik were exclusively found sheltered between limestone boulders, underscoring the critical role of this outcrop as their refuge for survival. Consequently, conserving this biodiversity-rich limestone area becomes paramount to prevent the local extinction of these land snail species and possibly other organisms that depend on the unique attributes of the limestone for their survival. We also provide detailed descriptions of Plectostomawallaceikudikense, a new subspecies of the genus Plectostoma which is endemic to Batu Kudik. A description of a new subspecies Plectostomawallaceikudikense subsp. nov.

Biogeography of vine thickets and open woodland in subtropical eastern Australia: a case study of three camaenid land snail genera

Dry rainforests and open woodlands occur across much of eastern Australia. However, the biogeographic history of these habitats remains poorly known, especially when compared to nearby moist rainforest areas. Land snails are commonly used as model organisms to understand patterns of origins of regional endemism due to their low vagility. Here we present an analysis of patterns of mitochondrial genetic diversity in three camaenid snail lineages with distributions centred on vine-thicket and open woodland habitats of eastern Queensland, specifically Euryladra from open woodlands, Brigaladra from inland semievergreen vine thickets, and Figuladra from coastal vine thickets. Lineages from habitats west of the Great Dividing Range show relatively low genetic divergence between localities, with particularly low structuring in the open woodland taxon Euryladra. Figuladra from vine-thicket habitats closer to the coast shows relatively deeper genetic divergence, with marked divergences between some upland and lowland areas in south-east Queensland, and across the St Lawrence Gap. This structuring suggests that taxa associated with vine thicket habitats have had a more discernible history of isolation than open woodlands. This said, genetic divergence across many vine thickets patches in lowland coastal regions is also shallow, suggesting many apparently disjunct vine thicket habitats and their associated species also have a recent history of connectivity.

The terrestrial gastropods in three Dodecanese islands, Rhodes, Symi, Chalki (Aegean Sea, Greece)

Rhodes, Symi and Chalki are three islands with different characteristics in the southeastern part of the Aegean Sea. In this work, we present their complete land snail fauna based on recent survey, samples from the collections of the Natural History Museum of Crete and a thorough bibliographic review. We report 67 land snail species from Rhodes, 34 species from Symi, and 32 from Chalki, with 4, 20 and 9 new records for each island, respectively. Also, one species has been added to the malacofauna of Greece, while many names, which were mentioned mainly in the 19th century, have been clarified, synonymised or abolished from the lists of the islands. Our results once again demonstrate the importance of the reproductive system as a tool for reliable assessment of the taxonomy of Aegean land snails, and that sampling during the rainy season should be the preferred methodological approach for collecting land snails in the Greek islands.

Interactions between Galba truncatula (Gastropoda, Lymnaeidae) and two land snail species on the acid soils of central France

ABSTRACT Interactions between Galba truncatula and two species of land snails (Cochlicopa lubrica, Succinea putris) that colonise lymnaeid habitats in June-July were studied by introducing G. truncatula into new sites (Experiment A) or removing it from its natural habitats (Experiment B). Snail counts were performed in late May or early June for the eight years following introduction or removal of G. truncatula. The results were compared to those observed at control sites where G. truncatula was absent. In sites where G. truncatula was introduced (Experiment A), the mean density of the lymnaeid peaked in the second year and gradually decreased in subsequent years. Conversely, the mean density of the land snails decreased sharply in the second year before increasing rapidly for S. putris and gradually for C. lubrica in subsequent years. Removal of G. truncatula from its natural habitats (Experiment B) had no significant effect on the mean density of C. lubrica. In contrast, that of S. putris peaked in the second year and decreased rapidly to lower values in subsequent years. Density interactions between G. truncatula and the two land snail species indicate that there is probably competition between these species for space in lymnaeid habitats in May and June.

Mycophagy and feeding on other native land snails by the black snail Macrocyclis peruvianus (Gastropoda, Macrocyclidae)

AbstractLand snails are among Chile's least studied invertebrates. Their natural history and ecology are poorly studied, even when it comes to striking species such as the black snail Macrocyclis peruvianus. This large and easily recognizable species inhabits the forest floor of southern Chile; however, we do not know its eating habits. In this natural history note, we describe the first records of mycophagy in M. peruvianus in native Chilean forests. The records were obtained thanks to citizen science (iNaturalist, Instagram and Facebook), which provided a complete data set with habitat remarks. We registered 21 records of mycophagy, from which we identified three fungus species (Marasmiellus alliodorus, Aleurodiscus vitellinus and Grifola gargal) and five genera (Armillaria, Boletus, Mycena, Pholiota and Ramaria). Of the consumed fungi, 58.82% grew in coarse woody debris and 64.70% belong to the order Agaricales, followed by Boletales, Gomphales, Russulales and Polyporales. In addition, we described the first record of M. peruvianus feeding on the native land snail Plectostylus peruvianus. Coarse woody debris could be a key element for black snails because their frequent food – the Agaricales fungi species – grows on them. Finally, M. peruvianus feeding on other native land snails could be rare in the wild because they co‐occur in the same distribution but in different microhabitats.

Many roads to success: alternative routes to building an economic shell in land snails.

Land snails exhibit an extraordinary variety of shell shapes. The way shells are constructed underlies biological and mechanical constraints that vary across gastropod clades. Here, we quantify shell geometry of the two largest groups, Stylommatophora and Cyclophoroidea, to assess the potential causes for variation in shell shape and its relative frequency. Based on micro-computed tomography scans, we estimate material efficiency through 2D and 3D generalizations of the isoperimetric ratio, quantifying the ratios between area and perimeter of whorl cross-sections (2D) and shell volume and surface (3D), respectively. We find that stylommatophorans optimize material usage through whorl overlap, which may have promoted the diversification of flat-shelled species. Cyclophoroids are bound to a circular cross-section because of their operculum; flat shells are comparatively rare. Both groups show similar solutions for tall shells, where local geometry has a smaller effect because of the double overlap between previous and current whorls. Our results suggest that material efficiency is a driving factor in the selection of shell geometry. Essentially, the evolutionary success of Stylommatophora likely roots in their higher flexibility to produce an economic shell.

A new species of land snail, Xanthomelon amurndamilumila, from the North East Isles off Groote Eylandt (= Ayangkidarrba), Gulf of Carpentaria, Australia (Stylommatophora, Camaenidae)

This paper introduces Xanthomelon amurndamilumilasp. nov., a newly-discovered land snail species inhabiting the North East Isles, offshore from Groote Eylandt (= Ayangkidarrba), north-western Gulf of Carpentaria, in the Northern Territory, Australia. Specimens of this species were first collected during the 2021 Bush Blitz expedition to Groote Eylandt, a large offshore archipelago previously unexplored for land snails. The taxonomic status of the new species was established through a comprehensive analysis of comparative morphology and mitochondrial genetics: X. amurndamilumila forms a maximally supported clade closely related to X. arnhemense and is characterised by a unique combination of morphological characteristics, including smaller shell size, distinctive sculpture of collabral ridges and specific features of its reproductive anatomy. The genetic divergence and phylogenetic relationships suggest historical isolation. While the discovery of X. amurndamilumilasp. nov. enriches our understanding of land snail diversity in the Northern Territory, its conservation status is of concern on North East Island because of habitat degradation caused by feral deer.

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

The land snail genus Pilsbrylia Hylton 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 that Pilsbrylia belongs 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, whilst Pilsbrylia has a “typical” dextral shell.

Assessment of terrestrial snails’ diversity and composition in six forests of west central - Morocco along an altitudinal gradient

This study aims to investigate the diversity of terrestrial gastropods in west-central Morocco. It also examines how elevation and other abiotic factors affect the distribution and composition patterns of said malacofauna. The sampling covered six different forest sites with thirty stations spanning on an altitudinal gradient that ranges from 24 to 2434m. The influence of abiotic factors on species richness and abundance was evaluated via the Pearson correlation. The Shannon index evaluated the malacofaunal diversity within each station. Whittaker’s index assessed heterogeneity of each forest site. The similarity between the forest sites was determined by multivariate analyses; namely the Jaccard index and the Nonmetric Multi-Dimentional Scaling analysis (NMDS). A total of 31312 specimens representing 30 species were recorded. Low altitude stations display the highest values of diversity and uniformity, while the highest altitude stations present the opposite trend. The NMDS analysis revealed that the elevation and vegetation type represent the principal factors affecting the distribution of land snails in the six forest sites.

The find of six species new to Belgium highlights the role of the stone trade as a pathway for non-native land snails (Gastropoda: Stylommatophora

Surveys in stone yards in Wallonia (southern Belgium) led to the find of six taxa of land snails being new to Belgium and one being new to Wallonia. The new taxa can be divided into two groups: living animals of the European species Charpentieria itala, Laciniaria plicata, Chilostoma cingulatum, and Theba pisana, and shells with remains of the dead animals in the case of the Asian taxa Cathaica fasciola, Acusta sp., and Bradybaena jourdyi. The latter are widespread in their respective Asian native range while Acusta sp. and B. jourdyi had never been reported from Europe. We discuss the role of stone yards as hubs for the dispersion of land snails. The individuals of the newly observed taxa may have arrived in several waves (with successive arrivals of stones) and may not reproduce in the stone yard. We explore the risks of settling. In this study, we provide evidence that the doorsnails C. itala and L. plicata have already settled elsewhere in Wallonia. Theba pisana, C. fasciola and Acusta sp. have the potential to behave as invasive

The value of targeted biological surveys: An assessment of Australia's Bush Blitz programme

AbstractAimBiodiversity assessment and decisions rely on knowledge of the spatial distribution of species, yet most global biodiversity is inadequately represented by occurrence records. Efforts to improve our knowledge of biodiversity distribution include targeted taxon survey programmes aimed at generating records of new, or previously unrecorded, species. Here, we evaluate nearly 8 years of biodiversity record collection by Bush Blitz, Australia's largest species discovery programme, to test how efficiently knowledge was added through the programme.LocationContinental Australia.MethodsBecause we expect locations that are environmentally distinct in comparison with those already surveyed to harbour novel records of species, we assess the extent to which Bush Blitz surveys complement continental environmental diversity (ED). We then assess how effectively this improvement in sampling of ED translates into the accumulation of records of new, or previously unrecorded, species. Our assessment is based on Bush Blitz data for six taxa (amphibians, spiders, land snails, moths and butterflies, reptiles and vascular plants), benchmarked against data accumulated over the same period by the Atlas of Living Australia (ALA)—Australia's largest aggregation of biodiversity records—as a comparison of effectiveness to the Bush Blitz programme.ResultsEnvironments surveyed through the Bush Blitz programme are highly complementary to environments from which ‘background’ observations were made over the same period and aggregated in the ALA. Bush Blitz surveys result in large numbers of records of new, or previously unrecorded, species. Across most biological groups considered, additions were made highly efficiently with respect to survey effort, relative to background survey effort represented in the ALA.Main ConclusionsOur results demonstrate the ability of the Bush Blitz programme to contribute valuable data to conservation assessment and planning and the important role of surrogate‐based assessments of ED complementarity in planning new targeted biological surveys.

Geographical and environmental patterns of Carpathian land snail faunas in a region of high endemicity

The land snail faunas of limestone gorges of Romanian Carpathians were sampled to test the effect of geographic and environmental factors on the malacofauna richness and composition. A total of 134 sites within 28 limestone gorges were surveyed during 2011–2019 using a combined strategy of visual search and litter/topsoil analysis. Environmental variables such as geographic location, altitude, climate, microhabitat type, dominant vegetation, tree cover and width of the gorge were recorded to detect the relationship with species richness and composition. While the numbers of species, their identities and their abundance varied greatly among samples, both presence and absence data and quantitative multivariate analyses showed that region and climate or altitude (both strongly associated with region) accounted for far more variation than differences in tree cover and dominant microhabitat. Nevertheless, the effects of different habitat preferences were evident. The mixture of species with very restricted ranges within this Pleistocene refugium and those that have spread widely during the Holocene raise questions about the meaning of region when related to local richness and composition.

Thermal Impact and the Relevance of Body Size and Activity on the Oxygen Consumption of a Terrestrial Snail, Theba pisana (Helicidae) at High Ambient Temperatures.

Metabolism, mainly driven by oxygen consumption, plays a key role in life, as it is one of the main ways to respond to extreme temperatures through internal processes. Theba pisana, a widespread Mediterranean land snail, is exposed to a wide range of ambient temperature. In this species the oxygen consumption was tested as a response variable by multiple regression modelling on the "explanatory" variables shell-free mass, temperature, and relative humidity. Our results show that the oxygen consumption of T. pisana can be well described (73.1%) by these three parameters. In the temperature range from 23 °C to 35 °C the oxygen consumption decreased with increasing temperature. Relative humidity, in the range of 67% to 100%, had the opposite effect: if it increases, oxygen consumption will increase as well. Metabolism is proportional to an individual's mass to the power of the allometric scaling exponent α, which is between 0.62 and 0.77 in the mentioned temperature range. CT scans of shells and gravimetry revealed the shell-free mass to be calculated by multiplying the shell diameter to the third power by 0.2105. Data were compared to metabolic scaling exponents for other snails reported in the literature.

Addressing the taxonomic confusion of Mesocoelium Odhner, 1910 (Trematoda: Plagiorchioidea: Mesocoeliidae) in Japanese urodelan and anuran amphibians.

Trematodes of the genus Mesocoelium Odhner, 1910 (Digenea: Plagiorchioidea: Mesocoeliidae) are globally distributed and parasitize amphibians, reptiles, or occasionally fishes. This genus is one of the most confusing taxa in trematodes because of its poor morphological features. In this study, we examined species of Mesocoelium collected from Japanese amphibians and found that they can be morphologically assigned to two species of Mesocoelium. Mesocoelium brevicaecum Ochi in Goto and Ozaki, 1929 parasitizes various both urodelan and anuran amphibians and occurred widely in Japan, while M. japonicum Goto and Ozaki, 1930 parasitizes a few hynobiid species in a limited part of Japan. We proposed ceca length as a valid key characteristic for species identification in this genus. M. elongatum Goto and Ozaki, 1929, M. lanceatum Goto and Ozaki, 1929, M. minutum Park, 1939, M. ovatum Goto and Ozaki, 1930, and M. pearsei Goto and Ozaki, 1930 are junior synonyms of M. brevicaecum, while M. japonicum can be distinguishable from them by morphologically and molecularly. Our molecular study supported the validity of both species and showed intraspecific divergence associated with geographic distance. Molecular identification suggests that the land snail Euhadra quaesita can serve as the first intermediate host for M. japonicum in Japan. This study also indicates the extremely low specificity of this genus for vertebrate hosts. Finally, we conclude that at least three species of Mesocoelium (M. brevicaecum, M. japonicum, and Mesocoelium sp. 1) are distributed in Japan. Further studies in other regions are undoubtedly required for a better understanding of the taxonomy and ecology of the genus Mesocoelium.

Species richness patterns and community structure of land snail communities along an urban-rural gradient in river floodplains

Urbanisation is widely considered as having a large impact on most native species. However, the species response to urbanisation varies among taxonomic groups, and its generalisation might lead to contradictory or incorrect management decisions in urban planning. Land snails, as an understudied group in this sense, are good subjects to study the impact of urbanisation due to their low dispersal capabilities and mobility. The study aimed to determine how land snail diversity patterns and community structure are influenced by urbanisation through an urban-to-rural gradient. A total of 59 terrestrial gastropod species and more than 4600 individuals were recorded at 24 alluvial sites distributed along an urban-to-rural gradient in three Slovak cities (Bratislava, Zvolen and Prešov). Most species belonged to euryecious, hygrophilous and forest specialist ecological groups; seven species were non-native to Slovakia. The results clearly highlight the negative effect of densely built areas on land snail community structure, since the proportion of indigenous and specialist species decreased progressively towards urban sites. The highest mean number of species was found in suburban zones and the lowest in urban zones, suggesting that most species favour intermediate levels of urbanisation. Some species (e.g. Arion vulgaris) were evenly distributed along the urbanisation gradient, supporting the importance of river floodplains as bio-corridors for the dispersal of gastropods.

Survey and population dynamics of land snails at Sharkia Governorate, Egypt.

Land snails are a destructive agricultural pest in economic crops, but the populations for that pest are highly influenced by temperature and humidity, therefore climatic changes affected their behavior, distribution and population dynamics, for these reasons researchers should follow up on the changes in their behavior, distribution, and population dynamics. In this study, a survey study was conducted to define land snail species existing at Sharkia Governorate, Egypt, from January 2019 to March 2022 in horticultural, vegetable, and field crops and study the population dynamics for the dominant land snail species. Results showed that there are six species of land snails, these species were, Monacha cartusiana, Succinea putris, Eobania vermiculata, Theba pisana, Helicella vestalis, and Cochlicella acuta. The population dynamics of two prevalent land snail species (M. cartusiana and S. putris), were conducted during two successive growing seasons, the Egyptian clover harbored the highest number of M. cartusiana followed by wheat, while the onion was the lowest one during the study period. In the same trends, the land snail S. putris recorded the highest numbers during the growing season of the Egyptian clover crop. Finally, it is concluded that the land snail M. cartusiana considered the first grade of infestation existed everywhere at Sharkia Governorate, and the population density of the land snail is increase gradually after winter till reach the maximum density in spring.

Activities of antioxidant enzymes and Hsp levels in response to elevated temperature in land snail species with varied latitudinal distribution.

Land snails occupy a variety of habitats, with differing temperature and humidity regimes and exhibit a wide span of adaptations, to withstand abiotic condition changes. The present work's aim was to examine the correlation of habitat's thermal adversity in different Mediterranean type habitats with the land snail's antioxidant and heat shock responses. For this purpose, snails of different species from populations along a north-south axis from the islands and mainland of Greece were exposed to elevated temperature and antioxidant enzyme activities, and Hsp70 and Hsp90 levels were determined in their tissues. The ATP, ADP, and AMP levels and the adenylate energy charge (AEC) were also determined. The comparison of protein levels and enzymatic activities across time intervals revealed significant differences for all factors examined. While the gradation pattern over time for a given factor was similar in all populations the absolute values over time differed. Catalase activity and the Hsp90 protein levels had the higher contribution in separating the different species and populations, followed by the activity of glutathione reductase and Hsp70 protein levels which contributed to a lesser degree. In general, populations from the southern part of their distribution in Greece tend to display a faster increase than northern populations in induction levels of all factors examined. Our data seem to be in line with the concept of preparation for oxidative stress (POS) while the changes in the AEC indicate an early preparation to cover the energy demand for the induction and synthesis of antioxidant enzymes and Hsps.