Shell colouration and different introductions of the land snail Cepaea hortensis (Gastropoda: Helicidae) into Western Ukraine

The primary introduction of C. hortensis into Western Ukraine, most likely in the second half of the 20th century, led to the formation of many populations characterised not only by a reduced phenotypic composition, but also by a peculiar phenotypic marker (absence of banded shells with a non-white ground colour). White banded shells, common in Western Ukraine, are also found in different parts of the present species range, but less frequently than yellow banded ones. When studying the shell colour and banding polymorphism in C. hortensis, white shells are often combined into one group with yellow ones. Therefore, the findings of these two phenotypes as well as white unbanded shells in Europe were mapped based on the analysis of more than 7 thousand photographs from citizen science database iNaturalist. The results of later introductions of C. hortensis to Western Ukraine, which may occur through different garden centres, are easily distinguished by the presence of yellow banded and/or pink shells. And the presence of a dark lip in all pink shells can be a phenotypic marker of snails, whose ancestors were introduced to the west of Ukraine through the garden centre “Club of Plants” near Lviv. Only near this garden centre were also found three brown-shelled snails not known for other introduced Eastern European populations of C. hortensis.

Arboreal snail genus Amphidromus Albers, 1850 of Southeast Asia: Shell polymorphism of Amphidromus cruentatus (Morelet, 1875) revealed by phylogenetic and morphometric analyses

Species of colourful arboreal snails of the genus Amphidromus from Southeast Asia commonly exhibit high intraspecific variation in shell morphology. Although highly polymorphic Amphidromus specimens with different colouration have been collected at the same locality and were revealed to possess similar genital organs, there is yet no morphometric or DNA analyses of these different shell morphs. This study is the first to reveal that both striped and stripeless morphs of A. cruentatus from Laos and Vietnam belong to the same mitochondrial (COI and 16S rRNA) lineage. Although the shell colouration between the striped and stripeless morphs is markedly different, morphometric and shell outline-based analyses indicated an overall similarity in shell shape. We also revised the systematics of A. cruentatus, in which we treated similar related species, namely A. eudeli, A. fuscolabris, A. thakhekensis, A. gerberi bolovenensis, A. goldbergi, A. pengzhuoani, A. eichhorsti and A. pankowskiae as junior synonyms of A. cruentatus. Amphidromus daoae, A. anhdaoorum, A. stungtrengensis, A. yangbayensis and A. yenlinhae, which were formerly regarded as junior synonyms, are considered as species different from A. cruentatus based on shell morphology and morphometric analyses. Preliminary phylogenetic analyses also retrieved some Amphidromus species groups as distinct mitochondrial lineages.

Comparative analysis of phenotypic variability of introduced land snail Cepaea nemoralis (Gastropoda: Helicidae) in two large Eastern European cities

Variation in the shell colour and banding polymorphism of Cepaea nemoralis was recorded in 20 sites in Minsk, Belarus (a total of 3965 adults collected in 2014–2021). This variation was compared with that in 16 sites from Lviv, Western Ukraine (total 3235 adults collected in 2019–2021). Unlike in Lviv, a remarkable spatial differentiation of the phenotypic composition was found in Minsk. The samples collected in the north-eastern part of Minsk were characterized by a greater degree of phenotypic diversity and by higher frequencies of unbanded and brown shells. Samples from the southern and eastern parts of the city were generally lighter and characterised by high frequencies of shells with a single central band (mid-banded). Differences between the two parts of Minsk were greater than those between Minsk and Lviv. This may be related to the history of colonization of Minsk by C. nemoralis. The Lviv samples were, on average, darker, they contained less frequently mid-banded shells and more frequently unbanded shells, especially pink unbanded ones. The Fst values characterizing the level of phenotypic variability and calculated for Minsk and Lviv are quite high and comparable with those for other urban areas recently colonized by C. nemoralis.

Deep structure, long-distance migration and admixture in the colour polymorphic land snail Cepaea nemoralis

Although snails of the genus Cepaea have historically been important in studying colour polymorphism, an ongoing issue is that there is a lack of knowledge of the underlying genetics of the polymorphism, as well as an absence of genomic data to put findings in context. We, therefore, used phylogenomic methods to begin to investigate the post‐glacial history of Cepaea nemoralis, with a long‐term aim to understand the roles that selection and drift have in determining both European‐wide and local patterns of colour polymorphism. By combining prior and new mitochondrial DNA data from over 1500 individuals with ddRAD genomic data from representative individuals across Europe, we show that patterns of differentiation are primarily due to multiple deeply diverged populations of snails. Minimally, there is a widespread Central European population and additional diverged groups in Northern Spain, the Pyrenees, as well as likely Italy and South Eastern Europe. The genomic analysis showed that the present‐day snails in Ireland and possibly some other locations are likely descendants of admixture between snails from the Pyrenees and the Central European group, an observation that is consistent with prior inferences from mitochondrial DNA alone. The interpretation is that C. nemoralis may have arrived in Ireland via long‐distance migration from the Pyrenean region, subsequently admixing with arrivals from elsewhere. This work, therefore, provides a baseline expectation for future studies on the genetics of the colour polymorphism, as well as providing a comparator for similar species.

Convergent evolution of

East Asian terrestrial snails of the family Camaenidae Pilsbry, 1895a are diverse in terms of genus and species numbers, shell morphology and mode of living. This family also includes colourful conical arboreal snails that traditionally have been assigned to the genus Amphidromus Albers, 1850. Yet, the present study shows that, despite their deceiving conchological similarity, some of these East Asian arboreal snails do not belong to the genus Amphidromus or the subfamily Camaeninae Pilsbry, 1895a. The presence of a dart complex comprising a mucous gland, a dart sac, an accessory sac and a proximal accessory sac, along with a pronounced penial caecum and molecular phylogenetic analyses revealed that former ‘Amphidromus’ dautzenbergi, ‘A.’ roemeri and ‘Camaena’ mirifica, and one additional new species belong to Aegistohadra Wu, 2004 (subfamily Bradybaeninae Pilsbry, 1934). Aegistohadra dautzenbergi, comb. nov. and Aegistohadra roemeri, comb. nov. are conical with colourful spiral bands, whereas Aegistohadra mirifica, comb. nov. and Aegistohadra zhangdanae, sp. nov. are heliciform to conical with colourful, variegated spiral and transverse banding patterns. DNA sequence analyses also revealed that each variety of Aegistohadra dautzenbergi could not be differentiated by mitochondrial (cytochrome c oxidase subunit I and 16S rRNA) gene fragments. The phylogenetic position of Aegistohadra within the East Asian camaenids revealed that the similar appearance in shell morphology, microhabitat use and diet to arboreal snails in the genus Amphidromus is homoplastic. Moreover, the presence or absence of a dart complex is also homoplastic and is unsuitable for suprageneric classification. By contrast, the presence of a flagellum and a penial caecum is useful for the suprageneric classification.

Cepaea nemoralis (L.) On Öland, Sweden: recent invasion and unexpected variation

Cepaea nemoralis is a recently introduced species on Öland. Discounting an early and debateable record, the species has been recorded only in the 21st century, despite intensive earlier faunistic surveys. A recent survey has yielded records from the whole length of the island (137 km), but the majority of known populations are in its southern half, most particularly around the settlements of Mörbylånga, Gräsgård and Färjestaden. Populations are usually in anthropogenic habitats. Most appear small and isolated by less disturbed areas. Nearly all samples are polymorphic for both colour and banding morphs, and the variation among populations is low when compared with similar sets from other places where recent colonisation has occurred. There is no latitudinal variation in morph frequencies, nor is any spatial autocorrelation apparent. While a relatively uniform and rigorous selection regime could account for the patterns seen, a single initial introduction followed by transport of propagules large enough to minimise founder effects is also possible.

Cepaea spp. as a source of Brachylaima mesostoma (Digenea: Brachylaimidae) and Brachylecithum sp. (Digenea: Dicrocoeliidae) larvae in Poland

Parasite diagnostics were carried out on 11 Polish populations of Cepaea spp. In three of them, coming from the roadside ditches of a village (Rytel, northern Poland), very high (up to 60%) prevalence of Brachylaima mesostoma was observed. This study provides the first molecular evidence of the presence of B. mesostoma inside Cepaea spp. in Europe. In a few snails from a population found in a private garden in a small town (Chełmża, northern Poland), larvae of Brachylecithum sp. were present. Cercariae and/or metacercariae of B. mesostoma were observed in both species of Cepaea: C. hortensis and C. nemoralis, whereas larvae of Brachylecithum sp. were found only in C. nemoralis. Both species of parasites inhabited snail hepatopancreas whose structure was significantly damaged by larvae. There was no significant connection between parasite invasion and snail host morphotype. The research did not allow the reasons for the high prevalence of B. mesostoma in Cepaea spp. to be explained, and also did not explicitly indicate how the parasite invaded Cepaea spp. individuals making them, at the same time a second intermediate host. However, it poses important questions about the life cycle of the parasite that may threaten extensively kept small-size farms of poultry.