Demographic and spatial structure at the stage of expansion in thepopulations of some alien land snails in Belgorod city (CentralRussian Upland)

Studying of the demographic characteristics of populations of alien species at the stage of expansion makes it possible to assess their invasive potential. Field studies of alien terrestrial gastropods Xeropicta derbentina (Gastropoda,Stylommatophora, Hygromiidae), Brephulopsis cylindrica (Gastropoda, Stylommatophora, Enidae) and Harmozica ravergiensis (Gastropoda, Stylommatophora, Hygromiidae) have been carried out in Belgorod city, the southern part of the Central Russian Upland (Russia). All studied species are native to the Black Sea region and the Caucasus; in the southern part of the Central Russian Upland, they have been registered over the past ten years. The population density, demographic structure, and spatial structure have been analyzed for three years of observations (2017, 2019, 2020). During this period, the changes in the population density have been noted for all studied species. The most pronounced changes have been observed in X. derbentina, whose population density has significantly decreased, and the spatial structure has changed from clustered type to random distribution. In addition, the age structure of X. derbentina population had a pronounced change at the beginning of the snail activity season of 2020. The expansion of the other two invaders, B. cylindrica and H. ravergiensis, is proved as more successful. At the same time, H. ravergiensis is distributed throughout the city. This species has stable population density and random type of spatial population structure on most sites. B. cylindrica has the highest population density: in 2020, it has reached 406 ind./m2 on average, with the maximum of 1215 ind./m2.Meantime, the species keeps the clustered spatial structure, which is explained by both high population density and adaptation to the arid conditions of its natural range.

A new subspecies of Ruthenica filograna(Pulmonata: Clausiliidae) from Croatia

A new subspecies of land snails of the clausiliid genus Ruthenica has been found on the territory of Republic of Croatia. Illustrated description is presented. New subspecies differs from others in shell shape, semi-apostrophic aperture and sculpture pattern.

Sample preparation of glochidial shells (Bivalvia, Unionidae) for scanning electron microscopy

Mature glochidia of freshwater bivalves can give additional features for taxonomic revisions. To study morphology of glochidia with the scanning electron microscope (SEM), special collecting techniques, storage and preparation are required. Based on extensive personal experience, an overview of various techniques is presented, both positive and negative. The interactions of chemicals used for the storage of glochidia and dissolution of glochidial tissue are described. Techniques for cleaning and mounting the glochidial shells of Unionidae for investigations by SEM are described and compared.

Harmozica zangezurica (Gastropoda, Pulmonata, Hygromiidae) - a cryptic species of land molluscs from southern Armenia

Additional material collected in September 2019 made it possible to clarify the range of conchological variability of Harmozica zangezurica recently described from the Syunik region of Armenia, which largely overlaps with that of Harmozica pisiformis thus rendering impossible the reliable identification of empty shells. At the same time the stability has been proven of a diagnostic feature of H. zangezurica - very long vaginal appendages whose length is approximately equal to the total length of the penis and epiphallus. This character allows reliable distinguishing of H. zangezurica not only from the conchologically similar species H. pisiformis , but also from other representatives of the genus Harmozica . Some data on the ecology and life cycle of H. zangezurica were obtained.

A new species of the genus Coryphella(Gastropoda: Nudibranchia) from the Kuril Islands

A new species of the family Coryphellidae, Coryphella alexanderi sp. nov. is described based on specimens collected in the Kuril Islands, NorthWest Pacific, from the upper sublittoral to 200 m depth. An integrative analysis was conducted, including a molecular phylogenetic analysis based on four markers (COI, 16S, H3, 28S), an automatic species delimitation method ABGD, and an analysis of the external and internal morphology using light and scanning electron microcopy. The distinctiveness of Coryphella alexanderi sp. nov. is well established both morphologically and genetically, and it differs from externally similar species in radular characters. Phylogenetically Coryphella alexanderi sp. nov. is closely related to Coryphella trophina, which occurs sympatrically in the same geographic and bathymetric ranges. Coryphella alexanderi sp. nov. appears to be restricted to the middle and northern Kuril Islands, which is consistent with the high numbers of endemic taxa in this area.

The great Empire’s malacologist: Alexander von Middendorff’s contribution to the study of molluscs

The contribution to malacology made by the eminent Russian scientist and traveler, Alexander Theodor von Middendorff (1815-1894) is reviewed. Middendorff’s research is rightly considered the highest achievement of Russian malacology in the 19th century. It is shown, despite the relatively short timespan of his malacological activity, Middendorff could reach substantial progress in the knowledge of the Russian malafauna, both marine, and continental, and authored more than 15 malacological publications, including a series of fundamental systematic works. Middendorff’s views on taxonomy, variability, and zoogeography of molluscs are discussed, and the research program in malacology, proposed by him, is reviewed as well as the impact of his studies on the further development of malacology in the Russian Empire. The full list of all molluscan taxa described by Middendorff is provided as an “Appendix” to the article.

Freshwater gastropods of the western part of the Kola Peninsula and northern Karelia (northern Europe)

The species composition and distribution of freshwater gastropods in the western part of the Kola Peninsula and northern Karelia has been studied. The explored region lies in the far north of Europe and covers several landscape zones: from the northern taiga to the tundra. In sum, seventeen species were found, for each of them the distribution maps and photographs of intraspecific forms of conchological variability are presented. The taxonomic remarks are also given when appropriate. Gyraulus acronicus (Planorbidae) and Ampullacena balthica (Lymnaeidae) are the most common species in the studied region. Two species ( Ampullacena balthica and Galba truncatula ) have been recorded in the Barents Sea islands off the Kola Peninsula. A single non-indigenous species, Physella acuta (Physidae) has been registered in the studied territory. Based on the results of a comparison of the faunas of gastropods from various areas within the whole territory studied and other regions of northern Europe and Western Siberia, it has been shown that the most dramatic reduction in the species composition occurs during the transition from taiga to tundra landscapes.

Occurrence of an invasive slug Limacus flavus (Stylommatophora: Limacidae) in the trees of an urban landscape in Kyiv city (Ukraine), with remarks on its colouration

The importance of trees for an invasive Mediterranean cellar slug, Limacus flavus , was studied within one block of a residential area in Kyiv city (Central Ukraine) from spring of 2020 to spring of 2021. Slugs tended to occur in the old poplars ( Populus nigra var. italica ). Live animals or their traces were found on the 71 of 320 poplars and on 17 trees of other species in the studied area. Slugs often go up to at least 12 m above the ground on these poplars and feed on the lichens there. Animals breed and spend the daytime inside at least some of these trees under the bark. Slugs were wintering in some of these trees in 2020-2021 and probably also at least in 2019-2020, while previously L. flavus was reported from Eastern Europe only in connection to cellars, basements and greenhouses. Apparently these slugs are occupying additional habitats in response to climate change and their occurrence in the trees may become common in Eastern Europe with the warming of climate. The colouration of L. flavus and closely related L. maculatus is discussed. Various differences of the colouration were suggested in the literature to distinguish the two species, most notably the central light stripe on the back of L. flavus , but this character is absent in most of the studied specimens and, therefore, the overall colouration overlaps in the studied populations of the two species.

New record of the genus Mastoniaeforis(Gastropoda: Triphoridae) from Vietnam

Species of the genus Mastoniaeforis are mainly distributed in the Indo-West Pacific with ten species being recorded in the world. To date this genus was not recorded in Vietnam. Specimens of three species, M. chaperi , M. lifuana and M. speciosa, were collected in two field trips from May, 2019 to October, 2020 in Truong Sa archipelago (Spratly Islands), Khanh Hoa Province, Vietnam. The diagnostic characters, distribution, and illustrations of three Mastoniaeforis species in Vietnam are provided.

Growth and morphometric characteristics of the scallop Flexopecten glaber (Bivalvia: Pectinidae) reared in cages off the coast of Crimea (Black Sea)

The spat of the scallop Flexopecten glaber were collected in cages with the Pacific oyster Crassostrea gigas cultured on a mussel-and-oyster farm (outer roadstead of Sevastopol Bay). For two years they were reared in plastic cages at a depth of 2-3 m. The cages were periodically withdrawn to measure the size and weight parameters of the molluscs: the length (L, mm), height (H, mm), and width (D, mm) of shells and the total live weight (W, g). The correlations among the parameters under study are presented. The changes in the indices of the frontal (D/L) and sagittal (H/L) curvatures, convexity ((H+D)/L) and conditional volume (H×D×L/1000) of the shells in ontogenesis are shown. Upon reaching a shell length of 30-35 mm, the allometry of the volumetric and weight growth of molluscs changed from positive to negative. The largest values of the shell convexity index were registered in thesame length range. A conclusion about the interval-type growth of F. glaber in linear size and weight is made. It is suggested that the optimal strategy of shell formation in F. glaber in ontogenesis implies the ripening and the first reproduction of the molluscs occurring at the highest volumetric characteristics of the shell. The relationships for the linear size and weight growth ofF. glaber in the first two years of life are obtained. It is concluded that the scallop F. glaber should be considered as a possible element for the diversification of the existing aquaculture of molluscs (mussels and oysters) off the coast of Crimea.