Volume 31

Three small but abundant in specimens isolated colonies of Helix lutescens have been found in the eastern part of Moscow City in the central part of European Russia for the first time. This is an easternmost known colony of the species. Differences from the related and similar small form of H. pomatia are given and discussed.

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.

Two colonies of an invasive West European land snail Cepaea nemoralis are reported from Kyiv region of Ukraine, as well as a third locality where snails were present in 2019, but no living individuals were found in 2020. One more locality is reported from Odessa City in Southern Ukraine. These localities are the most south-eastern ones for the range of C. nemoralis and are the first known records of this species in Ukraine outside its western regions, with closest previously published confirmed colonies in more than 400 km. Distribution of this species in Eastern Europe is discussed, it is argued that invasion of C. nemoralis is probably driven by the same processes as invasion of the Spanish slug, Arion vulgaris, that invaded Eastern Europe during the last decades.

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 the same 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 of F. 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.

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.

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 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.

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 malafocauna, 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.