Carl Agardh Westerlund (1831–1908) was a prominent Swedish malacologist, who studied taxonomy and distribution of continental molluscs (terrestrial and freshwater). He established a number of new taxa, some of them are still accepted as valid. In this study, we provide information on type materials of 41 species of freshwater snails introduced by Westerlund and accepted in the current Russian taxonomy. The study is based on examination of materials from original Westerlund’s collection dispersed now among three large scientific institutions (Göteborgs Naturhistorska Museum, Swedish Museum of Natural History, and Zoological Institute of the Russian Academy of Sciences). For each species an account containing all relevant information on its type series is given. Taxonomic and nomenclatorial notes are also presented. For the majority of taxa, shells of type specimens are illustrated. The lectotypes for Limnaea truncatula var. sibirica Westerlund 1885, Planorbis dispar Westerlund 1871, Planorbis concinnus Westerlund 1881, Planorbis stroemi Westerlund 1881 and Physa sibirica Westerlund 1881 as well as the neotype for Planorbis borealis Lovén in Westerlund, 1875 are designated here.

The intricate history of Trophon birileffi Lischke, 1871 is analyzed. A lectotype is designated from 36 syntypes discovered in the Zoological Institute of the Russian Academy of Sciences in St. Petersburg, Russia. The species is redescribed and other specimens as well as the protoconch and the radula are illustrated. Two species, Sistrum alfredensis and Fusus pachyraphe formerly considered as synonyms of Trophon birileffi, are removed from its synonymy.

The information on reproductive characteristics of more than 100 species of the pulmonate molluscs (clutch size, egg size, hatching success, etc.) is summarized. It is shown that the pulmonates demonstrate a very wide range of reproductive strategies that serve to enhance the survival of species in different (sometimes very unfavorable) environmental conditions.

The problem of generic and subgeneric rank in Ariantinae is briefly discussed. A review of existing views on the system of non-helicine Helicidae (Ariantinae, Murellinae, and Thebinae) and differential diagnoses of the taxa are presented. Special attention is paid to the morphology of the atrial stimulator and, especially, penial papilla, because these organs play an important role in evolution of helicoid groups, providing the functioning of a pre-copulatory isolating mechanism.

Anatomical study has shown that the species described as Helix duporti Bavay et Dautzenberg, 1908 belongs to the genus Trachia Martens, 1860. A brief discussion of the problems of the taxonomy of snails having helicoid shells in the fauna of Vietnam.

В лабораторных условиях определен знак фототаксиса брюхоногого легочного моллюска Radix peregra (Müller, 1774). R. peregra показывает положительный фототаксис, который согласуется с его дневным типом активности и высоким уровнем освещенности мест обитания. Положительная реакция на свет обеспечивает моллюску нахождение мест обитания с благоприятными для жизнедеятельности световыми условиями и реализацию функции дыхания.

The visual acuity of a gastropod pulmonate mollusk Radix peregra (Müller, 1774) was estimated on the basis of phototaxis in the laboratory conditions. White cards with black vertical stripes of different angular width were used as visual stimuli. A value of the resolving angular distance of photoreceptors was 1-2°, and the calculated on its basis visual acuity -33-16.5 rad-1. The mollusc has a diurnal type of activity and lives at well-illuminated surface patches of ponds on aquatic caulescent plants that it feeds on. The results of behavioral investigation presented in this work and morpho-optical study of the eye carried out earlier allow to consider that R. peregra can identify caulescent plants, suitable for its inhabitation, feeding and travelling to the water surface.

The spectral sensitivity of the eye of a gastropod pulmonate mollusk Radix peregra (Müller,1774) was investigated on the basis of phototaxis in the laboratory conditions. The monochromatic light of tendifferent wavelengths in diapason 400-600 nm servedas a test stimulus. According to the results obtained R. peregra has monochromatic visual system with a possible visual pigment rhodopsin, that may be based on the retinal A and absorption maximum of which falls on a blue-green range of the spectrum about 490 nm.

Rare European species Pupilla pratensis is registered in the same calcareous fen in the Crimean Mountains, where Vertigo moulinsiana, another rare European species, was found earlier. Both species are known in Ukraine only from this one small site (less than 0.01 km2), which is disturbed and not protected, therefore both species are clearly “Critically Endangered” here. In the materials of Pupilla muscorum from Ukraine there are some unusual large specimens with shell width 1.9-2.0 mm were revealed, therefore these two species can’t be distinguished only by this characteristic, how it was partly considered before.

This paper presents the first data on seasonal quantitative dynamics of Gastropoda - dominant group of macrozoobenthos in three hydrodynamically different stony littoral areas of Lake Baikal. These studies were performed on the western shore of Southern Baikal (Cape Beryozovy) for 13 months in spring-autumn of 2002-2004. Species composition of gastropods varied with depth (1-20 m) from 10 to 17 species. Five species constantly inhabited the inshore area (depth 1-2,5 m), whereas in the wave-cut area (3-5 m) and the area of wave weakening (7-20 m) there were detected 6 species. During most of the investigation period, total density and biomass of gastropods was higher in the wave-cut area than that in two other regions of the lake. The rise of density and biomass of mollusks was recorded at all depth zones in autumn, whilst their quantitative values varied during other seasons. The main contributors to the total abundance of gastropods were Maackia herderiana and Choanomphalus maacki in the inshore area, whereas in the wave-cut area and area of wave weakening one species Maackia herderiana. Seasonal and inter-annual fauna dynamics of littoral gastropods was determined from changes in quantitative characteristics of species-dominants.

The structure of the distal parts of the reproductive system of the majority of the species of the genus Helicopsis occuring in Crimea and Black Sea Lowland (H. retowskii, H. dejecta, H. striata) were studied. The special attention was given to the intraspecific variability of the penial papilla shape and some proportions of the genitalia. Basing on the anatomical characters, the wide range of the conchological variability of H. retowskii has been shown. The area of this species goes out from limits of the Crimea. It is suggested that H. paulhessei (=H. gasprensis) and Xerophila elata are the synonyms of H. retowskii. The key for the determination of the Crimea molluscs of the genus Helicopsis on the anatomical characters is provided.

Anatomical study of the species described as Bradybaena boevi Uvalieva, 1967 has shown that this species does belong to the genus Bradybaena (Fruticicola in current sense). The contradictions in the literature, are related to the errors in the original description, in particular, Uvalieva took penial retractor for the flagellum.

An Illustrated description of the shell and reproductive tract of Pyramidula kuznetsovi is given. The presence of a distinct peripheral angle distinguishes this species from all known species of the genus. Both anatomically studied specimens had well-developed embryos in the uterus, whereas distal parts of the male section of reproductive tract were much reduced. Therefore it is hard to judge about anatomical differences of P. kuznetsovi from other species of the genus, in particular, the question on the presence of penial caecum remains open.

Terrestrial mollusk Laciniaria plicata from the family Clausiliidae was discovered in Penza forest-steppe territory in 2010-2011. Now it is the eastermost population of the species.

Thesbia nana is recorded for the first time in the Russian part of the Barents Sea. The species was previously known from the North Atlantic with reported Eastern distribution limit in Finmark. The brief species description is provided.

The genus Plicifusus Dall, 1902 has been revised on the basis of available anatomical data. 13 valid recent species are recognised, for 9 of them detailed descriptions of anatomy are provided. 4 names were synonymized: Plicifusus obtusatus Golikov, 1985 = Plicifusus maehirai Tiba, 1980; Colus okhotskana Tiba, 1973 = Plicifusus elaeodes (Dall, 1907); Tritonofusus (Plicifusus) aurantius Dall, 1907 and Plicifusus (Aulacofusus) rhyssoides Dall, 1918 = Plicifusus rhyssus (Dall, 1907). Plicifusus parvus, Tiba, 1980 and Plicifusus saginatus Tiba, 1980 are considered as junior synonyms of Retifusus roseus (Dall, 1877). Plicifusus laticordatus (Dall, 1902) excluded from the genus Plicifusus.

Land snail Cylindrus obtusus (Draparnaud, 1805) is an endemic of Eastern Alps. The mollusk has very unusual for helicids pupilloid shell, but its reproductive tract is quite typical for the subfamily Ariantinae (Helicidae). Neither this species nor any similar forms are totally absent in fossil deposits (the earliest records of C. obtusus conventionally dated by the "pre-Pleistocene"). According to suggested hypothesis, this species is very young and was formed within the existing area at the end of Würm glaciation due to mutation of some representative of Ariantinae.

The ecological consequences of abnormal high water temperatures in summer 2010 on mussel Mytilus galloprovincialis and mytilaster Mytilaster lineatus colonies on the concrete traverses in coastal beach areas of the Odessa Bay (Lanzheron Cape, Northwestern Black Sea, Ukraine) has been studied. The negative impact of prolonged period of high water temperatures (up to 29-30ºC in the end of July and first half of August) reduced the density, biomass and share of mussels in total mass of biofouling from 3750 spec./ m2, 8.075 kg/m2 and 83.2% in June to 700 spec./m2, 0.410 kg/m2 and 23.8% in September, respectively. At the same time, mytilaster increased its density from 3280 to 6800 spec./m2, biomass from 0.481 to 0.672 kg/m2 and its share in biofouling from 7.6 to 49.8%. This demonstrates a higher tolerance to long-term periods of abnormal temperature conditions in mytilasters.

Slug Boettgerilla pallens was found in 4 localities in Crimea in 1987-1988. Three of these localities are situated in the urban landscapes on the south coast of Crimea. The fourth locality is in the natural mountain forest of the Crimean Nature Reserve. Short description of the slugs is given, reproductive system illustrated. The concomitant terrestrial molluscs are specified. The borders of B. pallens native range are discussed.

Results of ecological and zoogeographical study of the Middle Sarmatian gastropod molluscs of the Eastern Paratethys are presented. A comprehensive list of species and taxonomical remarks on some groups is provided. Some autecological characters of gastropods as well as the ratio of life forms with different diets are analyzed. The geographical areas of high abundance and maximal diversity of gastropods in the Eastern Paratethys correspond to the limits of bryozoan bioherms distribution; the latter are considered here as a chain of islands. Bryozoans served as edificatory factor for the Bessarabian Basin reef community in which gastropods played the leading role. The faunal characteristic is provided for the Sarmatian Bioherm Zoogeographical Province previously proposed by the authors. Malacofauna of the province is characterized by a high degree of endemism – around 55% of species and about 30% of genera are endemic. The distinctiveness of this zoogeographical unit started to form around end of the Early-Sarmatian time, it was most pronounced during the Middle Sarmatian (Bessarabian), and fauna became extinct during the freshening of the Sarmatian Basin during Late Sarmatian time. Taxonomic composition of gastropod fauna of different regions of the Middle Sarmatian (Bessarabian) Basin shows that Galician Gulf (West Ukraine and Moldavia) is the principal centre of diversity and origin of mollusks within the Eastern Paratethys and, perhaps, in the whole Sarmatian basin. This was caused by the fact of existence of bioherms at the Badenian and Early-Sarmatian time. A latitude gradient registered in the molluscs diversity – impoverishing from west to east connected with an asynchrony (retardation) of the bioherms formation in other regions i.e. Enikale Strait (Kerch and Taman peninsulas), Stavropol Strait (Central Ciscaucasus) and Mangyshlak Archipelago (northern part of Mangyshlak peninsula). The term ephemerous faunas is suggested for the Sarmatian and others shortly-lived endemic faunas of the Paratethys.