Volume 26

A new chiton species of the genus Leptochiton is described from the intertidal zone of False Bay, South Africa. The new species is distinguishable from other congeneric species by ribbed ventral scales, a wide tail valve and the number of micraesthetes per each megalaesthete.

Adventive fauna is a heterogenic and regarding to the entry time, heterochronic group of species in a regional fauna formed as a result of migrations through a direct or an indirect human influence. 96 species of terrestrial snails are found in the Moscow and Tver Regions. 25(26%) of them are alien. The adventive species belong to 15 genera of 9 families. The alien species are classified herein by geographical, chronological and ecological parameters. According to their naturalization degree, the alien species can be classified into 3 groups. Domestizoids are the species inhabiting buildings (as houses, cellars, vegetable stores, greenhouses, etc). Colonozoids are species inhabiting secondary biotopes for a long time but not dispersing further. Epecozoids are species that have occupied anthropogenic biotopes and are continuously dispersing. Negative influence of the alien species on the aboriginal malacological fauna is recorded but that does not diminish the terrestrial species diversity in this area yet.

Aestivation is the state of dormancy that occurs in snails when the weather condition is harsh, either dry season or warm season. During this period, the giant African land snails form epiphragm, sealing the aperture of the shell which serves as water preservative strategies, preventing mechanical damage of the inner soft tissues. A study on the formation and mineral composition of the epiphragm in three species of giant African land snails namely: Achatina achatina, Achatina fulica and Archachatina marginata was carried out. Twenty matured snails were used for this experiment. They were induced into aestivation by withdrawing food and water. The snail weight, shell length, aperture length, and epiphragm weight were measured during aestivation as well as duration of epiphragm formation. The ionic concentration (calcium, iron and phosphorus) of the epiphragm was also analyzed. The morphometric analysis showed that A. marginata formed the heaviest epiphragm while the least was formed by A. fulica during aestivation. Analysis of the ions revealed that calcium was the most abundant ion in the epiphragm of the snails. Comparison of mean values reveals that A. achatina has the highest ionic composition in the epiphragm when compared to other species. Regression analysis (r2) revealed that a positive relationship existed between the aperture length and days for epiphragm formation (+0.62) on one hand and between weight of epiphragm formed and the days of its formation on the other hand (+0.77).

The nomen “Pisidium zoctanum Poli, 1876” was ambiguously used for some bivalve mollusk of the family Sphaeriidae inhabiting Karani-Koba Cave (Crimean Mountains, Karabi Massif). Literature and analysis of available museum material has shown that the nomen is not valid. This is due in part to the fact that this species has never been described and thus appears to be a ghost-taxon. To date, Euglesa crimeana Stadnichenko, 1980 is the only correctly established name for the sphaeriids from Karani-Koba Cave.

The paper reveals high intra- and interspecific variability of conchological characters, features of the reproductive system, as well as ISSR- DNA markers in steppe snails Helicopsis spp. (Gastropoda, Pulmonata), that imposes certain restrictions on the use of these indicators for species identification. Therefore, these characters were supplemented by the sequences of the conservative fragments of nuclear and mitochondrial genes (18S rDNA, 16S rDNA and COI) with good taxonomic signal, which increased the accuracy of our phylogenetic reconstructions. It is demonstrated that along with Western European species Helicopsis striata, a previously unknown Helicopsis sp. inhabits territory of the Southern Mid-Russian Upland. This species is phylogenetically close to the Crimean group of species of this genus. It has been shown that the rate of mitochondrial genes evolution in different species of Helicopsis differ, with the highest value found in taxa with broad distribution range.

The data on the fauna and distribution of Bivalvia in the Malyi Yugan River basin (Western Siberia, Tyumen Region) are provided. The aquatic malacofauna of this territory has not been studied previously. In 2013-2014, the Malyi Yugan River as well as seven its tributaries, two connected waterbodies, seven floodplain lakes and a singe moraine lake have been sampled. As a results, the data on average density and biomass of bivalves in the waterbodies, a list of 49 species belonging to 4 families, and a brief zoogeographical characteristic of the fauna are provided. The malacofauna of rivers whose drainage basins are situated in swampy areas proved to be rather specific due to unusual life conditions for molluscs. Some peculiarities of behavior of molluscs in different habitats are discussed. The species composition of bivalves in sampled by us rivers drastically differs between waterbodies.