Volume 33

A new species belonging to the Fionidae (sensu Cella et al., 2016), Eubranchus flexus sp. nov. is described based on specimens collected in Nha Trang, Vietnam, South China Sea, Indo-West Pacific, from the upper sublittoral depth. An integrative analysis was conducted, including a molecular phylogenetic analysis based on three markers (COI, 16S, H3), and an analysis of the external and internal morphology using light and scanning electron microscopy. The distinctiveness of Eubranchus flexus sp. nov. is well established both morphologically and genetically. Phylogenetically Eubranchus flexus sp. nov. represents a derived branch in the phylogeny of Eubranchus, but its relationships with other Eubranchus species are unresolved likely due to low taxon sampling. Eubranchus flexus sp. nov. is the first representative of the genus Eubranchus for the nudibranch fauna of Vietnam and for now its range is restricted only to the type locality.

Using light and scanning electron microscopy the first data on morphology of mature glochidia of freshwater bivalve Beringiana beringiana from Dalneye Lake in Kamchatka were received. Based on literature data a comparison with glochidia from other populations of this species is given. Among the Russian Far East populations of the discussed species, glochidia from the Dalneye Lake were the smallest, with shell sizes up to 287 µm and with a hook that does not exceed 1/3 of the glochidium height. Microsculpture of the outer surface of glochidia was tight-looped all over the whole valves.

Chuatienpupa megacanalis gen. et sp. nov. is described from Hoa Binh province, northern Vietnam. Chuatienpupa gen. nov. is characterized by a small, pupoid-shaped, smooth, glossy shell. Peristome with two canals; anterior canal twisted funnel-shaped, appearing as a very wide groove, opening on the basal side; posterior canal continues vertically upward and forming a wide groove, which is divided by the upper palatal plica. The operculum bowl-shaped, strongly convex, its outer surface smooth, glossy, and covered by a glaze. Both shell and opercular characters distinguish this new genus from other Southeast Asian pupinid genera. General shell morphology of Chuatienpupa gen. nov. is most similar to Pupina Vignard, 1829. However, the new genus differs in having two palatal and basal plicae, a twisted anterior canal, opening on the basal side, and a solid, bowl-shaped operculum, with outer surface dome-shaped and completely smooth.

Here we present detailed morphological and molecular comparison of the Tonicia species and ecotypes along Southeastern Pacific coast. Several specimens were examined by scanning electron microscopy and based on plates morphology we propose a new taxonomic key for identification of species and ecotypes of Tonicia. A total of 566 specimens were measured to explore morphological differences between ecotypes and ecoregions by means of multivariate analyses. Genetic distances and a maximum likelihood (ML) phylogeny were estimated using Cytochrome Oxidase I (cox1) to compare species and ecotypes. Morphometry and multivariate analyses revealed morphological differences between ecotypes in each species. However, cox1 genetic distances were low between ecotypes in both species (T. calbucensis and T. chilensis) and the ML phylogeny revealed an absence of monophyletic relationships between ecotypes in each species clades. The new key will be useful to identify Tonicia species by morphology without molecular analysis.

The work is based on a study of long-term collections of molluscs of the family Bithyniidae from the waterbodies of the Tyumen region (Western Siberia), located within the world's largest Ob-Irtysh natural focus of opisthorchiasis. Difficulties with species identifications of bithyniid snails, the first intermediate hosts of Opisthorchis, necessitate the publication of photographic images of Bithyniidae shells and an identification key based on discrete morphological characters. It has been established that 14 species of Bithyniidae belonging to five genera inhabit the Tyumen region, an annotated list of species is given, and a brief zoogeographical description is given. The most abundant species are Digyrcidum starobogatovi and Boreoelona sibirica, whereas Paraelona milachevitchi were found solitary.

A new camaenid Aegistohadra baii sp. nov., close to Aegistohadra delavayana but having smaller and more conical shell and anatomically different, was described from Yunnan, southwest China. Helix seraphinica Heude, 1889 was confirmed to be an Aegistohadra species based on structure of genital organs. Cryptozona yunlongensis Chen Y., Chen D. et Zhang, 1997 is transferred to Aegistohadra based on shell and genital characters.

Described is a new species of the genus Stenosemus from the Gulf of Alaska. It differs from the other species of this genus from the Northeast Pacific by having longitudinal undulating folds in the pleural areas of the intermediate valves, flattened, smooth dorsal calcareous corpuscules on perinotum and rectangular central teeth of radula.

On the basis of the collections of the R/V Vityaz in the Banda Sea, Indonesia, a review of the chiton fauna of the genera Belknapchiton and Leptochiton was carried out. Leptochiton commandorensis, until now known only from the northern Pacific near the Commander Islands, is here added to the four known Indonesian deep sea species. This species turned out to be with juveniles in the pallial groove. A scanning electron microscope study of the collected specimens of B. giganteus made a corrected, supplemented description of this rare species possible. The age variability of the valves shape and shell sculpture of the two collected species was studied. Particular attention is paid to the age variability of the number of micraesthetes on the tegmentum grains and the position of the mucro.

In terrestrial pulmonate gastropods Cochlodina laminata, Monachoides incarnata, Helicigona lapicida, Arianta arbustorum, Cepaea hortensis, Trochulus hispidus and Succinea putris, the morphological properties of the pupil of camera-like eyes were studied for the first time: location, spatial orientation, change in spatial orientation, structure, shape, shape change, relative size, change in relative size. Several methods were used in the work: making of preparations of isolated eyes, making of histological preparations of eyes, light microscopy, morphometric analysis, statistical analysis, calculations. All the studied morphological properties of the pupil of the camera-like eyes of C. laminata, M. incarnata, H. lapicida, A. arbustorum, C. hortensis and T. hispidus are similar to the analogous morphological properties of the pupil of the camera-like eyes of other species of terrestrial pulmonates. One of the studied morphological properties of the pupil of the camera-like eye of S. putris – the relative size – differs from the analogous morphological property of the pupil of the camera-like eyes of other species of terrestrial pulmonates.

The article reports the finding of a population of freshwater snails morphologically and genetically identified as Ladislavella cf. terebra (Westerlund, 1885), in a reservoir situated in Penza City. This is the first reliable record of representatives of the genus Ladislavella on the territory of European Russia, at a considerable distance from the previously known boundaries of its range. Molecular data suggest that the examined population belongs to the previously unknown species of Ladislavella. The morphoanatomic and ecological characteristics of the studied population and some information about parasites and commensals of mollusсs are given.