Vol 43, No 7 (2016)

The external and internal morphology of a new species of excavate flagellate which inhabits the saline Novoe Lake (Orenburg oblast, Russia) is considered. A cell of the flagellate has four naked flagella (one long and three short) extending parallel to each other. The long and one short flagella terminate with an acroneme. Three microtubular bands reinforce the longitudinal ventral groove. The vesicular nucleus lies in the anterior part of the cell. The mithochondria have discoid cristae. The system of submembrane microtubules originates from the fibrils close to the kinetosome and extends to the end of the posterior cell. A small bulbous projection is seen at the tip of the end of the posterior cell. Dictyosomes of the Golgi apparatus are not found. The lifecycle includes spherical thick-walled cysts that have a single hole with a plug. The external structure of the cell and cysts of a similar species, Percolomonas cosmopolitus, is compared to that in P. lacustris. The new species differs from the known ones by the presence of a posterior bulbous projection, a hole and plug inside the cyst, an acroneme of one short flagellum, and other features.

This paper gives an illustrated description of a new genus and species of endemic Baikal planarians, Microarchicotylus ochroleucus gen. et sp. n. The morphological similarity in the structure of the pharynx, male copulative organs, and external features allowed the authors to include two more species, M. stringulatus (Korotneff 1912) and M. elegans (Porfiriev et Timoshkin 2009), formerly belonging to a poorly investigated genus Archicotylus, into the new genus. Microarchicotylus gen. et sp. n. planarians are attributed to dwarf forms, since their maximal body length does not exceed 5–6 mm. One more distinctive external feature of these Microarchicotylus species is a bright and uneven coloration of the dorsal part of the body, sometimes being dark brown, light brown, or ochreous with distinct white transverse strokes or without them. The anterior part of the body is bright orange or blackish, its color always being different from the remaining body, separated by a white transverse collar behind the pair of eyes. The pharynx is either short cylindrical barrelshaped (length-to-width ratio of ~1) or elongated cylindrical (ratio, 3: 1). The copulative organ is compact and resides behind the pharynx, with its apical part directed downwards. The seminal receptacle, its canal, and the male and common atriums are asymmetrically located relative to the medial longitudinal body axis and centrally located gonopore.

Bivalves collected in Vestfold Hills during the 55th Russian Antarctic Expedition (RAE, 2009−2010) are represented by five species. Four of them (Laternula elliptica, Thracia meridionalis, Adamussium colbecki, and Philobrya sublaevis) were collected in the sediments that filled the coastal lake terraces during the Holocene; these species are still abundant on the Antarctic shelf at present. Bivalves were found in eight samples, with L. elliptica shells and fragments thereof found in seven of those samples. The sample collected near Deep Lake had the most diverse species composition, as it contained all four species named above. Shells of named species widely occurring in present-day Antarctica were found high above sea level in the marine sediments of the oasis. This indicate to the similarity of the oasis habitats in the past and the recent marine conditions. Fragments of shells of the fifth (now extinct) species Ruthipecten tuftsensis were found in glacial–marine sediments of the Marine Plain dating back to the late Pleistocene. The present study of fossil bivalves from the late Cenozoic marine sediments in Vestfold Hills is the first of its kind in Russia.

The integral influence of harsh climatic conditions on the main ecological characteristics (seasonal and diurnal activities, dynamics of the sex–age structure, fecundity of females and its variation in different waterbodies, etc.) of the Siberian salamander (Salamandrella keyserlingii Dybowski 1870) was studied in populations from two types of waterbodies in the northeastern outskirts of the range near the city of Magadan. The majority of the studied characteristics appeared to be similar to those in other populations, including the most southern ones. Regardless of the harsh climatic conditions and the short period of activity (4–4.5 months vs. 6–6.5 months in the southern part of the range), the abundance of the salamanders in the northern Sea of Okhotsk is extremely high and the spectrum of inhabited biotopes is wide. A numerous group of animals (up to a quarter of specimens captured in the first half of summer) was found that had reached the age of sexual maturity (subadultus). This group was not identified in populations from other regions, most likely owing to the small number of samples and their incomplete analysis. In general, the state of the population makes it possible to characterize the studied outskirt part of the range as located in one of the areas of the ecological optimum. Only the data on the size of animals contradict the suggestion stated above because due to the high portion of small adult specimens the average body length of adult salamanders is lower in the vicinity of Magadan compared to many other regions.

The breeding, molting, and wintering ranges of the common eider (Somateria mollissima) were mapped and described in the southern part of the Barents Sea region, including the White Sea population in the western White Sea and the Murmansk population in the northwestern White Sea and the southeastern Barents Sea. The present-day abundance was determined for both populations: since the 1950s, it was the highest in the 2000s for the entire period of ornithological monitoring in the region. Aerial survey from a helicopter is considered to be the only reliable method for estimation of the total population number. The best season for surveying the White Sea population is March–early April (wintering); the most favorable period for surveying the Murmansk population is August (postbreeding/molting). The population status of the common eider in the northern and eastern parts of the Barents Sea has not yet been evaluated. On Franz-Josef Land, the common eider is distributed sporadically, and its number was assessed using expert estimates. The current abundance of the common eider on Novaya Zemlya is unknown. Helicopter-based aerial survey performed in late summer during the postbreeding season is the only relevant method to obtain reliable estimates for the population of the common eider inhabiting Franz-Josef Land and Novaya Zemlya.

The thick-billed warbler (Phragamaticola aedon) is known as one of the main host species for the common cuckoo (Cuculus canorus) in Primorsky Krai and the environs of Khabarovsk. The interaction of these species in the middle Amur River basin is discussed for the first time. In 2013–2014, at the Khingan Nature Reserve, four cuckoo eggs were found in the nests of thick-billed warblers. There are also unpublished data on the findings of cuckoo eggs and nestlings in the nests of the thick-billed warbler from the same area. The similarity of coloring of the parasite and host eggs confirms that the thick-billed warbler is one of the main host species for the common cuckoo in the middle Amur River basin. At the same time, our observations, as well as data from other researchers, show that, in the studied area, the thick-billed warbler usually recognizes cuckoo eggs and destroys them. A description of cuckoo eggs found in Khingan Nature Reserve is given, and the problems of interactions between the nest parasite and its host species are discussed.

New and previously published data on the distribution of 12 bat species in the Cis-Urals and South Urals (Republic of Bashkortostan) are summarized. Data on their subspecies status are given. There is a need to clarify the taxonomic status of the pipistrelle bats Pipistrellus pipistrellus/pygmaeus. In terms of composition, the bat fauna of the Republic of Bashkortostan is a variant of the Central European fauna. It was revealed that the territory in question marks the eastern limits of distribution of Nyctalus leisleri and P. pipistrellus/pygmaeus. An important feature of the territory of Bashkortostan is the presence of places of mass wintering of bats of natural origin: more than 980 karst caves used by bats not only in winter, but also during the period of activity. According to the results of captures in 14 caves, data on the frequency and relative abundance of sedentary bat species in the Republic of Bashkortostan are given.

Contrary to the pre-existing concepts based on morphological and karyological data on the impossibility of hybridization between hamster species of the genus Allocricetulus (A. curtatus and A. eversmanni), F1 hybrids in both combinations, and backcrosses, were obtained for the first time. Some restrictions of hybridization between females of A. eversmanni and males of A. curtatus were detected. Analysis of the synaptonemal complex in the hybrids produced by crossing a female of A. curtatus with a male of A. eversmanni demonstarted that a significant portion of the cells was subject to arrest and selection at the stage of meiosis prophase I. Nevertheless, some spermatocytes still generate viable spermatozoa. Thus, the possibility of hybridization in the laboratory between two Allocricetulus species with different numbers of chromosomes may testify to a relatively low divergence between them.

The degree of development of the mechanisms of postcopulatory isolation was evaluated on the basis of experimental hybridization of representatives of three subspecies of M. musculus (M. m. musculus, M. m. wagneri, and M. m. gansuensis) and remote populations of the subspecies M. m. musculus. Experimental crosses between the different subspecies and populations indicated the presence of initial stages of postcopulatory reproductive isolation between some forms of house mice. In a number of crosses conducted between different populations and subspecies of M. musculus, asymmetry was observed. In one variant of mating, M. m. musculus (male) × M. m. wagneri (female), a reduced intensity of breeding and nonviability of pups were observed. A decrease in the intensity of reproduction was found in all variants of crosses that used male M. m. musculus from the city of Ishim. These data are assumed to confirm the previous assumption about the hybrid origin of mice inhabiting that city. The results confirm a significant level of divergence of the subspecies M. m. musculus and M. m. wagneri. Thus, initial stages both of post- and precopulatory isolation mechanisms between M. m. wagneri and M. m. musculus were shown.