In this study we aimed to provide a neuroanatomy atlas derived from cross-sectional and magnetic resonance imaging (MRI) of the encephalon of the brown bear (Ursus arctos). A postmortem brain analysis using magnetic resonance imaging (MRI – 1,5T; a high-resolution submillimeter three-dimensional T1-3D FFE) and cross-sectional macroscopic anatomy methods revealed major embryological and anatomical subdivisions of the encephalon, including the ventricular system. Most of the internal structures were comparably identifiable in both methods. The tractus olfactorius medialis, corpus subthalamicum, brachium colliculi rostralis, fasciculus longitudinalis medialis, nuclei vestibulares, velum medullare rostrale, nucleus fastigii, fasciculi cuneatus et gracilis were identified entirely by cross-sectional macroscopic analysis. However, the glandula pinealis, lemniscus lateralis and nuclei rhaphe were visualized only with MRI. Gross neuroanatomic analysis provided information about sulci and gyri of the cerebral hemispheres, components of the vermis and cerebellar hemispheres, and relative size and morphology of constituents of the rhinencephalon and cerebellum. Similarities and discrepancies in identification of structures provided by both methods, as well as hallmarks of the structures facilitating identification using these methods are discussed. Finally, we compare the brown bear encephalon with other carnivores and discuss most of the identified structures compared to those of the domestic dog, the domestic cat, Ursidae and Mustelidae families and Pinnipedia clade.

Background: Snakes exhibit sexual dimorphism in both head size and shape. Such differences are often attributed to different reproductive roles and feeding habits. We aim to investigate how sexual dimorphism is displayed in the highly specialised fish-egg-eating snake,Aipysurus eydouxii, by analysing two complementary features: body size and skull morphology.Methods: We used data on body length, weight, and skull shape from 27 measurements of 116 males and females ofA. eydouxii. We investigated both sexual dimorphism and allometric (multivariate and bi-variate) properties of skull growth in the analysed data set.Results: We found that although there was female-biased sexual size dimorphism in body length, females were not heavier than males, contrary to what is commonly observed pattern among snakes. Moreover, females tend to possess relatively smaller heads than males. However, we only found very subtle differences in skull shape reflected in nasal width, mandibular fossa, quadrate crest and quadrate length.Discussion: We suggest that the feeding specialisation inA. eydouxiidoes not allow for an increase in body thickness and the size of the head above a certain threshold. Our results may be interpreted as support for prey-size divergence as a factor driving skull dimorphism since such species in which the sexes do not differ in prey size also shows very subtle or no differences in skull morphology.

Phoxinus sedelnikowi is a Central Asian representative of the genus Phoxinus, occurring in the tributaries of Lake Zaisan at the southern foot of the Altai Mountains. Its systematic position has so far been unclear. It was considered a subspecies of Rhynchocypris czekanowskii, R. lagowskii and P. phoxinus. Here, we sequenced the cytochrome b gene and ATP-ase subunits 6 and 8 of representatives of P. sedelnikowi and two populations of P. phoxinus (including the topotypical population) and R. czekanowskii, R. lagowskii, and R. percnurus. We also performed an analysis of the shapes of the seven bones of the skull of all six forms examined and then performed a phylogenetic interpretation of the obtained results. Both P. sedelnikowi and Phoxinus sp. from the Solonovka population appeared to be separate from P. phoxinus from the topotypical population by Cytb: 0.11 and ATP: 0.13 distance. Therefore, they may be considered as independent species within the genus Phoxinus. We found the generic level genetic distance between Phoxinus and Rhynchocypris (Cytb: 0.24 and ATP: 0.68), which thus confirmed their independence. Genetic analyses revealed that one of the studied individuals of R. lagowskii shares the ATP haplotype with R. czekanowskii. The Cytb haplotype of this individual is also closest to that of R. czekanowskii, indicating an introgression between these forms and questioning their species status. The UPGMA and MP analysis of the selected osteological features confirmed the differentiation between Phoxinus and Rhynchocypris on the generic level. The results at lower taxonomic levels are not consistent with the identified genetic diversity, suggesting that osteological features may not be sufficient to distinguish forms at the intra-generic level.

The lake minnow Eupallasella percnurus is distributed throughout a vast area that includes most of Europe and northern Asia and displays a wide range of morphological variation, which resulted in five distinguished subspecies. There are no previous conclusive morphometric analyses of samples from different parts of the distribution area. This paper presents results of multidimensional analyses of morphometric characters of 19 widely scattered populations of the species. The results of the analyses show considerable inter-population differences. Morphometric evidence suggests that three morphologically different groups exist within the studied species. The population from the Volga river basin represents a distinct species tentatively called the ‘Volga lake minnow’. The populations from Poland; central, northern and northeastern Russia; and northern Kazakhstan form a group closely related to the nominative subspecies E. percnurus percnurus, whereas populations from southeastern Russia (including Sakhalin) ...