Effects of Brain Size on Adult Neurogenesis in Shrews

Shrews are small animals found in many different habitats. Like other mammals, adult neurogenesis occurs in the subventricular zone of the lateral ventricle (SVZ) and the dentate gyrus (DG) of the hippocampal formation. We asked whether the number of new generated cells in shrews depends on their brain size. We examined Crocidura russula and Neomys fodiens, weighing 10–22 g, and Crocidura olivieri and Suncus murinus that weigh three times more. We found that the density of proliferated cells in the SVZ was approximately at the same level in all species. These cells migrated from the SVZ through the rostral migratory stream to the olfactory bulb (OB). In this pathway, a low level of neurogenesis occurred in C. olivieri compared to three other species of shrews. In the DG, the rate of adult neurogenesis was regulated differently. Specifically, the lowest density of newly generated neurons was observed in C. russula, which had a substantial number of new neurons in the OB compared with C. olivieri. We suggest that the number of newly generated neurons in an adult shrew’s brain is independent of the brain size, and molecular mechanisms of neurogenesis appeared to be different in two neurogenic structures.

Data on the distribution of Hystrichopsylla orientalis fleas (Siphonaptera) in Lithuania

The aim of this study was to present data on the distribution of Hystrichopsylla fleas collected from different animals in Lithuania. The study was done by analyzing collections of fleas from 2011 to 2017. A total of 96 fleas of the genus Hystrichopsylla were collected from nine mammalian species (Apodemus flavicollis, Apodemus agrarius, Micromys minutus, Myodes glareolus, Microtus oeconomus, Microtus arvalis, Sorex araneus, Neomys fodiens, and Glis glis). Morphological analysis showed that all fleas were of the species Hystrichopsylla orientalis Smit, 1956.

Research into the mammal fauna of the Sviatoshynsko-Bilychansky forest within the Holosiivsky National Nature Park

In 2017–2019, a survey of the mammal faune of the Sviatoshynsko-Bilychansky forest, which is located nearby to the northwestern outskirts of Kyiv, was carried out. The following species of mammals were recorded: Neomys fodiens, Neomys anomalus, Sorex araneus, Sorex minutus, Talpa europaea, Erinaceus concolor, Alces alces, Capreolus capreolus, Sus scrofa, Lepus europaeus, Sciurus vulgaris, Castor fiber, Ondatra zibeticus, Muscardinus avellanarius, Apodemus agrarius, Sylvaemus flavicollis, Sylvaemus sylvaticus, Micromys minutus, Clethrionomys glareolus, Vulpes vulpes, Lutra lutra, Meles meles, Mustela vison, Martes martes, and Martes foina.

Finds of rare and non-abundant species of small mammals in the territory of Kharkiv Oblast, Ukraine

Eight of the eleven expected rare and non-abundant species of small mammals were recorded in the studied territory: Crocidura suaveolens, Sorex minutus, Neomys fodiens, Dryomys nitedula, Cricetulus migratorius, Terricola subterraneus, Micromys minutus, and Mus spicilegus. Crocidura suaveolens was found in both dry meadows and floodplain biotopes, and it was also recorded nearby to field-protective plantations and human settlements. Sorex minutus was also more common in dry meadows and in floodplain biotopes. Neomys fodiens is a typical floodplain endemic. Dryomys nitedula was more common in oak forests and it is prone to synanthropy. Cricetulus migratorius was found in steppe areas and near fields of agricultural crops. Terricola subterraneus was recorded only in a dry maple-linden oak forest. Micromys minutus prefers floodplain biotopes. Mus spicilegus was found on agricultural crops and in steppe areas.

Size increase without genetic divergence in the Eurasian water shrew Neomys fodiens

When a population shows a marked morphological change, it is important to know whether that population is genetically distinct; if it is not, the novel trait could correspond to an adaptation that might be of great ecological interest. Here, we studied a subspecies of water shrew, Neomys fodiens niethammeri, which is found in a narrow strip of the northern Iberian Peninsula. This subspecies presents an abrupt increase in skull size when compared to the rest of the Eurasian population, which has led to the suggestion that it is actually a different species. Skulls obtained from owl pellets collected over the last 50 years allowed us to perform a morphometric analysis in addition to an extensive multilocus analysis based on short intron fragments successfully amplified from these degraded samples. Interestingly, no genetic divergence was detected using either mitochondrial or nuclear data. Additionally, an allele frequency analysis revealed no significant genetic differentiation. The absence of genetic divergence and differentiation revealed here indicate that the large form of N. fodiens does not correspond to a different species and instead represents an extreme case of size increase, of possible adaptive value, which deserves further investigation.