Evidence for co-invasion events: different chigger species (Actinotrichida,Trombidioidea: trombiculidae) share a host

Cases of co-invasion of various chigger species parasitizing murids and cricetids in various habitats were analysed using morphological and molecular approaches. Here we provide evidence for 25 new cases of co-parasitism of chigger mites on rodent hosts (Myodes glareolus, Apodemus flavicollis, Apodemus agrarius) accounting for 8.6% of all host-parasite associations observed in this study. The results confirm higher incidence of co-parasitism in vertebrate-associated Parasitengona mites compared to arthropod-associated ones. Among factors influencing the occurrence of co-parasitism in Trombiculidae the body constitution and year-round availability of hosts associated with lower host specificity of larvae should be considered.     

Structure and Seasonal Dynamics of the Ectoparasite Community of the Pygmy Shrew <Emphasis Type="Italic">Sorex minutus</Emphasis> in the Ilmen-Volkhov Lowland

The species composition and seasonal dynamics of ectoparasites of the pygmy shrew Sorex minutus L., 1756 were studied in coniferous and mixed forests of the Ilmen-Volkhov Lowland (Novgorod Province of Russia) in 1999–2003. Examination of 265 specimens of the pygmy shrew revealed 670 specimens of ectoparasites that belonged to 13 species: 8 species of fleas, 2 species of ixodid ticks, 1 species of gamasid mites, and 2 species of myobiid mites. In total, 55.8% of shrew specimens were infested with ectoparasites. No more than 4 species of ectoparasites were found simultaneously on one host, and most of the examined shrews (64.8%) were infested with only 1 ectoparasite species. The pygmy shrew had lower infestation intensity and species diversity of acarines and fleas as compared with those of the common shrew Sorex araneus L., 1758 and the bank vole Myodes glareolus (Schreber, 1780) (13 vs. 23 and 29 species, respectively). Unlike these two other hosts, the prevalent ectoparasite of the pygmy shrew was the tick Ixodes trianguliceps Birula, 1895.     

Number and distribution of dominant species of common shrews of <Emphasis Type="Italic">Sorex</Emphasis> genus across Kuznetsk Alatau Ridge

The numbers of dominant shrew species, Sorex araneus and Sorex tundrensis, vary in various altitudinal belts of the Kuznetsk Alatau Ridge. The common shrew is the most abundant in dark-coniferous forests of herbaceous type, i.e. belongs to the mesophyte environmental complex. The greatest numbers of Sorex tundrensis are found in habitats of thinned tree layer with moderate humidification; therefore, this species is categorized xeromesophytic.     

Three-dimensional organization of interphase fibroblast nuclei in two closely related shrew species (<Emphasis Type="Italic">Sorex granarius</Emphasis> and <Emphasis Type="Italic">Sorex araneus</Emphasis>) differing in the structures of their chromosome termini

A FISH with a probe for telomeric and rDNA repeats and immunofluorescence with ANA CREST and antibodies to nucleolae protein B23 were used to study the three-dimensional (3D) organization of fibroblast interphase nuclei in two shrew twin species, Sorex granarius and Sorex araneus, of the Cordon race. Karyotypes of these species are composed of nearly identical chromosomal arms and differ in the number of their metacentrics and the structures of their terminal chromosome regions. In the short arms of S. granarius, 32 of the acrocentrics have large telomeres that contain an average of 218 kb telomere repeats, which alternate with ribosomal repeats. These regions also contain active nucleolar organizing regions (NORs). In contrast, in active NORs in S. araneus are localized at the terminal regions of 8 chromosomal arms (Zhdanova et al., 2005; 2007b). Here, we show that associations of chromosomes by telomeres and the contact of a part of the telomere clusters with the inner nuclear membrane and nucleolus characterize the interphase nuclei of both Sorex granarius and Sorex araneus. We also reveal the partial colocalization of telomere and ribosomal clusters and the spatial proximity of centomeric and telomeric regions in the interphase nuclei of S. granarius. It appears that only ribosomal clusters containing a sufficient number of active ribosomal genes exhibit a connection with the nucleolus. Nucleolus disassembly during the fibroblastís transition to mitosis and the role of the B23 protein in this process have been studied.     

Evaluation of the physiological activity of venom from the Eurasian water shrew <Emphasis Type="Italic">Neomys fodiens</Emphasis>

Background

Animal toxins can have medical and therapeutic applications. Principally, toxins produced by insects, arachnids, snakes and frogs have been characterized. Venomous mammals are rare, and their venoms have not been comprehensively investigated. Among shrews, only the venom of Blarina brevicauda has been analysed so far, and blarina toxin has been proven to be its main toxic component. It is assumed that Neomys fodiens employs its venom to hunt larger prey. However, the toxic profile, properties and mode of action of its venom are largely unknown. Therefore, we analysed the cardio-, myo- and neurotropic properties of N. fodiens venom and saliva of non-venomous Sorex araneus (control tests) in vitro in physiological bioassays carried out on two model organisms: beetles and frogs. For the first time, we fractionated N. fodiens venom and S. araneus saliva by performing chromatographic separation. Next, the properties of selected compounds were analysed in cardiotropic bioassays in the Tenebrio molitor heart.

Results

The venom of N. fodiens caused a high decrease in the conduction velocity of the frog sciatic nerve, as well as a significant decrease in the force of frog calf muscle contraction. We also recorded a significant decrease in the frog heart contractile activity. Most of the selected compounds from N. fodiens venom displayed a positive chronotropic effect on the beetle heart. However, one fraction caused a strong decrease in the T. molitor heart contractile activity coupled with a reversible cardiac arrest. We did not observe any responses of the insect heart and frog organs to the saliva of S. araneus. Preliminary mass spectrometry analysis revealed that calmodulin-like protein, thymosin β-10, hyaluronidase, lysozyme C and phospholipase A2 are present in the venom of N. fodiens, whereas thymosin β4, lysozyme C and β-defensin are present in S. araneus saliva.

Conclusion

Our results showed that N. fodiens venom has stronger paralytic properties and lower cardioinhibitory activity. Therefore, it is highly probable that N. fodiens might use its venom as a prey immobilizing agent. We also confirmed that S. araneus is not a venomous mammal because its saliva did not exhibit any toxic effects.

     

Evolutionary and taxonomic differentiation of shrew species in the “araneus” group of the genus <Emphasis Type="Italic">Sorex</Emphasis>: 2. Subdivision within the common shrew

This review summarizes available data on the problem of taxonomic and evolutionary differentiation in the “araneus” groups of species of the genus Sorex (Eulipotyphla, Mammalia). Report 2 describes the hierarchical structuring, population system, and interracial hybrid zones in the common shrew (Sorex araneus).     

Small mammals as sentinels of antimicrobial-resistant staphylococci

A total of 39 coagulase-negative staphylococci and seven Staphylococcus aureus strains were isolated from small mammal feces, i.e., the striped field mouse (Apodemus agrarius) and the yellow-necked mouse (A. flavicollis) in two sampling areas, deciduous forest and karst plains. MALDI-TOF analysis revealed five species of coagulase-negative staphylococci: S. sciuri, S. hominis, S. warneri, S. haemolyticus, and S. xylosus. All strains were susceptible to tetracycline, linezolid, vancomycin, and teicoplanin. Three MRSA strains with the mecA gene were detected. The beta-lactamase gene blaZ was detected in ampicillin-resistant staphylococci and in the high-level resistant strains (oxacillin over 2 mg/L) mecA gene. The mecC gene was not detected by PCR. Erythromycin-resistant staphylococci harbored the ermC gene and/or the efflux gene msrA. There were no detectable dfr genes in trimethoprim-resistant staphylococci and the rifampicin-resistant strains were without mutation in the rpoB gene. In summary, wild small mammals may serve as sentinels of mecA-positive S. aureus with erythromycin resistance genes ermC and efflux msrA. Small mammals appear to be useful indicators of antibiotic resistance.     

Quantitative estimation of population numbers of shrews (mammalia,insectivora) after wintering

Autumn-winter mortality in shrews (Sorex araneus, S. caecutiens, S. minutus) was estimated on the basis of long-term (12 years) live-trapping on the permanent transect lines in Tver oblast. Relative as well as absolute population numbers were estimated. Lesser shrew (S. minutus) has permanently low population numbers. Fall in this species made 40.1%, and it was scattered through this term. Common shrew (Sorex araneus) lose 89.3% of population and in masked shrew (S. caecutiens) those lost was 73.6%. The most lost was found in autumn and winter fall was as least as 38,2% and 30.4% in the latter two species. The mortality is positively dependent on population density in preceding summer and with severity of winter.     

The First Record of a Chigger Mite of the Genus <Emphasis Type="Italic">Neotrombicula</Emphasis> (Acariformes: Trombiculidae) in the Northwest of European Russia

A chigger mite species, Neotrombicula absoluta Schluger, 1966, previously known only from its type locality in Transcarpathian Region of Ukraine, was found in the vicinity of Kurgolovo Village (Kingisepp District, Leningrad Province, Russia). A single specimen of this species was collected off the common shrew Sorex araneus L. This is the first record of the genus Neotrombicula (which includes the most usual causative agents of trombiculiasis of humans and domestic animals in Europe) in the northwestern part of European Russia.     

A new chromosomal race of the common shrew <Emphasis Type="Italic">Sorex araneus</Emphasis> (Lipotyphla,Mammalia) found in Russia

Karyotyping of the common shrews Sorex araneus from the poorly studied region of the Northwest of Russia revealed the belonging of individuals to two chromosomal races, Lemi and St. Petersburg. The Lemi race, previously known only from Finland, was discovered for the first time on the territory of Russia and thus replenished the list of S. araneus chromosomal races that are distributed within the Russian part of the species range (27 races out of 74 known in the whole species range at the moment). The studied individuals showed a high level of chromosomal polymorphism, caused by Rb translocations.     

Inter-species interactions and ecosystem effects of non-indigenous invasive and native tree-killing bark beetles

Frequent bark beetle outbreaks cause biome-scale impacts in boreal and temperate forests worldwide. Despite frequent interceptions at ports of entry, the most aggressive bark beetle species of Ips and Dendroctonus in North America and Eurasia have failed to establish outside their original home continents. Our experiments showed that Ips typographus can breed in six North American spruce species: Engelmann spruce, white spruce¸ Sitka spruce, Lutz spruce, black spruce and red spruce. This suggests that differences between the Eurasian historical host and North American spruce species are not an insurmountable barrier to establishment of this tree-killing species in North America. However, slightly diminished quality of offspring beetles emerged from the North American spruces could reduce the chance of establishment through an Allee effect. The probabilistic nature of invasion dynamics suggests that successful establishments can occur when the import practice allows frequent arrivals of non-indigenous bark beetles (increased propagule load). Model simulations of hypothetical interactions of Dendroctonus rufipennis and I. typographus indicated that inter-species facilitations could result in more frequent and severe outbreaks than those caused by I. typographus alone. The potential effects of such new dynamics on coniferous ecosystems may be dramatic and extensive, including major shifts in forest structure and species composition, increased carbon emissions and stream flow, direct and indirect impacts on wildlife and invertebrate communities, and loss of biodiversity.     

The role of interspecies differences in the ratio of choline-containing phospholipid fractions of rodent erythrocytes in response of these cells to the effect of membranotropic compounds

In in vitro experiments, interspecies differences were revealed in the erythrocyte responses in varied rodent species—laboratory mice (Mus musculus L.), tundra voles (Microtus oeconomus Pall.) and bank voles (Myodes glareolus Pall.)—to the effect of chemical agents able to interact with membrane lipids and disrupt the membrane structure (detergent Triton X-100, oxidative stress inductor AAPH, antioxidant ionol or BHT, uranyl ion). It was hypothesized that these differences are due to physicochemical peculiarities of the erythrocyte membrane structure, specifically, the ratio of choline-containing fractions of phospholipids (phosphatidylcholine and sphingomyelin). The use of blood erythrocytes as an in vitro experimental model to study the mechanisms of toxicity as well as antioxidant and membrane-protective properties of compounds of different nature was shown to imply the choice of an adequate source of erythrocytes in view of considerable speciesdependent structural specificity of the lipid component of mammalian erythrocyte membranes.     

High Frequency Responsiveness in Rodents at the Level of the Inferior Colliculus

PREVIOUS work on the cochlear microphonic (CM) response of three species of rodents showed a second peak of sensitivity coinciding in frequency with the ultrasound emitted in each species¹. It was indicated that the microphonic response did not necessarily represent hearing, but Sewell's² finding that Apodemus can hear the ultrasonic cries of its young makes an investigation into the neural response to ultrasound seem necessary. The gross inferior collicular (IC) response of the same three species, Apodemus sylvaticus Linnaeus, Clethrionomys glareolus Schreber and Meriones shawi Rozet, has now been studied together with the CM response of the same individuals.     

Concentration and size distribution of plant fiber in the digestive tract of muroid rodents

The weight parameters that characterize the size and the degree of fullness of fermentation chambers (forestomach and cecum), namely, the weight of the walls and the content of these organs, and the concentration and size distribution of fibers in the chyme have been investigated in five muroid rodent species (Arvicola terrestris, Microtus oeconomus, Microtus arvalis sp., Clethrionomys glareolus, and Sylvaemus flavicollis). No distinct regularities were observed in the above-mentioned parameters of the forestomach. These parameters of the cecum were generally found to be in good agreement with the conventional concept of dietary specialization of the rodent species under investigation, but the results have provided a more precise assessment of the role of dietary fiber in the diet of free-living rodents under specific environmental conditions.     

Analysis of animal spatial patterns on the basis of marking on transects: An example of red-toothed shrews

The spatial patterns of individually marked juveniles of red-toothed shrews—the masked shrew (Sorex caecutiens), common shrew (S. araneus), and pygmy shrew (S. minutus)—have been determined by comparing the ratio of traps visited by different numbers of animals (0, 1, 2, 3, etc.) with the Poisson distribution and by using the index of relative variance σ²/m. These tests characterize both the distribution of animal load over different points of the study area and the spatial pattern of individual home ranges. A random type of spatial pattern within relatively uniform biotopes prevails in juveniles of all three red-toothed shrew species, regardless of their properties, abundance, and factors accounting for it. This facilitates the formation of a system of non-overlapping home ranges of adult females after wintering. The stability of spatial patterns contributes to the efficiency of population self-regulation.     

Fine-root trait plasticity of beech (<Emphasis Type="Italic">Fagus sylvatica</Emphasis>) and spruce (<Emphasis Type="Italic">Picea abies</Emphasis>) forests on two contrasting soils

Aim

The fine roots of trees may show plastic responses to their resource environment. Several, contrasting hypotheses exist on this plasticity, but empirical evidence for these hypotheses is scattered. This study aims to enhance our understanding of tree root plasticity by examining intra-specific variation in fine-root mass and morphology, fine-root growth and decomposition, and associated mycorrhizal interactions in beech (Fagus sylvatica L.) and spruce (Picea abies (L.) Karst.) forests on soils that differ in resource availability.

Methods

We measured the mass and morphological traits of fine roots (i.e. ≤ 2 mm diameter) sampled to 50 cm depth. Fine-root growth was measured with ingrowth cores, and fine-root decomposition with litter bags. Mycorrhizal fungal biomass was determined using ingrowth mesh bags.

Results

Both tree species showed more than three times higher fine-root mass, and a ten-fold higher fine-root growth rate on sand than on clay, but no or marginal differences in overall fine-root morphology. Within the fine-root category however, beech stands had relatively more root length of their finest roots on clay than on sand. In the spruce stands, ectomycorrhizal mycelium biomass was larger on sand than on clay.

Conclusions

In temperate beech and spruce forests, fine-root mass and mycorrhizal fungal biomass, rather than fine-root morphology, are changed to ensure uptake under different soil resource conditions. Yet enhancing our mechanistic understanding of fine-root trait plasticity and how it affects tree growth requires more attention to fine-root dynamics, the functional diversity within the fine-roots, and mycorrhizal symbiosis as an important belowground uptake strategy.

     

Body temperature variation in free-living and food-deprived yellow-necked mice sustains an adaptive framework for endothermic thermoregulation

In many mammalian species, variation in body temperature (T_b) exceeds the values suitable for defining homeothermy, making it justifiable and even necessary to resort to the term “heterothermic”. However, T_b data are only available for ca. 1% of extant mammalian species. We investigated variations in T_b in wild free-living and experimentally food-deprived yellow-necked mice Apodemus flavicollis, during the temperate-zone autumn-winter period. In line with the adaptive framework for endothermic thermoregulation, we hypothesised that T_b in the mice should be adjustable with the energetic cost-benefit trade-off associated with maintaining homeothermy. In laboratory conditions, mice clearly entered a state of daily torpor when food-deprived. Our study thus makes it clear that A. flavicollis is a heterothermic species in which food deprivation results in switching between endothermic and poikilothermic thermoregulation. We also assumed that, in free-living mice, heterothermy increases with elevated environmental challenges, e.g. when the ambient temperature (T_a) decreases. Consistent with this was the inverse correlation noted between variation in T_b in free-living mice and T_a, with most individuals clearly becoming torpid when T_a decreases below 0 °C. It is the increased cost of food hoarding under cold conditions that most likely triggers a state of torpor as a last result. Overall, our study indicates that yellow-necked mice can provide a further example of species sustaining an adaptive framework for endothermic thermoregulation.     

Distribution of sediment bacterial and archaeal communities in plateau freshwater lakes

Both Bacteria and Archaea might be involved in various biogeochemical processes in lacustrine sediment ecosystems. However, the factors governing the intra-lake distribution of sediment bacterial and archaeal communities in various freshwater lakes remain unclear. The present study investigated the sediment bacterial and archaeal communities in 13 freshwater lakes on the Yunnan Plateau. Quantitative PCR assay showed a large variation in bacterial and archaeal abundances. Illumina MiSeq sequencing illustrated high bacterial and archaeal diversities. Bacterial abundance was regulated by sediment total organic carbon and total nitrogen, and water depth, while nitrate nitrogen was an important determinant of bacterial diversity. Proteobacteria, Acidobacteria, Actinobacteria, Bacteroidetes, Chlorobi, Chloroflexi, Cyanobacteria, Firmicutes, Gemmatimonadetes, Nitrospirae, Planctomycetes, and Verrucomicrobia were the major components of sediment bacterial communities. Proteobacteria was the largest phylum, but its major classes and their proportions varied greatly among different lakes, affected by sediment nitrate nitrogen. In addition, both Euryarchaeota and Crenarchaeota were important members in sediment archaeal communities, while unclassified Archaea usually showed the dominance.     

Genetic variation and phylogeography of the bank vole (<Emphasis Type="Italic">Clethrionomys glareolus</Emphasis>, Arvicolinae,Rodentia) in Russia with special reference to the introgression of the mtDNA of a closely related species,red-backed vole (<Emphasis Type="Italic">Cl. rutilus</Emphasis>)

Totally, 294 bank voles (Clethrionomys glareolus) and 18 red-backed voles (Cl. rutilus) from 62 sites of European Russia were studied. Incomplete sequences (967 bp) of the mitochondrial cytochrome b gene were determined for 93 Cl. glareolus individuals from 56 sites and 18 Cl. rutilus individuals from the same habitats. Analysis of the cytochrome b gene variation has demonstrated that practically the entire European part of Russia, Ural, and a considerable part of Western Europe are inhabited by bank voles of the same phylogroup, displaying an extremely low genetic differentiation. Our data suggest that Cl. glareolus very rapidly colonized over the presently occupied territory in the post-Pleistocene period from no more than two (central European and western European) refugia from ancestral populations with a small effective size. PCR typing of the mitochondrial cytochrome b gene allowed us to assess the scale of mtDNA introgression from a closely related species, Cl. rutilus, and to outline the geographical zone of this introgression. Comparison with the red-backed vole haplotypes in the habitats shared by both species favors the hypothesis of an ancient hybridization event (mid-Holocene) and a subsequent introgression. These results suggest that the hybridization took place in the southern and middle Pre-Ural region.     

Changes in individual quality during a 3-year population cycle of voles

In small mammal populations with multiannual oscillations in density, the occurrence of large individuals in the peak phase (the "Chitty effect") is a typical feature, but mechanisms behind this phenomenon have remained unclear. We analysed long-term data sets collected in western Finland between 1984 and 1992 to: (1) find out how the body size and body condition of voles (Microtus agrestis, M. rossiaemeridionalis, Clethrionomys glareolus) and shrews (Sorex araneus) was associated with the 3-year population cycle of voles, and (2) relate the quality (body condition) of the individuals to changes in the biotic environment in order to detect how the different hypotheses about the mechanisms behind the Chitty effect can explain the observed variation. In the 3-year cycle studied, the mean body size and quality were strongly related to density oscillations in voles but not in sympatric shrews. Voles were lean in the decline phase but very stocky in the summer of the peak phase. This pattern appeared to be mainly caused by changes in body condition or body shape rather than mere size (body length). The quality of voles appeared to be delayed density dependent, especially in autumn when the dominant time lag was 12 months. Previous vole density was strongly related to changes in the environment (activity of specialist predators, production of hay until early summer). We suggest that the previous density of voles mainly affects the quality of voles indirectly through changes in the biotic environment, and that the proximate cause behind the Chitty effect is the combined effect of changes in predation pressure and availability of food.