A list of 40 species is presented of the rodents and insectivores collected during a 15-year period from the Republic of Mordovia. The dataset contains more than 24,000 records of rodent and ...insectivore species from 23 districts, including Saransk. A major part of the data set was obtained during expedition research and at the biological station. The work is based on the materials of our surveys of rodents and insectivorous mammals conducted in Mordovia using both trap lines and pitfall arrays using traditional methods.
Beavers are well-known for their ability to fell large trees through gnawing. Yet, despite this impressive behavior, little information exists on their masticatory musculature or the biomechanics of ...their jaw movements. It was hypothesized that beavers would have a highly efficient arrangement of the masticatory apparatus, and that gnawing efficiency would be maintained at large gape. The head of an American beaver,
Castor canadensis
, was dissected to reveal the masticatory musculature. Muscle origins and insertions were noted, the muscles were weighed and fiber lengths measured. Physiological cross-sectional areas were determined, and along with the muscle vectors, were used to calculate the length of the muscle moment arms, the maximum incisor bite force, and the proportion of the bite force projected along the long axis of the lower incisor, at occlusion and 30° gape. Compared to other sciuromorph rodents, the American beaver was found to have large superficial masseter and temporalis muscles, but a relatively smaller anterior deep masseter. The incisor bite force calculated for the beaver (550–740 N) was much higher than would be predicted from body mass or incisor dimensions. This is not a result of the mechanical advantage of the muscles, which is lower than most other sciuromorphs, but is likely related to the very high percentage (>96 %) of bite force directed along the lower incisor long axis. The morphology of the skull, mandible and jaw-closing muscles enable the beaver to produce a very effective and efficient bite, which has permitted beavers to become highly successful ecosystem engineers.
It has been suggested that beavers affect biogeochemical processes and the environment on a relatively large scale, thus acting as ecosystem engineers. In this long-term study we evaluated the ...effects of beavers on water chemistry in small boreal lakes of Southern Finland. We addressed the following three questions; does water chemistry differ between beaver and non-beaver lakes; does water chemistry differ between the flood years in comparison to the antecedent years; and does the flood impact downstream lakes? The results showed that beaver lakes had higher dissolved organic carbon (DOC) concentrations but lower dissolved oxygen (DO) concentrations than non-beaver lakes. DOC concentration increased during the first three beaver-impoundment years when compared to the pre-impoundment situation, and DO concentrations simultaneously decreased. Lake DOC concentrations furthermore declined back to initial levels after the impoundment had lasted for 4–6 years. The opposite occurred with DO. No clear effects caused by beaver impoundments were found in downstream lakes however. Beaver activity had no effect on N and P concentrations in lakes, but our results emphasize that the beaver affects the carbon cycling in the boreal zone. Further research is therefore needed to clarify its effect on the carbon balance at different spatial scales.
Five castorid teeth from the (early) middle Miocene locality Gračanica in Bosnia-Herzegovina, probably originating from lower lacustrine lignite-rich deposits, were available for study. These teeth ...from the upper jaw are similar in preservation, wear stage, and size and may represent only one single individual. Due to their size and morphology (mainly state of hypsodonty and closing hypostria in P4), they are referred to
Stenefiber depereti
. Since a semiaquatic lifestyle is assumed for
Steneofiber
, it may be assumed that the teeth are of autochthonous origin.
Haematology parameters (N = 24) and serum biochemistry parameters (N = 35) were determined for wild Eurasian beavers (Castor fiber), between 6 months - 12 years old. Of the population tested in this ...study, N = 18 Eurasian beavers were from Norway and N = 17 originating from Bavaria but now living extensively in a reserve in England. All blood samples were collected from beavers via the ventral tail vein. All beavers were chemically restrained using inhalant isoflurane in 100% oxygen prior to blood sampling. Results were determined for haematological and serum biochemical parameters for the species and were compared between the two different populations with differences in means estimated and significant differences being noted. Standard blood parameters for the Eurasian beaver were determined and their ranges characterised using percentiles. Whilst the majority of blood parameters between the two populations showed no significant variation, haemoglobin, packed cell volume, mean cell haemoglobin and white blood cell counts showed significantly greater values (p<0.01) in the Bavarian origin population than the Norwegian; neutrophil counts, alpha 2 globulins, cholesterol, sodium: potassium ratios and phosphorus levels showed significantly (p<0.05) greater values in Bavarian versus Norwegian; and potassium, bile acids, gamma globulins, urea, creatinine and total calcium values levels showed significantly (p<0.05) greater values in Norwegian versus Bavarian relict populations. No significant differences were noted between male and female beavers or between sexually immature (<3 years old) and sexually mature (≥3 years old) beavers in the animals sampled. With Eurasian beaver reintroduction encouraged by legislation throughout Europe, knowledge of baseline blood values for the species and any variations therein is essential when assessing their health and welfare and the success or failure of any reintroduction program. This is the first study to produce base-line blood values and their variations for the Eurasian beaver.
Echinococcus multilocularis is an important pathogenic zoonotic parasite of health concern, though absent in the United Kingdom. Eurasian beavers (Castor fiber) may act as a rare intermediate host, ...and so unscreened wild caught individuals may pose a potential risk of introducing this parasite to disease-free countries through translocation programs. There is currently no single definitive ante-mortem diagnostic test in intermediate hosts. An effective non-lethal diagnostic, feasible under field condition would be helpful to minimise parasite establishment risk, where indiscriminate culling is to be avoided. This study screened live beavers (captive, n = 18 or wild-trapped in Scotland, n = 12) and beaver cadavers (wild Scotland, n = 4 or Bavaria, n = 11), for the presence of E. multilocularis. Ultrasonography in combination with minimally invasive surgical examination of the abdomen by laparoscopy was viable under field conditions for real-time evaluation in beavers. Laparoscopy alone does not allow the operator to visualize the parenchyma of organs such as the liver, or inside the lumen of the gastrointestinal tract, hence the advantage of its combination with abdominal ultrasonography. All live beavers and Scottish cadavers were largely unremarkable in their haematology and serum biochemistry with no values suspicious for liver pathology or potentially indicative of E. multilocularis infection. This correlated well with ultrasound, laparoscopy, and immunoblotting, which were unremarkable in these individuals. Two wild Bavarian individuals were suspected E. multilocularis positive at post-mortem, through the presence of hepatic cysts. Sensitivity and specificity of a combination of laparoscopy and abdominal ultrasonography in the detection of parasitic liver cyst lesions was 100% in the subset of cadavers (95%Confidence Intervals 34.24-100%, and 86.7-100% respectively). For abdominal ultrasonography alone sensitivity was only 50% (95%CI 9.5-90.6%), with specificity being 100% (95%CI 79.2-100%). For laparoscopy alone sensitivity was 100% (95% CI 34.2-100%), with specificity also being 100% (95% CI 77.2-100%). Further immunoblotting, PCR and histopathological examination revealed one individual positive for E. multilocularis, whilst the other individual was positive for Taenia martis.
Over 13 months, 465 beavers, foxes, muskrats, otters, and raccoons were trapped in four counties in eastern Maryland and examined by molecular methods for microsporidia. A two-step nested PCR ...protocol was developed to amplify a 392-bp fragment of the internal transcribed spacer region of the rRNA gene of Enterocytozoon spp., with the use of primers complementary to the conserved regions of published nucleotide sequences. Fifty-nine PCR-positive samples were sequenced. Multiple alignments of these sequences identified 17 genotypes of Enterocytozoon spp. (WL1 to WL17); of these, 15 have not been reported before. Most of the genotypes were found in multiple species of wildlife and belonged to a major group consisting of all the previously described Enterocytozoon bieneusi genotypes from human and domestic animals. Some of the isolates from muskrats and raccoons formed two distinct groups. Results of this study indicate that fur-bearing mammals, especially those closely associated with surface water, can be a potential source of human-pathogenic E. bieneusi. However, there are also host-adapted Enterocytozoon genotypes in wildlife, which may represent species different from E. bieneusi and have no apparent public health significance. This is the first report of E. bieneusi in wildlife.
Beavers are one of the largest and ecologically most distinct rodent species. Little is known about their evolution and even their closest phylogenetic relatives have not yet been identified with ...certainty. Similarly, little is known about the timing of divergence events within the genus Castor.
We sequenced complete mitochondrial genomes from both extant beaver species and used these sequences to place beavers in the phylogenetic tree of rodents and date their divergence from other rodents as well as the divergence events within the genus Castor. Our analyses support the phylogenetic position of beavers as a sister lineage to the scaly tailed squirrel Anomalurus within the mouse related clade. Molecular dating places the divergence time of the lineages leading to beavers and Anomalurus as early as around 54 million years ago (mya). The living beaver species, Castor canadensis from North America and Castor fiber from Eurasia, although similar in appearance, appear to have diverged from a common ancestor more than seven mya. This result is consistent with the hypothesis that a migration of Castor from Eurasia to North America as early as 7.5 mya could have initiated their speciation. We date the common ancestor of the extant Eurasian beaver relict populations to around 210,000 years ago, much earlier than previously thought. Finally, the substitution rate of Castor mitochondrial DNA is considerably lower than that of other rodents. We found evidence that this is correlated with the longer life span of beavers compared to other rodents.
A phylogenetic analysis of mitochondrial genome sequences suggests a sister-group relationship between Castor and Anomalurus, and allows molecular dating of species divergence in congruence with paleontological data. The implementation of a relaxed molecular clock enabled us to estimate mitochondrial substitution rates and to evaluate the effect of life history traits on it.
Among the dominant twentieth century conceptual models of geomorphology that rely on insights resulting from field-based research are Stanley A. Schumm's formulations of complex response, intrinsic ...thresholds, river metamorphosis, and spatial zonation of drainage basins. Schumm's research focused primarily on finer grained alluvial channels in lower relief environments. As a result of his work, most investigators now approach river process and form within a framework based on three fundamental assumptions. First, channel changes are abrupt and driven by crossing external and internal thresholds. Second, channel change is likely to be asynchronous, resulting in different portions of a river or a river network behaving in very different manners at a given point in time. Third, different portions of a river network are dominated by distinct disturbance regimes and resulting suites of geomorphic processes and forms. More recent research on resistant-boundary mountain channels illustrates how field evidence demonstrates that river process and form are inherently nonlinear, with spatial and temporal thresholds. Multithread channels can form within unconfined valley segments in mountainous river networks of the Colorado Front Range, but only in the presence of biotic drivers in the form of (i) old-growth forest that facilitates the formation of closely spaced, channel-spanning logjams or (ii) beavers that build dams. Thresholds of channel and valley geometry govern the occurrence and persistence of jams and dams, and these channel obstructions initiate specific nonlinear responses in valley and channel form. When the biotic drivers are removed, river metamorphosis occurs. Alluvial channels, which are typically regarded as being relatively responsive to changes in water and sediment yield and substrate composition, and channels with more resistant boundaries that typically respond to external changes over longer timespans exhibit nonlinear complex behavior. In both cases, the nonlinear behavior of rivers with numerous interdependent variables, multiple internal and external thresholds, and complex responses would be difficult to conceptualize and quantify in the absence of extensive field data. One of the management implications of complex, nonlinear behavior is that a one-size-fits-all approach to managing rivers is inadequate. Field research, initially focused on understanding specific examples of river process and form, revealed underlying patterns that give rise to conceptual models broadly applicable within fluvial geomorphology.
causes the diarrheal disease known as giardiasis; transmission through contaminated surface water is common. The protozoan parasite's genetic diversity has major implications for human health and ...epidemiology. To determine the extent of transmission from wildlife through surface water, we performed whole-genome sequencing (WGS) to characterize 89
isolates from both outbreak and sporadic infections: 29 isolates from raw surface water, 38 from humans, and 22 from veterinary sources. Using single nucleotide variants (SNVs), combined with epidemiological data, relationships contributing to zoonotic transmission were described. Two assemblages, A and B, were identified in surface water, human, and veterinary isolates. Mixes of zoonotic assemblages A and B were seen in all the community waterborne outbreaks in British Columbia (BC), Canada, studied. Assemblage A was further subdivided into assemblages A1 and A2 based on the genetic variation observed. The A1 assemblage was highly clonal; isolates of surface water, human, and veterinary origins from Canada, United States, and New Zealand clustered together with minor variation, consistent with this being a panglobal zoonotic lineage. In contrast, assemblage B isolates were variable and consisted of several clonal lineages relating to waterborne outbreaks and geographic locations. Most human infection isolates in waterborne outbreaks clustered with isolates from surface water and beavers implicated to be outbreak sources by public health. In-depth outbreak analysis demonstrated that beavers can act as amplification hosts for human infections and can act as sources of surface water contamination. It is also known that other wild and domesticated animals, as well as humans, can be sources of waterborne giardiasis. This study demonstrates the utility of WGS in furthering our understanding of
transmission dynamics at the water-human-animal interface.
causes large numbers of gastrointestinal illness in humans. Its transmission through the contaminated surface water/wildlife intersect is significant, and the water-dwelling rodents beavers have been implicated as one important reservoir. To trace human infections to their source, we used genome techniques to characterize genetic relationships among 89
isolates from surface water, humans, and animals. Our study showed the presence of two previously described genetic assemblages, A and B, with mixed infections detected from isolates collected during outbreaks. Study findings also showed that while assemblage A could be divided into A1 and A2, A1 showed little genetic variation among animal and human hosts in isolates collected from across the globe. Assemblage B, the most common type found in the study surface water samples, was shown to be highly variable. Our study demonstrates that the beaver is a possible source of human infections from contaminated surface water, while acknowledging that theirs is only one role in the complex cycle of zoonotic spread. Mixes of parasite groups have been detected in waterborne outbreaks. More information on
diversity and its evolution using genomics will further the understanding of the epidemiology of spread of this disease-causing protozoan.
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