The beaver (Mammalia,Castoridae) from the Miocene of Sandelzhausen (southern Germany)

The Early/Middle Miocene boundary locality Sandelzhausen (MN5, southern Germany) yielded three beaver teeth: one lower incisor fragment and two strongly worn upper premolars, a right and a left one. The latter are so similar in wear, height, size, and enamel pattern that they probably represent one individual. Although the teeth have been referred to Chalicomys jaegeri Kaup, 1832 (e.g., Hugueney 1999, Fahlbusch 2003), it seems more likely that they belong to Steneofiber depereti Mayet, 1908. However, the assignment of the present material to either one of these species is difficult, because in the advanced wear stage some diagnostic characteristics cannot be assessed. As to ecological implications for the locality Sandelzhausen the taxonomic identity of these two beaver species may not be important. Both are known from riverine, lacustrine or swamp sediments, and it can be assumed that they usually lived in close vicinity to water. Thus, the presence of beaver remains supports the presence of water at Sandelzhausen. However, the teeth might have an allochthonous origin from creeks of the rising Alps.      

Development of nine new microsatellite loci for the American beaver, Castor canadensis (Rodentia: Castoridae), and cross-species amplification in the European beaver, Castor fiber

We developed nine new nuclear dinucleotide microsatellite loci for Castor canadensis. All loci were polymorphic, except for one. The number of alleles ranged from two to four and from five to 12 in populations from Arizona and Wisconsin, respectively. Average heterozygosity ranged from 0.13 to 0.86 per locus. Since cross-species amplification in Castor fiber was successful only in four loci, we tested also nine recently published C. canadensis loci in the Eurasian species. Eight of the published loci amplified; however, three were monomorphic. The number of alleles was lower in C. fiber than in C. canadensis at all loci tested.     

The early extinction date of the beaver (Castor fiber) in Britain

This paper re-examines the evidence for the extinction of the beaver (Castor fiber) in South Britain and Scotland. Much of the evidence found by previous scholars is discounted as unreliable or outdated. A new study looks at reliable historical sources and studies references to the beaver in the context of references to comparable mammals, especially the most ecologically comparable [polecat (Mustela putorius), pine marten (Martes martes), otter (Lutra lutra) and badger (Meles meles)]. Each of these mammals was present in every period studied, meaning that medieval authors were reliable witnesses to the species' presence. The beaver is present in comparable numbers to the other mammals in South Britain 1188–1307 and in Scotland 1526–1600, meaning that as a species it was frequently recorded by humans. References to it cease after 1308 in South Britain, except a single anomalous entry, and after 1600 in Scotland. The idea that this reflects a sample bias or random chance is discounted. The paper rejects the late extinction scenario and concludes that the beaver became extinct by 1300 in South Britain and by 1600 in Scotland.     

Isolation and characterization of microsatellite loci in the beaver (Castor canadensis)

We have isolated and characterized 10 microsatellite loci in the beaver (Castor canadensis). Sixty individuals from southern and central Illinois were screened at each locus. All loci exhibited moderate levels of polymorphism, ranging from five to 13 alleles per locus with average heterozygosity ranging from 0.317 to 0.867. Locus Cca5 deviated significantly from HWE (P < 0.001). The locus pair Cca4/Cca5 was shown to be in linkage disequilibrium in southern Illinois, but not in the central Illinois population. The remaining eight loci will be useful in investigations of mating and kinship patterns in beaver populations in Illinois.     

Morphological and neuroanatomical study of the mammary gland in the immature and mature European beaver (Castor fiber)

This study investigated general morphology and immunohistochemical properties of nerve fibres supplying the mammary gland (MG) in the European beaver. The microscopic analysis of the beaver mammary gland revealed the presence of morphological structures which are characteristic for mammals. There were no distinct differences in the morphological features of the mammary gland between the juvenile and non-pregnant mature beaver.The nerve fibres were visualized using antibodies against protein gene product 9.5 (PGP) and biologically active substances including β-hydroxylase tyrosine (DβH), neuropeptide Y (NPY), calcitonine gene-related peptide (CGRP) and substance P (SP). The study has revealed that the MG in the juvenile and mature beaver is richly supplied with PGP-immunoreactive (PGP-IR) nerve fibres. The most abundant innervation was observed in the nipple and less numerous nerve terminals supplied the glandular tissue. Double-labelling immunohistochemistry disclosed that the majority of PGP-IR nerve fibres associated with blood vessels and smooth muscle cells in both the nipple and glandular tissue were also DßH-IR. However, these nerve terminals were less numerous in the glandular tissue than in the nipple. Most of the DßH-IR axons associated with arteries and smooth muscle cells in the entire gland also stained for NPY. Small number of DßH/NPY-IR fibres supplied veins. CGRP-IR fibres were more abundant than those expressing SP. No distinct differences in the distribution and immunohistochemical characteristic of nerve fibres were observed between the juvenile and adult animals. The distribution and immunohistochemical properties of nerve fibres supplying the gland in the beaver remind those previously described in other mammalian species.     

A ctenodactylid rodent (Mammalia: Rodentia) from the Middle Miocene of Chios Island (Greece)

Field work carried out in 1991 and 1993 at the Middle Miocene locality of Thymiana (Chios Island, Greece), produced much rodent material including a number of ctenodactylid dental specimens. They represent a single taxon whose upper and lower cheek tooth morphology clearly differs from Prosayimys flynni and all Sayimys species known so far, except for Sayimys intermedius. The ctenodactylid teeth from the Middle Miocene of Chios are identified as pertaining to the latter species, despite minor differences from the Pakistani and Saudi Arabian representatives of S. intermedius.     

Mitochondrial phylogeography of the Eurasian beaver Castor fiber L

Nucleotide variation in an approximately 490 bp fragment of the mitochondrial DNA control region (mtDNA CR) was used to describe the genetic variation and phylogeographical pattern in the Eurasian beaver (Castor fiber) over its entire range. The sampling effort was focused on the relict populations that survived a drastic population bottleneck, caused by overhunting, at the end of the 19th century. A total of 152 individuals grouped into eight populations representing all currently recognized subspecies were studied. Sixteen haplotypes were detected, none of them shared among populations. Intrapopulation sequence variation was very low, most likely a result of the severe bottleneck. Extreme genetic structure could result from human-mediated extinction of intermediate populations, but it could also be an effect of prior substantial structuring of the beaver populations with watersheds of major Eurasian rivers acting as barriers to gene flow. Phylogenetic analysis revealed the presence of two mtDNA lineages: eastern (Poland, Lithuania, Russia and Mongolia) and western (Germany, Norway and France), the former comprising more divergent haplotypes. The low level of sequence divergence of the entire cytochrome b gene among six individuals representing six subspecies suggests differentiation during the last glacial period and existence of multiple glacial refugia. At least two evolutionary significant units (ESU) can be identified, the western and the eastern haplogroup. The individual relict populations should be regarded as management units, the eastern subspecies possibly also as ESUs. Guidelines for future translocations and reintroductions are proposed.     

Gliridae (Rodentia,Mammalia) with a simple dental pattern: a new genus and new species from the European Early and Middle Miocene

A new genus of Gliridae, Simplomys gen. nov. is proposed. It contains glirids with a simplified dental pattern from the European Early and Middle Miocene. Simplomys gen. nov. includes several species originally described as Pseudodryomys such as Simplomys simplicidens, Simplomys robustus, Simplomys julii, and Simplomys aljaphi. In addition, a new species, Simplomys meulenorum sp. nov. , is proposed from the Spanish Miocene. The species of this genus share not only a very reduced and simplified dental morphology, but also unique dental proportions that clearly separate them from any other genera of Gliridae. Simplomys gen. nov. is recorded in most of the fossil faunas from the Early and Middle Miocene of the Iberian Peninsula, and shows the maximum diversity in this area during Mammal Neogene Zones MN 3 and MN 4. The genus has been also recorded in other European countries such as France, Germany, and Switzerland, conferring to this very characteristic taxon an important role for biochronological correlations within the European continent. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 157 , 622–652.     

Intraspecific variability of beaver teeth (Castoridae: Rodentia)

The metric variability of the teeth of Castor fiber Linné, 1758 and Castor canadensis Kuhl, 1820 with age are assessed. The ages of the studied specimens of C. fiber range from about 2 months to 16–17 years. Measurements of all teeth are given, and show a large range of size variation over all ages. The greatest size ranges can be observed for incisors, premolars, and third molars. Size variations of the fossil beavers Steneofiber eseri v. Meyer, 1846, Steneofiber castorinus Pomel, 1847, Anchitheriomys suevicus Schlosser, 1884, and Trogontherium cuvieri Fischer de Waldheim, 1809 are compared with those of C. fiber, and are of the same range and magnitude. It seems that it is nearly impossible to age beavers exactly with non‐invasive methods on the basis of tooth morphology, namely by the form and pattern of enamel islands on the chewing surface of the cheek teeth. Therefore, in conclusion, it is suggested that the observed variability in the size of fossil beaver teeth should be interpreted as changes with age in accordance with the overall size range in C. fiber. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 155 , 926–936.     

Sperm morphology of the Eurasian beaver, Castor fiber: an example of a species of rodent with highly derived and pleiomorphic sperm populations

The structural organization of the spermatozoon from the Eurasian beaver, Castor fiber (Family: Castoridae), was determined and compared to that of other sciuromorph rodents. The beaver spermatozoon has a head, which is variable in form but usually paddle-shaped, with a small nucleus and very large acrosome, and a tail that is relatively short compared to that of most other rodents. Transmission electron microscopy indicates that in most testicular spermatozoa the acrosome projects apically, although in a few it becomes partly flexed. During the final stages of maturation, however, the acrosome becomes highly folded so that the apical segment comes to lie alongside part of the acrosome that occurs lateral to the nucleus, with, in some cases, fusion taking place between the outer acrosomal membranes. The sperm nucleus is wedge-shaped, being broader basally and narrowing apically with an occasional large nuclear vacuole occurring. This spermatozoon structure is markedly different from that found in the other species of Geomyoidea, which is the sister group of the Castoridae. The findings thus emphasize the highly divergent nature of the beaver spermatozoon and demonstrate that, within the proposed Infraorder Castorimorpha, very large differences in sperm structure have evolved.     

Nitrogen fixation in subarctic streams influenced by beaver (Castor canadensis)

Nitrogen fixation was measured in four subarctic streams substantially modified by beaver (Castor canadensis) in Quebec. Acetylene-ethylene (C₂H₂ C₂H₄) reduction techniques were used during the 1982 ice-free period (May–October) to estimate nitrogen fixation by microorganisms colonizing wood and sediment. Mean seasonal fixation rates were low and patchy, ranging from zero to 2.3 × 10^–3 µmol C₂H₄ · cm^–2 · h^–1 for wood, and from zero to 7.0 × 10^–3 µmol C₂H₄ · g AFDM^–1 · h^–1 for sediment; 77% of all wood and 63% of all sediment measurements showed no C₂H₂ reduction. Nonparametric statistical tests were unable to show a significant difference (p > 0.05) in C₂H₂ reduction rates between or within sites for wood species or by sediment depth.Nitrogen contributed by microorganisms colonizing wood in riffles of beaver influenced watersheds was small (e.g., 0.207 g N · m^–2 · y^–1) but greater than that for wood in beaver ponds (e.g., 0.008 g N · m^–2 · y^–1) or for streams without beaver (e.g., 0.003 g N · m^–2 · y^–1). Although mass specific nitrogen fixation rates did not change significantly as beaver transform riffles into ponds, the nitrogen fixed by organisms colonizing sediment in pond areas (e.g., 5.1 g N · m^–2 · y^–1) was greater than that in riffles (e.g., 0.42 g N · m^–2 · y^–1). The annual nitrogen contribution is proportional to the amount of sediment available for microbial colonization. We estimate that total nitrogen accumulation in sediment, per unit area, is enhanced 9 to 44 fold by beaver damming a section of stream.     

Patterns of morphological variability in reintroduced populations with two beaver subspecies Castor fiber orientoeuropaeus and Castor fiber belorussicus (Castoridae, Rodentia) as an example

Taking as an example two beaver subspecies (Castor fiber orientoeuropaeus and Castor fiber belorussicus) with documented history of population formation, the patterns of morphological variability in translocated groups of mammals are studied. The variability of quantitative and qualitative traits in the formed populations is not characterized by a single direction. The main trend consists in increasing of adaptive norms diversity as related to body size. There observed a slight increase in the level of fluctuating asymmetry, reduction in polymorphism of nonmetric traits, and increase in fraction of rare aberrations. All these may be caused by inbreeding taking place during the period of prapopulations formation. The results of the study allow for considering the intraspecific differentiation as a consequence of adaptive variability (adaptatiogenesis) or subspecies hybridization. As for stochastic processes (genetic drift, founder effect), they seem to not influence the morphological variability significantly. The differences between discrete and dimensional traits are indicative of population groups' peculiarity.     

Bony labyrinth morphometry indicates locomotor adaptations in the squirrel-related clade (Rodentia,Mammalia)

The semicircular canals (SCs) of the inner ear detect angular acceleration and are located in the bony labyrinth of the petrosal bone. Based on high-resolution computed tomography, we created a size-independent database of the bony labyrinth of 50 mammalian species especially rodents of the squirrel-related clade comprising taxa with fossorial, arboreal and gliding adaptations. Our sampling also includes gliding marsupials, actively flying bats, the arboreal tree shrew and subterranean species. The morphometric anatomy of the SCs was correlated to the locomotion mode. Even if the phylogenetic signal cannot entirely be excluded, the main significance for functional morphological studies has been found in the diameter of the SCs, whereas the radius of curvature is of minor interest. Additionally, we found clear differences in the bias angle of the canals between subterranean and gliding taxa, but also between sciurids and glirids. The sensitivity of the inner ear correlates with the locomotion mode, with a higher sensitivity of the SCs in fossorial species than in flying taxa. We conclude that the inner ear of flying and gliding mammals is less sensitive due to the large information flow into this sense organ during locomotion.     

The composition and properties of beaver (Castor fiber) meat

We analyzed the meat composition of ten females and seven males of sexually mature European beavers (Castor fiber L.). Cutting yield, percentage of particular elements, and chemical composition of the meat were determined. On average, a beaver carcass constitutes 48.6% of beaver body mass and contains 62.8% of meat, 14.5% of fat and 22.4% of bones. The thigh was found to be the largest and most valuable element constituting 33.4% of carcass weight and containing 66.7% of meat. Beaver meat has a high concentration of protein (20.9–21.8% wet wt.) and minerals (1.27–1.31%). The fat was characterized by a high proportion of polyunsaturated fatty acids (48.0–53.1%).     

Molecular Relationships Among Octodontidae (Mammalia: Rodentia: Caviomorpha)

We examined ten species of octodontid rodents and representatives of three outgroups in a complete 13 × 13 DNA-hybridization matrix. The results were indexed as differences in median melting-point depressions (T,_ms), symmetrized, subjected to phylogenetic analysis using FITCH, bootstrapped, and exhaustively taxon-jackknifed. Within Octodontidae, four clades were recovered with 100% bootstrap and complete jackknife support: Tympanoctomys barrerae with Octomys mimax, Octodontomys gliroides alone, Octodon spp., and Aconaemys spp. with Spalacopus cyanus; the latter two clades were closer to each other than either was to Octodontomys or Octomys-Tympanoctomys, but were slightly nearer to and united with Octodontomys, with 89% bootstrap support. However, relationships among the three Aconaemys species and Spalacopus were not completely resolved by our experiments. Ctenomys coyhaiquensis, Abrocoma bennetti, and Lagostomus maximus represented successive outgroups to Octodontidae, while one-way comparisons with Cavia porcellus and Microcavia australis suggested that these caviids are almost as distant from octodontoids as is the chinchilloid Lagostomus. When the data were suitably corrected for percentage hybridization and saturation, division of the distances by the rate previously determined for most amniotes (0.48%/myr) suggested that the basal divergence among the caviomorph rodents examined occurred about 59 myrbp, and that Octodontidae originated 40 myrbp and diversified into extant lineages beginning 14 myr ago. Calibration against the date of the earliest known caviomorph (late Eocene or about 37.5 myrbp) gave a rate of 0.75%/myr, which would suggest later dates for subsequent caviomorph cladogenesis. It is notable that, based respectively on the slower or faster rates, the tetraploid Tympanoctomys barrerae must have diverged from its sister-taxon Octomys mimax 10 or 6.5 myr ago.     

Diving behavior in a free‐living,semi‐aquatic herbivore,the Eurasian beaver Castor fiber

Semi‐aquatic mammals have secondarily returned to the aquatic environment, although they spend a major part of their life operating in air. Moving both on land, as well as in, and under water is challenging because such species are considered to be imperfectly adapted to both environments. We deployed accelerometers combined with a depth sensor to study the diving behavior of 12 free‐living Eurasian beavers Castor fiber in southeast Norway between 2009 and 2011 to examine the extent to which beavers conformed with mass‐dependent dive capacities, expecting them to be poorer than wholly aquatic species. Dives were generally shallow (<1 m) and of short duration (<30 s), suggesting that the majority of dives were aerobic. Dive parameters such as maximum diving depth, dive duration, and bottom phase duration were related to the effort during different dive phases and the maximum depth reached. During the descent, mean vectorial dynamic body acceleration (VeDBA—a proxy for movement power) was highest near the surface, probably due to increased upthrust linked to fur‐ and lung‐associated air. Inconsistently though, mean VeDBA underwater was highest during the ascent when this air would be expected to help drive the animals back to the surface. Higher movement costs during ascents may arise from transporting materials up, the air bubbling out of the fur, and/or the animals’ exhaling during the bottom phase of the dive. In a manner similar to other homeotherms, beavers extended both dive and bottom phase durations with diving depth. Deeper dives tended to have a longer bottom phase, although its duration was shortened with increased VeDBA during the bottom phase. Water temperature did not affect diving behavior. Overall, the beavers’ dive profile (depth, duration) was similar to other semi‐aquatic freshwater divers. However, beavers dived for only 2.8% of their active time, presumably because they do not rely on diving for food acquisition.     

Higher-level systematics of rodents (Mammalia,Rodentia): Evidence from the mitochondrial 12S rRNA gene

Phylogenetic relationships among major rodent superfamilies traditionally have been difficult to establish because of the apparent high level of convergence and parallelism seen among morphological characters and/or rapid differentiation of rodent groups in the Paleocene/Eocene. Nucleotide sequence data from the mitochondrial 12S rRNA gene were used to clarify phylogenetic relationships among the major groups of rodents as defined by Brandt (1855) and Tullberg (1899). Based on the approximately 800 bp analyzed for the 12S rRNA gene in 59 mammalian species, including 25 of the 32 extant rodent families, the major rodent groups that could be defined as monophyletic clades were the Hystricognathi, the Muroidea, and the Geomyoidea. In addition, support for superfamilial sister-group relationships was found for Aplodontoidea with Sciuroidea and Dipodoidea with Muroidea.