The occurrence of Centrorhynchus (Acanthocephala) in shrews (Sorex araneus and Sorex minutus) in the United Kingdom

Encysted acanthocephalans belonging to the genus Centrorhynchus were found in the body cavities of Sorex araneus (common shrew) and Sorex minutus (pygmy shrew) from Boxworth, Cambridgeshire, U.K. Fifty percent of the male S. araneus and 67% of the male S. minutus examined were found to be infected, with the mean intensity (+/-SD) being 54.3 +/- 91.3 and 14.7 +/- 18.4, respectively. The species of Centrorhynchus in the shrews may be Centrorhynchus aluconis, which is distributed widely in tawny owls, Strix aluco, in the United Kingdom. Shrews appear to serve as paratenic hosts for C. aluconis.     

Spatial Variability of Resident and Nonresident Populations of Small Mammals on a Forest Plot

Biology Bulletin - Abstract—The resident population density and the numbers of nonresident common shrew (Sorex araneus), Laxmann’s shrew (S. caecutiens), and the bank vole...     

Analysis of biodiversity parameters of shrew communities of the Altai Mountains

The communities of insectivorous mammals of the Altai Mountains, each consisting of 4–9 species, are quite similar in species composition and principles of organization. The forest belt of mountains is dominated by the common shrew (Sorex araneus), with the Laxmann’s (Sorex caecutiens), lesser (Sorex minutus), and tundra (Sorex tundrensis) (rarely even-toothed (Sorex isodon)) shrews being codominants. With altitude, the dominants change and some species disappear but no significant changes in the dominance structure of the community occur. Positive correlations between abundance rates recorded in different years and on different plots indicate the stability of communities under study. Analysis of informational indices of diversity reveals four basic possible conditions of communities: a) relatively safe, b) slightly disturbed, c) disturbed, and d) high-altitude slightly evened.     

Patterns of sequence variation in the mitochondrial D-loop region of shrews

Direct sequencing of the mitochondrial displacement loop (D-loop) of shrews (genus Sorex) for the region between the tRNA(Pro) and the conserved sequence block-F revealed variable numbers of 79-bp tandem repeats. These repeats were found in all 19 individuals sequenced, representing three subspecies and one closely related species of the masked shrew group (Sorex cinereus cinereus, S. c. miscix, S. c. acadicus, and S. haydeni) and an outgroup, the pygmy shrew (S. hoyi). Each specimen also possessed an adjacent 76-bp imperfect copy of the tandem repeats. One individual was heteroplasmic for length variants consisting of five and seven copies of the 79-bp tandem repeat. The sequence of the repeats is conducive to the formation of secondary structure. A termination-associated sequence is present in each of the repeats and in a unique sequence region 5' to the tandem array as well. Mean genetic distance between the masked shrew taxa and the pygmy shrew was calculated separately for the unique sequence region, one of the tandem repeats, the imperfect repeat, and these three regions combined. The unique sequence region evolved more rapidly than the tandem repeats or the imperfect repeat. The small genetic distance between pairs of tandem repeats within an individual is consistent with a model of concerted evolution. Repeats are apparently duplicated and lost at a high rate, which tends to homogenize the tandem array. The rate of D- loop sequence divergence between the masked and pygmy shrews is estimated to be 15%-20%/Myr, the highest rate observed in D-loops of mammals. Rapid sequence evolution in shrews may be due either to their high metabolic rate and short generation time or to the presence of variable numbers of tandem repeats.      

Density compensation in allopatric populations of the pygmy shrewSorex minutus on Gotland and the outer hebrides: evidence for the effect of interspecific competition

Pygmy shrewsSorex minutus occur allopatrically in Ireland, the Outer Hebrides and Gotland in Sweden, and sympatrically with common shrewsS. minutus on the European mainland and in England. Competition theory redicts higher population density in allopatric populations as a consequence of relaxed competition. Here this prediction is tested by comparing allopatric populations of pygmy shrews in the Outer Hebrides and in Gotland with sympatric populations on the Swedish mainland. Population densities were higher in allopatry than in sympatry. Lower summed densities in allopatry, which is predicted by niche theory, was found on the Outer Hebrides, but not on Gotland. Size distributions of carabids, which are important food items, could not explain the differences in population densities. Since both avian predators and snakes are present in all areas, population density of pygmy shrews during autumn in concluded to be regulated primarly by competition with common shrews in areas of sympatry.     

Factors explaining increased body size in common shrews (Sorex araneus) on Scottish islands

Aim  Island populations of small mammals are often characterized by a larger body size compared with neighbouring mainland or continental populations of the same species. A number of reasons have been put forward to explain this phenomenon. The aim of this study was to test which of these hypotheses can best explain the increase of body size in common shrews ( Sorex araneus ) on islands.
Location  The fieldwork for this study was carried out on the islands of the Inner Hebrides, Clyde Islands and the west coast of Scotland.
Methods  This study compared body sizes of common shrews from mainland and island sites on the west coast of Scotland, based on measurements of hind foot lengths. On 10 of the 13 islands sampled, common shrews were significantly larger than on the mainland. Body size did not vary significantly among mainland populations. We used the directional contrasts method to test the relative contributions of possible factors explaining the large body size observed in the island populations.
Results  We found that body size of common shrews on islands was positively related to distance from mainland, negatively related to average annual temperature, negatively related to island size, and may also be influenced by the presence or absence of pygmy shrews ( Sorex minutus ) on the island.
Main conclusions  Our results suggest a role for founder events, Bergmann's rule and K -selection in determining body size of common shrews on islands.     

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.     

Physiological response in the even-toothed shrew <Emphasis Type="Italic">Sorex isodon</Emphasis> to fasting and refeeding

The red-toothed shrews (genus Sorex) are one of the smallest mammals. The amount of food they consume a day exceeds their own weight, and without food they can survive for only few hours. Representatives of this genus have extremely high metabolic rates. This study addressed the effect of 8-h fasting and 13-h refeeding on the body weight, blood glucose level, liver glycogen and lipid levels, and relative weight of inguinal and interscapular adipose tissues in the even-toothed shrews (S. isodon). Fasting led to a decrease in the body weight, blood glucose and liver glycogen levels. The relative weight of adipose tissue also decreased, while the liver lipid level increased significantly. After refeeding, blood glucose and liver glycogen levels were considerably higher than in control, while other parameters remained almost the same as in control. Physiological response to fasting develops in S. isodon quite rapidly, promoted by the high metabolic rate.     

How did pygmy shrews colonize Ireland? Clues from a phylogenetic analysis of mitochondrial cytochrome b sequences.

There is a long-standing debate as to how Ireland attained its present fauna; we help to inform this debate with a molecular study of one species. A 1110 base pair fragment of the mitochondrial cytochrome b gene was sequenced in 74 specimens of the pygmy shrew, Sorex minutus, collected from throughout its western Palaearctic range. Phylogenetic analysis of these sequences revealed several well-supported lineages. Most of the 65 haplotypes belonged to a northern lineage, which ranged from Britain in the west to Lake Baikal in the east. The other lineages were largely limited to Iberia, Italy and the Balkans. One exception, however, was a lineage found in both Ireland and Andorra. This affinity, and the large difference between the mitochondrial sequences of Irish and British individuals, suggest that pygmy shrews did not colonize Ireland via a land connection from Britain, as has been previously supposed, but instead were introduced by boat from southwest continental Europe. All the Irish pygmy shrews analysed were identical or very similar in cytochrome b sequence, suggesting an extreme founding event.     

Population diversity of the pygmy shrew

A morphogenetic comparison of pygmy shrews (Sorex minutus Linnaeus, 1766) from two geographical regions in the North of European Russia, located 1000 km apart, showed a relatively high stability in all of their parameters.     

Habitat occurrence and prey distribution of a multi-species community of shrews in the Siberian taiga

The habitat occurrence and invertebrate prey distribution of nine species of shrew in the mid-taiga of central Siberia were investigated. Species richness ranged from 4–9 shrews per habitat. Sorex araneus and S. caecutiens were numerically dominant in all seven habitats (44 and 36% of the total catch, respectively) while Sorex minutus, S. tundrensis, S. isodon , and S. roboratus each constituted 4–6% and Sorex minutissimus, S. daphaenodon , and Neomys fodiens were rare (< 1% each). There was no overall correlation between abundance of shrews and invertebrate prey, but flood-plain habitats supported the greatest abundance and species richness of shrews, and high density and biomass of prey. Oligochaete-eating shrews were twice as numerous here as in other habitats, coincident with high abundance of oligochaetes. The large, earthworm-feeding Sorex roboratus occurred only here. The more acid, typical taiga habitats had lower adundance and species richness of shrews. They had the lowest density and biomass of prey, particularly oligochaetes, and far fewer oligochaete-eating shrews. The relative paucity of shrews in bush-meadow habitats, despite abundant prey, implied that habitat structure influences shrew distribution. Differential numbers of certain species in the presence or absence of larger congeners also suggested that interspecific competitive effects influence habitat selection by shrews. The high species richness of shrews here in the mid-taiga may be accounted for by the heterogeneous nature of the constituent habitats which provide niches for small and large species of shrew with a range of feeding habits.     

Intraspecific variability and phylogenetic relationships of the Pleistocene shrewSorex runtonensis (Soricidae)

Intraspecific variability of the Pleistocene speciesSorex runtonensis Hinton, 1911 from different Polish and Russian (Caucasus Mts.) localities and its relationships to Recent red-toothed shrews of similar body size and mandibular morphology,S. caecutiens Laxmann, 1788 andS. tundrensis Merriam, 1990, are explained on the grounds of multivariate statistics. The remains ofS. runtonensis from different localities form a single group and differ fromS. caecutiens. They resembleS. tundrensis by the first canonical root related to a mandibular size and proportions. This may indicate thatS. runtonensis andS. tundrensis are closely related but separated components of the species complextundrensis.     

Small mammal populations in relation to hedgerow structure in an arable landscape

The population ecology of small mammals in hedgerows in arable farmland in eastern England is described. Features of hedgerows of importance to individual species are examined. Some 97% of the total 3042 mammals captured were wood mouse Apodemus sylvaticus , yellow-necked mouse Apodemus flavicollis , bank vole Clethrionomys glareolus and common shrew Sorex araneus . Small numbers of harvest mice Micromys minutus , field voles Microtus agrestis , pygmy shrews Sorex minutus and water shrews Neomys fodiens were also caught. Wood mouse, the most numerous species, showed a typical pattern of large numbers in autumn and winter, followed by a simultaneous decline over all hedges in early spring. Population changes were less clear in yellow-necked mouse and bank vole but the yellow-necked mouse was more scarce in the second year of study. Common shrews were most numerous in summer and declined rapidly in autumn. Hedgerow coppicing had a marked effect on yellow-necked mouse numbers but not on wood mouse. In an extensive survey of mammal numbers in relation to hedgerow features, ground cover was found to be the single largest factor influencing size of bank vole populations. Hedgerow condition (lack of gaps) was important to yellow-necked mice, which thrived only in well-established hedgerows. Wood mice appeared little influenced by the characteristics of the hedge. Common shrews were more abundant in hedgerows with adjacent permanent water.     

Basal rate of metabolism and temperature regulation in Sorex coronatus and S. minutus (Soricidae: Mammalia)

1. The basal rate of metabolism (BMR), body temperature and thermal conductance of Sorex minutus and Sorex coronatus were studied. Special attention was given to measuring BMR in resting and postabsorptive shrews. 2. Both species exhibit a high BMR, respectively 339 and 289% of the value expected on the basis of body mass. 3. The thermal conductance of both species is similar to the predicted value and their body temperature averages 38.6 and 37.6 degrees C respectively. 4. Available data suggest that a very high BMR may be a common feature within the genus Sorex.     

Morphometric difference between the Novosibirsk and Tomsk chromosome races of<Emphasis Type="Italic">Sorex araneus</Emphasis> in a zone of parapatry

A hybrid zone between the Novosibirsk and Tomsk chromosome races of the common shrewSorex araneus Linnaeus, 1758 was found near Novosibirsk city (West Siberia, Russia) in an area unimpeded by geographic barriers. In this zone, the shrews of both races and their hybrids were trapped and karyotyped and 22 features of their cranial and postcranial skeleton were measured. Canonical discriminant analysis revealed 3 distinct groups of individuals, which corresponded to the 3 karyotypic categories involved in the analysis. The first discriminant function reflected the differences in the size of skeletal elements. The Novosibirsk shrews and the hybrids were significantly smaller than the Tomsk shrews. The second discriminant function was interpreted as a parameter of skeletal proportionality. The hybrids were significantly less proportional than the parental races. This study revealed one of the clearest examples of morphological differentiation between chromosome races of the common shrew.     

The genus Sorex (Mammalia, Soricidae)–distribution and evolutionary aspects of Eurasian species

There are about 60 species of shrews of the genus Sorex distributed over the Nearctic and Palaearctic regions; these are usually divided into the subgenera Sorex, Otisorex and Microsorex . The Old World species are listed and their phylogeny discussed, with special emphasis laid on the karyotypes. It is proposed that the Old World forms should be divided into the subgenera Homalurus, Sorex and Otisorex . It is also suggested that the subgenus Sorex could be divided into at least three taxonomic units.     

Genetic variation in Irish pygmy shrews Sorex minutus (Soricomorpha: Soricidae): implications for colonization history

The status of the pygmy shrew ( Sorex minutus L.) as a native or an introduced species in Ireland has been subject to much debate. To examine this and other aspects of the colonization history of the Irish pygmy shrew, genetic variation was determined in 247 pygmy shrews collected throughout Ireland, using mitochondrial control region sequences and five polymorphic microsatellite loci. Genetic diversity was low for both types of marker. The median-joining network for control region sequences was star-like, suggesting that the colonization of Ireland involved a small number of founders and rapid population expansion thereafter; this was supported by other statistics. Molecular dating with both mitochondrial DNA and microsatellite data is consistent with a human introduction. This would have been several thousand years ago; a recent colonization within historical times can be ruled out. This is the first detailed population genetic study of the pygmy shrew anywhere in its range.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 918–927.     

Molecular phylogeny and evolution of Sorex shrews (Soricidae: insectivora) inferred from mitochondrial DNA sequence data

Shrews of the genus Sorex are characterized by a Holarctic distribution, and relationships among extant taxa have never been fully resolved. Phylogenies have been proposed based on morphological, karyological, and biochemical comparisons, but these analyses often produced controversial and contradictory results. Phylogenetic analyses of partial mitochondrial cytochrome b gene sequences (1011 bp) were used to examine the relationships among 27 Sorex species. The molecular data suggest that Sorex comprises two major monophyletic lineages, one restricted mostly to the New World and one with a primarily Palearctic distribution. Furthermore, several sister-species relationships are revealed by the analysis. Based on the split between the Soricinae and Crocidurinae subfamilies, we used a 95% confidence interval for both the calibration of a molecular clock and the subsequent calculation of major diversification events within the genus Sorex. Our analysis does not support an unambiguous acceleration of the molecular clock in shrews, the estimated rate being similar to other estimates of mammalian mitochondrial clocks. In addition, the data presented here indicate that estimates from the fossil record greatly underestimate divergence dates among Sorex taxa.     

Karyotype evolution of eulipotyphla (insectivora): the genome homology of seven sorex species revealed by comparative chromosome painting and banding data

The genus Sorex is one of the most successful genera of Eulipotyphla. Species of this genus are characterized by a striking chromosome variability including XY1Y2 sex chromosome systems and exceptional chromosomal polymorphisms within and between populations. To study chromosomal evolution of the genus in detail, we performed cross-species chromosome painting of 7 Sorex species with S. granarius and S. araneus whole-chromosome probes and found that the tundra shrew S. tundrensis has the most rearranged karyotype among these. We reconstructed robust phylogeny of the genus Sorex based on revealed conserved chromosomal segments and syntenic associations. About 16 rearrangements led to formation of 2 major Palearctic groups after their divergence from the common ancestor: the S. araneus group (10 fusions and 1 fission) and the S. minutus group (5 fusions). Further chromosomal evolution of the 12 species inside the groups, including 5 previously investigated species, was accompanied by multiple reshuffling events: 39 fusions, 20 centromere shifts and 10 fissions. The rate of chromosomal exchanges upon formation of the genus was close to the average rate for eutherians, but increased during recent (about 6-3 million years ago) speciation within Sorex. We propose that a plausible ancestral Sorex karyotype consists of 56 elements. It underwent 20 chromosome rearrangements from the boreoeutherian ancestor, with 14 chromosomes retaining the conserved state. The set of genus-specific chromosome signatures was drawn from the human (HSA)-shrew comparative map (HSA3/12/22, 8/19/3/21, 2/13, 3/18, 11/17, 12/15 and 1/12/22). The syntenic association HSA4/20, that was previously proposed as a common trait of all Eulipotyphla species, is shown here to be an apomorphic trait of S. araneus.     

Studies on the biology of the Pygmy shrew Sorex minutus in the West of Ireland

Pygmy shrews were snap-trapped over one year in grassland and occasionally in other habitats. The bodies yielded data on tooth-wear, body and skull dimensions, moulting, reproduction, food and parasites. The shrews appeared equally abundant in grassland and woodland and were more active in the day. The breeding season, population turnover, and winter body and skull regression were similar to those of other Sorex species. However, cranial regression was more marked: this may be associated with the animal's exceptionally small size. Moulting extended in autumn from August to November, and in spring from March to May, the latter in males starting earlier and perhaps lasting longer. Simultaneous and patch moults were also recorded. The litter size dropped as the breeding season progressed. The main foods were beetles, woodlice, Diptera and insect larvae; all except Diptera were eaten consistently over the year. There was a wide variety of other foods, many showing seasonal fluctuations. The commonest flea was Doratopsylla dasycnema. Palaeopsylla soricis, a common shrew-flea, widespread in the British Isles, is at least locally absent. Pygmy shrews may be the principal host of Hystrichopsylla talpae in Ireland. Rates of infestation by the trematodes and one cestode appeared to increase as the hosts aged. The tapeworm Hymenolepis scutigera, however, was commonest in juveniles. It is postulated that Doratopsylla dasycnema is its intermediate host, allowing infection of young before they leave the nest. Sorex araneus is sympatric with Sorex minutus over most of its range, but not in Ireland. In its absence, S. minutus may have been able to exploit its niche, the apparent abundance of the latter in woodland and wider variety of food consumed providing grounds for such a hypothesis.