Geographic variation of the Greater white-toothed shrew (Crocidura russula Hermann, 1780 Mammalia, Soricidae)

A multivariate morphometric study of the Greater white-toothed shrew ( C. russula ) throughout its Palearctic range was carried out to search for patterns of geographic variation within the species boundary. Burnaby's and multiple group principal component analysis allowed the adjustment of raw data with respect to within-sample allometric variation. Multivariate 'size-free'results show a stepped cline with the phenotypical trait reduction and shape change from the eastern to the western Maghreb. Pleistocene fossil mandibles proved to have low phenetic distances with eastern populations (Tunisia, east Algeria) and it is argued that their character set is the primitive condition. The ancestral Mid-Pleistocene shrews lived in a relatively more humid climate. Geo-climatic changes in the north African range during the Quaternary provoked phenetic variation of C. russula and, it can be argued, evolution of the modern western C.r. yebalensis. A historical process can thus be assumed as the main cause of this categorical variation, by segmentation of the species range due to geo-climatic events. Morphometric discontinuity within the C. russula Maghreb range is shown to be congruent with karyological and biochemical studies. Moroccan and Tunisian shrews differ, for example, in NFa chromosomes and electrophoretical traits. A stasipatric process should be invoked to explain categorical variation in the Maghreb range. Colonization and divergence of insular populations results in more or less differentiated geographic races. The populations of Ibiza and Pantelleria are close to the species threshold (Nei's D ≥ 0.1). The process of speciation undergone by the Greater white-toothed shrew results in a complex pattern of geographic variation, including both allopatric and non-allopatric modes.     

Post-Pleistocene evolution of Bornean shrews Crocidura foetida (Mammalia, Soricidae)

Fossil mandibles of the Bornean shrew Crocidura foetida recovered from excavations at the west mouth of Niah cave, Sarawak, Malaysia, show that the late Pleistocene population at this lowland location was comparable in size with the large subspecies Crocidura foetida doriae , presently occurring at inland, upland locations. Two Holocene specimens fall in the size range of the smaller lowland subspecies C. f. foetida . Comparable post-Pleistocene size-reduction is known among other mammals of Borneo, but this is the first instance of dated examples. The evolutionary trend conforms with Bergmann's 'rule' but, other than climate change, no selective agent is apparent.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 413–419.     

河南信阳发现台湾灰麝鼩北大核心CSCD

于2013年和2018年在河南信阳新县与浉河共采集到3号鼩鼱成年个体标本,基于齿色特征初步鉴定为劳亚食虫目鼩鼱科麝鼩属(Crocidura)物种。对所采3号标本的Cyt b基因进行PCR扩增和测序,测序结果与GenBank数据库进行比对,并通过构建系统发育关系树进一步明确所采3只标本的分类地位。根据标本形态、头骨特征,结合分子生物学证据,确定该物种为台湾灰麝鼩(C.tanakae),为河南哺乳动物分布新记录种。标本现存于郑州大学生物多样性与生态学研究所(编号分别为IBE20131005、IBE2018100501和IBE2018100502)。     

安徽黄山和宣城发现台湾灰麝鼩

2018年11月在安徽省黄山市太平湖国家湿地公园(30°34′42″N,118°41′47″E)和宣城市旌德县蔡家桥镇(30°21′26″N,118°30′11″E)的针阔混交林采集到3只麝鼩属小型兽类。3只个体体型较小,体重11～14 g;背毛灰褐色,腹部毛色稍淡;尾短而粗壮,上下异色,基部2/3散生稀疏的长刚毛,这些特征与台湾灰麝鼩(Crocidura tanakae)描述一致。基于Cyt b全序列构建的最大似然树显示,这3号标本与从GenBank下载的台湾灰麝鼩(GenBank登录号KX946002～KX946006、AB175080、AB175081)构成单系群(支持率为100%)。这3号标本Cyt b全序列与台湾灰麝鼩地模标本(GenBank登录号AB175080、AB175081)的遗传距离在0.76%～0.85%之间。基于以上结果,确定这3号标本为台湾灰麝鼩,这是该物种在安徽省的首次发现,也是其在华东地区的首个分布记录。     

Helminth associations in white-toothed shrews Crocidura russula (Insectivora: Soricidae) from the Albufera Natural Park, Spain

The helminths of 218 white-toothed shrews from 29 sites in 2 biotopes in the Albufera Natural Park (Valencia, Spain) were examined from July 1990 to August 1991. An association analysis of helminths occurring at a prevalence of more than 4% was carried out for 4 species of cestodes located in the intestine (Hymenolepis pistillum, H. scalaris, H. tiara, and Pseudhymenolepis redonica) and 3 species of nematodes (Pseudophysaloptera sp. located in the stomach, Stammerinema rhopocephala larvae in the intestine and abdominal cavity, and Porrocaecum sp. in the thoracic and abdominal cavities). Bivariate (species pairs) versus multivariate analyses (associations within the entire set of species) were performed of presence-absence and of quantitative records (influence of intensity on associations). The associations were evaluated with respect to the sex and age of the host and to the sampling date and sites. The host and environment played a limited role, and the major determinant of species assemblage was phylogenetic. Positive associations were found among both the cestodes and the nematodes, whereas negative associations were found between cestodes and nematodes. The type of life cycle was probably the second greatest determinant of species associations. Nematodes using shrews as a paratenic host or as their definitive host were both positively associated.     

Phylogeographical footprints of the Strait of Gibraltar and Quaternary climatic fluctuations in the western Mediterranean: a case study with the greater white-toothed shrew, Crocidura russula (Mammalia: Soricidae)

We used mitochondrial cyt b sequences to investigate the phylogenetic relationships of Crocidura russula (sensu lato) populations across the Strait of Gibraltar, western Europe, Maghreb, and the Mediterranean and Atlantic islands. This revealed very low genetic divergence between European and Moroccan populations. The application of a molecular clock previously calibrated for shrews suggested that the separation of European from Moroccan lineages occurred less than 60 000 bp, which is at least 5 million years (Myr) after the reopening of the Strait of Gibraltar. This means that an overwater dispersal event was responsible for the observed phylogeographical structure. In contrast, genetic analyses revealed that Moroccan populations were highly distinct from Tunisian ones. According to the molecular clock, these populations separated about 2.2 million years ago (Ma), a time marked by sharp alternations of dry and humid climates in the Maghreb. The populations of the Mediterranean islands Ibiza, Pantelleria, and Sardinia were founded from Tunisian populations by overwater dispersal. In conclusion, overwater dispersal across the Strait of Gibraltar, probably assisted by humans, is possible for small terrestrial vertebrates. Moreover, as in Europe, Quaternary climatic fluctuations had a major effect on the phylogeographical structure of the Maghreb biota.     

Sperm characters of the digenean Nephrotrema truncatum (Troglotrematidae): a kidney parasite of Crocidura russula (Soricidae) and their phylogenetic significance

ABSTRACT

Spermatological characteristics of the troglotrematid digenean Nephrotrema truncatum, a parasite of the shrew Crocidura russula, have been investigated by means of transmission electron microscopy. The ultrastructural study reveals that the mature spermatozoon of N. truncatum exhibits many ultrastructural characters previously described in most gorgoderoideans. These are two axonemes of the 9+‘1‘ trepaxonematan pattern, four attachment zones, a lateral expansion, an external ornamentation of the plasma membrane associated with spine-like bodies and cortical microtubules, and in the posterior part of the anterior spermatozoon region, two bundles of parallel cortical microtubules with the maximum number located in the anterior part of the spermatozoon, a nucleus, two mitochondria, and granules of glycogen. The obtained results are compared with those of other digeneans, particularly the Gorgoderoidea. The sperm cells gorgoderoideans are of type IV, characterised by a 9+‘1‘ pattern of axonemes, the presence of an external ornamentation associated with cortical microtubules and located in the posterior area of the anterior extremity, the presence of two bundles of cortical microtubules, the maximum number of cortical microtubules located in the anterior region of the spermatozoon, and the presence of generally two mitochondria. However, dicrocoeliids and troglotrematids have spermatozoa with ornamentation of the plasma membrane and lateral expansions.     

Systematics of white-toothed shrews (Crocidura) (Mammalia: Insectivora: Soricidae) of Taiwan: Karyological and morphological Studies

We define the species boundaries of white-toothed shrews (genus Crocidura ) in Taiwan using karyological and morphological characteristics. Ninety-nine animals were obtained from all over Taiwan at capture rates usually less than 10%. Three species are recognized by distinct cytotypes: Crocidura attenuata tanakae 2n = 40, FN = 56; Crocidura suaveolens hosletti 2n = 40, FN = 50; Crocidura kurodai 2n = 40, FN = 54. A suite of six morphological characters diagnose the three species: shape of skull, position of incisive foramina, shape of fourth upper premolar, shape of pinna, tail vibrissae, and foot pads. A species key and notes on the life history of each species are provided. Finally, we discuss chromosomal evolution and biolgeography of Crocidura in East and South East Asia.     

Molecular phylogenetics of shrews (Mammalia: Soricidae) reveal timing of transcontinental colonizations

We sequenced 2167 base pairs (bp) of mitochondrial DNA cytochrome b and 16S, and 1390 bp of nuclear genes BRCA1 and ApoB in shrews taxa (Eulipotyphla, family Soricidae). The aim was to study the relationships at higher taxonomic levels within this family, and in particular the position of difficult clades such as Anourosorex and Myosorex. The data confirmed two monophyletic subfamilies, Soricinae and Crocidurinae. In the former, the tribes Anourosoricini, Blarinini, Nectogalini, Notiosoricini, and Soricini were supported. The latter was formed by the tribes Myosoricini and Crocidurini. The genus Suncus appeared to be paraphyletic and included Sylvisorex. We further suggest a biogeographical hypothesis, which shows that North America was colonized by three independent lineages of Soricinae during middle Miocene. Our hypothesis is congruent with the first fossil records for these taxa. Using molecular dating, the first exchanges between Africa and Eurasia occurred during the middle Miocene. The last one took place in the Late Miocene, with the dispersion of the genus Crocidura through the old world.     

Comparative aspects of lipid metabolism in two shrews (Suncus etruscus and Crocidura russula).

1. The amounts of tissue lipids were higher in S. etruscus than in C. russula. 2. The level of liver phospholipids was specially low in C. russula, 2650 mg/100 g as opposed to 3725 g in S. etruscus. 3. This is in good agreement with a reduced rate of the labelled acetate incorporation into the lipids of C. russula. 4. The proportion of unsaturated fatty acids was greater in the liver of S. etruscus; however, the percentage of arachidonic acid was higher in C. russula--15% as opposed to 8%.     

White-toothed shrews (Mammalia, Soricomorpha, Crocidura) of coastal islands of Vietnam

New findings of the white-toothed shrews (Crocidura spp.) from offshore islands of Vietnam are reported. The species identifications have been confirmed by the analysis of complete mitochondrial cytochrome b gene (1140 bp). Crocidura phuquocensis is the only species found in the Phu Quoc Island. Crocidura fuliginosa has been recorded from two islands of the Con Dao Archipelago (Con Son and Bai Canh). The occurrence of Crocidura fuliginosa in Vietnam has been genetically confirmed for the first time. Crocidura attenuata has been collected from the Cat Ba Island for the first time, and this finding corresponds well with the proposal that the species' distribution is confined to the north and east of the Red River only.     

Soricidae (Mammalia) from the Early Pleistocene of Olduvai Gorge, Tanzania

Soricid remains collected from Bed I of Olduvai Gorge are described. The great majority of the specimens are mandibles. A survey of the mandibles of living African species revealed many differences in characters of the lower teeth and jaw that can be used for identification. On the basis of these characters, nine species are distinguished in the Olduvai collection, of which six are well enough preserved to permit a discussion of their relationships to living species. Three new species and one new subspecies are described. All the Olduvai shrews differ in some respects from their nearest living relatives; three species are close to species from Makapansgat, Swartkrans and Sterkfontein, RSA, though there appear to be slight differences. A change in the soricid fauna takes place within Bed I, interpreted as due to increasing aridity.     

Phylogenetic evolution and biogeography of Southeast Asian shrews (genus Crocidura: Soricidae)

Genetic variation of 20 species of shrews from the Malay peninsula, Sumatra, Java, Borneo, the Philippines and Sulawesi was assessed by allozyme electrophoresis at 32 loci. According to Mantel's tests, the genetic differentiation of these species of shrews is not a function of the geographic distance separating them (r = 0.09, NS), but is correlated to the water depth surrounding the islands where they live (r = 0.49, P < 0.01). The results are just the reverse if the correlations are computed for the Sunda Shelf taxa only. In this case, the sampled populations show an isolation-by-distance relationship (r = 0.32; P < 0.01), while no significant correlation with water depth was detected (r = 0.20; P - 0.07). Qualitative predictions based on eustatic sea level variation and water depth were formulated as a model of historic connections between the islands. This palaeogeographic model was tested through Brooks Parsimony Analysis. The assumption of a simple vicariant evolution of the shrews was rejected, but several concordant patterns indicate that the phytogeny of these mammals was indeed shaped by these events. Homoplasies demonstrated that the SE Asian species of Crocidura include composite zoogeographic histories. Sulawesi, for example, supports at least six species, five of which are closely related, while the last one, C. nigripes, is more closely related to a Bornean taxon. This pattern was interpreted as the result of a first wave of colonizers which subsequently radiated, followed by a more recent, second colonization event from Borneo. The overall small genetic distance found within the assemblage of the five old endemics (D_N= 0.151 pL 0.041) suggests that the radiation was not accompanied by extensive differentiation, although from a karyological point of view, they exhibit unusual variations when compared to other Indomalayan Crocidura. By contrast, the four species found on Sumatra are more differentiated (D_N= 0.221 pL 0.063) and never form sister-group relationships in any phylogenetic reconstruction; each one is more closely related to different taxa living outside Sumatra. This suggests that they are probably remnants of an important centre of dispersal for the entire Malay Archipelago. The standard genetic distance averaged among all Southeast Asian species (D_N= 0.235 pL 0.094) is about half that measured within Palearctic or African taxa. Such an overall lower mean level of genetic variability is consistent with the hypothesis of a relatively recent colonization of the Malay Archipelago by shrews of the genus Crocidura.     

西藏林芝发现烟黑缺齿鼩

2018年11月,在西藏自治区林芝地区波密县扎木镇（29°48′25″ N,95°41′56″ E）海拔3 400 m处捕获1只缺齿鼩属动物。该个体背毛深灰色,腹面毛色稍淡,呈苍灰色;尾长明显大于头体长,背腹异色不明显,尾部末端缺少簇毛;头骨坚固,头盖骨隆起明显,颧骨板很窄,齿式3.1.1.3/2.0.1.3 = 28,这些特征与烟黑缺齿鼩（Chodsigoa furva）的鉴别特征一致。通过测定其Cyt b基因全序列,并结合从GenBank下载的缺齿鼩属已有同源序列构建的最大似然树显示,该个体与烟黑缺齿鼩聚为一支（支持率BS为100）,与云南地区烟黑缺齿鼩的遗传距离在2.25% ~ 2.34%之间。基于以上形态和分子结果确认该个体为烟黑缺齿鼩,是该物种在西藏的首次分布记录。     

Habitat, morphology and karyotype of the Saharan shrewCrocidura tarfayaensis (Mammalia: Soricidae)

The Saharan shrewCrocidura tarfayaensis Vesmanis and Vesmanis, 1980, has a limited disribution along the Atlantic coast of Sahara, south of Agadir (Morocco) through Western Sahara into Mauritania and is only known from few captures and some owl pellets. Here we report field data from the successful trapping of five specimens ofC. tarfayaensis in the Guelmim region. The habitat was characterized by sand dunes along a river, with dense shrubberies ofTamarix sp., the huge grassErianthus ravennae (Poaceae) and flat bushes of Atriplex glauca var. ifniensis (Chenopodiaceae). Morphological discrimination withC. whitakeri were examined. The chromosomes ofC. tarfayaensis revealed a karyotype of 2n = 36, similar to that of the Canary shrewC. canariensis and the Sicilian shrewC. sicula. In conclusion,C. tarfayaensis seems to be a descendant of the presumed continental ancestor of the two island species.     

Coevolution between simple sequence repeats (SSRs) and virus genome size

ABSTRACT: BACKGROUND: Relationship between the level of repetitiveness in genomic sequence and genome size has been investigated by making use of complete prokaryotic and eukaryotic genomes, but relevant studies have been rarely made in virus genomes. RESULTS: In this study, a total of 257 viruses were examined, which cover 90% of genera. The results showed that simple sequence repeats (SSRs) is strongly, positively and significantly correlated with genome size. Certain repeat class is distributed in a certain range of genome sequence length. Mono-, di- and tri- repeats are widely distributed in all virus genomes, tetra- SSRs as a common component consist in genomes which more than 100 kb in size; in the range of genome < 100 kb, genomes containing penta- and hexa- SSRs are not more than 50%. Principal components analysis (PCA) indicated that dinucleotide repeat affects the differences of SSRs most strongly among virus genomes. Results showed that SSRs tend to accumulate in larger virus genomes; and the longer genome sequence, the longer repeat units. CONCLUSIONS: We conducted this research standing on the height of the whole virus. We concluded that genome size is an important factor in affecting the occurrence of SSRs; hosts are also responsible for the variances of SSRs content to a certain degree.