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PubMed1996

Heart and respiratory rates and their significance for convective oxygen transport rates in the smallest mammal, the Etruscan shrew Suncus etruscus.

Heart and respiratory rates of the smallest mammal (mean adult body mass 2g), the Etruscan shrew Suncus etruscus, were determined at rest and under stress conditions. Heart rate was obtained from electrocardiograms (ECGs), recorded via foot electrodes. The mean +/- S.D. heart rate of resting animals (ambient temperature 22 degrees C) was 835 +/- 107 min-1, the mean maximal rate amounted to 1093 +/- 235 min-1. The highest single value recorded was 1511 min-1, which is the highest heart rate reported so far for an endotherm. The respiratory rate was also obtained from ECG recordings, which showed the electrical activity of the breathing muscles during inhalation, and additionally by recording the movements of the thoracic wall with a laser autofocus system. The mean resting respiratory rate was 661 +/- 93 min-1, the mean maximal rate was 758 +/- 109 min-1 and the highest single value recorded was 894 min-1. At 22 degrees C, the specific oxygen consumption rate is 67 times higher in resting S. etruscus than in resting humans. Under these conditions, the respiratory rate of the shrew is 47 times higher but the heart rate only 12 times higher than in man. Therefore, to achieve an adequate circulatory oxygen transport rate, the product of relative stroke volume and arterio-venous O2 difference has to be 5.6 times higher in the shrew than in man, whereas for an appropriate ventilatory oxygen transport rate the product of relative tidal volume and oxygen extraction has to be only 1.4 times higher in this small insectivore than in man. The maximal possible oxygen transport rates of the ventilatory and the circulatory system have been estimated and compared with the diffusional transport capacity of the lung. These rates amount to approximately 1000 ml O2 kg-1 min-1. According to our results and data in the literature, an aerobic scope of 7-10 seems to be realistic for the Etruscan shrew.

Animals↗
PubMed1999

Sequence variation and evolution of the mitochondrial DNA control region in the musk shrew, Suncus murinus.

The complete mitochondrial DNA (mtDNA) control region was cloned and sequenced in the musk shrew, Suncus murinus, Insectivora. The general aspect was similar to that found in other mammals. We have found in two locations of this region the presence of arrays of tandem repeats like those in other shrew species. One array was located in the left domain containing the termination-associated sequences (TAS) and the length of a copy was 77 bp. The other repeats were situated upstream from the recognition site for the end of H-strand replication in the right domain and were 20 bp long. The left halves of the control region containing the former repeats were sequenced and compared in several laboratory lines and wild animals from different localities, variations in copy number of repeated sequences were found both among individuals and within an individual. A comparative study of repeated sequences provides useful indication for the origin and evolution of tandem repeated sequences. Strand slippage and mispairing during replication of mtDNA with concerted manner is currently regarded as a dominant theory to account molecular mechanism for tandemly repeated sequences, and the pattern of sequence and length variation in our study supports this theory. Our results, however, suggest that the evolution of the repeated sequences containing the TAS in the musk shrew might go through the process of two steps; at the first step one complete repeated and several incomplete repeated sequences had reproduced in common ancestor of the shrew, and the second stage step-up of complete repeated sequences occurred with concerted evolution after differentiation into continental and insular groups.

Animals↗
PubMed1995

Relationships between morphometric and mitochondrial DNA differentiation in laboratory strains of musk shrews (Suncus murinus).

Morphometric differentiation among six strains of musk shrews (Suncus murinus) originating in Bangladesh (BAN), Sri Lanka (SRI), and four Japanese areas, Nagasaki (NAG), Okinawa Island (OKI), Tokunoshima Island (TKU), and Taramajima Island (TR), was examined by use of skull and external measurements. These data were compared with mitochondrial DNA (mtDNA) differentiation previously reported. Significant sexual dimorphism was observed in all morphometric characters of the six strains, except for two characters in the TR strain. The six strains were clearly grouped by principal component analysis into three body-size types: large BAN shrews, intermediate SRI shrews, and small Japanese shrews. By canonical discriminant analysis, the NAG strain was further distinct from the other three Japanese strains despite their apparent similarities in external morphology, and was characterized by having the most unusual shape in the six strains. No individuals were misclassified as to their geographic origin for both sexes of the six strains. The morphometric differentiation pattern based on only the first canonical variate, extracting an overall size factor, was concordant with the mtDNA differentiation pattern (rss = 0.944, P < 0.001 in males and rss = 0.930, P < 0.001 in females). In contrast, the morphometric differentiation pattern estimated from the second to the fifth canonical variates, representing shape factors, was apparently discordant with the mtDNA differentiation pattern (rss = 0.467, P > 0.05 in both sexes). It was previously reported that a partial premating reproductive isolation mechanism is caused by the difference in body size between mating pairs. Thus, body size may be a factor useful for understanding the mechanisms of population differentiation in this species.

Animals↗
PubMed1999

Morphological features of the spermatic cord in the musk shrew (Suncus murinus) with special reference to extratesticular Leydig cells.

Morphological features of the testicular artery and vein in the spermatic cord of the musk shrew (Suncus murinus) were evaluated by light microscopy, transmission electron microscopy, corrosion cast technique combined with scanning electron microscopy and immunohistochemistry. The vascular architecture in the spermatic cord of the musk shrew was simple. The testicular artery in the musk shrew was straight and accompanied by 1 to 3 branches of testicular vein. The testicular vein was also straight and anastomosed with each other in some points along its length, but it did not form a delicate pampiniform plexus. In the middle and distal portions of the spermatic cord, the tunica adventitia of the artery and vein was joined together to form a single connective tissue septum. Clusters of cells were found in this connective tissue septum in the middle portion of the cord. These cells were located close to the arterial wall and nerve endings, but they did not appear inside of neurium. They showed several typical characteristics similar to Leydig cells, and they were positive for 3beta hydroxysteroid dehydrogenase (HSD) antibody. Ultrastructural and immunohistochemical studies also indicated that the cells in cluster found in the vascular wall of the musk shrew spermatic cord may be equivalent to Leydig cells in testes. These extratesticular Leydig cells had characteristics of the active steroid-producing cell and seemed to be another source of testosterone.

3-Hydroxysteroid Dehydrogenases↗
PubMed1996

Hair growth and skin in the kinky-coat (kc) musk shrew, Suncus murinus.

Hair growth and skin structure were examined in kinky coat (kc) musk shrews, Suncus murinus. The first hair growth cycle and the development of hair bulbs were normal. Histological characteristics of hair follicles and bulbs were similar in kc/kc and normal +/kc shrews. The mean thickness of epidermis and dermis did not differ significantly between the kc/kc and +/kc shrews. And no histological abnormalities were observed in the epidermis, dermis and hypodermis of the kc/kc shrews. Consequently, it is clear that the kc mutation had no effects on the hair growth and skin structure, but caused hair shaft modifications as previously observed. These characteristics of the kc mutation were quite distinct from those of the previously reported rodent mutations causing complicated abnormalities in the hair and skin.

Animals↗
PubMed2001

Diabetic cataract of the musk shrew (Suncus murinus, Insectivora) exhibiting spontaneous non-insulin dependent diabetes mellitus (NIDDM).

The EDS colony, developed as a new laboratory colony of the musk shrew, is characterized by a high incidence of early-onset spontaneous non-insulin dependent diabetes mellitus (NIDDM). In this colony, a few diabetic shrews exhibited a cataract at 1 month after the onset of diabetes, and all diabetic shrews had bilateral cataracts at 5 months after the onset of diabetes. In contrast, cataractous animals were never observed among non-diabetic shrews. These results suggest that the cataract in the EDS colony is a diabetic complication.

Animals↗
PubMed1992

Red-eyed dilution (rd), a novel coat-color mutant gene in the musk shrew (Suncus murinus, Insectivora).

A novel coat-color mutant was found in the musk shrew (Suncus murinus). Mutant shrews were characterized by light-gray coat, pinkish skin and red eyes. Mating experiment demonstrated that the mutant character was controlled by a single autosomal recessive gene. The gene could be traced back to at least four heterozygous carriers captured in Naha city, Okinawa in 1983. The name, red-eyed dilution, was proposed for this mutant character with the gene symbol rd. Linkage analysis proved no close relationship of the rd locus with the cr (cream coat color) and ch (curly hair) loci. The red-eyed dilution shrews (+/+, rd/rd) could easily be distinguished from the cream coat shrews with dark-red eyes (cr/cr, +/+) and the double homozygotes exhibiting light-cream coat with pink eyes (cr/cr, rd/rd). The rd gene has been maintained in the OKI line about at 75% of its frequency in every generation. We have started to develop a new line triple-homozygous for the cr, ch and rd genes.

Animals↗
PubMed2003

Microparasite assemblages of conspecific shrew populations in southern California.

The microparasite component communities of 2 species of shrews, Notiosorex crawfordi and Sorex ornatus, were investigated for the first time in 2 isolated and 3 continuous landscapes in southern California. With microscopical examination, a total of 6 parasite species was found in N. crawfordi and 8 species in S. ornatus. The highest number (5) of parasite species was detected in the lungs. The corrected estimate of parasite species richness did not significantly correlate with the host abundance in either shrew species. Altitude, and also latitude in N. crawfordi, appeared to be significantly positively associated with the parasite species richness, but this could be due to a false association because of the rare occurrence of some of the parasites or the small altitude range (or both). No other landscape variable analyzed (location, size of the study site, disturbance) was significantly associated with the parasite species richness of the shrews. The parasite assemblages of the 2 shrew species were similar despite the fact that N. crawfordi has a lower metabolic rate than S. ornatus.

Animals↗
PubMed2002

Origin and migration of interneurons of the olfactory bulb in the musk shrew, Suncus murinus.

The olfactory bulb of the musk shrew, Suncus murinus, is characterized by the presence of various interneurons. Our previous report (Kakuta et al., 2001) demonstrated that positive immunoreactions for calretinin were observed in periglomerular and perinidal cells in the glomerular layer, small ovoid neurons in the external plexiform layer, and granule cells in the granule cell layer of the olfactory bulb in the musk shrew aged 1 to 5 weeks, in addition to calretinin-immunoreactive bipolar cells distributed in the anterior subependymal layer and in each layer of the olfactory bulb. To examine the origin and migration of interneurons of the olfactory bulb, we labeled generated cells by injecting 28-day-old musk shrews with 5-bromo-2'-deoxyuridine (BrdU), and detected the labeled progeny cells that survived after several intervals. BrdU-labeled cells originated in the subependymal layer around the anterior horn of the lateral ventricle, and rostrally migrated in the subependymal layer from the anterior wall of the lateral ventricle into the center of the olfactory bulb, where they radially migrated into the granule cell layer, external plexiform layer, and glomerular layer. It took 2 days to migrate rostrally in the subependymal layer from the anterior lateral ventricle to the center of the olfactory bulb, and 2 to 6 days to migrate radially from the bulbar subependymal layer into the three layers mentioned. The rate of rostralward migration of the labeled cells was estimated to be 38 microm/h, while that of radial migration, 7 to 25 microm/h. The present BrdU-labeling study, together with our previous immunohistochemical study (Kakuta et al., 2001), indicates that anterior subependymal cells differentiate into granule cells in the granule cell layer, into Van Gehuchten cells in the external plexiform layer, and into periglomerular and perinidal cells in the glomerular layer of the olfactory bulb in the musk shrew.

Animals↗
PubMed2004

Inter-male mating-like behavior in the domesticated house musk shrew, Suncus murinus.

In the present study, inter-male interaction of the domesticated house musk shrew was observed in detail under laboratory conditions. In most cases, during inter-male interaction, male house musk shrews exhibited a sequence of behavior items including tail-wagging, following, mounting and thrusting. In the minority of cases, males did not progress beyond following. Offensive behavior was not sufficiently violent to cause injury. It appeared that role assignment was decided by contact manner and vocalization. One of fundamental characters of this animal made a start of following, in which one shrew followed another, who touched and then separated. Role assignment (i.e., which male led and which followed) was decided in status battle. Roles were often reversed during following. Following behavior was maintained by 'polite' mutual contact, and the interaction progressed to thrusting in the majority cases. After role assignment, the variation in contact manner decreased. The ratio of time spent in front-and-behind contact to that spent in multi-lateral contact increased when both males commenced following behavior simultaneously. This ratio was maintained until the following male snapped after he finished thrusting. Even if the following male did not reach thrusting, he mounted the preceding male. The pairs who did not reach thrusting repeated following behavior or mounting. In those cases, while one male concentrated on touching the other to maintain following, the other attempted to divert attention from the following behavior. Male shrews were able to reach thrusting irrespective of sex.

Animals↗
PubMed1979

The occurence of coxiellosis among rodents and shrews in the Tarai area of Uttar Praedesh.

Rodents and shrews were screened for serologic evidence of Coxiella burnetii. Attempts were made to isolate the organism from the spleen and liver. Seroreactors: total positive/total tested (% positive), in rats (Rattus rattus, R. norvegicus), ground shrews (Suncus murinus), bandicoots (Bandicota indica, B. bengalensis) and the house mouse (Mus musculus), respectively, were 13/105 (12.38), 6/42 (14.3), 2/15 (13.3) and 1/7 (14.3). Of the eight rickettsial isolants recovered including four from field and household rats, three from ground shrew and one from bandicoots, only three comprising one each from rat, shrew and bandicoot, could be typed as C. burnetii. This appears to be the first record of rodents and an insectivore as reservoirs of C. burnetii in India.

Animals↗
PubMed1999

Cortical organization in shrews: evidence from five species.

Cortical organization was examined in five shrew species. In three species, Blarina brevicauda, Cryptotis parva, and Sorex palustris, microelectrode recordings were made in cortex to determine the organization of sensory areas. Cortical recordings were then related to flattened sections of cortex processed for cytochrome oxidase or myelin to reveal architectural borders. An additional two species (Sorex cinereus and Sorex longirostris) with visible cortical subdivisions based on histology alone were analyzed without electrophysiological mapping. A single basic plan of cortical organization was found in shrews, consisting of a few clearly defined sensory areas located caudally in cortex. Two somatosensory areas contained complete representations of the contralateral body, corresponding to primary somatosensory cortex (S1) and secondary somatosensory cortex (S2). A small primary visual cortex (V1) was located closely adjacent to S1, whereas auditory cortex (A1) was located in extreme caudolateral cortex, partially encircled by S2. Areas did not overlap and had sharp, histochemically apparent and electrophysiologically defined borders. The adjacency of these areas suggests a complete absence of intervening higher level or association areas. Based on a previous study of corticospinal connections, a presumptive primary motor cortex (M1) was identified directly rostral to S1. Apparently, in shrews, the solution to having extremely little neocortex is to have only a few small cortical subdivisions. However, the small areas remain discrete, well organized, and functional. This cortical organization in shrews is likely a derived condition, because a wide range of extant mammals have a greater number of cortical subdivisions.

Animals↗
PubMed1999

Diversity of the calretinin immunoreactivity in the dentate gyrus of gerbils, hamsters, guinea pigs, and laboratory shrews.

We have recently reported that calretinin (CR) immunoreactivity in the mouse dentate gyrus (DG) is prominently different from that in the rat and monkey dentate gyrus. The CR-immunoreactive (IR) neuronal components characteristic of mouse DG were (1) mossy cells in the ventral hilus, (2) punctate elements in the inner molecular layer, (3) Cajal-Retzius cells in the molecular layer, and (4) immature granule cells at the basal part of the granule cell layer, which were also IR for highly polysialylated neural cell adhesion molecule. In this study, we examine the CR-IR elements in the DG of the gerbil, hamster, guinea pig, and laboratory shrew, and compare them with those of the rat, monkey, and mouse, reported previously. We show that mossy cells are distributed throughout the dorsoventral axis in all these animals, but mossy cells in the ventral hilus of the hamster, gerbil, and laboratory shrew are CR-IR, resembling those of the mouse, whereas mossy cells of the guinea pig are CR negative, like those of the rat. The inner molecular layer, the target zone of mossy cells, was observed to contain CR-IR punctae in the hamster, gerbil, and laboratory shrew, which corresponds to the CR immunoreactivity of the mossy cells. In addition, we observed CR-IR presumed Cajal-Retzius cells in all animals examined. On the other hand, CR-IR immature granule cells were encountered in the laboratory shrew, but not in other animals. The present study reveals prominent species differences in the CR-IR elements of the DG.

Animals↗
PubMedDate not supplied

[Involvement of the common shrew, Sorex araneus (Insectivora, Soricidae), in circulation of the tick-borne encephalitis virus in south-western Siberia].

We presented the data on the abundance of immature instars of the taiga tick Ixodes persulcatus Schuize on the common shrews Sorex araneus L. in natural foci of tick-borne encephalitis in the south of Western Siberia. Basing on the results of virological and serological studies we demonstrated a low effectiveness of this host species as a donor of disease agent strains, which are predominant in the territory under study, for ticks feeding on shrews. The analysis of samples taken from the young shrews in winter and spring using reverse RNA transcription with polymerase chain reaction and ELISA revealed occurRence of subvirion components of the tick-borne encephalitis (RNA and capsid protein E) ether in brain, liver or spleen in 90 percent of shrews (n = 42). Neither hemagglutination antigen nor infectious virus have been detected. We discussed a possible epizootic role of the maintenance of non-infectious tick-borne encephalitis virus in overwintering animals.

Animals↗
PubMed2001

Anatomic and physiologic reference values in least shrews (Cryptotis parva).

BACKGROUND AND PURPOSE: The least shrew is an established animal model for reproductive and pharmacologic research. Biologic reference data are needed to assess animal health status and provide a rationale for use of novel statistical programs to evaluate the effects of orally administered substances in toxicologic and pharmacologic studies. METHODS: Organ weights, blood biochemical and hematologic values, and food and water consumption data were collected from 50-day-old shrews after two weeks' consumption of a standard feline diet. RESULTS: In general, data correlated well with values reported for other mammalian species. Plasma phosphorus concentration was high. There was a significant difference in food and water consumption per gram of body weight between shrews at lower and upper (+/- 1 SD) weight ranges for the study. The 3.2-g animals consumed 27% more food per gram of body weight than did the 5.0-g animals. CONCLUSIONS: The high phosphorus concentration was attributed to hemolysis resulting from the axillary cut method of blood sample collection. The small size of the shrew allowed demonstration of the Kleiber effect within a +/- 1 SD weight range in a single species. The phenomenon necessitates the use of statistical methods other than the typical tests establishing the significance of the differences between the means of groups for oral toxicologic and pharmacologic studies.

Animals↗
PubMed2004

A morphometric study of the amygdala in the common shrew.

The characteristic features of the common shrew amygdala (CA), as shown by volumetric comparisons of the individual nuclei, are the poor development of the lateral (LA) and basomedial (BM) nuclei as well as the particularly strong formation of the basolateral (BL) and lateral olfactory tract (NLOT) nuclei. The central (CE), cortical (CO) and medial (ME) nuclei are also well organised in this species. All these features are even more distinctly visible when the total number of neurons in the nuclei referred to are compared. A comparison of the densities of neurons in the individual nuclei with the mean numerical density of cells in the CA indicates that there are the 3 different regions within the common shrew's CA. The densities of neurons in the LA, BL, and BM are significantly lower than the mean density of cells in the CA (p < 0.05). In the CE this value does not differ from the mean (p > 0.05). In the CO, ME and NLOT the density values are significantly higher than the mean (p < 0.05). Furthermore, a similar division of the shrew's CA can, to some extent, be performed using the size parameters of the amygdaloid neurons as a marker. Interestingly, the large neurons populate less densely organised CA areas like the LA, BL and BM, whereas the small cells populate the ME and NLOT, where the neurons are densely arranged. The CE and CO occupy intermediate positions, with the neurons similar in size to the mean for the shrew's CA.

Amygdala↗
PubMed2004

Early-life nutritional environment and spatial navigation in the water shrew, Sorex palustris (Insectivora).

Studies were conducted to study the effects of early-life nutritional environment on spatial navigation ability in the water shrew (Sorex palustris), as well as to provide information on life history traits and husbandry. The mean longevity of males and females in captivity was 652.3 +/- 33.8 SD and 616.2 +/- 22.5 days, respectively. Litter sizes ranged from 5 to 8 and neonatal mass ranged from 0.71 to 0.83 g. Spatial navigation was examined by use of the Morris water apparatus, where animals were required to locate the position of an escape platform in a circular tank of water. The platform was visible (proximal cue version of the task) in some tests. In other tests it was hidden beneath the surface (distal cue version) by making the water opaque using a non-toxic white dye. The tank was divided into 4 quadrants and the position of the plafform in any quadrant could be fixed for any subject or varied between subjects. Early-life under-nutrition was achieved by maintaining some shrews on a restricted diet (received half the amount of food as did controls). Under-nutrition was found to have an adverse effect on spatial navigation. Regardless of nutritional status, shrews were able to locate a hidden plafform that was placed at the center of a given quadrant more rapidly (escape latency) when it was visible (44 to 69 sec) than when it was hidden (83 to 164 sec). Results also showed that these shrews utilize both proximal and distal cues in this spatial task. Control subjects spent more time at a location where the platform had been in a previous test (69% of the trial period) than their undernourished counterparts (45 to 51%). This is the first experimental analysis of spatial navigation and the effects of early-life under-nutrition on this task, for S. palustris.

Analysis of Variance↗
PubMedDate not supplied

[The helminth fauna of the shrew genus Sorex (Insectivora: Soricidae) in the Kandalksha nature reserve].

The helminth fauna of shrews (Sores araneus, S. caecutiens, S. minutus, S. minutissimus) from the Karelian coast and islands of the Kandalaksha nature reserve was studied. 18 helminth species belonging to 3 taxonomic groups, Trematoda (3), Cestoda (8), and Nematoda (7) were found. The main body of the helminth fauna of shrews is represented by the nematodes species Longistriata codrus, L. didas, and the cestode species Ditestolepis diaphana. Inhabiting of shrews in the insular localities leads to the decrease of the species diversity and the abundance of their helminths. The distribution ranges of the shrew parasites have been outlined more accurately.

Animals↗