Enzootic transmission of deer tick virus in New England and Wisconsin sites. (33/710)

To determine whether rodents that are intensely exposed to the deer tick-transmitted agents of Lyme disease, human granulocytic ehrlichiosis, and human babesiosis are also exposed to deer tick virus (DTV), we assayed serum samples from white-footed mice (Peromyscus leucopus) and meadow voles (Microtus pennsylvanicus) in sites densely infested by deer ticks. To conduct serosurveys, we developed an enzyme-linked immunosorbent assay (ELISA) and Western blot assay by cloning, expressing, and purifying a portion of the DTV envelope glycoprotein (DTV rE) for use as test antigen. Sera from mice and voles trapped in Massachusetts, Rhode Island, and Wisconsin were screened by ELISA for IgG reactive to DTV rE. Samples that were positive or borderline by ELISA were subsequently analyzed by immunoblotting. Samples reactive in both assays were considered to be positive. Three percent of 264 mouse samples collected from sites in Rhode Island, 3.8% of 52 samples from mice trapped in Wisconsin, and 3.9% of 282 samples collected from mice trapped on Nantucket Island, MA were positive. No samples from either Great Island, MA, or voles from any study site were reactive. A reverse transcriptase-polymerase chain reaction yielded molecular evidence of DTV infecting questing adult deer ticks in sites where seroreactive mice were trapped, but not from ticks collected where serologic evidence of virus perpetuation was absent. White-footed mice appear to be exposed to DTV in certain sites where other deer tick-borne agents perpetuate. This virus may be maintained in the same enzootic cycle.  (+info)

Nonlinearity in the predation risk of prey mobility. (34/710)

Odorous waste products such as urine and faeces are unavoidable for most animals and are widely exploited by predators and their prey. Consequently, waste accumulations can be risky and prey which increase their mobility in order to disperse and dilute their waste should avoid a high predation risk until this benefit is balanced by the increasing risks of random predator encounter. This hypothesis was tested for voles (Microtus spp.) in Finland which are vulnerable to predation due to the scent and ultraviolet attractiveness of their urine. The mortality and mobility of radio-collared voles showed a U-shaped relationship, regardless of vole sex, species or population cycle phase. The low risks for prey making intermediate movements suggest that predation risk can exert strong selective pressures on prey such that they have little respite from the risk of being killed.  (+info)

Mechanisms of reproductive suppression in female pine voles (Microtus pinetorum). (35/710)

In co-operatively breeding birds and mammals, philopatric females are often reproductively suppressed. Many studies have focused on the functional significance of reproductive suppression, but further investigation of the mechanisms involved is required for a complete understanding of this process. This study investigated whether reproductive suppression in non-reproductive female pine voles (Microtus pinetorum) occurs as a result of lack of gamete maturation or lack of increase in LH. The behaviour of male pine voles was also examined to determine whether they show a preference for the mother versus her daughter, as lack of male stimulation may inhibit an increase of LH in daughter pine voles. Ovarian development and circulating LH concentrations were investigated in females housed with a prospective mate in the presence or absence of a parent. Maturation of gametes was not affected by the presence of a parent. In the presence of the mother, there was no increase in LH, as was observed in females housed with or exposed to a novel male. Males spent more time with mothers and possibly showed a preference for mating with the mother. These results are consistent with the contention that ovulation does not occur in female pine voles housed in the presence of their mother; however, it is not clear whether the lack of ovulation is caused by lack of stimulation from the male or suppression by the mother.  (+info)

DNA sequence variation in the mitochondrial control region of red-backed voles (Clethrionomys). (36/710)

The complete mitochondrial DNA (mtDNA) control region was sequenced for 71 individuals from five species of the rodent genus Clethrionomys both to understand patterns of variation and to explore the existence of previously described domains and other elements. Among species, the control region ranged from 942 to 971 bp in length. Our data were compatible with the proposal of three domains (extended terminal associated sequences [ETAS], central, conserved sequence blocks [CSB]) within the control region. The most conserved region in the control region was the central domain (12% of nucleotide positions variable), whereas in the ETAS and CSB domains, 22% and 40% of nucleotide positions were variable, respectively. Tandem repeats were encountered only in the ETAS domain of Clethrionomys rufocanus. This tandem repeat found in C. rufocanus was 24 bp in length and was located at the 5' end of the control region. Only two of the proposed CSB and ETAS elements appeared to be supported by our data; however, a "CSB1-like" element was also documented in the ETAS domain.  (+info)

A new geographical gradient in vole population dynamics. (37/710)

A new geographical gradient in the dynamics of small rodents is demonstrated by analysing 29 time series of density indices of the common vole (Microtus arvalis) from Poland, the Czech Republic and the Slovak Republic. This gradient extends from more stable northerly populations in coastal Poland to more variable and cyclic populations in the southernmost parts of the Slovak Republic, and is hence a reversal of the Fennoscandian gradient. All studied variables (such as mean density, cycle amplitude, density variability and the coefficients in a second-order autoregressive model) exhibit consistent latitudinal variation. Possible underlying factors are discussed. In particular, we suggest that seasonality may be a key element in explaining the observed new gradient.  (+info)

Facilitation of affiliation and pair-bond formation by vasopressin receptor gene transfer into the ventral forebrain of a monogamous vole. (38/710)

Behaviors associated with monogamy, including pair-bond formation, are facilitated by the neuropeptide vasopressin and are prevented by a vasopressin receptor [V1a receptor (V1aR)] antagonist in the male prairie vole. The neuroanatomical distribution of V1aR dramatically differs between monogamous and nonmonogamous species. V1aR binding is denser in the ventral pallidal region of several unrelated monogamous species compared with nonmonogamous species. Because the ventral pallidum is involved in reinforcement and addiction, we hypothesize that V1aR activation in this region promotes pair-bond formation via a mechanism similar to conditioning. Using an adeno-associated viral vector to deliver the V1aR gene, we increased the density of V1aR binding in the ventral pallial region of male prairie voles. These males exhibited increased levels of both anxiety and affiliative behavior compared with control males. In addition, males overexpressing the V1aR in the ventral pallidal region, but not control males, formed strong partner preferences after an overnight cohabitation, without mating, with a female. These data demonstrate a role for ventral pallidal V1aR in affiliation and social attachment and provide a potential molecular mechanism for species differences in social organization.  (+info)

Immunological characteristics of natural resistance in Microtus fortis to infection with Schistosoma japonicum. (39/710)

OBJECTIVE: To explore the immunological characteristics of natural resistance to Schistosoma japonicum infection in Microtus fortis (MF) living in the Dongting Lake area. METHODS: Passive transfer of sera from uninfected laboratory bred MF (BMF) to albinao mice (AM) was performed to observe the acquired protection. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and enzyme-linked immunoblotting (ELIB) methods were used to recognize 4 different life-cycle stage antigens of S. japonicum by sera from wild MF (WMF), BMF, BMF13 and BMF19. Tests were also performed on in vitro killing effect of sera and/or lymphocytes from BMF and WMF to schistosomulae; quantitative determination of C3 and C4 by immunoturbidometry, and interleukin-4 (IL-4) and antibodies to the 4 stage antigens in sera from WMF, BMF and infected BMF by ELISA. RESULTS: Compared with the control group, stool eggs per gram (EPG) of AM in the test group was significantly reduced by 81.54%, miracidium hatching rate, by 50.67%, liver egg counts, by 72.07%, the diameter of hepatic egg granuloma, by 70.39 microns. Western blotting probed with the 4 MF sera all revealed 7 specific bands for SSA, 3 for AWA and SEA, but none for CA antigens. The sera and/or lymphocytes from WMF and BMF gave obvious killing effects on schistosomulae with an adjusted death rate of 64.12%-78.83%. The levels of "natural antibodies" produced by MF to S. japonicum were in the following order: anti-SSA > anti-AWA > anti-SEA > anti-CA, all of which increased significantly after the infection. Serum levels of C3, C4 and IL-4 in uninfected BMF were significantly higher than those in AM. After infection, levels of C3 and C4 were further increased respectively by 72.83% and 295.49% in the 4th week and IL-4 by 303.83% in the 9th day. CONCLUSIONS: Immunological characteristics of innate resistance in M. fortis to S. japonicum infection were existed with no significant difference between WMF and BMF.  (+info)

Phase coupling and synchrony in the spatiotemporal dynamics of muskrat and mink populations across Canada. (40/710)

Population ecologists have traditionally focused on the patterns and causes of population variation in the temporal domain for which a substantial body of practical analytic techniques have been developed. More recently, numerous studies have documented how populations may fluctuate synchronously over large spatial areas; analyses of such spatially extended time-series have started to provide additional clues regarding the causes of these population fluctuations and explanations for their synchronous occurrence. Here, we report on the development of a phase-based method for identifying coupling between temporally coincident but spatially distributed cyclic time-series, which we apply to the numbers of muskrat and mink recorded at 81 locations across Canada. The analysis reveals remarkable parallel clines in the strength of coupling between proximate populations of both species--declining from west to east--together with a corresponding increase in observed synchrony between these populations the further east they are located.  (+info)