Species composition,abundance, and annual cycles of fleas (Siphonaptera) on bank voles (Clethrionomys glareolus) in the western part of Vologda Province (Babaevo District)

A total of 383 fleas of 11 species were collected off 428 bank voles (Clethrionomys glareolus) captured near Babaevo (59°4′N, 35°8′E). Three of the species recorded (Amphipsylla rossica, Doratopsylla dasycnema, and Palaeopsylla soricis) were not typical of these rodents, infesting the latter occasionally from other animals, such as the common vole Microtus arvalis and shrews inhabiting adjacent or the same biotopes. Peromyscopsylla bidentata, infesting the bank vole in most part of its range, was recorded only as a single female. Megabothris turbidus was also very rare, being sporadically recorded from May to October; the examined territory probably lies at the northern boundary of its range. The most abundant species, Ctenophthalmus uncinatus, had two peaks of abundance: in April, when adults emerged from overwintered cocoons, and in July. Then their abundance decreased and the last occasional individuals were recorded till December. The year-round parasite Amalaraeus penicilliger was most abundant in winter. Other species were few in number. Adults of Megabothris rectangulatus were recorded from April to August with two peaks of abundance: in April, when they emerged from overwintered cocoons and in July, when the second generation emerged. The univoltine species Peromyscopsylla silvatica emerged in July–August and parasitized till September. Rhadinopsylla integella was the most abundant in October–December, but occasional specimens were recorded in January. The polyxenous species Hystrichopsylla talpae emerged in late July and occurred till September.     

The seasonal dynamic of fleas (Siphonaptera) abundance on apodemus uralensis in the northen part of Novgorod Region

Seven fleas species were revealed on Apodemus uralensis. Only three of them (Ctenophthalmus agyrtes, Ct. uncinatus, Megabothris turbidus) are the main parasites of this rodent species and have similar phenology of imago. They appear in April, parasitise during spring and summer periods and disappear in autumn, in September-October. The abundance of all three species shows two peaks in a year, which correspond to two generations. Four species (Amalaraeus penicilliger, Ct. bisoctodentatus, Peromyscopsylla bidentata, P. silvatica) are not peculiar to Apodemus uralensis. They pass on this host species occasionally from other animals inhabiting forest biotopes.     

Androgen-dependent proteins in the urine of bank voles (Clethrionomys glareolus)

The concentration of proteins in the urine of adult bank vole males was higher than that in urine of immature males and females. After separation of the urine by polyacrylamide gel electrophoresis in the presence of SDS, the principal urinary protein had a slightly lower mobility than cytochrome C. Urine from females or castrated males contained only trace amounts of this protein. Injection of testosterone into castrated males increased this protein band. We suggest that bank vole males, like those of rats and mice, synthesize and release in their urine an androgen-dependent protein fraction.     

Breeding of captive bank voles (Clethrionomys glareolus) related to dynamics of source populations

Proportionately fewer female bank voles from cyclic or dense populations bred than did females from sparse or non-cyclic populations when brought into a laboratory and kept as monogamous pairs for at least 1 year. Similarly, fewer litters were produced by females from cyclic or dense populations. Breeding frequency and litter production did not differ in the second laboratory generation. Large variance in litter numbers indicated further changes in reproduction in response to the laboratory environment. Certain differences between origins still persisted after long-term laboratory breeding. The regional variations between field-born animals are most parsimoniously explained by differences in sensitivity to density.     

Seasonal effects on sexual maturation of male bank voles (Clethrionomys glareolus)

The weights of the testes and accessory glands, and the degree of morphological and functional development of the seminiferous tubules, were used as indicators of sexual maturation in male bank voles. Males reared under constant laboratory conditions showed a significant relationship between the seasons and sexual maturation. Young males reached maturity most rapidly in the reproduction season (mid-April to mid-October), while adult males matured earlier, in the spring season (mid-January to mid-April). The influence of season on animals reared in outdoor cages was much more pronounced. One of the important factors was the photoperiod: animals reared from 3 to 12 weeks of age in a short photoperiod (8L:16D) matured less rapidly than did those reared in 16L:8D.     

Delayed implantation in lactating bank voles, Clethrionomys glareolus.

The time of blastocyst implantation in lactating and non-lactating female bank voles was studied. In primiparous females implantation started 4 days and 9-11 h after mating. A delayed implantation of at least 1 1/2 days was found in lactating, multiparous females when compared to non-lactating, multiparous and primiparous females.     

Indication of a genetic basis of stereotypies in laboratory-bred bank voles (Clethrionomys glareolus)

The development of stereotypies was studied in two successive laboratory-bred generations of bank voles representing F1 (n=248) and F2 (n=270) of an originally wild caught stock. It was shown that the propensity to develop stereotypies under barren housing conditions strongly relates to the same propensity of the parents. Stereotypies were approximately seven times more frequent in the offspring of stereotyping parents than in the offspring of permanent non-stereotypers. This held true even when only one of the parents was stereotyper. The paternal and maternal contributions to stereotypies in the offspring appeared to be equal. Males showing stereotypies but prevented from any physical contact with the offspring were as potent as stereotyping females in producing stereotyping offspring. Moreover, the specific type of stereotypy appearing in the offspring after isolation was very much related to the type of stereotypy developed in the mothers. We found no support for the possible importance of social facilitation from littermates, in that the development of stereotypies was independent of the length of time the voles were kept socially with littermates before isolation. We suggest that the possible genetic basis of individual differences in the propensity to develop stereotypies in captivity may result from differences in genetic predispositions and their interactions with discrete frustrating stimuli early in life and/or to genetically different predispositions to cope with frustrating experiences later in life.     

Hantavirus antibody occurrence in bank voles (Clethrionomys glareolus) during a vole population cycle

Puumala virus, genus Hantavirus, is the etiologic agent of nephropathia epidemica, a mild form of hemorrhagic fever with renal syndrome. The bank vole (Clethrionomys glareolus) is the natural reservoir species of this hantavirus. We initiated sampling of bank voles at sites of recently identified human nephropathia epidemica cases and paired control sites in the fall of 1995 in coastal areas of northern Sweden. Sites were trapped annually in spring and fall until 1999. Prevalence of antibody to Puumala virus was similar among local bank vole populations in the two types of sites over time. During peak years, however, the absolute number of bank voles was higher in case sites than control sites. Consequently, the likelihood of Puumala virus exposure was increased at case sites during population highs. This would imply that the risk of Puumala virus exposure to conspecifics and humans is habitat and site dependent with a temporal component.     

Influence of age and artificial vaginal stimulation on fertility in female bank voles (Clethrionomys glareolus)

Female bank voles mated when 30-50 days old showed only 20-25% fertility at the first mating, but fertility increased to about 80% in animals greater than 100 days of age at the first mating. Young females subjected to artificial cervical stimulation after the completion of a normal mating showed a much higher fertility than normally mated controls (76 compared with 29%). The reason for the low fertility therefore appears to be that young females require more stimulation to activate the corpora lutea than is normally received at a mating.     

Behavioural development of conspecific odour preferences in bank voles,Clethrionomys glareolus

Biological odours of conspecifics are known to have strong influences on behavioural interaction in bank voles Clethrionomys glareolus. This experiment tested two hypotheses. (1) Olfactory cues from familiar and unfamiliar mature opposite-sex conspecifics differ in their attractiveness to males and females, and their behavioural reactions change with age. (2) A genetically based mechanism is involved in female recognition of kin.In a two-choice preference test, prepubertal males and females were more attracted to familiar than to unfamiliar odours of opposite-sex conspecifics, as manifested by more time spent sniffing familiar voles. As the young reached sexual maturity they shifted their odour preferences. Mature males and females preferred the novel odour of unrelated opposite-sex conspecifics to that of relatives. The results of experiments testing the second hypothesis indicate that females use a genetically based mechanism to recognise their kin. Young and mature females were able to recognise the odour of their biological but socially unknown fathers, and showed the same pattern of behaviour as females in previous experiments.The possible biological functions of kin recognition in bank voles are discussed.     

The influence of cage size and environmental enrichment on the development of stereotypies in bank voles (Clethrionomys glareolus)

Bank voles were bred and lived in 4 different environments: small barren cages (SB), small enriched cages (SR), big barren cages (BB) and big enriched ones (BR). Ten different behaviours were recorded at the age of 30, 45, 60, 61, 75 and 90 days. Between day 60 and 61, within each experimental environment, the group of voles performing stereotypies (ST) and the group of those which did not (NST) were each split in two, one part being transferred to a new environment, the other remaining in the same as control. For each of the 10 behaviours, differences between the 4 environments and therein differences between the ST and the NST animals and between the age groups were analysed with a split-plot ANOVA.The results indicated that enrichment is more determinant than cage size, as more voles developed stereotypies in SB and BB than in SR and BR.Improving the environment after day 60 inhibited the stereotypies in most ST animals, while smaller and/or barren environments elicited them in very few NST.ST voles performed significantly more rearing and walking-sniffing and showed significantly less immobility than NST ones. These differences remained linked to the ST/NST status when an animal reversed it after day 60.Within different environments, some individuals are more prone to react actively to frustration, including the development of stereotypies. The performance of stereotypies is associated with a more general behavioural activation.     

Morphological variations in the preputial gland of wild bank voles, Clethrionomys glareolus

The size and appearance of the preputial glands of Clethrionomys glareolus showed variations which were associated with season, sex and maturation. The glands were by far largest in mature males followed by mature females, and subadult males and females, in that order. There was a positive relationship between the length, fresh weight and dry weight of the glands. The possible role of the preputial glands in relation to territorially, social status and sexual attraction is discussed.     

Ultrastructural studies on the thymus gland after the administration of phenylhydrazine to bank voles (Clethrionomys glareolus)

The thymus glands of wild and laboratory reared bank voles (Clethrionomys glareolus) were examined for ultrastructural changes before and after the administration of low (20 mg/kg) and high (60 mg/kg) doses of phenylhydrazine (PhZ) given intraperitoneally on days 0, 1 and 3 of a dosing regime. Erythrocytes developed in focal aggregations in the subcapsular and outer cortical zones. There was a marked depletion of the subcapsular cortex following drug treatment that was reversed with time. A large number of granulocytes were visible in the cortex after PhZ, and mast cells developed in situ.     

Sex and age-specific differences in ultraviolet reflectance of scent marks of bank voles (Clethrionomys glareolus)

Scent markings of voles are visible via their ultraviolet reflection. Kestrels, and possibly other diurnal raptors, may use this property when hunting. We performed a laboratory study on bank voles to determine whether UV-reflectance of scent marks differs in relation to sex, age and social status. When reflectance spectra of scent marks were measured with a spectroradiometer, we found UV reflectance to be strongest in mature males. There were no differences between mature females and immature juveniles, nor between sexes in juveniles or mature and immature individuals in females. Moreover, we did not find any difference in UV reflectance between dominant and subordinate mature males. The results of this study support earlier findings that UV sensitive predators may use UV reflectance of scent marks as a prey cue. Consequently, studies on differing vulnerability of voles to avian predators should take into account not only their space use and behaviour but also the UV reflectance of their scent marks. Accepted: 21 August 1999     

Biological activity of soils in the settlements of southern (Microtus rossiaemeridionalis) and bank (Clethrionomys glareolus) voles

The effect of southern (Microtus rossiaemeridionalis) and bank (Clethrionomys glareolus) voles on the biological activity of soddy-podzolic soil and agrozem has been studied. To estimate this effect, the activity of nitrogen and carbon transformation in the soil taken from the paths and different chambers of the holes of these rodents, as well as from the control plots where there were no voles, has been determined. The contents of organic carbon and nitrogen in the soil have been found. The parameters of functional diversity of the microbial community of soil have been studied. It has been noted that the effect of voles on the biological activity of the above soils manifested itself in increased intensity of aerobic and anaerobic destruction of organic matter and changes in the parameters of functional diversity of the microbial community of soils.     

Fertility of the post-partum bank vole (Clethrionomys glareolus)

Analysis of records of a bank vole breeding colony suggests that fertility is high immediately post partum, declines during established lactation and rises after weaning of young. Mating tests with lactating females and females whose young had been removed at birth showed that receptivity is reduced during lactation, although amongst the females which did mate there was no difference between lactating and non-lactating animals in the proportion which produced litters. However, average size of litters at birth was significantly larger for the lactating than for the non-lactating females. There is some evidence suggesting that this difference may arise after ovulation has occurred. Virgin females were no more receptive or fertile than lactating females.