A redescription of the Long-tailed Nesokia, Nesokia bunnii, and designation of a neotype (Rodentia: Muridae).

Long-tailed Nesokia, Nesokia bunnii, is a large rat restricted to the Mesopotamian marshes in Basra Province in southern Iraq. The species is known from five museum vouchers collected between March 1974 and January 1977. The type and the paratype, deposited in the Natural History Research Centre and Museum, University of Baghdad, Iraq, were destroyed during War on Iraq in 2003. By studying morphological details on three museum specimens in the Senckenberg Institution, Frankfurt a. M., Germany, we show that N. bunnii is unique among the Bandicoot rats (Nesokia and Bandicota) in having (1) rufous dorsal pelage, (2) facial mask of rufous, dark brown, grey and whitish areas, (3) whitish belly which is clearly demarcated along flanks, (4) ventral hairs white to bases, (5) woolly underfur, (6) long front claws, and (7) large tail annulation. Similar to N. indica, but in contrast to Bandicota, N. bunnii displays short incisive foramina, posterior margin of hard palate which terminates at the level of the third molar, and robust, hypsodont and laminate molars which lack posterior cingula. To objectively define the taxon we designate a neotype, which was collected at Saraifa, 30 km north of Qurna, Iraq. Our study highlights the importance of museum collections in documenting biodiversity and the indifference of decision makers and international institutions regarding their safe future.

A new species of the rodent genus Hylomyscus from Angola, with a distributional summary of the H. anselli species group (Muridae: Murinae: Praomyini).

A new species of Hylomyscus, H. heinrichorum, is described from mountains in western Angola. Based on morphological traits and cranial morphometry, the new species is assigned to the H. anselli species group and is hypothesized to be most closely related to H. anselli Bishop proper, a species named from Zambia. Members of both the H. anselli and H. denniae species groups occupy the Afromontane Biotic Zone, found in various mountain systems to the south and east of the Congo Basin. Evidence is reviewed that supports the independent radiation of these two species groups within montane forest from different Guineo-Congolian ancestral stocks.

Dietary protein influences the life-history characteristics across generations in the African striped mouse Rhabdomys.

The level of dietary protein determines the onset of reproduction, affects offspring growth and maturation, and hence influences life-history traits and fitness. However, to date, the long-term life-history consequences of protein deficiency are not well understood. We studied the transgenerational effects of different levels of dietary protein on the life-history and level of maternal behavior of the striped mouse Rhabdomys dilectus chakae in captivity. Breeding pairs were assigned to three treatments based on the percentage of dietary protein: baseline (BP; 19%); high protein (HP; 24%); and low protein (LP; 10%). Reproductive output and offspring ontogeny was diminished in the LP treatment compared to the other treatments. Transgenerational effects were studied by breeding F2 females raised on the LP or HP diets on the same (HP-HP, LP-LP) or altered diets (HP-LP, LP-HP). The LP-LP treatment had no reproductive success, while reproductive capacity in the remaining treatments was determined mainly by the diet of mothers at breeding. Pups from protein-restricted females (LP, HP-LP) showed post-weaning compensatory growth. Timing of sexual maturity was age-dependent in female and mass-dependent in male offspring. Females fed low protein diets during breeding (LP, HP-LP) displayed lower levels of maternal behavior than females from the other treatments. This study demonstrates that the level of dietary protein influences the life-history of R. d. chakae in predictable ways. The taxon responds to changes in dietary protein at breeding, largely regardless of its nutrition during rearing. Such phenotypic flexibility in life-history parameters allows Rhabdomys to adaptively respond to unpredictable environmental changes.

Age at weaning, immunocompetence and ectoparasite performance in a precocial desert rodent.

We studied the effects of early weaning on immunocompetence and parasite resistance in a precocial rodent Acomys cahirinus. We hypothesized that if parasite resistance is energetically expensive and nutritional and immunological support from mothers are necessary for the long-term health of offspring, then early weaned animals would be immunologically weaker and less able to defend themselves against parasites than later weaned animals. We weaned pups at 14, 21 or 28 days after birth and assessed their immunocompetence and resistance against fleas Parapulex chephrenis when they attained adulthood. Immunocompetence was assessed using leukocyte concentration (LC) and a phytohaemagglutinin injection assay (PHA test). To estimate resistance against fleas, we measured performance of fleas via the number of produced eggs and duration of development and resistance to starvation of the flea offspring. We found a significant positive effect of weaning age on the PHA response but not on LC. The effect of age at weaning on flea egg production was manifested in male but not female hosts, with egg production being higher if a host was weaned at 14 than at 28 days. Weaning age of the host did not affect either duration of development or resistance to starvation of fleas produced by mothers fed on these hosts. We conclude that even in relatively precocial mammals, weaning age is an important indicator of future immunological responses and the ability of an animal to resist parasite infestations. Hosts weaned at an earlier age make easier, less-resistant targets for parasite infestations than hosts weaned later in life.

Growing up in the family or growing up alone influences behavior and hormones, but not arginine vasopressin receptor 1a expression in male African striped mice.

In many species males display alternative reproductive tactics (ARTs). While males of different tactics differ behaviorally in the field, it is often not known whether these behavioral differences would also occur under standardized laboratory conditions, nor how ARTs are regulated by the brain. In the present study we kept male African striped mice (Rhabdomys pumilio) in captivity either in family groups or solitary, to mimic ARTs observed in the field. This allowed us to study these males behaviorally under standardized conditions, to replicate physiological findings from the field, and to study the expression of the arginine vasopressin 1a receptor (AVPR1a) in their brains. Changes in either peptide release or receptor expression (or both) might regulate ARTs with differential timelines, with peptide secretion being faster than receptor expression. As observed in the field, family living males had higher corticosterone but lower testosterone levels than singly housed males. Surprisingly, singly housed males were less aggressive while at the same time having higher testosterone levels. We found no differences in AVPR1a expression. In a previous study it was shown that singly housed males have higher levels of AVP stored in their brain, which potentially could be secreted when the social situation changes, for example to establish social bonds. Our study on AVPR1a suggests the hypothesis that, given that the receptor distribution and expression of singly housed males do not differ from that of family-living males, the brains of singly-housed males have a similar capacity to be responsive to AVP when given the chance to interact socially.

Population dynamics and breeding patterns of multimammate mouse, Mastomys natalensis (Smith 1834), in irrigated rice fields in eastern Tanzania.

BACKGROUND: Multimammate mice are the most important vertebrate pests in Sub-Saharan Africa and are also reservoirs of many zoonotic diseases, including sylvan plague. This study investigated the population dynamics and breeding patterns of this mouse in irrigated rice cropping systems in eastern Tanzania. RESULTS: The multimammate mouse, Mastomys natalensis, population varied with habitat and months. Fallow land had a more abundant population than rice fields. The highest population peak was observed during the dry season from July to October. Mastomys natalensis is sexually active throughout the year in the study area, although it reaches the highest level in June and December when rice is at the maturity stage. This suggests that breeding is highly influenced by the presence of a rice crop in both seasons. More juvenile individuals were recorded in August and September, indicating that they were produced in the previous breeding months. The sex ratio of M. natalensis was not skewed to either males or females, indicating that it was at parity. CONCLUSION: Rodent population dynamics during the study periods in all habitats indicated that high birth rates accounted for the rapid population growth and turnover. Regular control and sustainable operations are thus essential if rodent pest populations are to be kept within tolerable limits.

Sexually dimorphic placental development throughout gestation in the spiny mouse (Acomys cahirinus).

OBJECTIVES: It has been hypothesized that male fetuses down regulate placental growth during periods of accelerated fetal growth. We aimed to investigate this, and determine whether sexual dimorphism was apparent in the spiny mouse placenta. We hypothesized that expression of fetal growth promoters would be higher in placentas of males, whereas genes involved in placental structural development would be more highly expressed in placentas of females. METHODS: Spiny mouse dams, a precocial rodent with an in utero endocrine milieu dissimilar from other rodents, but akin to humans, were sacrificed at gestational ages 15-37 (term = 39 days). Placentas were collected and processed for histology or qPCR analysis of selected genes (GCM1, MAP2K1, SLC2A1, NR3C1, IGF1, IGF1R). RESULTS: Fetal and placental weights were similar for both sexes. Placentas of female fetuses had less spongy zone (P(SEX) < 0.0001), and more labyrinth (P(SEX) < 0.0001) than males. Early placenta and labyrinth expression of SLC2A1 was higher in males than females (P(SEX) < 0.05). Labyrinthine IGF1R remained constant until term in the female, compared with male where expression increased until term. Peak MAP2K1 expression occurred earlier in the male placenta than the female. Spongy zone SLC2A1 remained constant until term in the female, compared with male where expression increased until term. CONCLUSIONS: The spiny mouse is a species that exhibits sexually dimorphic placental development. We suggest that these sex differences in placental gene expression and structure may underlie or compound the male vulnerability to a sub-optimal in utero environment.

Mast pulses shape trophic interactions between fluctuating rodent populations in a primeval forest.

How different functional responses of consumers exploiting pulsed resources affect community dynamics is an ongoing question in ecology. Tree masting is a common resource pulse in terrestrial ecosystems that can drive rodent population cycles. Using stable isotope (δ(13)C, δ(15)N) analyses, we investigated the dietary response of two fluctuating rodent species, the yellow-necked mouse Apodemus flavicollis and the bank vole Myodes glareolus, to mast events in Bialowieza Forest (NE Poland). Rodent hair samples were obtained non-invasively from faeces of their predators for an 11-year period that encompassed two mast events. Spectacular seed crops of deciduous trees, namely oak Quercus robur and hornbeam Carpinus betulus, occur after several intermediate years of moderate seed production, with a post-mast year characterised by a nil crop. While a Bayesian isotopic (SIAR) mixing model showed a variety of potential vegetation inputs to rodent diets, the isotopic niche of the yellow-necked mouse was strongly associated with mast of deciduous trees (>80% of diet), showing no variation among years of different seed crop. However, bank voles showed a strong functional response; in mast years the vole shifted its diet from herbs in deciduous forest (~66% of diet) to mast (~74%). Only in mast years did the isotopic niche of both rodent species overlap. Previous research showed that bank voles, subordinate and more generalist than mice, showed higher fluctuations in numbers in response to masting. This study provides unique data on the functional response of key pulse consumers in forest food webs, and contributes to our understanding of rodent population fluctuations and the mechanisms governing pulse-consumer interactions.

Follicular atresia in the prepubertal spiny mouse (Acomys cahirinus) ovary.

This study was designed to determine follicular atresia in the newborn and the prepubertal spiny mouse. We analyzed the processes of follicle loss using classical markers of apoptosis (TUNEL reaction, active caspase-3) and autophagy (Lamp1). Numerous small clear vacuoles and autophagosomes as well as strong Lamp1 staining were observed in dying oocytes of all follicle types, especially of the primordial and primary ones. Active caspase 3 and the TUNEL reaction were detected only in the granulosa cells of large secondary and antral follicles. The expression of apoptosis and autophagy markers was also changing during the prepubertal period. Western blot analysis indicated that at the moment of birth, females undergo an increased rate of follicular atresia mediated by autophagy, while apoptosis is the dominant form of ovarian atresia in consecutive postnatal days. On the basis of these observations, we concluded that apoptosis and autophagy are involved in follicular atresia and these processes are cell and developmental stage-specific.

[The cytogenetic consequences of chronic irradiation in rodent populations inhabiting the Eastern Urals Radioactive Trace zone].

In bone marrow cells of rodents (Apodemus (Sylvaemus) uralensis Pall., 1811, Apodemus agrarius Pall., 1771) inhabiting the Eastern Urals Radioactive Trace (EURT) zone (Kyshtym radiation accident 1957) and adjacent areas of Urals, the chromosome instability and 90Sr accumulation in bones were investigated. Intensive mutagenic process in both species from impact plots (the soil pollution by 90Sr 2322-16690 kBq/m2) was found. Significant positive correlation of aberrant cells frequencies and 90Sr was shown. Possible causes of the lack of resistance to long-term mutagenic factor (over 100 generations since 50 years from the accident) such as migration of animals and specific configuration of the EURT zone (narrow extended territory with sharply falling gradient of radionuclide pollution), which considerably decrease the probability that certain changes will be fixed and inherited in a series of generations of rodents, are discussed.

Multiple mesodermal lineage differentiation of Apodemus sylvaticus embryonic stem cells in vitro.

BACKGROUND: Embryonic stem (ES) cells have attracted significant attention from researchers around the world because of their ability to undergo indefinite self-renewal and produce derivatives from the three cell lineages, which has enormous value in research and clinical applications. Until now, many ES cell lines of different mammals have been established and studied. In addition, recently, AS-ES1 cells derived from Apodemus sylvaticus were established and identified by our laboratory as a new mammalian ES cell line. Hence further research, in the application of AS-ES1 cells, is warranted. RESULTS: Herein we report the generation of multiple mesodermal AS-ES1 lineages via embryoid body (EB) formation by the hanging drop method and the addition of particular reagents and factors for induction at the stage of EB attachment. The AS-ES1 cells generated separately in vitro included: adipocytes, osteoblasts, chondrocytes and cardiomyocytes. Histochemical staining, immunofluorescent staining and RT-PCR were carried out to confirm the formation of multiple mesodermal lineage cells. CONCLUSIONS: The appropriate reagents and culture milieu used in mesodermal differentiation of mouse ES cells also guide the differentiation of in vitro AS-ES1 cells into distinct mesoderm-derived cells. This study provides a better understanding of the characteristics of AS-ES1 cells, a new species ES cell line and promotes the use of Apodemus ES cells as a complement to mouse ES cells in future studies.

Immunohistochemical localization of estrogen receptors ERalpha and ERbeta in the spiny mouse (Acomys cahirinus) ovary during postnatal development.

This study was designed to determine the expression pattern of estrogen receptor (ER) subtypes in the Acomys cahirinus ovarian cells during its postnatal development. Immunohistochemical studies revealed the presence of ERalpha and ERbeta in germinal epithelium cells and interstitial tissue. Both these ER subtypes were also seen in granulosa cells and oocytes of growing follicles, however, the level of ERbeta expression was higher in comparison with ERalpha. In contrast to ERbeta, ERalpha protein was also present in theca cells. The expression of ERs increased with animals' age, but it decreased during follicular maturation. Moreover, the immunolocalization of ER subtypes in luteal cells showed that not ERbeta, but ERalpha expression is up-regulated throughout corpus luteum development. These immunohistochemical studies demonstrate, for the first time, that ERalpha is also expressed in the mouse granulosa cells and it may be a mediator of estrogen action in granulosa cells proliferation and differentiation.

Effects of predation and dispersal on Mastomys natalensis population dynamics in Tanzanian maize fields.

1. We investigate the effects of different levels of predation pressure and rodent dispersal on the population dynamics of the African pest rodent Mastomys natalensis in maize fields in Tanzania. 2. Three levels of predation risk were used in an experimental set-up: natural level (control), excluding predators by nets and attracting avian predators by nest boxes and perch poles. Because dispersal of the rodents could mask the predation pressure treatment effects, control and predator exclusion treatments were repeated with enclosed rodent populations. 3. Population growth during the annual population rise period was faster in the absence of predators and peak population size was higher, but otherwise dynamics patterns were similar for populations where predators had access or were attracted, indicating that compensatory mechanisms operate when rodents are exposed to high levels of predation risk. Reducing dispersal of rodents removed the effect of predation on population growth and peak size, suggesting that local predators may play a role in driving rodent dispersal, but have otherwise little direct effect on population dynamics.