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Background The colonial habit of Brandt’s vole (Lasiopodomys brandtii) differs from that of most other species of the genus Microtus. The demographic history of this species and the patterns shaping its current genetic structure remain unknown. Here, we explored patterns of genetic differentiation and infered the demographic history of Brandt’s vole populations through analyses of nuclear microsatellite and D-loop sequences. Results Phylogenetic analyses divided the sampled populations into three main clusters, which represent the southeastern, northeastern and western parts of the total range in Mongolia and China. Molecular data revealed an ancestral area located in the southeast of the extant range, in the Xilinguole District, Inner Mongolia, China, from where Brandt’s vole populations began expanding. A gene flow analysis suggested that the most likely colonization route was from the ancestral area and was followed by subsequent northeastward and westward range expansions. We identified decreases in genetic diversity with increasing distance from the founder population within the newly occupied regions (northeastern and western regions), clinal patterns in the allele frequencies, alleles that were rare in the original area that have become common in the newly occupied regions, and higher genetic differentiation in the expanded range compared with the original one. Conclusion Our results indicate that L. brandtii most likely originated from the southeastern part of its current geographic range, and subsequently colonized into the northeastern and western parts by expansion. The genetic patterns among the derived populations and with respect to the original population are consistent with that expected under genetic surfing models, which indicated that genetic drift, rather than gene flow, is the predominant factor underlying the genetic structure of expanding Brandt’s vole populations. Electronic supplementary material The online version of this article (doi:10.1186/s12862-017-0995-y) contains supplementary material, which is available to authorized users.

The current study evaluated effects of quinestrol on oxidative stress and abnormal spermatogenesis for male Mongolian gerbils. Gerbils were randomly divided into multi-dose treated, single-dose treated, control groups. At 15 days after treatment antioxidant enzymes (SOD, GSH-Px) activities and T-AOC were decreased whereas the MDA concentration was significantly increased, testicular weight and seminiferous tubular areas decreased, germ cells were rarefied and showed irregular distribution in seminiferous tubules, apoptosis was pronounced among spermatocytes and spermatids, the number of dead and abnormal acrosomes of spermatozoa increased significantly in quinestrol treated groups. At 30 days following treatment the testicular histopathological changes were more severe, sperm quality and antioxidant capacity continued to decline, and multi-dose treatment produced more damage to gerbils testes compared with single-dose treatment. The physiological indicators were recovered by 60 days of treatment withdrawal. The results showed oxidative stress induced by quinestrol in relation to abnormal spermatogenesis.

Effects of sasanguasaponin (SGS), a compound from defatted seeds of Camellia oleifera, on abnormal spermatogenesis were studied in adult male mice using daily intragastric administration of 100, 200 and 400 mg/kg body weight (BW) for 6 weeks. The sperm counts decreased and the number of abnormal spermatozoa increased in mice treated with SGS at 400 mg/kg dose level. Testicular weight and seminiferous tubular area gradually decreased as dosage increased to 400 mg/kg SGS. Germ cells were rarefied and showed irregular distribution in seminiferous tubules (STs). Apoptosis was pronounced among spermatocytes and spermatids at the 400 mg/kg dose level. Antioxidant enzymes including superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and total antioxide capacity (T-AOC) markedly decreased and malondialdehyde (MDA) concentration increased in the testes. These results suggest that adult exposure to SGS (400 mg/kg) induces spermatogenic apoptosis through increased oxidative stress in male mice.

Levonorgestrel and quinestrol, commonly known as EP-1, has long been used in the control of wild rodents. Up to the present time, however, no method for simultaneous quantification of levonorgestrel and quinestrol in rat plasma has been reported. In the present study, a sensitive reverse-phase high-performance liquid chromatography with ultraviolet detection (RP-HPLC-UV) method for quantification of levonorgestrel and quinestrol in rat plasma has been developed. It uses a Kromasil ODS C(18) column and acetonitrile-0.1% formic acid (85 : 15, v/v) mobile phase at ambient temperature. The plasma sample was prepared by hexane-isoamyl alcohol extraction (90 : 10, v/v). The flow rate and detection wavelength were 1.0 mL/min and 230 nm. The correlation coefficients were greater than 0.9995 within 0.08-50 microg/mL for levonorgestrel and 0.12-50 microg/mL for quinestrol, and the limits of detection were 0.02 and 0.05 microg/mL for levonorgestrel and quinestrol, respectively. Average recovery ranged from 92.5 to 96.3% and inter-day RSDs were less than 7.56%. This method can be applied to the further pharmacokinetic study of levonorgestrel and quinestrol in rat plasma.

Rodent pest population outbreaks occur frequently in grassland ecosystems in northern China. The Mongolian gerbil (Meriones unguiculatus) is a dominant pest rodent which is distributed across the semi-desert grasslands of Inner Mongolia, China. In 2009, we studied the contraceptive effect of levonorgestrel-quinestrol (EP-1), concentration 50 ppm, on a wild Mongolian gerbil population. The one-off contraceptive treatment was compared with a control group using a semi-monthly live trapping method in the Ordos Semi-desert Grassland Region of Inner Mongolia. The results show that juveniles were not recruited in spring in the treatment group. Ratios of juveniles in the control and treatment groups showed significant semi-monthly differences from spring to summer (one-way ANOVA, F2, 14 = 7.53, P < 0.05). Between both groups, annual fluctuations of juvenile and total population densities were significantly different respectively (F2, 14 = 4.64, P < 0.05; F2, 18 = 7.72, P < 0.05). The contraceptive EP-1 delayed the normal reproductive pattern of Mongolian gerbil populations. This suppressed birth rates of gerbil populations, reduced their densities, and changed their age structures. The period of EP-1 baiting should be extended but it could be an ideal method for controlling Mongolian gerbil populations during each breeding season.

Fertility control has been identified by studies in the laboratory and the field as a more appropriate and long-term control strategy for rodent pests than lethal control. In this study, we investigated the effects of quinestrol on mass of reproductive organs and on social behaviors in female and male Indochinese forest rat (Rattus andamanensis (Blyth, 1860)] using approach of morphometrics and genetics). [corrected]. A total of 16 adult females and 16 adult males were randomly assigned to 4 groups. One male and one female group were fed rice with 0.005% quinestrol by weight for 7 days, and another 2 groups were fed rice only. After 7 days, rats were assigned to 10 min dyadic encounters between groups, and investigation, aggression, defense and attack latency were quantified. All animals were killed on day 10, and reproductive organs were dissected and weighed. Dyadic encounter data showed that there were obvious changes in social behaviors of quinestrol-treated rats. Quinestrol significantly inhibited the investigative behavior of quinestrol-treated males toward control females in Rattus nitidus, but seldom affected investigation between control males and quinestrol-treated females. Aggression of control females toward quinestrol-treated males was higher than that of quinestrol-treated females, and defense of quinestrol-treated males toward control females was more remarkable than that of control males. Quinestrol remarkably decreased wet masses of epididymis and spermotophore in males and ovaries in females, but had no effect on wet masses of testes and uteri after quinestrol treatment. These results indicate that the anti-fertility effects of quinestrol on R. nitidus are attributed to not only suppressing reproductive organs but also impacting social behaviors associated with territory defense and mate choice.

In natural conditions, animals have to cope with fluctuations of food resources. Animals having experienced prolonged decrease in feeding opportunities may increase their reproductive success when meeting abundant food. Though food restriction is well known to reduce reproductive success of animals, it is not clear whether re-feeding can restore or even overcompensate the reproductive success. In this study, we investigated the differences in reproductive parameters between food-restricted and refed (FR-RF) group and control group of Brandt's vole (Lasiopodomys brandtii). For 4 weeks, FR-RF voles were provided with 70% of their normal daily food intake and then they were fed ad libitum for the next 4 weeks. Voles of control group were fed ad libitum for 8 weeks. Females (FR-RF or control) were mated to non-littermate males of the same group (FR-RF or control), and we found that the mean litter size and survival rate of F1 pups of FR-RF group were significantly higher than those of control group. We also provided a field example showing that the litter size of Brandt's voles tended to be higher if they experienced two consecutive dry and wet months than that of voles didn't have this experience. Our results suggest that re-feeding may have evoked an overcompensatory mechanism of food-restricted voles in reproductive success. This may be an adaptive strategy for Brandt's voles (with oscillating populations) to cope with the fluctuating food resources in natural conditions by adjusting their reproductive success.

Effects of diethylstilbestrol (DES), an endocrine disrupting chemical, on abnormal spermatogenesis were studied in adult hamster using daily subcutaneous injection of 0.01, 0.1 and 1.0 mg/kg body weight for 1 week. Testicular weight and seminiferous tubular area gradually decreased as dosage increased to 1.0 mg/kg DES. Germ cells were rarefied and showed irregular distribution in seminiferous tubules. Apoptosis was pronounced among spermatocytes and spermatids at the 1.0 mg/kg dose level. Antioxidant enzymes, including superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), and total antioxide capacity (T-AOC) markedly decreased and malondialdehyde (MDA) concentration significantly increased in the testes. These results suggest that DES (1.0 mg/kg) induces testicular oxidative stress and spermatogenic apoptosis in adult male hamsters to extend findings shown for prenatal and/or neonatal exposure.