Fuel source shift or cost reduction:Context-dependent adaptation strategies in closely related Neodon fuscus and Lasiopodomys brandtii against hypoxia

Oxygen is essential for most life forms.Insufficient oxygen supply can disrupt homeostasis and compromise survival,and hypoxia-induced cardiovascular failure is fatal in many animals,including humans.However,certain species have adapted and evolved to cope with hypoxic environments and are therefore good models for studying the regulatory mechanisms underlying responses to hypoxia.Here,we explored the physiological and molecular responses of the cardiovascular system in two closely related hypoxiaadapted species with different life histories,namely,Qinghai voles(Neodon fuscus)and Brandt’s voles(Lasiopodomys brandtii),under hypoxic(10%O_(2) for 48 h)and normoxic(20.9%O_(2) for 48 h)exposure.Kunming mice(Mus musculus)were used for comparison.Qinghai voles live in plateau areas under hypoxic conditions,whereas Brandt’s voles only experience periodic hypoxia.Histological and hematological analyses indicated a strong tolerance to hypoxia in both species,but significant cardiac tissue damage and increased blood circulation resistance in mice exposed to hypoxia.Comparative transcriptome analysis revealed enhanced oxygen transport efficiency as a coping mechanism against hypoxia in both N.fuscus and L.brandtii,but with some differences.Specifically,N.fuscus showed upregulated expression of genes related to accelerated cardiac contraction and angiogenesis,whereas L.brandtii showed significant up-regulation of erythropoiesis-related genes.Synchronized upregulation of hemoglobin synthesis-related genes was observed in both species.In addition,differences in cardiometabolic strategies against hypoxia were observed in the rodents.Notably,M.musculus relied on adenosine triphosphate(ATP)generation via fatty acid oxidation,whereas N.fuscus shifted energy production to glucose oxidation under hypoxic conditions and L.brandtii employed a conservative strategy involving down-regulation of fatty acid and glucose oxidation and a bradycardia phenotype.In conclusion,the cardiovascular systems of N.fuscus and L.brandtii have evolved different adaptation strategies to enhance oxygen transport capacity and conserve energy under hypoxia.Our findings suggest that the coping mechanisms underlying hypoxia tolerance in these closely related species are context dependent.

Effects of host identity on the gut microbiota:A comparative study on three microtinae species

Background:Gut microbiota exert an immense effect on host health and host environmental adaptation.Furthermore,the composition and structure of gut microbiota are determined by the environment and host genetic factors.However,the relative contribution of the environment and host genetic factors toward shaping the structure of gut microbiota has been poorly understood.Methods:In this study,we characterized the fecal microbial communities of the closely related voles Neodon fuscus,Lasiopodomys brandtii,and L.mandarinus after caged feeding in the laboratory for 6 months,through high-throughput sequencing and bioinformatics analysis.Results:The results of pairwise comparisons of N.fuscus vs.L.brandtii and L.mandarinus vs.L.brandtii revealed significant differences in bacterial diversity and composition after domestication.While 991 same operational taxonomic units(OTUs)were shared in three voles,there were 362,291,and 303 species-specific OTUs in N.fuscus,L.brandtii,and L.mandarinus,respectively.The relative abundances of Proteobacteria and Prevotella,which are reported to be enriched in high-altitude populations,were significantly higher in high-altitude N.fuscus than in low-altitude L.brandtii after domestication.Firmicutes,which produce various digestive enzymes for energy metabolism,and Spirochaetes,which can degrade cellulose,were found in higher abundance in subterranean L.mandarinus than that in L.brandtii which dwells on the earth surface.Conclusion:Our findings showed that some components of gut microbiota still maintained dominance even when different host species are reared under the same environmental conditions,suggesting that these bacteria are substantially influenced by host factors.

Anti-fertility effect of levonorgestrel and quinestrol in Brandt’s voles(Lasiopodomys brandtii)

The combination of levonorgestrel and quinestrol(EP-1)has been shown to have anti-fertility effects on several wild rodents,but the mechanism underlying these effects is poorly understood.We investigated the effects of EP-1 and each of its components,levonorgestrel(P)and quinestrol(E),on the fertility of Brandt’s voles(Lasiopodomys brandtii)by using a gastric gavage method.The doses for EP-1,E and P were 1,0.34 and 0.66 mg/kg body weight,respectively.Male voles(n=98)were treated daily for 5 or 14 days,then the testes and epididymides were collected,weighed and examined histologically at 30(D30),60(D60)or 90(D90)days after the end of treatment.Four males were allowed to mate with normal females at D90.Female voles(n=75)were treated for 3 days and a further 3 days after a 7-day interval.The uteri and ovaries were weighed and examined histologically at 15(D15),30(D30)or 75(D75)days after the end of treatment.Each of three females were mated with fertile males at D30 and D75,respectively.Our results indicated that quinestrol(E)significantly decreased the sperm numbers in the testes as well as the weight of the testes and epididymides,with both of these tissues showing obvious structural abnormalities,and significantly reduced the litter size and the pup weight for females mated with males of the E treatment group.For female voles,treatment with E,P or EP-1 resulted in no marked influence on the fertility status.These data indicate that quinestrol(E)alone has a significant anti-fertility effect on male Brandt’s voles,but is ineffective in combination with levonorgestrel(P).

Lasiopodomys fuscus as an important intermediate host for Echinococcus multilocularis:isolation and phylogenetic identification of the parasite

Background:Echinococcus multilocularis causes alveolar echinococcosis(AE)and is widely prevalent in Qinghai Province,China,where a number of different species have been identified as hosts.However,limited information is available on the Qinghai vole(Lasiopodomys fuscus),which is hyper endemic to Qinghai Province and may represent a potential intermediate host of E.multilocularis.Thus,L.fuscus could contribute to the endemicity of AE in the area.Methods:Fifty Qinghai voles were captured from Jigzhi County in Qinghai Province for the clinical identification of E.multilocularis infection via anatomical examination.Hydatid fluid was collected from vesicles of the livers in suspected voles and subjected to a microscopic examination and PCR assay based on the barcoding gene of cox 1.PCR-amplified segments were sequenced for a phylogenetic analysis.E.multilocularis-infected Qinghai voles were morphologically identified and subjected to a phylogenetic analysis to confirm their identities.Results:Seventeen of the 50 Qinghai voles had E.multilocularis-infection-like vesicles in their livers.Eleven out of the 17 Qinghai voles presented E.multilocularis infection,which was detected by PCR and sequencing.The phylogenetic analysis showed that all 11 positive samples belonged to the E.multilocularis Asian genotype.A morphological identification and phylogenetic analysis of the E.multilocularis-infected Qinghai voles confirmed that all captured animals were L.fuscus.Conclusions:L.fuscus can be infected with E.multilocularis and plays a potential role in the life cycle and epidemiology of E.multilocularis in the Qinghai-Tibetan Plateau of China.

温度驯化对布氏田鼠肝脏温敏瞬时受体电位通道蛋白表达的影响

肝脏是哺乳动物基础代谢产热的关键器官。温敏瞬时受体电位通道蛋白(Thermosensitive transient receptor potential channels,Thermo-TRPs)参与了调控肝细胞的生理功能。为了解Thermo-TRPs是否参与肝脏的代谢产热,以成年布氏田鼠(Lasiopodomys brandtii)为研究对象,测定了不同驯化温度下6种Thermo-TRPs在肝脏中的表达,分析其与肝脏产热相关蛋白和信号通路蛋白的关系。结果显示:(1)与高温组相比,低温增加了肝脏解偶联蛋白1(uncoupling protein 1,UCP1)的表达;而与常温组相比,低温降低了肝脏解偶联蛋白3(uncoupling protein 3,UCP3)的表达;(2)6种Thermo-TRPs均在肝脏中表达,与高温组相比,低温显著降低了TRP vanilloid 4(TRPV4)的表达,同时显著增加了腺苷酸活化蛋白激酶(AMP-activated protein kinase,AMPK)的表达;(3)低温显著增加了布氏田鼠血清三碘甲状腺原氨酸(T_(3))水平,提高了T_(3)/T_(4)比值;T_(3)/T_(4)比值与肝脏UCP1和AMPK呈显著正相关,肝脏中UCP1与TRPM2和AMPK呈显著正相关。这些结果表明,肝脏TRPV4和AMPK可能参与了低温环境中代谢产热等生理功能的调节过程。

不同不育比例对布氏田鼠种群增长的影响

在围栏条件下采用重捕法跟踪了不同比例不育个体对种群的影响。结果表明:正常繁殖组(对照)6-8月份均有新生小鼠,9月份以后停止繁殖。其中6月份雌鼠繁殖率为45%,7月份雌鼠繁殖率为40%,8月份雌鼠繁殖率为33%。繁殖期后,种群数量下降。在当年数量波动呈单峰型曲线。而各不育比例的试验组则均呈下降趋势;无论雄性或雌性的完全不育组的种群均在3-4个月的时间内全部灭绝。说明在没有新生幼鼠的加入种群更替的情况下,由越冬鼠组成的种群将很快消亡;部分不育组的繁殖率均低于对照组。其中1/3雄性不育组及1/3雌性不育组的繁殖率均高于2/3雄性不育组及2/3雌性不育组,这种现象意味着该鼠的婚配制度并非混交制。在试验期间所有部分不育的种群均呈负增长;部分不育组中,当年出生的鼠没有参加繁殖。可能是不育个体干扰了其交配。因此,使用不育剂可能成为控制布氏田鼠种群数量的有效对策。

Effect of temperature on antioxidant defense and innate immunity in Brandt’s voles

Ambient temperature is an importa nt factor in flue ncing many physiological processes, in eluding antioxidant defense and immunity. In the present study, we tested the hypothesis that antioxidant defense and immunity are suppressed by high and low temperature treatme nt in Bran dt's voles (Lasiopodomys brandtii). Thirty male voles were randomly assigned into different temperature groups (4, 23, and 32℃, n=10 for each group), with the treatment course lasting for 27 d. Results showed that low temperature in creased gross en ergy in take (GEI) and liver, heart, and kidney mass, but decreased body fat mass and dry carcass mass. With the decline in temperature, hydrogen peroxide (H2O2) concentration, which is indicative of reactive oxyge n species (ROS) levels, in creased in the liver, decreased in the heart, and was unchanged in the kidney, testis, and small intestine. Lipid peroxidation indicated by malonaldehyde (MDA) content in the liver, heart, kidney, testis, and small intestine did not differ among groups, implying that high and low temperature did not cause oxidative damage. Similarly, superoxide dismutase (SOD) and catalase (CAT) activities and total antioxidant capacity (TAOC) in the five tissues did not respond to low or high temperature, except for elevation of CAT activity in the testis upon cold exposure. Bacteria killing capacity, which is indicative of innate immunity, was nearly suppressed in the 4℃ group in contrast to the 23℃ group, whereas spleen mass and white blood cells were un affected by temperature treatment. The levels of testosterone, but not corticostero ne, were in flue need by temperature treatment, though neither were correlated with innate immunity, H2O2 and MDA levels, or SOD, CAT, and TAOC activity in any detected tissues. Overall, these results showed that temperature had different in flue nces on oxidative stress, an tioxida nt en zymes, and immunity, which depended on the tissues and parameters tested. Up-regulation or maintenance of an tioxida nt defe nse might be an importa nt mechanism for voles to survive highly variable environmental temperatures.