Physiological And Behavioral Responses To Changes In Food Quality Of Eothenomys Miletusis Distributed At Different Altitudes

A major challenge for survival and reproduction of small mammals in the wild was the uncertainty and instability of habitat environmental ecological factors,especially the conditions of food resources that fluctuate with seasonal changes.Lower temperatures and poor food resources in winter pose great challenges to the survival energy requirements of small rodents with poor mobility and to reserve energy for spring breeding.Quality of food available can determine the absolute energy intake of small rodents and whether they need to increase or decrease their activities.Body mass regulation was one of the apparent strategies for small mammals in the wild to cope with changes in food resources.Leptin,as an adipose secreting factor,was positively correlated with body mass and played an important role in body mass regulation.The hypothalamus had several feeding centers,among which two kinds of appetite neuropeptides in the arcuate nucleus(ARC)played an important role in regulating food intake and controlling body weight.They were Neuropeptide Y(NPY)and Agouti related peptide(Ag RP);Pro-opiomelanocortin(POMC)and Cocaine and amphetamine regulated peptide(CART).Resting metabolic rate(RMR)may also reflect the animals' tolerance to extreme physical conditions.Species that lived at high altitudes tend to had higher RMR and were better able to adapt to and coped with extreme environmental conditions.Adjustment of morphology of digestive tract and the changes of behavior pattern were another survival strategy for animals to adapt to different environmental conditions.The difference of activity and behavior were not only reflected in the interspecies,but also the significant difference of the internal habitat.Heng duan Mountain regions were rich in vegetation and wildlife because of their special geological,geomorphic,hydrological and other biological characteristics.Eothenomys miletusis was a inherent species in Heng duan Mountain regions,for a more comprehensive and systematic understanding of the survival mechanism of E.miletusis adapted to Heng duan Mountain regions without migration and diffusion,on the basis of our previous researches,the present paper from the aspects of food factors,to explore the survival mechanism of E.miletusis in the face of changes and differences in food quality,do E.miletusis at different altitudes had different regulatory mechanisms? Winter is the season with the worst food condition,and it is also the season in which small rodents need the most energy.Higher fat and sugar food had enough advantages in providing energy.Therefore,our study selected the most obvious phenotypic differentiation in Xianggelila(XGLL)and Jianchuan(JC)areas of the voles as the research object,in winter sampling,high-fat and sugar food on its physiological indicators and behavior patterns of the study,fed with high-fat food or high sugar food for 4 weeks and refeeding standard food for another 4 weeks,in the process of the experiment to determine body mass and food intake,RMR and activity behavior.And serum leptin levels,hypothalamic neuropeptide expressions and body composition were measured on day 0,28 and 56,objective to explore the difference of survival adaptation mechanism of voles with different food quality in different regions.This paper consists of two parts:(1)Physiological and behavioral adaptation strategies of E.miletus at different elevations of Heng duan Mountain regions in the face of high-fat food changesHigh-fat food treatment experiments were carried out on the E.miletus in two areas and the above indexes were measured.The results showed that the influence of region and high-fat food on body mass,food intake and RMR were significant,and region had significant effect on activity behavior,but high-fat food had not affected activity behavior.Meantime,there were significant differences in the effects of leptin and NPY expression between regions and high-fat diets,with leptin positively correlated with body mass and negatively correlated with NPY expression.In addition,E.miletus from two regions also showed some physiological adaptation differences.For example,RMR and food intake in XGLL were higher than that of JC,but body mass was lower than that of JC.The E.miletus in JC reduced body mass quickly after feeding standard diet,while those in XGLL decreased body mass gradually.All of the results showed that body mass of E.miletus in two regions increased when faced with high-fat food,which returned to the control levels after re-feeding standard diet,showing strong plasticity.Leptin and NPY expression may play an important role in body mass regulation and energy balance.Phenotypic differentiations of two regions may be closely related to food resources,and temperature in two regions.(2)Physiological and behavioral adaptation strategies of E.miletus at different elevations of Heng duan Mountain regions in the face of high-sugar food changesHigh-sugar food treatment experiments were carried out on the E.miletus in two areas and the above indexes were measured.The results showed that regional and high-sugar food had significant effects on body mass and food intake,but only regional differences existed in RMR and activity behavior.At the same time,regional and high-sugar food had significant differences in the influence of leptin,and NPY expression in hypothalamus had significant regional differences.Leptin was positively correlated with body mass,but not with neuropeptide expression.In addition,the physiological characteristics of E.miletus in the two regions also showed regional differences.For example,RMR and food intake in XGLL were higher than that of JC,but their body mass was lower than that of JC.After refeeding with standard diet,body mass in JC was still higher,but it gradually decreased in XGLL.All of the results showed that body mass in E.miletus in the two regions increased when they were exposed to the high-sugar food,but it was significantly different after they were fed the standard diet,showing a great difference between the two regions.Leptin levels and NPY expression may play an important role in body mass regulation and energy balance in E.miletus in various regions.Location-determined environmental factors(food resources,temperature)may be central to determining phenotypic differences between biological regions and their adaptation to extreme environmental conditions.In conclusion,food quality was of great importance to the survival of E.miletus in winter,and there are significant differences in physiological and behavioral patterns of E.miletus in different areas.E.miletus of XGLL was more sensitive to changes in food quality,but also more malleable,and more tolerant to habitats with greater environmental or ecological factor volatility;long-term natural selection under habitat conditions,such as food resources,was the main reason for the difference in phenotypic differentiation in E.miletus at different regions.