Search

In order to investigate the ability of constant temperature and thermoregulation in Apodemus chevrieri, body temperature and rest metabolic rate (RMR) were measured during postnatal development (1～42 day) when the A. chevrieri exposed different ambient temperature. The result showed that: body temperature and RMR of pups in A. chevrieri increased according to the increase of ambient temperature during 1 day to 7 day, showed character of poikilotherms; body temperature of pups were lower in low temperature(5 oC and 10 oC), relatively and RMR significant increased when day age is 14 day, it indicated that the pups showed a certain degree of thermoregulation in this phase. Its thermoregulation ability developed quickly during 7 day to 14 day. RMR of pups was extreme significantly higher in low temperature than that in other temperature when day age was 21 day, it showed that the pups had some thermoregulation to low temperature stimulation. The RMR of pups was showed increasing trend in high temperature(35 oC) when 28 day; when day age was 35 day and 42 day, the thermal neutral zone were 22.5 to 30 oC and approaching its adult level. All of these results indicated that pups of A. chevrieri in the different growing period had different thermogenesis and energy allocation to maintain stable to body temperature, thermogenesis was weaker in the early phase of postnatal development, most of energy is used to its growth. After pups were weaned, the ability of constant temperature and thermoregulation developed quickly to adjust variations of environment during postnatal development.

In order to investigate the changes of plasticity of visceral organs and digestive tract morphology in Apodemus chevrieri which inhabit in Hengduan mountain region, the organ masses and digestive tract which include the changes of heart, lung, liver , spleen and kidney as well as the length and weight of stomach, small intestine, large intestine and cecum were measured during cold and warm acclimation. The results showed that the weight of heart and liver of cold acclimation group were obviously higher than that of warm acclimation group. The weight and length of small intestine showed significant differences between two groups. All of the results indicated that A. chevrieri maintain their normal life activities by increasing the weight of related organ masses and adjusting the weight and length of small intestine under cold temperature.

Environmental cues play important roles in the regulation of an animal’s physiology and behavior. In the present study, we performed a factorial experiment (temperature/photoperiod) in which Tupaia belangeri was acclimated to different photoperiods (long photoperiod, 16L:8D; short photoperiod, 8L:16D) and temperatures (warm, 30 oC; cold,5 oC) to test the hypothesis that photoperiod, temperature, or both together can trigger changes in energy budgets and endocrine hormones concentrations. The results showed that temperature, photoperiod had a significant effect on energy intake, and digestible energy intake. Both short photoperiod and cold caused animal's gross energy intake to increase by 25.6% and 89.1 %, and caused digestible energy intake to increase by 24.1% and 83.5% respectively compared with that of the initial, but there was no significant interaction between photoperiod and temperature on energy intake and digestible energy intake. Temperature had significant effect on serum thyrotropin (TSH) concentrations, serum leptin level, photoperiod had a significant effect on TSH and melatonin. The present results suggested that T. belangeri adapt cold stress or short photoperiod by increasing energy intake, and may be regulated by endocrine hormones. Furthermore, leptin and melatonin seem to be involved in the regulation of body mass and energy balance in T. belangeri.

The aim of the present study was to examine the energy strategy in response to the cold temperature and food shortage. The survival rate, body mass, body fat content, serum leptin levels, basal metabolic rate (BMR) and nonshivering thermogenesis (NST) as well as masses and the morphology of visceral organs and the digestive tract were measured in Eothenomys miletus that was subjected to the cold temperature (5°C) and food restriction (80% of ad libitum food intake). The results showed that body mass, body fat content, serum leptin levels, brown adipose tissue (BAT) mass and dry mass of digestive tract in cold and food restriction group were lower than those in control group. In contrasts, BMR and NST in cold and food restriction group was significantly higher relative to control group. The rate of survival was 18.18% in E. miletus during cold and food restriction after 4 weeks acclimation. In addition, serum leptin levels were positively correlated with body mass and body fat content, and negatively correlated with BMR and NST. These results suggested that E. miletus apply physiological adjustments to adapt cold and food lacking external environment by reducing body mass, body fat content, and increasing energy metabolism. However, energy intake is insufficient to compensate for the increase in energy requirement due to cold, led to body mass decreased and mortality rate increased. Moreover, serum leptin may acts as a fat signals, and may be involved in the regulation of energy balance and body mass in E. miletus under the cold temperature and food restriction.

Nonshivering thermogenesis (NST)is an important thermogenic mechanism for small mammals. Quantitative measurement of NST is usually stimulated by injection of norepinephrine. The injection dosage of norepinephrine (NE) is critical for eliciting the maximum NST. Three empirical equations of NE dosages were often referenced in previous studies: (1) NE (mg / kg)= 2.53W-0.4; (2) NE(mg/kg) = 3.3W-0.458 and (3) NE(mg/kg)= 6.6W-0.458. In the present study , we used tree shrews (Tupaia belangeri) as experiment subjects to test the effects of the three dosages of NE on NST. Results showed that all the three dosages of NE could induce the maximum NST for T. belangeri. No significant differences were found in NST among groups and the NST was respectively 2.63±0.12 (formula 1), 2.66±0. 11 (formula 2) and 2.78±0.15 (formula 3). However, when injected with NE dosage from formula 3, the increase of body temperatures was significantly higher than the other two NE dosages (increased 1.5±0. 1 oC (formula 3), 0.8±0. 2 oC (formula 2), and 0.6±0. 1 oC (formula 1), respectively). In order to prevent the death because of hyperthermia, formula 1 or 2 is recommended to be used.

The thermogenic mechanisms were measured in the two small rodents, Eothenomys milletus and Apodemus chevrieri in Hengduan mountain region during cold exposure. The main results were as follows: 1. RMR and NST incredsed 68.34%, 36.34% during the cold exposure in E. miletus, RMR and NST incredsed 32.84%, 56.17% during the cold exposure in A. chevrieri, respectively. 2. During cold exposure, total protein content in liver, the total protein content (TP) and mitochodrnal protein content (MP) in brown adipose tissue (BAT), the content of uncoupling protein (UCP1) were increased in E. miletus, which increased 18.66%, 25.18%, 70.01%, 99.39%, respectively. Total protein content in liver, the total protein content (TP) and mitochodrnal protein content (MP) in brown adipose tissue (BAT), the content of uncoupling protein (UCP1) were increased in A. chevrieri, which increased 18.11%, 33.29%, 34.51%, 235.95%, respectively. All of the results indicated that the mechanism of heat production for adaptative changes was similar in two rodents, but it showed different increased amplitude of heat production, it may considered that the difference of heat production was related to origin of species and inhabitats.

Environmental cues, such as temperature, play important roles in the regulation of physiology and behavior in small mammals. The aim of the present study was to test the hypothesis that ambient temperature was a cue to induce adjustments in body mass and thermogenic capacity in Apodemus chevrieri. It showed that A. chevrieri increased resting metabolic rate (RMR), nonshivering thermogenesis (NST) and energy intake and decreased body mass and body temperature when exposed to the cold while showed a significant increase in body mass and body temperature after rewarming. The decrease of body temperature can reduce the difference in temperature in environment, save energy consumption. The increase in body mass after rewarming was associated with the higher energy intake. Together, these data supported our hypothesis that ambient temperature was a cue to induce changes in body mass and metabolism in A. chevrieri.

Eothenomys miletus and Apodemus chevrieri are typical species of small mammals inhabiting in Hengduan mountains region. The characteristics of thermoregulation and thermogenesis of two mammals were measured to search their physiological and ecological characteristics of adaptations to this region in different seasons. All results indicated: the body weight of E. miletus and A. chevrieri in summer was separately 47.29±0.73g, 32.74±0.54g, and their body weight in winter was separately 39.28±0.61g, 31.70±0.76g; the thermal neutral zones (TNZ) of E. miletus and A. chevrieri in summer were separately 25 ～32.5 oC and 25 ～30 oC, and their TNZ in winter were all of 22.5 ～ 27.5 oC; their basal metabolic rates (BMR) in summer were respectively 3.76± 0.07 ml O2/g.h, 4.58±0.09 ml O2/g.h, and their BMR in winter were respectively 4.46±0.04 ml O2/g.h, 5.23±0.01 ml O2/g.h; their maximum nonoshivering thermogenesis (NST) in summer was respectively 5.70±0.18 ml O2/g.h, 7.12±0.31 ml O2/g.h, and their NST in winter was respectively 6.67±0.05 ml O2/g.h, 7.42±0.04 ml O2/g.h; their NST scope (NST/BMR) in summer was separately 1.52±0.05, 1.46±0.04, and their NST scope in winter was separately 1.49±0.01, 1.42±0.01. Their thermogenic characteristics and thermoregulatory styles possibly reflected features of small rodents in Hengduan mountains region which have lower body temperatures and NST scope, higher BMR, Cm and NST and could keep their body temperatures stable in narrower ambient temperatures comparing with other rodents. Body temperature, Cm BMR and NST of A. chevrieri were higher than these of E. miletus. A. chevrieri could keep body temperature stable in a wider range of ambient temperatures than E. miletus. NST scope of E. miletus was higher than it of A. chevrieri. Their TNZ and the ambient temperature range in which they could keep C stable in winter were narrower than these indexes in summer. The body temperature and body weight in winter were lower comparing with the summer. The BMR, F-value and NST maxin winter were significantly higher than the summer. The TNZ in winter was shifted to the lower ambient temperature comparing with the summer.