Effects of random food deprivation on body mass, behavior and serum leptin levels inEothenomys miletus(Mammalia: Rodentia: Cricetidae)

Abstract

The value of phenotypic plasticity in energy metabolism and behavioral patterns in response to variations of food availability was handled in adult male voles (Eothenomys miletus) acclimated to random food deprivation (FD) for 4 weeks. During this period, in which voles were fed ad libitum for a randomly assigned 3 days each week, changes in body mass, food intake, resting metabolic rate (RMR), non-shivering thermogenesis (NST) and serum leptin levels were measured. Behavioral observations were made to examine behavioral patterns including activity, feeding, grooming and resting behaviors. The results showed that food intake and gastrointestinal mass increased significantly, but RMR and NST decreased significantly in the FD group compared to the control group. Moreover, the FD group had a significantly higher percentage of feeding behavior and lower activity than those in control group. In addition, serum leptin levels were positively correlated with body fat mass, but showed no significant differences between FD and the control group. These results suggest that E. miletus can compensate for an unpredictable reduction of food availability by engaging in an energetic strategy related to food intake and a decrease in energy expenditure associated with RMR, NST plus general activity, together with the mobilization of body fat as well as the adjustment of the gastrointestinal tract, which consequently play an important role in adaptations to food shortage in unpredictable environments.

The evolution of body fatness: trading off disease and predation risk

“…As with studies on birds, the evidence with respect to stochastic variations in food supply are less clear cut compared with the impacts of modified predation risk. There is some limited support for the idea that increased stochasticity drives elevated fat storage Cao et al, 2009;Zhang et al, 2012;Zhu et al, 2014); however, other studies suggest the reverse (Monarca et al, 2015b). In humans, this idea is generally called the 'food insecurity' hypothesis, or the 'hunger-obesity' paradigm (Nettle et al, 2017;Dhurandhar, 2016), i.e.…”

Costs of exploratory behavior: the energy trade-off hypothesis and the allocation model tested under caloric restriction

“…Yet, at least three species of rodents (e.g., Mus musculus, Cricetulus barabensis, Eothenomys miletus) present a behavioral response considered as "paradoxical" in the face of stochastic deprivation of food or when fed on low-energy diets [13][14][15][16][17] . Indeed, enlargement of the intestine (see ref.…”

“…Indeed, enlargement of the intestine (see ref. in 18 ) and changes in behavioral patterns such as an increased locomotion and exploratory activities have been described 4,14,17,19 and consequently, animals display markedly increased locomotor behavior as well as a decrease in basal metabolic rates and NST 6 . This paradox would imply an investment in structure and function, despite the lack and unpredictable variation of trophic resources.…”

Effects of food restriction on body mass, energy metabolism and thermogenesis in a tree shrew (Tupaia belangeri)

“…Non-hibernating small mammals generally respond to a food shortage in one of two ways: either by reducing their energy metabolism levels (e.g. MF1 mice (Hambly and Speakman 2005), white-footed mouse ( Peromyscus maniculatus ) (Gutman et al 2007), chevrier’s field mouse ( Apodemus chevrieri ) (Zhu et al 2013) and yunnan red-backed vole ( Eothenomys miletus ) (Zhu et al 2014); or by maintaining or increasing their energy expenditure levels (e.g. KM mice, rats and guinea pigs ( Cavia porcellus ) (Williams et al 2002; Zhao et al 2009 a , 2009 b )).…”