Thesis defense: 'The inter-relationships among diet, fattening and the gut microbial community of the arctic ground squirrel,' Sept. 17

Thursday, Sept. 17, 11:30 a.m.-12:30 p.m. Fine Arts Building, Room 117

Please join the Department of Biological Sciences for the thesis defense of M.S. biological sciences student Jasmine Hatton.

Committee members: Khrys Duddleston, Ph.D., advisor Loren Buck, Ph.D., co-advisor Eric Bortz, Ph.D.

Defense abstract: Hibernation is an adaptation in which animals undergo extreme, endogenously programmed changes in morphology, physiology and behavior in order to survive periods of prolonged food shortage. The arctic ground squirrel (Urocitellus parryii) has evolved the most extreme phenotype of any known hibernator in response to the harsh Arctic environment. It experiences a short active season of about three months, during which it must reproduce, rear pups and fatten in preparation for hibernation. Arctic ground squirrels accumulate fat late in the summer, increasing fat mass as much as seven-fold in three weeks. It has been suggested that pre-hibernation fattening may be facilitated by an increase in consumption of high quality forage (i.e. seeds and berries) late in the active season that shifts energy balance toward fat gain. In combination with changes in host physiology, dietary changes late in the active season may induce shifts in the gut microbial community (composition or activity) that contribute to fattening. The objective of my thesis was to determine the effects of diet (calorie and fat content) on fattening and gut microbial community structure and function in arctic ground squirrels. Body condition (percent fat) as well as diversity and activity of the gut microbial community were assessed across the active season in squirrels fed high-fat, low-fat, restricted calorie and control diets. I found that the rate and degree of fattening was not significantly affected by diet. Furthermore, diversity and metabolic output of the gut microbial community did not differ from beginning to end of the fattening phase and was unaffected by diet manipulation. Although there were no changes in gut community structure and metabolic output, analysis of the gut microbial metatranscriptome uncovered changes in the function and relative activity of taxa among diet groups but not across time. The ability of arctic ground squirrels to gain the same rate and percentage of body fat despite differences in caloric or macronutrient content of the diet suggests that fattening is facilitated through mechanisms other than increased energy uptake. Additionally, the results support the extreme physiology of the arctic ground squirrel may have selected for a gut microbiota efficient in energy extraction and robust to dietary fluctuations.

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