William H. Karasov, Ph.D.

Room 221 Russell Laboratories
1630 Linden Drive
Madison, WI 53706
608-263-9319
wkarasov@wisc.edu

Emphasis Group:
Animal Nutrition

Principal Research Interest:
Regulation and adaptation of digestive tract structure and function to altered feeding rate and diet composition; effects of plant secondary metabolites on herbivore physiology and feeding; nutritional ecology of wild herbivores.

Research Summary:
Our broad research objectives are to understand the physiological mechanisms allowing for effective use of food, and the relation of those processes to wildlife ecology, medical biology, and agriculture.

Past studies with mammals, birds, reptiles, amphibians, and fish have focused on changes in gut structure and function concomitant with, and possibly permissive for, changes in diet and intake rate. Findings included changes in intestinal and pancreatic enzymes and in the specific transport mechanisms for their products (sugars, amino acids, and vitamins) in animals following changes in levels of these nutrients in the diet. Most recently, we are studying developmental changes in digestive physiology and the paracellular pathway of intestinal passive absorption of hydrophilic compounds.

Anti-nutritive properties of food are also an important determinant of diet choice and intake rate. In our studies with wild herbivores eating wild foods, plant secondary metabolites had modest or no effect on digestive functions. Their most important effects were post-absorptive. Herbivores limited their intake of food to avoid exceeding a threshold intake of xenobiotic chemical, and they experienced losses of energy and nitrogen in the course of detoxication and excretion of the chemical. We are also studying processes involved in blocking absorption or biotransforming toxins post-absorption.

Representative Publications:

Karasov, W.H., K.P. Kenow, M.W. Meyer, and F. Fournier (2007) Bioenergetic and pharmacokinetic model for exposure of Common Loon chicks to methylmercury. Environmental Toxicology and Chemistry 26: 67-685.

McWhorter, T.J. and W.H. Karasov (2007) Paracellular nutrient absorption in a gum-feeding New World primate, the common marmoset Callithrix jacchus. American Journal of Primatology 69:1-13.

Lavin, S.R., T.J. McWhorter, and W.H. Karasov (2007) Mechanistic bases for differences in passive absorption. Journal of Experimental Biology 210:2754-2764.

Karasov, W.H. and C. Martinez del Rio (2007). Physiological Ecology: How Animals Process Energy, Nutrients, and Toxins. Princeton University Press, Princeton.

Caviedes-Vidal, E., T.J. McWhorter, S.R. Lavin, J.G. Chediack, C.R. Tracy, and W.H. Karasov (2007) The digestive adaptation of flying vertebrates: high intestinal paracellular absorption compensates for smaller guts. Proceedings of the National Academy of Science, USA 104(4):19132-19137.

Naya, D.E., W.H. Karasov, and F. Bozinovic (2007) Phenotypic plasticity in laboratory mice and rats: a meta-analysis of current ideas on gut size flexibility. Evolutionary Ecology Research 9:1363-1374.

Tsurim, I., N. Sapir, J. Belmaker, I. Shanni, I. Izhaki, M.S. Wojciechowski, W.H. Karasov, and B. Pinshow (2008) Drinking water boosts food intake rate, body mass increase and fat accumulation in migratory blackcaps (Sylvia atricapilla). Oecologia 156:21–30.

Brzęk, P., K. Kohl, E. Caviedes-Vidal, and W.H. Karasov (2009) Developmental adjustments of House sparrow (Passer domesticus) nestlings to diet composition. Journal of Experimental Biology 212:1284-1293.