Spermatogenesis is modified by food intake in mice.

Spermatogenesis is generally viewed as being resistant to reduced food intake in inbred strains of adult mammals. This consensus stems from studies that have failed to place testicular responses within the context of a species' reproductive characteristics. We exposed two species of wild rodents, house mice and deer mice, to a mild but sustained food restriction (30% reduction of ad libitum consumption for 5 weeks). Reproductive adjustments made by each species to inanition were strikingly different. Food restriction failed to modify spermatogenesis in house mice, but evoked a continuum of testicular responses in deer mice ranging from normal spermatogenesis to azoospermia. These findings have several novel implications: 1) modest food restriction evokes species-specific adjustments in testicular function, and 2) intraspecific variation in spermatogenesis suggests robust individual differences in sensitivity to alterations in food intake. Taken together, our findings underscore the importance of considering the effects of food intake on male reproduction within the framework of a species' physiological and evolutionary background.