Energy acquisition and allocation in Peromyscus maniculatus exposed to aldicarb and cool temperatures

We hypothesized an energetic effect of the pesticide Aldicarb (an acetylcholinesterase inhibitor) through its action on gut innervation, and hence digestive efficiency, and tested this in deer mice ( Peromyscus mamculatus Rafinesque) exposed to both the pesticide and cold temperature. Growing deer mice were exposed to Aldicarb in their drinking water at concentrations of 0, 10, and 10,000 ppb and housed at 11 and 23°C. There were no changes due to Aldicarb in several measures of physiological energetics, including energy intake (food consumption, digestive efficiency, gut size) or in the allocation of energy to growth or activity. Two of eight measures of gut size (length and weight of the large intestine) increased significantly with exposure to Aldicarb at the high concentration. Also, there was significant interaction effect of exposure to Aldicarb and cool temperatures on the ratio of mucosal to serosal mass in the small intestine, such that mucosal mass increased when mice were exposed to low doses of Aldicarb at low temperatures but not under other conditions. Although increased absorptive area of the gut (i.e., size or mucosal mass) can be a compensatory response to energy shortfalls, there was no indication of that cause in Aldicarb‐exposed mice. Cold‐temperature treatment did increase energy costs, however, and both food consumption and gut size increased in mice housed at 11°C, so that digestive efficiency and allocation to growth and activity were no different from those of mice housed at warmer temperatures. Thus, Aldicarb is unlikely to produce any chronic effects on these mice in the wild through disruption of digestion or other causes of energetic shortfall.