Dietary acclimation affects dietary selection in the freshwater snail Planorbella trivolvis

Animals should naturally select diets that provide the most benefit for the least cost. Many factors, however, can alter diet selection and may impact the ability to choose optimal diets. For example, dietary history may play a large role in how quickly an animal will switch to a novel and perhaps more optimal diet. The current study first aimed to evaluate diet quality using growth rate as a proxy in Planorbella trivolvis (Planorbidae) fed a range of common laboratory lettuce diets. Next, we sought to determine the extent to which diet acclimation influenced subsequent diet selection using the same laboratory lettuce diets. Snails fed cooked green romaine grew significantly more than snails fed cooked yellow romaine, uncooked green romaine or cooked kale. In a series of acclimation/selection experiments, snails naive to all diets showed no selection, suggesting that prior experience with a diet item is necessary for rapid selection. When reared on a particular diet, however, snails showed a significant preference for that diet after a 5-d starvation period. Unexpectedly, we found that even snails reared on diets that yielded lower growth rates (e.g. uncooked lettuce) selected that same diet when also provided access to diets that were previously shown to yield higher growth rates. Diet acclimation clearly influenced subsequent dietary selection. The implications of acclimation and preference for different dietary items by wild snails are unknown, but are likely ecologically important.