Nutrition in extreme food specialists: an illustration using termites

Abstract

Recent nutritional ecology theories predict that an organism feeding on a single, highly predictable food should lack the typical active regulation of nutrient balance observed in all other organisms studied so far. It could instead limit itself to controlling the amount of food eaten alone. Such an animal would, however, be strongly affected by nutrient imbalances. Termites are an ideal model animal to test those predictions, because they are extreme food specialists. We investigated how the nutritional content of food affected termites’ intake and performance by constraining groups of Nasutitermes exitiosus to artificial diets varying in their macronutrient ratios. We showed that (a) termites, contrary to other insects, did not compensate for nutrient imbalance by adjusting food collection; (b) longevity in workers was strongly influenced by carbohydrate intake, while in soldiers it depended almost entirely on the number of workers remaining to feed them; (c) tunnelling activity increased with the quantity of food collected; and (d) intake had very little influence on lipid and protein termite body contents. We provide evidence that extreme food specialists might have lost the ability to regulate macronutrient intake. Our results highlight the importance of life history and ecology in the evolution of nutrient balancing strategies.