Behavioral regulation of nutrient intake in the mealworm beetle, Tenebrio molitor (Coleoptera : Tenebrionidae)

Abstract

Mealworm beetle, Tenebrio molitor L. (Coleoptera: Tenebrionidae), is an important model organism widely used for studying physiology and behaviour in entomological researches. In recent years, there is also a growing interest in the possibility of using T. molitor for animal feed and human consumption. However, little research has been conducted on the nutritional biology of this potentially important insect. In Chapter 1, the nutritional regulatory behaviour and post-ingestive nutrient utilisation efficiencies were described from adult T. molitor under controlled laboratory conditions. The beetles actively regulated their intake of protein and carbohydrate to a ratio of 1:1. When confined to a range of single suboptimal diets, they exhibited a strategy of nutrient balancing similar to that of other omnivorous insects with a broad range of diets. Chapter 2 tested whether T. molitor can fully recover from the negative consequences of ingesting nutritionally imbalanced diets by adjusting their nutrient preferences. When offered a choice between two nutritionally complementary diets after being exposed to an extreme nutritional imbalance, the beetles that had been previously deprived of protein preferentially selected a protein-rich diet and this compensatory feeding led them to quickly reinstate their optimal nutritional state. Chapter 3 investigated the effect of dietary protein:carbohydrate balance on the two important components of fitness (longevity and reproduction) in T. molitor. Both longevity and lifetime fecundity were maximized on a diet with equal ratio of protein to carbohydrate (1:1), a ratio which was preferentially selected by T. molitor when given a food choice. Collectively, these results provide experimental support to the prevailing notion that the optimal foraging has evolved in insects to maximize the Darwinian fitness through balancing the intake of multiple nutrients.