Gustatory sensitività and nutritional value of various carbohydrates in Drosophila suzukii.

The peripheral sensitivity and palatability of different carbohydrates was evaluated and their nutritional value assessed in adult insects of D. suzukii by means of an electrophysiological, behavioural and metabolic approach. The spike activity was recorded from the labellar sensilla stimulated with metabolizable mono- and disaccharides (glucose and maltose) and a non-metabolizable sugar (sucralose); the response rating and the palatability to the same sugars, evaluated by recording the proboscis extension reflex (PER), was maltose>glucose>sucralose. The nutritional value of carbohydrates was assessed by means of survival trials and the lipid content and so was the fatty acids profile. Flies fed on a diet containing maltose had a longer lifespan than flies on monosaccharides, while flies fed on a diet containing sucralose had a shorter lifespan. In addition, the ability to store fat seems to be influenced by the different sugars in the diet and is in relationship with their palatability. In fact, data showed a higher synthesis of palmitic and palmitoleic acids, most likely derived from de-novo lipogenesis with glucose as precursor, in flies fed with maltose and glucose than with non-metabolizable sucralose. In conclusion, these results suggest that the ability to select different sugars on the basis of their palatability may favour the storage of energy reserves such as fat by de novo lipogenesis, determining a longer survival capability during prolonged periods of fasting