Effects of proline on survival, locomotion and amino acid haemolymph composition of Osmia cornuta (Latreille, 1805)

Flower nectar, a sugar-rich solution containing amino acids as major secondary solutes, is the primary energy source for bees. Proline is one of the most abundant protein nectar amino acids, showing several effects on bee physiology. Mason bees are outstanding pollinators, often preferred to Apis mellifera for pollination of fruit trees. Among them, Osmia cornuta (Latreille) is one of the most successfully managed species on a commercial scale. In this work, the effects of 10 mM proline-enriched diet administration on O. cornuta feed consumption, survival, behaviour and haemolymph amino acid composition were investigated. Feed intake was higher for the proline diet, while survival rate was not affected. Behaviour was affected only in the senescence of the mason bees with a reduction in locomotor activity induced by proline intake. Proline diet also affected the haemolymph amino acid composition, decreasing concentration of tyrosine, methionine, leucine and phenylalanine after 10 days of feeding. These results were discussed in relation to the potential involvement of proline in oxidative stress in insects and proline's ability to be converted to other amino acids. Further investigations are necessary to better understand the molecular mechanisms of proline effects on locomotion and oxidative stress.