Two neuropeptides that promote blood feeding in Anopheles stephensi mosquitoes

Animals routinely need to make decisions about what to eat and when. These decisions are influenced not only by the availability and quality of food but also by the internal state of the animal, which needs to compute and give weights to these different variables before making a choice. Feeding preferences of female mosquitoes exemplify this behavioural plasticity. Both male and female mosquitoes usually feed on carbohydrate-rich sources of nectar or sap but the female also feeds on blood, which is essential for egg development. This blood-appetite is modulated across the female's reproductive cycle, yet little is known about the factors that bring it about. We show that mated, but not virgin Anopheles stephensi females, a major vector of urban malaria in the Indian subcontinent and West Africa, suppress blood feeding between a blood meal and oviposition. We identify several candidate genes through transcriptomics of blood-deprived and -sated An. stephensi central brains that could modulate this behaviour. We show that short neuropeptide F (sNPF) and RYamide (RYa) act together to promote blood feeding and identify a cluster of cells in the subesophageal zone that expresses sNPF transcripts only in the blood-hungry state. Such females also have more sNPF transcripts in their midguts. Based on these data, we propose a model where increased sNPF levels in the brain and gut promote a state of blood-hunger, which drives feeding behaviour either by sNPF's action in the two tissues independently or via a communication between them. This occurs in the context of the action of RYa in the brain.