From Sialomes to the Sialoverse: An Insight into Salivary Potion of Blood-Feeding Insects

To efficiently blood feed, insects have evolved a salivary concoction that disarms their host's haemostasis, a redundant physiological mechanism that includes blood clotting, platelet aggregation and vasoconstriction. Because vertebrate haemostasis is complex and redundant, haematophagous insect saliva is also complex and redundant, containing dozens of active compounds. Because this feeding mode evolved independently in several insect orders, the salivary composition among insects of different orders is very diverse, typical of a convergent evolutionary scenario. Perhaps due to the vertebrate immune response against salivary antigens, haematophagous insect salivary proteins are under a very fast pace of evolution, resulting in the appearance of novel protein families even within genera of the same family. In this chapter, we attempt a classification of the salivary compounds found in blood-sucking insects that might help to guide the task of functionally characterizing the salivary potion of these near 500 genera and 15,000 species that feed on vertebrate blood.