Blood-feeding arthropods: live syringes or invertebrate pharmacologists?

The habit of blood feeding evolved independently several times among the > 14,000 species and 400 genera of hematophagous arthropods. The specific need to remove blood from the host's skin led to sophisticated mechanical adaptations in invertebrate mouthparts. Moreover, the need to counteract the vertebrate host's hemostasis led to the evolution of salivary antihemostatic compounds injected into the host by these same mouthparts. The convergent evolution scenario for hematophagy has resulted in a large diversity of salivary anticlotting, antiplatelet, and vasodilatory substances. Thus, in addition to excelling as phlebotomists, hematophagous arthropods excel as pharmacologists.