Salivary gland anticoagulants in culicine and anopheline mosquitoes (Diptera:Culicidae).

Female salivary gland extracts from 9 mosquito species representing the 2 hematophagous subfamilies delayed coagulation of human plasma. All extracts significantly delayed recalcification time, prothrombin time, and activated partial thromboplastin time, indicating an effect on the common coagulation pathway. Chromogenic assays to determine the coagulation inhibition site were performed for coagulation factor Xa (FXa) and thrombin, the major components of the common pathway. Although variation existed in the degree of inhibition, all anophelines have thrombin-directed anticoagulants, and culicine mosquitoes have FXa-directed anticoagulants. Differences in the site of action of the anticoagulants most likely reflected the long period of independent adaptation of the 2 subfamilies to the challenges presented by vertebrate hemostasis.