STUDIES ON GAMETOCYTA ACTIVATING FACTOR IN THE SALIVARY GRAND OF ANOPHELINE MOSQUITOES

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Gametocyte activating factor (GAF) induces exflagellation of Plasmodium microgametes. We found GAF in the salivary glands of female mosquitoes, Anopheles stephensi. The exflagellation was induced in a concentration-dependent manner in the supernatant of salivary gland's crude homogenate. The exflagellation inducing activity (EIA) in the salivary gland was higher than that in the midgut and the head. GAF in the salivary glands was found to be heat stable and low molecule (< 3,000 molecular weight). Analysis of the supernatant by capillary electrophoresis and UV absorbance profile showed that the salivary glands contained xanthurenic acid, which was previously identified as GAF in the head of A. stephensi. EIA in the salivary gland declined immediately after a blood meal, implying that GAF was in the saliva, and was delivered into the midgut together with the blood and induced exflagellation in the midgut. Next, we compared EIA in the salivary glands of five mosquito species, Aedes aegypti, Ae. Albopictus, An. omorii, An. Stephensi and Culex pipiens pallens. As a result, all the mosquito species examined contained GAF in the salivary glands. An. omorii and An. Stephensi consumed more GAF than Ae. aegypti, Ae. albopictus and Cx. p. pallens during blood feeding, suggesting that more GAF might be introduced into the midgut of Anopheles mosquitoes. This would be one of the reasons why only anopheline mosquitoes can transmit mammalian malaria. (224 words)