THE ROLES OF TEMPERATURE, PH AND MOSQUITO FACTORS AS TRIGGERS OF MALEAND FEMALE GAMETOGENESIS OF PLASMODIUM-BERGHEI IN-VITRO

Developmentally arrested malarial gametocytes undergo gamete formation in the mosquito midgut immediately after ingestion of the infected bl oodmeal. In the rodent malaria parasite Plasmodium berghei male gameto genesis (exflagellation) can be induced in vitro by a temperature decr ease (from 39 degrees C in the vertebrate host to 20 degrees C) and a concomitant pH increase (from 7.3 in mouse blood to 8.0). We report th e presence of additional Gametocyte Activating Factor(s) (GAF) present in Anopheles stephensi tissue extracts, which induce both male and fe male gametogenesis at the otherwise nonpermissive pH of 7.3 in vitro b ut are unable to overcome the low temperature requirement. All constit uent cellular events of microgametogenesis studied here are induced by the same triggers in vitro. A temperature decrease is also required f or exflagellation in the mosquito midgut. The possible role of GAF as a second obligatory natural trigger of gametogenesis is discussed.