BLOOD-FEEDING SUCCESS OF THE MOSQUITO AEDES-AEGYPTI DEPENDS ON THE TRANSMISSION ROUTE OF ITS PARASITE EDHAZARDIA-AEDIS

We examined the effect of the microsporidian parasite Edhazardia aedis on the blood-feeding success of its host, the yellow fever mosquito A edes aegypti. To do so, we exposed mosquito larvae to parasite spores at four intensities and three ages. The amount of blood obtained by ad ult female mosquitoes increased with increasing age al exposure and wi th decreasing intensity of exposure. These associations were only part ly explained by the direct effects of the parasite on blood-feeding be haviour. Much of the associations were due to the parasite causing ind irect effects to the mosquito because of correlations among its life h istory traits. The parasite increased age at pupation and decreased wi ng length, both of which were associated with the size of blood meals. Thus, trade-offs implicit in the host's life history the correlations between wing length, age at pupation and blood meal size - were cruci al in determining the parasite's effect on the host's blood-feeding su ccess. E. aedis has two types of spores, a uninucleate spore used for horizontal transmission and a binucleate spore used for vertical trans mission. This allowed us to investigate the influence of different tra nsmission routes on the host's blood-feeding behaviour. While blood-fe eding success decreased as the number of uninucleate spores increased, it was not influenced by the number of binucleate spores. Thus the pa rasite decreases its impact on the host, i.e. its virulence, during th e part of the life cycle when transmission is vertical.