Anopheles albitarsis eggs: ultrastructural analysis of chorion layers after permeabilization.

Construction of transgenic Anopheles mosquitoes refractory to Plasmodium requires knowledge of mosquito developmental biology. In order to study Anopheles embryology the removal or, alternatively, the permeabilization of the melanized and sclerotized egg chorion were attempted. The protocol classically used for chorion removal of Drosophila eggs was applied, with partial efficacy, to Anopheles albitarsis, a neotropical malaria vector. Each step was monitored by scanning electron microscopy and the results suggest differences in chorion composition between the two taxa. As an alternative to chorion removal, mosquito eggs were permeabilized with benserazide, an inhibitor of Dopa Decarboxylase, one of the enzymes needed for mosquito eggshell sclerotization. Embryo morphology and viability were not affected by this treatment. Permeabilization of the egg chorion allowed the ultrastructural observation of an internal homogeneous endochorion and an external compound exochorion, the latter consisting of a basal lamellar layer and protruding tubercles.