Anopheles albitarsis eggs: ultrastructural analysis of chorion layers after permeabilization

Construction of transgenic Anopheles mosquitoes refractory to Plasmodium re quires knowledge of mosquito developmental biology. In order to study Anoph eles embryology the removal or, alternatively, the permeabilization of the melanized and sclerotized egg chorion were attempted. The protocol classica lly used for chorion removal of Drosophila eggs was applied, with partial e fficacy, to Anopheles albitarsis, a neotropical malaria vector. Each step w as monitored by scanning electron microscopy and the results suggest differ ences in chorion composition between the two taxa. As an alternative to cho rion removal, mosquito eggs were permeabilized with benserazide, an inhibit or of Dopa Decarboxylase, one of the enzymes needed for mosquito eggshell s clerotization. Embryo morphology and viability were not affected by this tr eatment. Permeabilization of the egg chorion allowed the ultrastructural ob servation of an internal homogeneous endochorion and an external compound e xochorion, the latter consisting of a basal lamellar layer and protruding t ubercles. (C) 1999 Elsevier Science Ltd. All rights reserved.