THE EGGSHELL OF THE CHERRY FLY RHAGOLETIS-CERASI

One of the major pests in Greek cherry orchards is the cherry fly Rhagoletis cerasi (Diptera: Tephritidae). In order to complete our comparative work on the chorion assembly of other representatives of the fruit flies (e.g. Ceratitis capitata and Dacus oleae) we studied eggshell morphogenesis in the cherry fly. The oocyte is surrounded by several distinct layers which are produced during choriogenesis. The eggshell consists of the vitelline membrane, a fibrous layer of possible water-proofing function, an innermost chorionic layer, endochorionic and exochorionic layers. The endochorion shows a branched configuration with irregular cavities, and the exochorion consists of inner and outer layers for better embryo protection. At the anterior region of the follicle, the hexagonal borders of the follicle cells are created by endochorionic material, covered by both inner and outer exochorion. This area resembles the D. melanogaster chorionic appendages and therefore can serve for plastron respiration. The structural results support the phylogenetic relationships among the tephritids (Rhagoletis is closer to Ceratitis than Dacus). The presence of peroxidase in the endochorion, detected by diaminobenzidine, is consistent with the eggshell hardening at the end of choriogenesis, following the same pattern with the other fruit flies studied so far. Two major chorionic proteins are found both in R. cerasi and in C capitata and therefore general conclusions can be drawn from this study, concerning the pattern of choriogenesis, which all dipteran insects follow, in order to create a resistant and functional eggshell, and the high conservation of the proteinaceous components of the chorion among species in the order

THE EGGSHELL OF THE ALMOND WASP EURYTOMA-AMYGDALI (HYMENOPTERA, EURYTOMIDAE) .1. MORPHOGENESIS AND FINE-STRUCTURE OF THE EGGSHELL LAYERS

The almond wasp Eurytoma amygdali (Hymenoptera: Eurytomidae) feeds and oviposits exclusively in almonds and therefore is characterized as an insect of economic importance. Its meroistic polytrophic ovaries include follicles with a tri-partite configuration. The mature follicles exhibit two filaments occupying the two poles of the egg. One is the micropylar filament while the other might serve for respiration since it is likely that its flattened end layers remain outside the almond fruit. The eggshell is formed by aposition and the follicle cells, which surround the follicle until the end of oogenesis, may be responsible for protein synthesis and secretion which finally lead to the assembly of the eggshell. The eggshell comprises the thin vitelline membrane, possibly a ‘wax’ layer of waterproofing function. a transluscent layer which appears amorphous even al the end of choriogenesis, a granular layer, including large and small electron-dense granules, and finally a columnar layer very similar to layers found in other insect species of the same or different orders. Peroxidase is histochemically found for the first time in an eggshell of the Hymenoptera order; the tranluscent layer in particular is positively stained (electron-dense). Two possible roles of this peroxidatic activity are discussed, first, in comparison to other fruit-infesting insects, we assume that elastic chorion is produced through the function of peroxidase induced bonds (resilin-type bonds): very important for avoiding premature breaking, while being oviposited through a narrow ovipositor. Second, referring to other studies, this layer can play a bactericidal role for additional embryonic protection