Structure and morphogenesis of the eggshell and micropylar apparatus in the olive fly, Dacus oleae (Diptera: Tephritidae)

Abstract

The egg of the olive fly, Dacus oleae (Diptera, Tephritidae), is laid inside olives and the larva eventually destroys the fruit. The oocyte is surrounded by several distinct layers which are produced during choriogenesis. The chorion covering the main body of the egg outside of the vitelline membrane includes a "wax" layer, an innermost chorionic layer, an endochorion consisting of inner and outer layers separated by pillars and cavities similar to their counterparts in Drosophila melanogaster, as well as inner and outer exochorionic layers. The anterior pole is shaped like an inverted cup, which is chiefly hollow around its base and has very large openings communicating with the environment. Holes through the surface of the endochorion result from deposition of endochorionic substance around follicular cell microvilli. An opening at the apex of the cup provides an entrance for sperm entering the micropylar canal, which traverses the endochorion and continues into a "pocket" in a thickened vitelline protrusion. The micropylar canal is formed by deposition of endochorion and vitelline membrane around an elongated pair of follicular cell extensions. These extensions later degenerate and leave an empty canal about 5 microns in diameter and the narrower pocket about 1 micron in diameter. Respiration is thought to be facilitated by openings at the base of the anterior pole as well as by openings through the "plastron" around the main body of the shell.

Embryonic development of the olive fruit fly, Bactrocera oleae Rossi (Diptera: Tephritidae), in vivo

“…The eggshell of B. oleae has a smooth chorion and is probably important in providing air to the developing embryos inside the fruit, as is known to be the case in other insect eggs (Hinton, 1981). The anterior and posterior poles that were photographed in living embryos in this study were described previously by Margaritis (1985) and Mouzaki and Margaritis (1991). The results of the present study were in agreement with their results by showing the anterior pole as inverted and cup-shaped.…”

The dual role of chorion peroxidase in Bactrocera oleae chorion assembly

“…Thus, it is very likely that the 76, 66 and 54 kDa proteins could confer similar protection shields against oxygen radicals-mediated destruction in the cell populations they are selectively produced. Having established that the completion of B. oleae oogenesis is mainly characterized by the H 2 O 2 -mediated chorion hardening (Mouzaki and Margaritis, 1991a;Margaritis and Mazzini, 1998), it seems reasonable to speculate that the 54 kDa peroxidase is directly involved in both the protein crosslinking process and the detoxification protection mechanism of the developing follicles. Since there are a limited number of reports describing the in vivo physiological functions of various peroxidases in different tissues, such as the nervous system (Ichmiya et al, 1997) and muscle (Knopp et al, 1999), the extensive study of the bPxd protein forms in B. oleae development and morphogenesis is an extremely important biological issue that needs further exploration.…”

Actin cytoskeleton reorganization of the apoptotic nurse cells during the late developmental stages of oogenesis inDacus oleae

“…oleae follicles were processed for conventional light and transmission electron microscopy (TEM) as described elsewhere [Margaritis et al, 1980;Margaritis, 1986]. Staging of the developing follicles during oogenesis was accomplished according to Margaritis [1986], Mouzaki et al [1991], and our observations. Visualization of actin filaments by TEM was achieved according to Guild et al [1997] with the following modifications: ovaries were dissected in Ringer's solution and fixed in 50 mM PBS containing 1% glutaraldehyde and 1% OsO 4 , pH 6.2, for 1 h at 4°C.…”