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PubMedDate not supplied

Egg production, egg weight, eggshell strength, and mortality in three strains of commercial layers vaccinated with F strain Mycoplasma gallisepticum.

Three strains of commercial leghorns vaccinated at 17 to 22 weeks of age with F strain Mycoplasma gallisepticum (MG) were maintained through 117 weeks of age. The three strains differed in both mortality and percent egg production per hen housed; however, the strains did not differ in egg weight (EW), eggshell strength (ESS), or percent daily egg production. Results of this study indicate EW and ESS for F strain MG-vaccinated hens follow patterns previously reported for uninfected layers. Further, mortality may account, in part, for differences in percent egg production per hen housed between strains of F strain MG-vaccinated hens.

Animals↗
PubMed1977

The morphology and histochemistry of eggshell formation in Cephaluris coloradensis, a parasite of pikas.

Histochemical and histological studies of Cephaluris coloradensis (Nematoda: Oxyuridae) a parasite of pikas (Ochotonidae), show that in this species the eggs are each enclosed by three shells. The inner shell is chitin with an operculum at one end; the operculum is chemically distinct. The other two shells are lipoprotein. The inner lipoprotein shell is new, not previously reported in nematode species. It forms after the outer lipoprotein shell but beneath it, and is believed to be a product of the egg. The new layer encircles part of the embryo. A thin mucoprotein cementing substance binds the inner lipoprotein shell to the chitinous shell. A thin outermost mucoprotein layer formed from secretions of the uterus covers the eggshell.

Animals↗
PubMed1991

Drosophila chorion genes: cracking the eggshell's secrets.

The chorion genes of Drosophila are amplified in response to developmental signals in the follicle cells of the ovary prior to their transcription. Their expression is regulated both temporally and spatially within this tissue. They thus serve as models both for the regulation of DNA replication and of developmental transcription. The regulatory elements for DNA amplification have been delineated. Their analysis reveals that amplification is mediated by several regulatory regions and initiates at defined origins within the chorion cluster. Proteins involved in amplification are being identified both by mutations affecting amplification and by DNA binding studies. Regulatory elements for temporal as well as spatial control of chorion gene expression have been characterized, and two candidate transcription factor genes have been cloned.

Animals↗
PubMed1991

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

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.

Animals↗