Abstract
The occurence of the two major yolk proteins in vitellogenic follicles at various stages of development in the house cricket, Acheta domesticus, was studied electrophoretically. Follicles were staged into size classes ranging from 0.75 mm (stage I) to β₯2.0 mm (stage IV) for unfertilized eggs (chorionated follicles) and the molar ratio of the two vitellins within follicles of each stage determined. The ratio of vitellin I to vitellin II during the early stages of vitellogenesis was found to be greater than that during later stages, suggesting the possibility of changing selectivity of vitellogenin uptake by follicles as they progress through the vitellogenic phases of oogensis. The relative distribution of vitellins I and II within the cytoplasm of unfertilized, chorionated follicles was studied by sectioning stage IV follicles into thirds and determining the molar ration of vitellin I to II in each third. It was found that a differential distribution of each vitellin is established during oogenesis such that vitellin I is present in greater quantities in the posterior region and vitellin II in greater quantities in the anterior region of the follicle.
The molecular weights of the two vitellins were estimated using native polyacrylamide gels of varying percents acrylamide. The molecular weights of vitellins I and II were estimated at 352,000 and 327,000 daltons, respectively.