Date of Award

1985

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Abstract

Oogenesis commenced on day 3 (day 0 = adult ecdysis) in Acheta domesticus L., which, based on degeneration of the flight muscles, was approximately when juvenile hormone was released. Starvation did not prevent the onset of oogenesis, although egg production was greatly reduced. Virgin females did not oviposit and the oviducts filled with eggs by day 15. Compaction appeared to be a factor limiting oogenesis. The digestive tract was compressed and feeding reduced, which might be the primary factors terminating oogenesis. The concentration of juvenile hormone esterase (JHE) did not change as virgins filled with eggs, which indicated that JHE was not involved with termination of oogenesis. Prostaglandin topically applied to the genital opening was 3x more effective in initiating oviposition than when injected. Testectomized males stimulated oviposition of unfertilized eggs, indicating that the prostaglandin synthetase was not produced in the testes. The male cemented the spermatophore in the female genital chamber; this seal probably reduced chances for degradation of the enzyme and increased the efficiency of semen transfer. The metabolic rate of virgin females was greatly reduced because the oxygen consumption by unfertilized eggs is very low. Although more than 90% of the eggs were derived directly from food, fat body reserves were used up during egg production. Mated females produced more eggs and lost more fat body than virgins or ovariectomized females. As females lost fat body, their survival time when starved decreased. Ovulated eggs stored in the oviducts could not be resorbed. The vitellogenin was partially purified and isolated by low-ionic-strength precipitation and DEAE-affinity chromatography. The molecular weight was estimated at 400,000 daltons by calibrated gel filtration, and the pI estimated at 5.7-6.4 by isoelectric focusing. It was a glycolipoprotein containing 9.6% lipid and 6.6% carbohydrate. At least two subunits having molecular weights of 112,000 and 40,000 daltons, respectively, were identified by calibrated SDS-polyacrylamide gels. Using an integrating densitometer on stained SDS-PAGE preparations, it was determined that starvation, age, and egg production reduced the vitellogenin titre and that ovariectomy elevated vitellogenin titre.

Pages

143

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