Changes in the fat body and oocysts during starvation and vitellogenesis in a mosquito, Aedes aegypti (L.)

Abstract

When Aedes aegypti females first emerge as adults, their oocytes possess no yolk. The abdominal fat body cells contain large quantities of lipid, protein, and glycogen, and possess many free ribosomes, but have very little rough endoplasmic reticulum (RER). When the females are starved for four days, their oocytes form fine lipid and protein yolk endogenously, the latter being located mainly around the nucleus. The adipocytes in these fasted mosquitoes have greatly reduced amounts of lipid, protein and glycogen and contain many cytolysosomes. Seven hours after 4-day-starved females had fed on blood, their oocytes begin filling with exogenous protein yolk at the oolemma, and lipid arises endogenously throughout the ooplasm. At this hour, the fat cells have synthesized more RER than is seen in unfed controls. Twenty-four hours post blood meal, the follicle cells have secreted discrete endochorionic plaques onto the oolemma. At this period, the adipocytes are densely filled with RER, and show for the first time many Golgi bodies and protein inclusions. They have noticeably less glycogen than at seven hours. Within 48 hours after mosquitoes have fed on blood, the endochorion forms a continuous layer around the steadily enlarging egg which is synthesizing additional protein and lipid yolk. Concurrently, the adipocytes show a greatly increased amount of glycogen and a significant reduction of RER. By the sixtieth hour after the blood meal, the follicle cells are attenuated, and the fat cells have less RER and more glycogen than at 48 hours. The nurse cells steadily decrease in size during vitellogenesis and release material onto the micropyle.