Male-grown eggs in Hyalophora: deficient follicle cell secretion as well as protein and lipid yolk deposition
1994
Pan, M.L. | Wiemerslage, L.J. | Telfer, W.H.
Ovaries transplanted to male Lepidoptera during late larva or pupal stages produce smaller and fewer chorionated eggs than those remaining in place or transplanted to other females. Small size is shown here in Hyalophora cecropia to result not only from a lack of vitellogenic hemolymph proteins but also from dysfunction of the follicular epithelium. Several aspects of egg formation can proceed normally in the male environment, including RNA deposition by the nurse cells, the conversion of lipophorin to a very high density form as the oocyte endocytoses it, and the customary period of osmotic swelling between the end of yolk deposition and the beginning of chorion formation. But as would be expected, male-grown eggs lack vitellogenin and contain very little microvitellogenin. They also contain lower than normal amounts of lipophorin, which is related to the male's poor ability to replace this protein as the oocyte removes it from the hemolymph. A low phospholipid content can be attributed to the absence of vitellogenin and a low triglyceride droplet content to the shortage of lipophorin. Two other deficiencies, however, could not be directly explained by the low levels of vitellogenic hemolymph proteins: paravitellogenin and chorion, both secretions of the follicle cells, are deposited in significantly reduced amounts. Males of this species, in addition to lacking sufficient vitellogenic proteins and lipids in their hemolymph, are thus unable to fully support the secretory activities of the follicle cells.
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