Larval hatching from vitellogenin-deficient eggs developed in male hosts of the silkworm

Abstract

Egg production in insects is generally considered to require the availability of the yolk precursor, vitellogenin. In most insects, the synthesis of this protein in the female fat body and its uptake into the ovaries are under the control of the hormones, juvenile hormone and ecdysone¹, which is somewhat analogous to the oestrogenic control in oviporous vertebrates². Indeed, vitellogenin constitutes ∼90% of total egg proteins in the cockroach, Leucophaea maderae³, and ∼40% in the silkworm, Bombyx mori (unpublished data). However, in some insects^4–9, rudimentary ovaries transplanted into male hosts are known to develop to mature eggs with chorion but lacking vitellogenin. Drosophila melanogaster is exceptional in that the ovaries themselves can produce vitellogenin, which accounts for its accumulation in ovaries transplanted into males⁸. Vitellogenin is believed to represent a reserve for use during embryogenesis^10,11. However, experiments on D. melanogaster¹² and B. mori (unpublished data) demonstrated that vitellin was not used rapidly during embryonic development and persisted at a considerable level in the newly hatched larvae. These facts suggest that vitellogenin may not be essential for ovarian development or for embryonic development. Therefore, the present experiments were carried out in order to establish whether the vitellogenin-deficient eggs that matured in male hosts, if activated by artificial parthenogenesis¹³, can compute embryonic and further post-embryonic development. We have found that they can.