Polyembryonic proliferation: from 2 to 2000

Polyembryonic wasps are parasitoids that lay their eggs inside the bodies of other insects. These eggs then undergo a clonal phase of development that results in production of multiple genetically identical offspring. Copidosoma floridanum produces up to 3000 morula stage embryos that form an assemblage called a polymorula. Many aspects of C. floridanum development are well studied but comparatively little is known about the proliferation phase of embryogenesis. In the present studies, spatio-temporal patterns of mitosis are characterized using cell cycle markers during the proliferation phase. Proliferation involved both mitosis of embryonic cells and partitioning of morulae by the inner embryonic membrane. All embryonic cells incorporated the S-phase marker bromodeoxyuridine (BrdU) but mitosis varied spatially and temporally. Additional observations indicated that the polymorula becomes associated with the tracheal system of the host; potential recruitment of the hosts tracheae to the parasitoid also is discussed.