Early nutrition and development of the congeneric parasitoids, Encarsia formosa and Encarsia pergandiella (Hymenoptera: Aphelinidae)
AuthorDonnell, David M.
AdvisorHunter, Martha S.
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PublisherThe University of Arizona.
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AbstractThe congeneric wasps, Encarsia formosa and E. pergandiella (Hymenoptera: Aphelinidae) are solitary endoparasitoids with an overlapping host range. Despite their similarities these wasps produce eggs that differ markedly in size. This dissertation details research conducted to determine differences in the egg provisioning strategies of these two wasp species and to understand how these differences correlate with differences in their early development. The use of the yolk protein, vitellogenin, was examined in the two wasps. A vitellogenin gene was isolated from E. formosa and the mature gene product observed in ovary extracts. Evidence for the use of vitellogenin was not found in an analysis of ovary extracts from E. pergandiella and a gene for vitellogenin was not detected in the genome of this wasp. Embryonic development times for the two parasitoids were studied in hosts of different ages. The embryonic development time of E. formosa is significantly shorter than that of E. pergandiella regardless of the host stage parasitized. This suggests that the rate of embryonic development of E. pergandiella is much more closely linked to that of the host than the development rate of E. formosa. The quantity and composition of amino acids in the eggs of the two wasps was followed over the course of embryonic development. The quantity of amino acid in the eggs of E. formosa does not increase during embryonic development while the eggs of E. pergandiella absorb more than 30 times the quantity of amino acids from the host hemolymph during embryonic development than is present in the eggs at the time oviposition. Only E. pergandiella appeared capable of absorbing and utilizing [¹⁴C]-labeled lysine in an in vitro system. The capacity of E. pergandiella eggs to absorb host nutrients is correlated with the development of a multinucleate extraembryonic membrane that grows to completely encompass the embryo at a very early stage of development. Evidence was found for pinocytosis of material by the embryo from the space bounded by the extraembryonic membrane. A similarly developed extraembryonic membrane was not observed in the eggs of E. formosa .
Degree ProgramGraduate College