Tuesday, 19 November 2002

This presentation is part of : Display Presentations, Section B. Physiology, Biochemistry, Toxicology, and Molecular Biology

Cotesia flavipes-egg surface features in suitable and unsuitable lepidopteran hosts

Marianne Alleyne1, James B. Nardi2, and Robert N. Wiedenmann1. (1) Illinois Natural History Survey, Center for Economic Entomology, 172 Natural Resources Building, 607 E. Peabody Drive, Champaign, IL, (2) University of Illinois at Urbana-Champaign, Department of Entomology, 320 Morrill Hall, 505 S. Goodwin Avenue, Urbana, IL

We studied surface features of eggs of the gregarious parasitoid Cotesia flavipes (Hymenoptera: Braconidae) before and after oviposition into either suitable or unsuitable hosts. Diatraea saccharalis (Lepidoptera: Pyralidae) is a suitable host; most eggs hatch successfully 3 to 4 days after oviposition. In contrast, Ostrinia nubilalis (Lepidoptera: Crambidae) is not a suitable host; parasitoid eggs are encapsulated and killed within 24 hours of oviposition. Parasitoid ovaries and host abdomens (which contained parasitoid eggs) were prepared and sectioned for scanning electron microscopy at different times after oviposition. Eggs were also dissected from ovaries or hosts and prepared for transmission electron microscopy. No differences in surface features, such as a protective fibrous layer or virus-like proteins, were observed between eggs dissected from ovaries, from suitable hosts or from unsuitable hosts before encapsulation commenced. It is likely that the functioning of other early-immunosuppressive factors, such as ovarian proteins and venom, rather than egg surface features, explain the differences in C. flavipes-egg encapsulation within these suitable and unsuitable hosts.

Species 1: Hymenoptera Braconidae Cotesia flavipes
Species 2: Lepidoptera Pyralidae Diatraea saccharalis (sugarcane borer)
Species 3: Lepidoptera Crambidae Ostrinia nubilalis (European corn borer)
Keywords: parasitoid, immune response

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