Principal Investigator: Matthias W. Lorenz
Adult female insects face a trade-off in energy allocation: energy that is invested into offspring (i.e. egg production) is not available for survival or general maintenance of the mother. Female G. bimaculatus from our lab colony exhibit a comparatively short pre-reproductive phase during which flight is possible. About 2-3 days after adult emergence vitellogenic egg growth starts, leading to high ovary weights. At the same time the flight muscles begin to histolyse and flight activity ceases. The age at which vitellogenesis and flight muscle histolysis commence can be quite variable and it is obvious that this high phenotypic plasticity ensures a comparatively rapid adaptation to changing environmental conditions. It is thought that in the field this plasticity depends on the specific quality of the habitat (e.g. predictable and/or suitable conditions for reproduction vs. unpredictable and/or inappropriate conditions), on the population structure and density, and on the presence or absence of parasites. Furthermore, we recently showed that also temperature affects the chronology of this trade-off. In the lab, the onset of vitellogenesis/flight muscle histolysis is easily altered by artificial selection, which we can take advantage of to investigate the endocrine mechanisms underlying the observed plasticity.
A few females (ca. 5-10%), however, manage to escape this trade-off: although carrying fully developed ovaries with a high egg number, they still possess functional flight muscles and some are even able to fly. According to what is known to date about the endocrine regulation of oogenesis and flight muscle histolysis in crickets, such females should not exist at all. Therefore, we take every effort to resolve this exciting puzzle.
For comparative purposes, we also study the physiological basis of the oogenesis flight-syndrome in large milkweed bugs (Oncopeltus fasciatus) which are subjected to short- or long-day conditions and in apterous and alate morphs of the pea aphid (Acyrthosiphon pisum).