Meeting Abstract
Body size is an important life history characteristic that determines fitness. The final body size is determined in part by the timing of attainment of two key body size checkpoints, the critical weight (CW) and the minimum viable weight (MVW). In Drosophila melanogaster, these two checkpoints are indistinguishable and refer to the minimum weight necessary to metamorphose on time. Manipulating the PG in Drosophila has indicated that the MVW/CW is also the point at which endoreplication and ecdysteroidogenesis in the PG become nutrient independent (Ohhara et al, 2017). In contrast, in Manduca sexta, unlike Drosophila, the CW and MVW are distinct checkpoints. In this study, the effects of starvation and hypoxia on Manduca PG size were examined to see how they affected gland growth. In addition, the expression of two P450 enzymes involved in ecdysone biosynthesis, phantom (phm) and disembodied (dib), along with a JH response gene, kruppel homolog (kr-h1), were analyzed at different larval weights. Our preliminary data suggest that unlike in Drosophila, ecdysteroidogenesis in Manduca is nutrient dependent throughout much of larval development, including post MVW/CW. Our findings indicate that the physiological regulation of growth is highly adapted to the feeding ecology of insect species.
