Meeting Abstract
Patterns of energy and resource allocation to maintenance, growth and reproduction are related to lifetime reproductive output. One mechanism that might drive allocation of resources is phenotypic plasticity of organ size. Animals can increase or decrease the size of metabolically active organs in response to certain environmental conditions; that might have consequences in overall expenditure and allocation of energy. We studied phenotypic plasticity of organ size in females of Diploptera punctata, a viviparous cockroach. Female D. punctata give birth 9-12 nymphs after a gestational period of 55-60 days. We used four groups of females: (1) pregnant females at day 55 fed with a high quality (HQ) diet, (2) pregnant females at day 55 fed with a low quality (LQ) diet, (3) non-pregnant females in which we switched diets from LQ to HQ, then back to LQ in periods of 30 days, and (4) non-pregnant females in which we switched diets from HQ to LQ then to HQ again in periods of 30 days. We measured metabolic rate (MR), and mass of digestive tract, abdominal organs, embryos in the pregnant females, and carcass. We found a positive relationship between gut mass and MR, and a negative association between the mass of abdominal organs and MR. There was a trade-off between gut mass and abdominal organ mass, and gut mass and reproductive output. Females acclimated to LQ adjusted their physiological traits in a manner dependent on the previous acclimation event, but when food availability was high in the first event, there was no relationship between changes in MR and diet. We conclude that changes in organ mass in response to environmental conditions determines complex patterns of allocation of resources to reproduction in D. punctata.
