Ph.D. Candidate - Insect Physiology
PO Box 110620
Gainesville, FL 32611
(352) 870-5346 x211
Metabolism is the chemistry of life, it is a collection of processes that allow organisms to grow, reproduce, and acclimate. However, metabolism occurs at many different levels within an organism. At the cellular level, organisms must break down organic compounds and rebuild others. On a larger scale, at the organismal-level, metabolic resources are regulated and allocated in response to internal and external environmental cues. The interaction of cellular and organismal-level metabolism is modified by and can shape the life history of organisms helping them to survive and successfully reproduce. Insects provide an excellent example of the diversity of life history strategies employed by organisms. Remarkably, they have adapted to fill nearly every possible terrestrial and freshwater niche on our planet! Therefore, insects are a natural model system for investigating the metabolic basis of life history evolution. My research focuses on two energetically demanding life history milestones, diapause and reproduction using the flesh fly, Sarcophaga crassipalpis to explore these questions.
1) Resource Allocation to Reproduction
2) Resource Conservation and Utilization during Diapause
Sarcophaga crassipalpis compared to Drosophila
Resource Allocation to Reproduction
Understanding the role of nutrient acquisition and allocation to reproduction is fundamental to the study of life history evolution and physiological ecology. In order to reproduce, a large amount of resources must be allocated to egg production. This may represent a significant life history cost, because resources may be shuttled away from other tissues. Determining how nutrient allocation changes over time, as the internal nutritional landscape changes, can lead to better understanding of the mechanistic basis of allocation decisions in animals.
Currently, I am using artificial diets labeled with naturally occurring stable isotopes to track how resources are allocated in S. crassipalpis. This method also allows me to look at how resource allocation changes from the first clutch of eggs to subsequent clutches. Unlike radioactive isotopes, stable isotopes are harmless and do not degrade. Used in conjunction with radioactive isotopes, they allow us to get a more complete picture of how resources are shuttled inside animals.
Resource Conservation and Utilization during Diapause
Seasonal fluctuations in temperature and rainfall can make conditions inhospitable during certain times of the year. To mitigate unfavorable conditions, insects may undergo diapause, an environmentally programmed resting state, similar to mammalian hibernation. Many insects diapause in non-feeding life stages such as eggs or pupae. Therefore, regulating metabolism during diapause is crucial because insects cannot feed or drink during these life stages. Insects that diapause as pupae must obtain sufficient resources prior to diapause, and retain enough reserves at the end of diapause to complete development. In addition, diapause can be metabolically expensive and there may be fitness costs associated with this life history transition. For example, diapausing S. crassipalpis females have reduced fertility compared to non-diapausing flies. This suggests that resources typically used for reproduction are reallocated to sustain diapause in over-wintering flies. Therefore, there may be a selective advantage to maintain a low metabolic rate during pupal diapause.
In order to better understand the mechanisms used to maintain this suppressed metabolic state, I am investigating fuel usage in diapausing flesh flies. I can measure metabolism indirectly using a technique called indirect calorimetry, or respirometry. This technique estimates energy expendature by looking at the levels of respiratory gasses.
|Copyright 2009 Frank Wessels|