Research
I work on connections between physiological processes and animal ecology and evolution. Processes of special interest include (i) temperature effects on metabolic systems and (ii) the transport of oxygen and water between animals and their environments. Collectively we know lots of textbook-style details about animal physiology, but many open, and spectacularly interesting, questions remain about how physiological systems evolve, how physiology works across different environmental scales, and how physiological plasticity is shaped by evolution. My lab takes a broad, integrative approach to answering such questions.
Two bits of basic physiology that organize my thinking:
Temperature-oxygen interactions: Metabolic rates of most ectotherms are quite sensitive to temperature, with Q10s between 2 and 4 (i.e., for a 10°C increase in temperature metabolic rate increases by 2 - 4 fold). By contrast, the oxygen diffusion coefficient is relatively insensitive to temperature, with a Q10 of about 1.5. Whether oxygen transport itself is as insensitive to temperature is unclear. Transport depends on both the kinetic energy of the diffusing molecules and the material properties of the substance in which diffusion occurs, and material properties may be temperature sensitive. However, as a start, a reasonable prediction is that in ectotherms (especially those for which diffusion is an important component of oxygen transport--i.e., most ectotherms) will face vastly different oxygen problems at low and high temperatures. At low temperatures, the potential oxygen supply should exceed oxygen demand (see figure at left); conversely, at high temperatures, oxygen demand should outstrip oxygen supply. How do organisms adjust physiology, morphology, or behavior in response to these dynamic supply-demand relationships?
I am exploring these questions using both insects and nudibranchs.
Oxygen-water tradeoffs: All terrestrial animals need oxygen, but getting it imposes costs-e.g., in building and maintaining structures for oxygen exchange and transport or in finding habitats with suitable oxygen levels. Another less obvious cost appears in the water budget. In particular, structures that transport oxygen into organisms-gills, lungs, skin, trachea, eggshells-also lose water to the environment. I am pursuing a basic set of questions about these tradeoffs: (1) Across terrestrial metazoa generally, what fraction of total water loss is accounted for by respiratory water losses? (2) How do physiological mechanisms affecting the oxygen-water tradeoff evolve in response to different environments?-e.g., How do desert organisms solve the water loss part of obtaining oxygen? (3) Are some kinds of respiratory systems better than others at minimizing water costs of obtaining oxygen-e.g., tracheae in insects versus tidal ventilation of the lungs in mammals? Most of my research in this area focuses on gas exchange across insect eggshells (see below).