• Mussel collecting by kayak
The Dr. E. Paul & Frances H. Reiff Professor of Biology



Office: LSP332B


B.A.S., 1987, Biological Sciences and Anthropology, Stanford University

M.S., 1987, Biological Sciences, Stanford University

Ph.D., 1995, Marine Biology, Scripps Institution of Oceanography (U.C. San Diego)


The work in our lab focuses on biochemical adaptations of marine organisms to extreme environments.  Why are some organisms able to survive conditions that are lethal to most others?  What are the biochemical mechanisms that allow these species to avoid damage on the cellular level, or repair that damage quickly and efficiently when it occurs?  Are the strategies that marine species employ sufficient to protect them from predicted environmental changes?  These broad questions form the basis for the research projects my students and I pursue.

Over the past several years, we have used proteomics techniques to develop a clearer picture of cellular responses to abiotic stresses.  Proteomics is the field of bioinformatics that describes the protein complement in a cell or tissue; the protein expression profiles we develop represent the phenotype of the organism, as opposed to the genotype presented by genomics data.  Because of this, proteomics data are uniquely valuable in describing and quantifying the protective or repair mechanisms that are induced by stress exposure.

We have chosen to focus our attention on a common intertidal mollusk found in the salt marshes along the east coast of the United States, Geukensia demissa, the ribbed salt marsh mussel.  While not particularly charismatic, G. demissa is a wonderful organism for studying stress responses on the cellular level – in its native habitat it experiences wide ranges of temperature, rapid changes in salinity, UV exposure, and long bouts of hypoxia when it is exposed at low tide.  We are using proteomic techniques to determine which proteins in G. demissa tissues change most significantly in abundance after exposure to one or more of these stresses, and to find out whether certain types of proteins, or suites of proteins, are seen across multiple stresses.  By identifying these proteins, we will be able to understand better how such a resilient species as G. demissa is able to survive in its highly variable and unpredictable environment.

We expect that our findings will have implications far beyond G. demissa itself, too, and will offer insights into how all metazoans respond to single and multiple stressors, helping to develop a framework for understanding how marine species will respond to natural and anthropogenic environmental changes.  If you are interested in exploring the interface between biochemistry and marine biology, while working with advanced proteomic techniques and equipment, contact me about opportunities to pursue research in my lab.

Grants & Awards

P. A. Fields. A proteomic analysis of stress responses in the ribbed salt marsh mussel, Geukensia demissa.  National Science Foundation RUI grant.  2009-2013.

P. A. Fields and L. Tomanek. Evolutionary and Ecological Physiology of Blue Mussels (genus Mytilus): Gene and Protein Expression and Molecular Evolution in Differently-adapted Congeners. National Science Foundation ROA grant. 2008.

P. A. Fields.  Structure and Function in Enzymes Adapted to Extreme Cold.  National Science Foundation RUI grant.  2003-2007.

P. A. Fields and G. N. Somero. Adaptation of Malate Dehydrogenases to Temperature and Hydrostatic Pressure: Complementary Changes in Amino Acid Sequence and Intracellular Milieu. National Science Foundation ROA grant.  2004.


Selected Publications (* denotes undergraduate author)

Fields, P. A., C. Eurich, W. L. Gao* and B. Cela*. (2014).  Changes in protein expression in the salt marsh mussel Geukensia demissa: evidence for a shift form anaerobic to aerobic metabolism during prolonged aerial exposure.  J. exp. Biol. 217: 1601-1612.

Fields, P. A., K. M. Cox* and K. R. Karch*.  (2012).  Latitudinal variation in protein expression after heat stress in the salt marsh mussel Geukensia demissa.  Integr. Comp. Biol.  52: 636-647.

Fields, P. A., M. J. Zuzow and  L. Tomanek. (2012). Proteomic responses of blue mussel (Mytilus) congeners to temperature acclimation.   J. exp. Biol. 215: 1106-1116.

Eurich, C., P. A. Fields and E. Rice.  (2012).  Proteomics:  Protein Identification Using Online Databases.  Amer. Biol. Teacher. 74: 250-255.

Fields, P. A., C. M. Strothers* and M. A. Mitchell. (2008). Function of muscle-type lactate dehydrogenase and citrate synthase of the Galapagos marine iguana, Amblyrhynchus cristatus, in relation to temperature. Comp. Biochem. Physiol. B. 150: 62-73.

Fields, P. A., E. L. Rudomin* and G. N. Somero. (2006). Temperature sensitivities of cytosolic malate dehydrogenases from native and invasive species of marine mussels (genus Mytilus): sequence-function linkages and correlations with biogeographic patterning. J. exp. Biol. 209: 656-667.
Fields, P. A. and D. A. Houseman*. (2004) Decreases in activation energy and substrate affinity in cold-adapted A4-lactate dehydrogenase: Evidence from the Antarctic notothenioid fish Chaenocephalus aceratus. Mol. Biol. Evol. 21: 2246-2255.

Fields, P. A., Y-.S. Kim, J. F. Carpenter and G. N. Somero (2002). Temperature adaptation in Gillichthys (Teleost: Gobiidae) A4-lactate dehydrogenases: identical primary structures produce subtly different conformations. J. Exp. Biol. 205: 1293-1303.

Fields, P. A., B. D. Wahlstrand* and G. N. Somero (2001). Intrinsic vs. extrinsic stabilization of enzymes: the interaction of solutes and temperature on A4-lactate dehydrogenase orthologs from warm-adapted and cold-adapted marine fishes. Eur. J. Biochem. 268: 4497-4505.

Fields, P. A. (2001). Protein function at thermal extremes: Balancing stability and flexibility. Comp. Biochem. Physiol. A 129: 417-431.

Fields, P. A. and G. N. Somero (1998). Hot spots in cold adaptation: Localized increases in conformational flexibility in A4-lactate dehydrogenase orthologs of Antarctic notothenioid fishes. Proc. Natl. Acad. Sci. USA 95: 11476-11481.

Fischer, J. M., P. A. Fields, P. G. Pryzbylkowski*, J. L. Nicolai* and P. J. Neale. (2005). Sublethal exposure to UV radiation affects respiration rates of the freshwater cladoceran Daphnia catawba. Photochem. Photobiol. 82: 547-550.

Lin, J-.J., T-.H. Yang, B. D. Wahlstrand*, P. A. Fields and G. N. Somero. (2002). Phylogenetic relationships and biochemical properties of the duplicated cytosolic and mitochondrial isoforms of malate dehydrogenase from a teleost fish, Sphyraena idiastes. J. Mol. Evol. 54:107-117.

Course Information

BIO 220. Principles of Physiology and Development
BIO 325. Marine Biology
BIO 334. Metabolic Biochemistry
FND 111P. Global Change