The Dr. E. Paul & Frances H. Reiff Professor of Biology



Office: Room 332B


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)

Postdoc, Hopkins Marine Station of Stanford Unversity

Courses Taught

BIO 220. Principles of Physiology and Development

BIO 325. Marine Biology

BIO 334. Metabolic Biochemistry

BIO 374. Tropical Biology

BIO 390/490.  Independent Research


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 an F&M student, and 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.


Selected Publications (* denotes undergraduate author)

Fields PA, EM Burmester*, KM Cox* and KL Karch*. 2016. Rapid proteomic responses to a near-lethal heat stress in the salt marsh mussel Geukensia demissa.  Journal of Experimental Biology.  doi: 10.1242/jeb.141176 PubMed

Fields PA, YW Dong, XL Meng and GN Somero. 2015. Adaptations of protein structure and function to temperature: there is more than one way to “skin the cat.” Journal of Experimental Biology 218: 1801-1811.  PubMed free article

Fields PA, C Eurich, WL Gao* and B Cela*. 2014.  Changes in protein expression in the salt marsh mussel Geukensia demissa: evidence for a shift from anaerobic to aerobic metabolism during prolonged aerial exposure.  Journal of Experimental Biology 217: 1601-1612. PubMed free article

Fields PA, KM Cox* and KR Karch*.  2012.  Latitudinal variation in protein expression after heat stress in the salt marsh mussel Geukensia demissa.  Integrative and Comparative Biology  52: 636-647. PubMed free article

Fields PA, MJ Zuzow and  L Tomanek. 2012. Proteomic responses of blue mussel (Mytilus) congeners to temperature acclimation.   Journal of Experimental Biology 215: 1106-1116. PubMed free article

Eurich C, PA Fields and E Rice.  2012.  Proteomics:  Protein Identification Using Online Databases.  Amer. Biol. Teacher 74: 250-255. Link to abstract

Fields PA, CM Strothers* and MA Mitchell. 2008. Function of muscle-type lactate dehydrogenase and citrate synthase of the Galapagos marine iguana, Amblyrhynchus cristatus, in relation to temperature. Comparative Biochemistry and Physiology. B 150: 62-73. PubMed

Fields PA, EL Rudomin* and GN 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. Journal of Experimental Biology 209: 656-667. PubMed free article
Fields PA and DA Houseman*. 2004 Decreases in activation energy and substrate affinity in cold-adapted A4-lactate dehydrogenase: Evidence from the Antarctic notothenioid fish Chaenocephalus aceratus. Molecular Biology and Evolution 21: 2246-2255. PubMed free article

Fields PA, Y-S Kim, JF Carpenter and GN Somero 2002. Temperature adaptation in Gillichthys (Teleost: Gobiidae) A4-lactate dehydrogenases: identical primary structures produce subtly different conformations. Journal of Experimental Biology 205: 1293-1303. PubMed free article

Fields PA, BD Wahlstrand* and GN 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. European Journal of Biochemistry. 268: 4497-4505. PubMed free article

Fields PA. 2001. Protein function at thermal extremes: Balancing stability and flexibility. Comparative Biochemistry and Physiology A 129: 417-431. PubMed

Fields PA and GN 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. PubMed free article

Fischer JM, PA Fields, PG Pryzbylkowski*, JL Nicolai* and PJ Neale. 2005. Sublethal exposure to UV radiation affects respiration rates of the freshwater cladoceran Daphnia catawba. Photochemistry and Photobiology 82: 547-550. PubMed

Lin J-J, T-H Yang, BD Wahlstrand*, PA Fields and GN Somero. 2002. Phylogenetic relationships and biochemical properties of the duplicated cytosolic and mitochondrial isoforms of malate dehydrogenase from a teleost fish, Sphyraena idiastes. Journal of Molecular Evolution 54:107-117. PubMed

Grants & Awards

P. A. Fields.  Biochemical adaptation to temperature in the coral-dinoflagellate symbiosis. National Science Foundation RUI grant.  2017-2020.

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.