Stanley Sessions, Professor of Biology

333 Johnstone Science Center

Areas of expertise:
developmental biology, regenerative biology, evolutionary cytogenetics, amphibian biology, tropical salamanders, deformed amphibians
Ph.D., University of California at Berkeley

Recent courses taught:

  • BIOL101: Biology in Practice: Biotechnology (FYS); Salamander Science (FYS); Astrobiology (FYS)
  • BIOL202/203: Concepts in Biology
  • BIOL241/341: Natural History of Costa Rica (J Term off-campus)
  • BIOL300: Animal Development
  • BIOL307: Vertebrate Zoology
  • BIOL313: Genetic Analysis
  • BIOL318: Evolution
  • BIOL399: Animal Science
  • BIOL420: Developmental Genetics (seminar)

Distinctions (awards, fellowships, grants):


  • US Professor of the Year Award, Council for Advancement and Support of Education, the Carnegie Foundation for the Advancement of Teaching; nominated by Hartwick College, 2013; 2014.



  • Core Teaching/Research Award, Department of Biology, Biotechnical Faculty, University of Ljubljana, Slovenia (2015-16; 2017): Non-Destructive Approach to Understanding Genome Evolution in Proteid Salamanders.

National Science Foundation

  • NSF S-STEM grant: “Biotechnology in Practice Scholarship Program at Hartwick College” ($552,000; 2010-2016); PI: S.K. Sessions; Co-PIs: Robert Gann, Douglas Hamilton, Laura Malloy, and Andrew Piefer.
  • NSF Planning grant: “Expanding Collaborative Research and Education Opportunities to Protect Biological Diversity on Public Lands in Upstate New York” ($25,000; 2010-2011); PI: Brian Hagenbuch.
  • NSF RUI research grant:  “Collaborative Research: Community ecology as a framework for understanding disease dynamics” ($86,527; Jan 2006 – Jan 2009); PI: S.K. Sessions.

Other Outside Grants and Awards (selected)

  • Corning Foundation Grant, Summer Research, 2017 (PI: SKSessions; co-PI: Eric Cooper) ($5,000).
  • Dean Graham Foundation Award, 2013-2015: Student/faculty Collaborative Research ($12,800).
  • Oregon Community Foundation Grant, 2011: Sex Reversal in Natural Populations of Frogs.
  • Cargill Foundation Grant for Environmental Science, Environmental Science and Policy program, Hartwick College, 2009-2014.
  • Rockefeller Foundation Fellowship: Imaging Biodiversity, Institute for Electronic Arts, Alfred University (2001-2002)
  • Oregon Community Foundation Grant to support research on deformed amphibians (1998).
  • Culpeper Grant for use of computer-assisted micro-image analysis in the classroom (1996)

Freedman Awards (Hartwick)

  • Freedman Award in Theatre (with members of the Fall 2012 HMS class and Marc Shaw: “What’s Real”).
  • Freedman Award in the Science Division (with Nalisha Bascom, ’12), Hartwick College: Seasonal Variation in Cell Proliferation in the Nasal Neuroepithelium of the Eastern Newt, (Notophthalmus viridescens)
  • Freedman Award in Science Division (with Jesse Werner, ’09), Hartwick College:  Pattern Formation in Regenerating Tails and Spinal Cords in Salamanders, 2009.
  • Freedman Award in Theatre (with Yuri Mataev, ’09, and Marc Shaw): Bridging the Ivory Towers, a conceptual performance art project attempting to build a bridge between the Biological Sciences and Theatre Arts, 2009.
  • Freedman Award in Science (with Dustin Jones, ’09), Hartwick College: Heart bioengineering in red-spotted newts, Notophthalmus viridescens, 2009.
  • Freedman Award in Cognitive Science (with Yuri Mataev, ’09), Hartwick College: Brain regeneration in the red-spotted newt, Notophthalmus viridescens, 2009.

Other Hartwick Grants and Awards

  • Outstanding Employee Award, Hartwick College, 2010.
  • Winifred D. Wandersee Scholar-in-Residence Award, Hartwick College, 2008-2009.
  • Margaret B. Bunn Award for Outstanding Teaching, Hartwick College, 2001.
  • Winifred D. Wandersee Scholar-in-Residence Award, Hartwick College, 1998.
  • Hartwick College Teacher/Scholar Award, Teacher Excellence Program of the Independent  College Fund of New York, 1996.
  • Hartwick College Board of Trustees Faculty Research Grants and Student Research Fellowships (1990-present).

Selected publications (* = Hartwick students or alumni):

Books and Book Chapters:

  • Sessions, S.K. 2012. Genome Size. In: The 2nd edition, Brenner’s Online Encyclopedia of Genetics, 2nd edition (S. Maloy and K. Hughes, eds.)
  • Rohr, J.R., T. Raffel, and S.K. Sessions. 2009. Parasites and Amphibians. Chapter 4, pp. 3067-3088 In: Amphibian Biology, Conservation and Decline of Amphibians (H, Heatwole, ed.) Chipping Norton, Australia: Surrey Beatty & Sons.
  • Green, D.M. and S.K. Sessions. Karyology and cytogenetics.  In:  Amphibian Biology, Vol. 7 (H. Heatwole and M. Tyler, eds.). Chipping Norton, Australia: Surrey Beatty & Sons.
  • Sessions, S.K. 2003. The Proteidae. In: Grzimek’s Animal Life Encyclopedia.  Gale Group.
  • Sessions, S.K. What is Causing Deformed Amphibians?  In:  Amphibian Conservation (R. D. Semlitsch, ed.), Smithsonian Press, Washington, D.C.
  • Sessions, S.K. and J.L. Wiktorowski*. Population cytogenetics of the plethodontid salamander Eurycea wilderaeIn:  The Biology of Plethodontid Salamanders (R. C. Bruce et al., eds.), Plenum.
  • Sessions, S.K. 1996. Chromosomes: Molecular Cytogenetics. In: “Molecular Systematics”, Second Edition (D.M. Hillis and C. Moritz, eds.), Sinauer Associates, Sunderland MA. pp. 121-168.
  • Green, D.M., and S.K. Sessions. 1991. Amphibian Cytogenetics and Evolution. Academic Press.

Articles and Reviews:

  • Griffing*, A.H., J. Bowerman, and S.K. Sessions (2017). Histology rev eals testicular oocytes and trematode cysts in the threatened Oregon spotted frog (Rana pretiosa). Northwestern Naturalist 98:24-32.
  • Sessions, S.K., D.M. Green, Trifonov, M. Ferguson-Smith, and L. Bizjak Mali (2016). Evidence for Sex Chromosome Turnover in Proteid Salamanders. Cytogenetic and Genomic Research 148:305-313. doi:10.1159/000446882.
  • Itgen*, M., and S.K. Sessions (2016). Offensive Tail Autotomy: Functional Morphology of Constriction-based Tail Autotomy in Plethodontid Salamanders. Copeia 104:182-188.
  • Iizuka, K., J. Lai, N.A. Poyarkov, and S.K. Sessions (2016). An integrative analysis of Asiatic salamanders, genus Hynobius, using cytogenetics, limb development, and life history. Bulltein of the Herpetological Society of Japan, May 2016 (1).
  • Raffel, T.R., J.O. Lloyd-Smith, S.K. Sessions, P.J. Hudson, and J.R. Rohr (2011). Does the early frog catch the worm? Disentangling potential drivers of a parasite age-intensity relationship in tadpoles. Oecologia. 165:1031-1042.
  • Sessions, S.K. and B. Ballengée (2010). Explanations for deformed frogs: Plenty of research left to do (a response to Skelly and Benard). Journal of Experimental Zoology (Mol Dev Evol) 314B:341-346.
  • Ballengeé, B. and S.K. Sessions (2009). Explanation for missing limbs in deformed amphibians. Journal of Experimental Zoology (Mol Dev Evol) 312B:1-10.
  • Sessions, S.K. and H.C. Macgregor. (2009). The Necessity of Darwin. Nature Precedings.> (2009)
  • Hecker*, L. L. Khait, S.K. Sessions, and R.K. Birla. (2008). Functional evaluation of isolated zebrafish hearts. Zebrafish 5:1-4.
  • Rohr, JR, T.R. Raffel, S.K. Sessions, and P.J. Hudson (2008). Understanding the net effects of pesticides on amphibian trematode infections. Ecological Applications 18:1743-1753.
  • Sessions, S.K., M. Stöck, D.R. Vieites, R. Quarles*, M.S. Min, and D.B. Wake (2008). Cytogenetic analysis of the Asian plethodontid salamander, Karsenia koreana: evidence for karyotypic conservation, chromosome repatterning, and genome size evolution. Chromosome Research 16:563-574.
  • Sessions, S.K. (2008). Evolutionary cytogenetics in salamanders. Chromosome Research 16:183-201.
  • Houck*, A., and S.K. Sessions (2006). Could atrazine affect the immune system of the frog, Rana pipiens? Bios 77:107-112.
  • Sessions, S.K. (2005). The Trouble with Amphibians:  An Example of Science in Action at the Undergraduate level.  Bios 76:134-136.
  • Stopper*, G., L. Hecker*, R.A. Franssen*, and Sessions, S.K., (2002). How parasites cause deformities in amphibians. Journal of Experimental Zoology (Mol Dev Evol) 294:252-263.
  • Sessions, S.K., R.A. Franssen*, and V.L. Horner* (1999). Morphological clues from multilegged frogs: are retinoids to blame?  Science 284:800-802.
  • Macgregor, H.C., S.K. Sessions, and J. W. Arntzen. An integrative analysis of phylogenetic relationships among newts of the genus Triturus (family Salamandridae), using comparative biochemistry, cytogenetics and reproductive interactions.  Journal of Evolutionary Biology 3:329-373.
  • Sessions, S.K. and S.B. Ruth. 1990. An explanation for naturally occurring supernumerary limbs in amphibians. Journal of Experimental Zoology 245:38-47.
  • Kezer, J., S.K. Sessions, and P. León (1989): The meiotic structure and behavior of the strongly heteromorphic X/Y sex chromosomes of neotropical plethodontid salamanders of the genus Oedipina. Chromosoma 98:433-442.
  • Sessions, S.K., D.M. Gardiner, and S.V. Bryant (1989). Compatible limb patterning mechanisms in urodeles and anurans. Developmental Biology 131:294-301.
  • Sessions, S.K., H.C. Macgregor, M. Schmid, and T. Haaf (1988). Cytology, embryology, and evolution of the developmental arrest syndrome in newts of the genus Triturus. Journal of Experimental Zoology 248:321-334.
  • Sessions, S.K. and S.V. Bryant (1988): Evidence that regenerative ability is an intrinsic property of limb cells in Xenopus. Journal of Experimental Zoology 247:39-44.
  • Villalobos, M., P. León, S.K. Sessions, and J. Kezer (1988). Enucleated erythrocytes in plethodontid salamanders. Herpetologica 44-243-250.
  • Sessions, S.K. and A. Larson (1987). Developmental correlates of genome size in plethodontid salamanders and their implications for genome evolution. Evolution 41:1239-1251.
  • Sessions, S.K. and J. Kezer (1987). Cytogenetic evolution in the plethodontid genus Aneides. Chromosoma 95:17-30.
  • Macgregor, H.C. and S.K. Sessions (1986). The biological significance of variation in satellite DNA and heterochromatin in newts of the genus Triturus: an evolutionary perspective. Trans. Roy.Soc. London B 312:243-259.
  • Sessions, S.K. and J.E. Wiley (1985). Chromosome evolution in salamanders of the genus Necturus. Brimleyana 10:37-52.
  • Sessions, S.K. (1982). Cytogenetics of diploid and triploid salamanders of the Ambystoma jeffersonianum Chromosoma 84:599-621.
  • Sessions, S.K., P. León, and J. Kezer (1982). Cytogenetics of the Chinese Giant Salamander, Andrias davidianus (Blanchard): the evolutionary significance of cryptobranchoid karyotypes. Chromosoma 86:341-357.
  • Kezer, J., P. Leon, and S.K. Sessions (1980). Structural differentiation of the meiotic and mitotic chromosomes of the salamander, Ambystoma macrodactylum. Chromosoma 81:177-197.
  • Sessions, S.K. (1980). Evidence for a highly differentiated sex chromosome heteromorphism in the salamander Necturus maculosus (Rafinesque). Chromosoma  77:157-168.
  • Kezer, J. and S.K. Sessions (1979). Chromosomal variation in the plethodontid salamander, Aneides ferreus. Chromosoma 71:65-80.
  • Sessions, S.K. (1978). The chromosomes of Anotheca spinosa (Stejneger), family Hylidae. Herpetologica  34:70-73.
  • Sessions, S.K. (1977). Egg capsules and embryos of the bolitoglossine salamander, Lineatriton lineola (Cope). Herpetologica  33:452-454.

College service and professional affiliations:

  • Faculty and advisory committees on college assessment and student retention.
  • 2003-2009: Coordinator of Environmental Science and Policy Program, Hartwick College.
  • 1994-1996: Coordinator Environmental Science and Policy Program, Hartwick College.
  • 1995: Chair of Science Division
  • Chair of Off-campus programs committee
  • American Association for the Advancement of Science
  • American Society of Ichthyologists and Herpetologists
  • Beta Beta Beta National Biology Honors Society (Advisor, 1990-93)
  • External reviewer, Department of Biology 5-year review, Siena College
  • Doctoral Committee, Brandon Ballengée, University of Plymouth/ University of the Arts, Zürich
  • Masters committee, Eric Dieffenbacher, Marshall University
  • Doctoral committee, Dr. Geffrey Stopper, Yale University
  • Doctoral committee, Dr. Sarah Turtle, University of New Hampshire
  • Doctoral committee, Michael Itgen, Colorada State University
  • Masters committee, Aaron Griffing, Villanova University
  • Co-Adviser, Masters graduate students, Biotechnical Faculty, University of Ljubljana, Slovenia
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