Lab Alumni


Weider Lab Fall 2019: back row (l-r) Larry Weider, Amber Woolley, Ekene Nwakoby; front row (l-r) Emily Kiehnau, Matt Wersebe, Kaylee Gibbons, Juliet Agadagba


Weider Lab Group Fall 2018; l-r Kristina Floyd, Matt Wersebe, Ritu Kulkarni, Silvia Markova, Larry Weider, Emily Kiehnau, Ekene Nwakoby, Brandon Day


Weider Lab Fall 2017: Back Row: L-R: Larry Weider, Jake Scott, Emily Kiehnau, Michael Onwuchuruba, Ronak Tapiavala; Front Row: L-R: Ritu Kulkarni, Rachel Hartnett


Weider Lab Fall 2016: L-R Larry Weider, Weston Speer, Rachel Hartnett, Emily Kiehnau, Michael Onwuchuruba, Christian Brewer


Weider Lab Spring 2015: L-R, L.J. Weider, R. Hartnett, D. Frisch, W. Speer, A. Yousey, B. Culver


Sabbatical Visitors

2018          Dr. Silvia Markova and Dr. Petr Kotlik, Institute of Animal Physiology and Genetics, Czech Academy of Sciences, (March-December)

2008         Dr. Teresa Crease, Department of Integrative Biology, University of Guelph, Ontario, Canada (February-May)


Postdoctoral Associates

 2012-15   Dr. Joaquin Muńoz, U. of Oklahoma Biological Station/Sevilla, Spain

2010-13   Dr. Philip Morton, U. of Oklahoma Biological Station (currently at the University of Oklahoma School of Denistry)

2007-15   Dr. Dagmar Frisch, U. of Oklahoma Biological Station (currently a Bioinformatics Instructor, Berlin, Germany)

2006-07   Dr. James Larson, U. of Oklahoma Biological Station (currently a Research Scientist, USGS Upper Midwest Environmental Science Center, La Crosse, Wisconsin)

2005-06   Dr. Chad Hargrave, U. of Oklahoma Biological Station (currently an Associate Professor, Dept. of Biological Sciences and Associate Vice-President for Research & Special Programs, Sam Houston State U., Texas)

2000-01   Dr. Richard Broughton, Dept. of Zoology/Biological Station, U. of Oklahoma (currently Professor and Chair, OU Dept. of Biology)

1997       Dr. Martin Cerny, Dept. of Hydrobiology, Charles University, Prague, Czech Rep.

1994-96   Dr. Piet Spaak, Centre for Limnology, Netherlands Inst. of Ecology, Nieuwersluis, NL(currently Head of the Dept. of Aquatic Ecology, EAWAG, Dubdendorf, Switzerland)

1995       Dr. France Dufresne, Dept. of Zoology, U. of Guelph, Ontario, Canada. (currently an Associate Professor, Dept. of Biology, U. of Quebec at Rimouski)

1994-95   Dr. Luc De Meester, Laboratory of Animal Ecology, U. of Ghent, Belgium. (currently Professor, Dept. of Biology, KU-Leuven, Belgium; effective 15 January 2020 – Scientific Director, Leibnitz Institute of Freshwater Ecology & Inland Fisheries – IGB, Berlin, Germany)

1991-93   Dr. Joanna Pijanowska, Dept. of Hydrobiology, U. of Warsaw, Poland (currently Head of this department since 2010).

Weider Lab Spring 2012: L-R, L. Weider, Quini Munoz, B. Culver, D. Frisch, Philip Morton


Graduate Student Alumni:

2012-2017   Rachel Harnett (Ph.D., former NSF Graduate  Research Fellow; currently a postdoc at Oklahoma State University)

Dr. Hartnett’s work has focused on how population dynamics influence community properties using Daphnia as a model organism.  She has been interested in potential mechanisms of size-distribution variation along an increasing experimental scale of size and ecological complexity (from life-history to mesocosm experiments).  From this work, she has focused on two main arms: 1) mechanisms and patterns of size distributions, and 2) the role of species evenness in community theory and application.  Rachel successfully defended her Ph.D. dissertation in November 2017, and was awarded her doctorate in December 2017.   She is currently finishing up the 3rd year of her Diversity Postdoctoral Fellowship in the College of Arts & Sciences (CAS) at Oklahoma State University.  She will be joining the faculty of Mount St. Mary’s University (Emmetsburg, MD) in August 2021 as a tenure-track Assistant Professor of Biology.  Please visit her website for more information.

2010-16   Billy Culver (Ph.D. student, U. of Oklahoma) (currently an Assistant Professor of Biology, School of Biological & Physical Sciences, Northwestern State University of Louisiana)

2013-15   Aime’e Yousey (M.S. student, U. of Oklahoma) (currently in the private sector in Albuquerque, N.M.)

2008-10   Mingyan Lin (M.S., U. of Oklahoma)

2002-07   Punidan Jeyasingh (Ph.D., U. of Oklahoma) (currently an Associate Professor, Dept. of Integrative Biology, Oklahoma State Univ.)

2000-01   Wenjun Wang (Ph.D. student, U. of Oklahoma)

1997-00   Petra Limburg (Ph.D., U. of Kiel, Germany) (currently in the private sector in Germany)

1996-99   Thomas Berendonk (Ph.D., U. of Kiel, Germany) (currently Professor of Limnology, Technical University-Dresden, Germany)

1997-98   Angelika Denk (M.Sc. student, U. of Regensburg, Germany)

1994-97   Suzanne E. Mitchell (Ph.D. – NERC-CASE, U. of Hull, England) (currently Director, Aeona Limited, Edinburgh, Scotland)

 1997       Lilla Pokutta (M.Sc. – U. of Hamburg, Germany)

1989-90   Mary H. Murdoch (M.Sc. – U. of Windsor, Canada) (currently Principal, Stantec Environmental Services, Fredericton, New Brunswick, Canada)


Undergraduate Student Alumni:

2018-2020 Ekene Nwakoby (B.S. Honors, U. of Oklahoma)

Ekene joined the lab in fall 2018. Her Honors Research project focused on F1 hybrid clones of Daphnia pulicaria that are the products of crossing a “modern” (i.e., decade-old “dam”) clone with an “ancient” (i.e., centuries-old “sire”) clone from South Center (SC) Lake in Minnesota. She examined physiological and life-history characteristics of this “clonal triad” when exposed to both high-quality (high P) and low-quality (low P) food, and varying food concentrations. Ekene successfully defended her Honors Thesis in December 2019, and presented her findings at the Annual OU Undergraduate Research Day in spring 2020.  (Ekene started medical school at NYU in August 2020.)


2019-2020 Juliet Agadagba (B.S., U. of Oklahoma)

Juliet joined the lab in August 2019 to begin an Independent Study project. Using a “resurrection ecology” approach, she examined genetic (clonal) differences in pH tolerance in a Daphnia pulicaria population from South Center (SC) Lake (MN) that has undergone rapid environmental changes over the past century or more.  (Juliet is slated to graduate from OU in December 2020.)


2019-2020 Amber Woolley (B.S., U. of Oklahoma)

Amber conducted an independent study research project, which utilized parental and F1 hybrid clones of Daphnia pulicaria  (i.e., “modern” decade-old “dam” clone crossed with an “ancient” centuries-old “sire” clone) from South Center (SC) Lake in Minnesota.  She examined the effects of synthetic estrogen (EE2), a common pollutant in aquatic systems world-wide, on life-histories of these clones in 21-day growth/life-table experiments.  (Amber started at the OU College of Pharmacy in August 2020.) 


2018-2019 Kristina Floyd (B.S. Honors, U. of Oklahoma)

Kristina worked as a summer Undergraduate Research Assistant (UGRA) for our lab in summer 2018.  Her Honors Research project examined the effects of food quality differences (i.e., high phosphorus – P vs low P food) on life-history fecundity patterns in a set of F2 recombinant inbred lines (clones) of Daphnia pulicaria established by selfing a F1 hybrid clone from two F0 parental lines from South Center (SC) Lake in Minnesota. (Kristina started at OU Dental School in June 2019.)


2018-2019 Brandon Day (B.S., U. of Oklahoma)

Brandon joined the lab in fall 2018, and he conducted Independent Study, in collaboration with Matt Wersebe.   He  examined salinity tolerance differences among Daphnia pulicaria clones isolated from Minnesota lakes. (Currently, Brandon has applied for the Environmental Law program – U. of Texas at San Antonio.)


2017-2019  Ritu Kulkarni  (B.S. Honors – U. of Oklahoma)

Ritu Kulkarni – Honors B.S. (Microbiology)

Ritu joined our lab in fall 2017.  Her Honors Research project focused on the interactions between food quality and predator kairomones on the life-history features of Daphnia pulex, D. pulicaria, and an experimentally-created hybrid clone between these two parental species.   She defended her Honors Research Thesis in December 2018, and presented her results at the Annual OU Undergraduate Research Day in Spring 2019.  (Ritu is currently a 5th-year senior as a double-major in Microbiology and Psychology here at OU.  She is slated to graduate in May 2021 with the intent to enter medical school after graduation.)


2017-2018  Ronak Tapiavala (B.S., U. of Oklahoma)

Ronak Tapiavala

Ronak’s research project involved the study of the artificial sweetener sucralose, and its potential impact on physiological and metabolic aspects of Daphnia. Sucralose is one of the main ingredients found in the artificial sweetener, Splenda, which is found in a wide variety of low-calorie beverages.  Given that sucralose is quite “metabolically stable”, much of it ends up into aquatic ecosystems via waste-water run-off.  Its role as a man-made eco-toxicant remains to be fully examined. One of the major assays that Ronak  performed involved testing the effects of sucralose on the heart rate of various clones of Daphnia, including both modern-day clones, as well as “ancient” (centuries-old) clones to determine if modern Daphnia clones have adapted to this artificial sweetener.  Here is a video clip of a Daphnia pulicaria female (carrying eggs/embryos) that has been exposed to sucralose.  You can see the beating heart just above the brood chamber, which contains developing embryos.  (Ronak graduated from OU in May 2018.  He began dental school at the UT Health San Antonio School of Dentistry in fall 2019.)


2017 – 2018 Jake Scott (B.S., U. of Oklahoma)

Jake Scott

Jake joined our lab in fall 2017.  He completed his independent study project in spring 2018, which was a comparative study on the “nutritional ecology” of several different algal food types and their impact on growth and reproduction among several species of Daphnia, including D. pulicaria, and D. mendotae.  Jake graduated from OU in May 2019.


2016-17   Michael Onwuchuruba (B.S., National Merit Scholar, U. of Oklahoma).  Michael graduated from OU in May 2018 and is applying to medical/DO schools.

Michael Onwuchuruba examined various cues (i.e., hormonal, food-level, photoperiod) that have been implicated in affecting the sex ratio of Daphnia offspring. He found no clear-cut effects of these cues on sex-ratio of offspring, but did find a significant effect of suppression of fecundity (i.e., egg production) in the presence of the juvenile hormone analog, methyl farnesoate (MF).


2016-17   Christian Brewer (B.S., U. of Oklahoma, National Merit Scholar, OU Honors College)(Christian started medical school in August 2017 at UT-Southwestern in Dallas).

Christian Brewer conducting a predator cue experiment and examining phototactic response in Daphnia prey


2015-16   Hayley Severson (B.S., U. of Oklahoma, National Merit Scholar, UROP award winner) (Hayley completed her Masters of Public Health, U. of Wisconsin-Madison, and began medical school at UWM in fall 2017).

OU Graduation May 2016 Hayley Severson with Dept of Biology Faculty Marshal L.J. Weider


2012-2016    Frank “Weston” Speer (B.S. Biology, 2016, U. of Oklahoma; UROP award winner)

Weston’s research project involved the study of the aquatic crustacean (brine shrimp) Artemia franciscana, a prominent model organism. With the aid of international colleagues, he obtained A. franciscana populations from several different countries. His project aimed to determine the optimal hatching cues for these populations. Additionally, he engineered a novel hatchery system that could be applied to an array of aquatic organisms.  The results of his independent study research were recently published in the journal Hydrobiologia.  In August 2018, Weston started medical school at Oklahoma State University (OSU)-Tulsa.

Frank “Weston” Speer (L) receives an Undergraduate Research (UROP) Award from OU (pictured here with L.J. Weider)

2015        Arianne Rick (B.S., U. of Oklahoma, OU Honors College) (started dental school at the U. of Florida in fall 2017)

2011-13   Jeff Medders (B.S., U. of Oklahoma)

2012-13   Alex Mutz (B.S., U. of Oklahoma)

2011        Rosa Yorks (B.S. , Oklahoma State Univ.)

2011       Tiffany Glover (B.S., Langston Univ., Oklahoma)

2011       Garrett Schulze (Kingston High, Oklahoma)(currently applying for entry into the Oklahoma State Trooper Academy)

2011       Kelsie Montgomery (high-school student, Red River Technology Center, Oklahoma)

2010       Michael Leitch (B.S., U. of Oklahoma)

2005-06   Laura Harolds (B.S. Honors, U. of Oklahoma, UROP award winner)

2003       Andrea Bean (B.S., U. of Oklahoma)

2003       Jaime Ramos (B.S., U. of Oklahoma)

2002       Robyn Moran (B.S., S.W. Okla. State)

2002       Lynette Matthews (B.S., Arizona State U.)

2002       Amy Ramsey (B.S., Botany, U. of Oklahoma)

2001       Jeremiah Smith (B.S., U. of Oklahoma)

2001       Kim Land (B.S., U. of Oklahoma)

2000       Amanda Warren (B.S., U. of Oklahoma)

1992       Gerhard Griebe (B.Sc. honors – U. of Oldenburg, Germany)

1992       Andreas Heinken (B.Sc. – Free University – Berlin, Germany)

1992       Adrian Howe (B.Sc. – EC Comet Program, U. of Swansea, Wales)

1989-90   Catherine Delvanminck (B.Sc. honors – U. of Windsor, Canada)