Current Lab Members


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


Current Graduate Students:

2015-       Emily Kiehnau (current Ph.D. student)

Emily Kiehnau holding a Glew gravity corer for sampling sediments in the Muskoka Lakes, Ontario, Canada  July 2016.

Emily’s research focuses on quantifying the plastic and evolutionary responses of native species to exotic introduced species and on identifying how these responses influence community level processes. She has been studying the exotic introduced zooplanktivore, Bythotrephes longimanus (a.k.a. spiny waterflea).  This species is a threat to pelagic biodiversity of North American lakes because of its heavy predation on native zooplankton, particularly Daphnia. Of the many Daphnia species found in North American lakes, only D. mendotae appears to thrive in the presence of B. longimanus. Emily’s research centers around identifying the antipredator response of Daphnia species to Bythotrephes via a variety of behavioral and morphological kairomone (i.e., chemical cue) studies conducted on pre- and post-invasion Daphnia populations.


2012-2017   Rachel Harnett (Ph.D., former NSF Graduate  Research Fellow)

Dr. Hartnett’s work has been 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 working up data and writing manuscripts from her dissertation.  She was awarded and has accepted one of the inaugural Diversity Postdoctoral Fellowships in the College of Arts & Sciences (CAS) at Oklahoma State University.  She will be taking up her new position effective 1 July 2018.  Please visit her website for more information.


Current Undergraduate Students:

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 (containing developing embryos).


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

Ritu Kulkarni – Honors B.S. (Microbiology)

Ritu joined our lab in fall 2017.  She has taken Honors Reading and is currently conducting Honors Research.  She started her independent research project in spring 2018.  She will be focusing 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. 


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

Jake Scott

Jake joined our lab in fall 2017.  He is currently a junior Biology major, and has begun his independent study project in spring 2018.  He is conducting 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.


2016-17   Michael Onwuchuruba (B.S., National Merit Scholar, U. of Oklahoma)

Michael Onwuchuruba has been examining the various cues (i.e., hormonal, food-level, photoperiod) that have been implicated in affecting the sex ratio of Daphnia offspring.