J. Rudi StricklerJ. Rudi Strickler
Shaw Distinguished Professor
Zooplankton Ecology

1965: Dipl. Natw., (MS) Abt. X Naturwissenschaften
Swiss Federal Institute of Technology (ETH), Zurich, Switzerland

1969: Dr. sc. nat., (Ph.D) Abt. X Naturwissenschaften
Swiss Federal Institute of Technology (ETH), Zurich, Switzerland

Office: WATER Institute 137
Phone: 414-382-1700
FAX: 414-382-1705
Email: jrs@uwm.edu
Lab webpage: http://www.planktonsafari.net/

Research Interests

UWM biologist pioneered the study of zooplankters (by Laura L. Hunt)

J. Rudi Strickler’s work in imaging microscopic aquatic zooplankters as they navigate and manipulate their watery habitats has reversed previous scholarship that asserted the tiny creatures survived by chance encounters.

epidaphalga1His research proved the tiny transparent relatives of shrimp, which populate both the sea and freshwater by the sextillions, act selectively in choosing their food, avoiding predators, and successfully pursuing a mate. It has redirected the course of inquiry in the field.

Strickler, a UWM and Shaw Distinguished Professor of biological sciences, has accomplished much of the work with the aid of high-speed video with optical systems he often has designed himself. His savvy use of laser beams, animated GIFs files and high-magnification equipment has allowed him to track and compare the behavior of copepods, the main constituent of zooplankton.

In 2000, the National Science Foundation recognized Strickler in its bound report, “50 Years of Ocean Discovery,” citing his research on zooplankton as one of four landmark achievements in biological oceanography.

Nine years later, he was recognized by the American Society of Limnology and Oceanography (ASLO) with the John Martin Award for research published in 1981 with Mimi Koehl, a professor at the University of California, Berkeley. The award is reserved for papers at least 10 years old that have led to fundamental shifts in subsequent research.

The pape,Copepod Feeding Currents: Food Capture at Low Reynolds Number, describes the novel method the scientists used to determine exactly how copepods feed in a watery environment that, at their scale, is thick and sticky.

In the 1970s, the prevailing view of copepod feeding was that the animal created water currents by moving its outer mouth parts very rapidly, bringing food particles, such as alga, close enough to be “raked in” by the outer mouth. Food was then thought to pass through a kind of sieve in the inner mouth that blocked large particles. Strickler and Koehl disproved this theory with video, showing how copepods manipulate the water around them so that targeted food particles are swept into a “feeding current.”

The inner mouth parts remain motionless until food is nearby and detected. Then a fast movement is executed to capture it. The movies demonstrated that copepods taste their food, eating certain particles and “spitting out” the rejects.

Filming the live copepod presented a challenge. The animal, barely visible, also moves its mouth parts at 60 times per second. So Strickler devised a technique to tether one to a single dog hair and then place it back in its environment with food available. Koehl introduced a stream of india ink to track the flow of water.

“This paper’s straightforward explanation of the role of viscosity in governing particle motion at very small spatial scales has been incorporated into many introductory-level textbooks,” the ASLO awards committee wrote of the work. “It has been cited over 200 times.”

Strickler joined the UWM faculty in 1990 with financial support for his professorship and high-tech laboratory from the Shaw Family Foundation, through the Greater Milwaukee Foundation. Before coming here, he was on the faculty at Johns Hopkins, Yale, Southern California and Boston universities and the University of Ottawa, Canada.

To see videos of copepod feeding, go to planktonsafari.net and clock on "open all" in the left-hand column. Recommendations (under ("Food Handling"): “Alga Arrives” and “Many Algae.”

Just for fun!

Selected Publications

Strickler, J. R. and A. K. Bal. 1973. Setae of the first antennae of the copepod Cyclops scutifer (Sars): Their structure and importance. Proc. Natl. Acad. Sci. USA 70, 2656-2659.

Strickler, J.R. and S. Twombly. 1975. Reynolds number, diapause and predatory copepods. Int. Ver. Theor. Angew. Limnol. Verh. 19, 2943-2950.

Friedman, M.M. and J.R. Strickler. 1975. Chemoreceptors and feeding in calanoid copepods (Arthropoda: Crustacea). Proc. Natl. Acad. Sci. USA 72, 4185-4188.

Strickler, J.R. 1975. Intra- and interspecific information flow among planktonic copepods: Receptors. Int. Ver. Theor. Angew. Limnol. Verh. 19, 2951-2958.

Strickler, J.R. 1975. Swimming of planktonic Cyclops species (Copepoda, Crustacea): Pattern, movements and their control. In: T.Y.-T. Wu, C.J. Brokaw and C. Brennan [Eds.], Swimming and Flying in Nature, Plenum Press, New York, 599-613.

Gerritsen, J. and J.R. Strickler. 1977. Encounter probabilities and community structure in zooplankton: A mathematical model. J. Fish. Res. Bd. Canada 34, 73-82.

Strickler, J.R. 1977. Observation of swimming performances of planktonic copepods. Limnol. Oceanogr. 22, 165-170.

Drenner, R.W., J.R. Strickler and W.J. O’Brien. 1978. Capture probability: The role of zooplankter escape in the selective feeding of planktivorous fish. J. Fish. Res. Bd. Canada 35, 1370-1373.

Alcaraz, M., G.-A. Paffenhofer and J.R. Strickler. 1980. Catching the algae: A first account of visual observations on filter-feeding calanoids. In: W.C. Kerfoot [Ed.], Evolution and Ecology of Zooplankton Communities. Special Symposium III American Society of Limnology and Oceanography. Univ. Press of New England, 241-248.

Kerfoot, W.C., D.L. Kellogg, and J.R. Strickler. 1980. Visual observations of live zooplankters: Evasion, escape, and chemical defenses. In: W.C. Kerfoot [Ed.], Evolution and Ecology of Zooplankton Communities. Special Symposium III American Society of Limnology and Oceanography. Univ. Press of New England, 10-27.

Koehl, M.A.R. and J.R. Strickler. 1981. Copepod feeding currents: Food capture at low Reynolds number. Limnol. Oceanogr. 26, 1062-1073.

Strickler, J.R. 1982. Calanoid copepods, feeding currents, and the role of gravity. Science 218, 158-160.

Paffenhofer, G.-A., J.R. Strickler and M. Alcaraz. 1982. Suspension-feeding by herbivorous calanoid copepods: a cinematographic study. Mar. Biol. 67, 193-199.

Price, H.J., G.-A. Paffenhofer and J.R. Strickler. 1983. Modes of cell capture in calanoid copepods. Limnol. Oceanogr. 28, 116-123.

Cowles, T.J. and J.R. Strickler. 1983. Characterization of feeding activity patterns in the planktonic copepod Centropages typicus Kroyer, under various food conditions. Limnol. Oceanogr. 28, 106-115.

Strickler, J.R. 1984. Sticky water: a selective force in copepod evolution. In: D.G. Meyers and J.R. Strickler [Eds.], Trophic Interactions within Aquatic Ecosystems, Westview Press, 187-239.

Strickler, J.R. 1985. Feeding currents in calanoid copepods: two new hypotheses. In: M.S. Laverack [Ed.], Physiological Adaptations of Marine Animals, Symp. Soc. Exp. Biol. 39, 459-485.

Alcaraz, M. and J. R. Strickler. 1988. Locomotion in copepods: pattern of movements and energetics of Cyclops. Hydrobiologia 167/168, 404-414.

Leonard, A.B., J.R. Strickler and N.D. Holland. 1988. Effects of current speed on filtration during suspension feeding in Oligometra serripinna (Echinodermata: Crinoidea). Mar. Biol. 97, 111-125.

Gerritsen, J., K.G. Porter and J.R. Strickler. 1988. Not by sieving alone: Suspension feeding in Daphnia. Bull. Mar. Sci. 43, 366-376.

Costello, J.H., J.R. Strickler, C. Marrase, G. Trager, R. Zeller and A.J. Freise. 1990. Grazing in a turbulent environment: Behavioral response of a calanoid copepod, Centropages hamatus. Proc. Natl. Acad. Sci. USA 87, 1648-1652.

Marrase, C., J.H. Costello, T. Granata and J.R. Strickler. 1990. Grazing in a turbulent environment: Energy dissipation, encounter rates and efficacy of feeding currents in Centropages hamatus. Proc. Natl. Acad. Sci. USA 87, 1653-1657.

Trager, G.C., J.-S. Hwang and J.R. Strickler. 1990. Barnacle suspension feeding in variable flow. Mar. Biol. 105: 117-127.

Davis, C.S., S.M. Gallager, M.S. Berman, L.R. Haury and J.R. Strickler. 1992. The video plankton recorder (VPR): Design and initial results. Arch. Hydrobiol. Beih. 36: 67-81.

Coughlin, D.J., J.R. Strickler and B.G. Sanderson. 1992. Swimming and search behaviour in clownfish (Amphiprion perideraion) larvae. Anim. Behav. 44: 427-440.

Hwang, J.-S., J.H. Costello and J.R. Strickler. 1994. Copepod grazing in turbulent flow: elevated foraging behavior and habituation of escape responses. J. Plankton Res. 16: 421-431.

Yen, J. and J.R. Strickler. 1996. Advertisement and concealment in the plankton: what makes a copepod hydrodynamically conspicuous? Invert. Biol. 115: 191-205.

Doall, M.H., S.P. Colin, J. Yen and J.R. Strickler. 1998. Locating a mate in 3D: The case of Temora longicornis. Phil. Trans. R. Soc. Lond. B 353: 681-690.

Strickler, J.R. 1998. Observing free-swimming copepods mating. Phil. Trans. R. Soc. Lond. B 353: 671-680.

Malkiel, E., J. Sheng, J. Katz and J.R. Strickler. 2003. The three-dimensional flow field generated by a feeding calanoid copepod measured using digital holography. J. Exp. Biol. 206: 3657-3666.

Lovern, S.B., J.R. Strickler and R. Klaper. 2007. Behavioral and Physiological Changes in Daphnia magna when Exposed to Nanoparticle Suspensions (Titanium Dioxide, Nano-C60, and C60HxC70Hx). Environ. Sci. & Technol. 41: 4465-4470.