JoAnn M. Burkholder, Howard B. Glasgow, Nora J. Deamer-Melia, J. Springer, Matthew W. Parrow, Cheng Zhang, and Paul J. Cancellieri

Abstract
We describe the two species of the toxic Pfiesteria complex to date (Pfiesteria piscicida and Pfiesteria shumwayae) , their complex life cycles, and the characteristics required for inclusion within this complex. These species resemble P. piscicida Steidinger & Burkholder and also have a) strong attraction to fresh fish tissues and excreta, b) toxic activity stimulated by live fish, and c) production of toxin that can cause fish death and disease. Amoeboid stages were verified in 1992-1997 by our laboratory (various stages from toxic cultures) and that of K. Steidinger and co-workers (filose amoebae in nontoxic cultures) , and in 2000 by H. Marshall and co-workers (various stages from toxic cultures) , from clonal Pfiesteria spp. cultures, using species-specific polymerase chain reaction-based molecular probes with cross-confirmation by an independent specialist. Data were provided from tests of the hypothesis that Pfiesteria strains differ in response to fresh fish mucus and excreta, algal prey, and inorganic nutrient (N, P) enrichment, depending on functional type or toxicity status. There are three functional types: TOX-A, in actively toxic, fish-killing mode ; TOX-B, temporarily nontoxic, without access to live fish for days to weeks, but capable of toxic activity if fish are added ; and NON-IND, noninducible with negligible toxicity in the presence of live fish. NON-IND Pfiesteria attained highest zoospore production on algal prey without or without inorganic nitrogen or inorganic phosphorus enrichment. TOX-B Pfiesteria was intermediate and TOX-A was lowest in zoospore production on algal prey with or without nutrients. TOX-A Pfiesteria spp. showed strong behavioral attraction to fresh fish mucus and excreta in short-term trials, with intermediate attraction of TOX-B zoospores and relatively low attraction of NON-IND cultures when normalized for cell density. The data for these clones indicated a potentially common predatory behavioral response, although differing in intensity distinct from a toxicity effect, in attack of fish prey. The data also demonstrated that functional types of Pfiesteria spp. show distinct differences in response to fish, algal prey, and inorganic nutrient enrichment. Collectively, the experiments indicate that NON-IND strains should not be used in research to gain insights about environmental controls on toxic strains of Pfiesteria spp. Key words: amoebae, complex life cycle, culture, dinoflagellates, estuaries, fish, noninducible, nutrients, strains, toxic Pfiesteria complex. -- Environ Health Perspect 109(suppl 5) :667-679 (2001) .

http://ehpnet1.niehs.nih.gov/docs/2001/suppl-5/667-679burkholder/abstract.html

This article is based on a presentation at the CDC National Conference on Pfiesteria: From Biology to Public Health held 18-20 October 2000 in Stone Mountain, Georgia, USA.

Address correspondence to J.M. Burkholder, Center for Applied Aquatic Ecology, North Carolina State University, 620 Hutton St., Suite 104, Raleigh, NC 27606 USA. Telephone (919) 515-2726. Fax (919) 513-3194. E-mail: joann_burkholder@ncsu.edu. Center website: http://www.pfiesteria.org

Funding support was provided by the N.C. General Assembly, the U.S. EPA, NSF, ECOHAB, an anonymous foundation, the Z. Smith Reynolds Foundation, NOAA, ECOHAB, and the NCSU College of Agriculture & Life Sciences. P. Glibert, A. Lewitus, M. Mallin, R. Reed, and S. Shumway provided counsel on the manuscript.

Received 8 January 2001 ; accepted 6 August 2001.