Pfiesteria piscicida
Coast watch (1979) (20471959890).jpg
Scientific classification edit
Clade: SAR
Infrakingdom: Alveolata
Phylum: Myzozoa
Superclass: Dinoflagellata
Class: Dinophyceae
Order: Thoracosphaerales
Family: Pfiesteriaceae
Genus: Pfiesteria
P. piscicida
Binomial name
Pfiesteria piscicida
Steidinger & Burkholder

Pfiesteria piscicida is a dinoflagellate species of the genus Pfiesteria that some researchers claim is responsible for many harmful algal blooms in the 1980s and 1990s on the coast of North Carolina and Maryland. North Carolinian media in the 1990s referred to the organism as the cell from hell. It is known to populate estuaries.[1] Piscicida means "fish-killer".

Life cycles

The complex life cycle of Pfiesteria piscidica. Red = toxic stages, yellow = possibly toxic stages, blue = passive stages
The complex life cycle of Pfiesteria piscidica. Red = toxic stages, yellow = possibly toxic stages, blue = passive stages

Early research suggested a very complex life cycle of Pfiesteria piscicida with up to 24 different stages, spanning from cyst to several amoeboid forms with toxic zoospores. Transformations from one stage to another depend on environmental conditions such as the availability of food.[2] However these results have become controversial as additional research has found only a simple haplontic life cycle with no toxic amoeboid stages[3] and amoebae present on attacked fish may represent an unrelated species of protist.[4][5]


Pfiesteria presumably kills fish via releasing a toxin into the water to paralyze its prey. This hypothesis has been questioned as no toxin could be isolated and no toxicity was observed in some experiments. However, toxicity appears to depend on the strains and assays used.[6] Polymerase chain reaction-analyses suggested that the organism lacks the DNA for polyketide synthesis, the type of toxins associated with most toxic dinoflagellates.[7] Researchers from the NOAA National Centers for Coastal Ocean Science, the National Institute of Standards and Technology, the Medical University of South Carolina, and the College of Charleston (S.C.) have formally isolated and characterized the toxin in the estuarine dinoflagellete Pfiesteria piscicida as a metal complex and free radical toxin and also have identified how the organism transforms from a non-toxic to toxic state.[8][9][10][11]

Human illness

Very little research on the human health effects of Pfiesteria toxins has been conducted. At a multi-state workshop at the Centers for Disease Control and Prevention (CDC) in Atlanta, U.S., at the end of September 1997, attendees agreed on clinical symptoms that characterize a new illness associated with Pfiesteria exposure. These clinical features include:

With these criteria and environmental qualifiers (e.g., 22% of a 50-fish sample, all of the same species, have lesions caused by a toxin), it is likely that Pfiesteria-related surveillance data can better track potential illnesses.

Pfiesteria toxins have been blamed for illness in those who have come in close contact with waters where this organism is abundant. Since June 1997, the Maryland Department of Health and Hygiene has been collecting data from Maryland physicians through a statewide surveillance system on illnesses suspected of being caused by Pfiesteria toxin. As of late October 1997, illness was reported by 146 persons who had been exposed to diseased fish or to waters that were the site of suspected Pfiesteria activity. Many of these persons are watermen and commercial fishermen.

The strongest evidence of Pfiesteria-associated human illness so far comes from case studies of two research scientists who were both overcome in their North Carolina laboratory in 1993. They still complain of adverse effects on their cognitive abilities, particularly after exercising. Duke University Medical Center researchers conducted experiments on rats, which showed that the toxin appeared to slow learning but did not affect memory.[12]

Treatment with Colestyramine shortly after exposure has been shown to alleviate symptoms.[13]

Public Domain This article incorporates public domain material from the United States Government document: "a report by the Congressional Research Service (CRS), part of the Library of Congress".


  1. ^ Lertzman, Renée Aron (1999). The wet, the wild and the weird : imagining Pfiesteria. Retrieved 2021-02-14.
  2. ^ Burkholder JM, Glasgow HB (1997). "Trophic controls on stage transformations of a toxic ambush-predator dinoflagellate". J. Eukaryot. Microbiol. 44 (3): 200–5. doi:10.1111/j.1550-7408.1997.tb05700.x. PMID 9183706. S2CID 13467281.
  3. ^ Litaker RW, Vandersea MW, Kibler SR, Madden VJ, Noga EJ, Tester PA (2002). "Life cycle of the heterotrophic dinoflagellate Pfiesteria piscicida (Dinophyceae)". Journal of Phycology. 38 (3): 442–463. doi:10.1046/j.1529-8817.2002.t01-1-01242.x.
  4. ^ "Study casts doubt on Cell from Hell's role in fish kills". Retrieved 2008-01-06.
  5. ^ Peglar MT, Nerad TA, Anderson OR, Gillevet PM (2004). "Identification of amoebae implicated in the life cycle of Pfiesteria and Pfiesteria-like dinoflagellates". J. Eukaryot. Microbiol. 51 (5): 542–52. doi:10.1111/j.1550-7408.2004.tb00290.x. PMID 15537089. S2CID 43191086.
  6. ^ Burkholder JM, Gordon AS, Moeller PD, et al. (2005). "Demonstration of toxicity to fish and to mammalian cells by Pfiesteria species: comparison of assay methods and strains". Proc. Natl. Acad. Sci. U.S.A. 102 (9): 3471–6. Bibcode:2005PNAS..102.3471B. doi:10.1073/pnas.0500168102. PMC 552923. PMID 15728353.
  7. ^ Berry JP, Reece KS, Rein KS, et al. (2002). "Are Pfiesteria species toxicogenic? Evidence against production of ichthyotoxins by Pfiesteria shumwayae". Proc. Natl. Acad. Sci. U.S.A. 99 (17): 10970–5. doi:10.1073/pnas.172221699. PMC 123194. PMID 12163648.
  8. ^ Moeller PD, Beauchesne KR, Huncik KM, Davis WC, Christopher SJ, Riggs-Gelasco P, Gelasco AK (2007). "Metal complexes and free radical toxins produced by Pfiesteria piscicida". Environmental Science & Technology. 41 (4): 1166–72. Bibcode:2007EnST...41.1166M. doi:10.1021/es0617993. PMID 17598275.
  9. ^ Engelhaupt, Erika; Pelley, Janet; Lubick, Naomi; Patel-Predd, Prachi; Cooney, Catherine M. (15 February 2007). "New Pfiesteria toxin identified | Scientists protest U.S. EPA library closures | News Briefs: Plastics component linked to breast cancer ' Megawatt mileage ' Bugs are everywhere-even on dust in city air ' Livestock and greenhouse gases ' State of the Arctic | New managing editor rejoins ES&T | Pesticides waft into pristine rainforests | Overlooked impacts of bioproducts | Mercury control costs drop". Environmental Science & Technology. 41 (4): 1060–1066. Bibcode:2007EnST...41.1060E. doi:10.1021/es072467g.
  10. ^ "Fish study backs N.C. scientist". Archived from the original on 2008-06-08. Retrieved 2008-01-06.
  11. ^ "Pfiesteria toxin breakthrough subject of teleconference briefing". Retrieved 2008-01-06.
  12. ^ Report on Pfiesteria and Related Harmful Blooms: Natural Resource and Human Health Concerns Archived 2006-12-21 at the Wayback Machine Congressional Research Service
  13. ^ Shoemaker, R C; Hudnell, H K (May 2001). "Possible estuary-associated syndrome: symptoms, vision, and treatment". Environmental Health Perspectives. 109 (5): 539–545. doi:10.1289/ehp.01109539. PMC 1240316. PMID 11401768.