Species of the toxic Pfiesteria complex, and the importance of functional type in data interpretation.

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 Pfiesteriastrains 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.

Eutrophication and harmful algal blooms: A scientific consensus

“…Thus, the toxic, heterotrophic dinoflagellate Pfiesteria spp. can be indirectly stimulated by inorganic nutrient enrichment, mediated through an increase in the abundance of algal prey that may be directly stimulated by specific nutrient forms (Burkholder et al, 2001, Glibert et al, 2006a). Similarly, Karlodinium veneficum may be stimulated by the growth of cryptophytes which may be stimulated by its preferred nutrient forms (Adolf et al, this issue).…”

“…Over time in culture, highly toxic strains have lost their ability to make toxin; strains also have changed in polyploidy, expression of life history stages, and responses to environmental conditions such as salinity and nutrient regimes (reviewed in Wood and Leatham, 1992 and Burkholder and Glibert, 2006). Pfiesteria spp., for example, have been shown to lose their toxicity when switched from a media that includes live to one with algal prey (Burkholder et al, 2001). Toxin production in a strain of Alexandium lusitanicum was also shown to loose toxicity after many years in culture, and although the exact reasons could not be ascertained, genetic mutations or prolonged use of antibiotics may have been the cause (Martins et al, 2004).…”

“…Thus, in conducting laboratory studies, the history of the culture should be carefully considered (e.g., location of isolation and duration in culture). It is also important to compare multiple strains of the same species to assess whether the characteristic of concern is strain-specific, and generalizations at the species level (or higher) based upon one to a few strains should be avoided (Burkholder and Glibert, 2006, Burkholder et al, 2001 and Burkholder et al, 2005). …”

Detection of the Dinozoans Pfiesteria piscicida and P. shumwayae: A Review of Detection Methods and Geographic Distribution1

“…A second challenge lies in the efficiency of extraction and purification of the nucleic acid from the field sample. Many dinoflagellates, including Pfiesteria spp., have varied life stages including amoeboid, vegetative, and cyst forms (Burkholder and Glasgow 2002; Burkholder et al (2001a, c; 2005) Pfiester and Popovský 1979). Thus, extraction buffers may not be equally efficient at lysing different forms of the target species.…”

“…Indeed, until a specific field test for Pfiesteria toxin is available, absolute determination of Pfiesteria as a causative agent remains problematic. Currently, the approach is a conservative application of Henle–Koch postulates (Burkholder et al 2001c), which rely as much on the absence of other causative factors as they do on the presence of toxic forms of Pfiesteria . Nevertheless, screening of fish lesion/kill events, including historical events, has suggested that Pfiesteria species have been active players in fish lesion or fish kill events in coastal waters (Burkholder et al 1995; Glasgow et al 2001b).…”