PFIESTERIA PISCICIDA GEN ET SP-NOV (PFIESTERIACEAE FAM NOV), A NEW TOXIC DINOFLAGELLATE WITH A COMPLEX LIFE-CYCLE AND BEHAVIOR

The newly described toxic dinoflagellate Pfiesteria piscicida is a pol ymorphic and multiphasic species with flagellated, amoeboid, and cyst stages. The species is structurally a heterotroph; however, the flagel lated stages can have cleptochloroplasts in large food vacuoles and ca n temporarily function as mixotrophs. The flagellated stage has a typi cal mesokaryotic nucleus, and the theca is composed of four membranes, two of which are vesicular and contain thin plates arranged in a Kofo idian series of Po, cp, X, 4', 1a, 5 '', 6c, 4s, 5triple prime, and 2 '''' . The plate tabulation is unlike that of any other armored dinofl agellate. Nodules often demark the suture lines underneath the outer m embrane, but fixation protocols can influence the detection of plates. Amoeboid benthic stages can be filose to lobose, are thecate, and hav e a reticulate or spiculate appearance. Amoeboid stages have a eukaryo tic nuclear profile and are phagocytic. Cyst stages include a small sp herical stage with a honeycomb, reticulate surface and possibly anothe r stage that Is elongate and oval to spherical with chrysophyte-like s cales that can have long bracts. The species is placed in a new family , Pfiesteriaceae, and the order Dinamoebales is emended.