A second species of ichthyotoxic Pfiesteria (Dinamoebales, Dinophyceae)

Abstract

A second toxic species within the family Pfiesteriaceae, Pfiesteria shumwayae Glasgow & Burkholder sp. nov., is described from the New River Estuary and the Neuse Estuary of the Albemarle-Pamlico Estuarine Ecosystem, USA. The species is polymorphic and multiphasic, with flagellated, amoeboid and cyst stages. The flagellated zoospores (diameter 8–24 μm) have permanently condensed chromosomes (mesokaryotic nucleus); a chrysophyte-like cyst (diameter 6–25 μm)with organic scales and bracts; and thin thecal plates arranged in a Kofoidian series of Po, cp, X, 4′, la, 6″, 6c, 4s, 5″′, 2″″. The benthic filopodial (filose), lobopodia1 (lobose) and rhizopodial amoeboid stages (5–250 μm) have an outer covering that ranges from rough to smooth in texture, depending on the stage of origin and the prey source. Pfiesteria shumwayae amoebae have a normal eukaryote nucleus and cysts of multiple sizes (diameter 4–25 μm) with a reticulate outer covering. Toxic strains of the two Pfiesteria species have overlapping distributions in the mid-Atlantic and southeastern United States and Scandinavia, with toxic P. shumwayae also having been verified from New Zealand. Pfiesteria shumwayae is similar to P. piscicida in its complex life cycle, general nutrition, attraction to live fish prey, and ichthyotoxic activity that is stimulated by the presence of live fish or their fresh tissues and excreta. However, it can be distinguished from P. piscicida morphologically by having six precingular plates and a four-sided la plate, as well as genetically, on the basis of its ISS ribosomal DNA sequence.