Pfiesteria shumwayae

Sexual

In sexual reproduction of P. shumwayae, (see diagram) two gametes fuse (1) to form a planozygote (2). The cell engages in nuclear cyclosis (3) which produces two flagellated offspring (4). Some of the steps in reproduction are unknown because of the difficulty researchers have in documenting information. The vegetative cells and the gametes look very similar, and fusion can easily be confused with division, making it difficult to differentiate between cycle phases (Parrow and Burkholder, 2003). That is why after nuclear cyclosis, it is unknown whether another division takes place before the excystment of offspring (5) and (6). According to Parrow and Burkholder’s research, reproduction in P. shumwayae seems to be unlinked to a survival strategy, and reverts to a sexual cycle because of self- sterility factors that favor outbreeding while taking advantage of food availability and environmental quality.