Species Description: Polykrikos schwartzii is a barrel-shaped non-thecate pseudocolonial species with mostly 4 (Figures 2, 3 ) or 8 (Figure 1) slightly compressed cells (occasionally 16), each individual of which has the general form of a Gymnodinium. Each individual, called a zooid, is closely appressed to its neighbor without separating cell membranes, each with a median cingulum but all sharing a common sulcus. The number of nuclei is normally one half the number of zooids. The zooids possess numerous prominent nematocysts, lack chloroplasts, and the cytoplasm is a transparent green or pink. Cysts are sometimes seen, and these are brown and covered with honeycomb-like ridges that produce a coarsely rugose appearance (Figure 5).
Potentially Misidentified Species: P. schwartzii resembles P. kofoidii in general appearance, but the latter is distinctly ridged on the hypotheca (hyposome) of each zooid, the cinguli are more displaced on each zooid, and the pseudocolony normally has only 4 cells. The cysts of the two species are almost indistinguishable. Polykrikos lebourae has 8 zooids, but has golden-brown chloroplasts (thus photosynthetic) and is benthic.
Habitat: The species is planktonic, mostly confined to coastal waters and estuaries.
Regional Occurrence: P. schwartzii apparently has a worldwide distribution in neritic environments, except for polar seas. However, confusion with P. kofoidii makes its exact distribution uncertain.
IRL Distribution: P. schwartzii has been found in the central IRL, the St. Lucie estuary and near Sebastian Inlet. It has not been found in the Mosquito Lagoon or Banana River.
Size: The 8-cell colony (Figure 1) is about 100-160 µm long and 40-80 µm wide.
Reproduction: Sexual reproduction has been reported (Hoppenrath et al. 2009), but reproduction is otherwise accomplished via asexual vegetative cell division.
Trophic Mode: Nutrition is holozoic, by phagocytosis of diatoms, dinoflagellates and other protists. Prey is probably captured by means of stinging nematocysts.
Dodge, JD. 1982. Marine Dinoflagellates of the British Isles. Her Majesty’s Stationery Office, London. 303 pp.
Hoppenrath, M & BS Leander. 2007. Character evolution in polykrikoid dinoflagellates. J. Phycol. 43: 366-377.
Hoppenrath, M et al. 2009. Marine Phytoplankton. Kleine Senckenberg-Reihe 49. E. Schweizerbart Science Publishers, Stuttgart Germany. 264 pp.