P. shiwahaense is a mixotrophic dinoflagellate reported from the highly eutrophic Shiwa Bay, Korea.
From Kang et al. 2010: Episome somewhat conical, smaller than the hemispherical hyposome. There is a wide and distinctive descending cingulum, which is displaced by 0.2-0.3 X cell length. The sulcus becomes wider toward the antapex. In transverse sections, the episome is almost round, while the hyposome is dorsoventrally slightly flattened. Cell length and width of cells growing photosynthetically 8.4-15.2 and 5.2-11.6 μm, respectively, but cells fed with A. carterae 8.4-19.3 and 6.1-16.0 μm, respectively. The ratio of cell length to cell width of live cells fed with A. carterae, 0.7-1.7, and that of live photosynthetically growing cells, 1.1-1.8. The nucleus was oval and located in the center or dorsal side of the cell. The cloroplasts were located in the cell periphery or near the nucleus. The AVs were arranged in 16 rows; 6 rows on the episome, 5 rows in the cingulum, and 5 rows on the hyposome. Peduncle present but eyespot, pusule, and pyrenoid absent.
This species has been observed in the highly eutrophic Shiwha Bay, Korea in May 2006, 18,8°C, 30.4 salinity. (From Kang et al. 2010)
P. shiwhaense has an amphiesmal plate pattern similar to other woloszynskoid dinoflagellates but does not have the apical line of narrow plates, the pair of elongate amphiesmal vesicles, apical grove or eye spot. This species also does not have the gymnodinoid characters of a nuclear envelop chamber, horseshoe-like apical groove and nuclear fibrous connective. This species does have chloroplasts and nematocysts, which are both present in very few dinoflagellates. (From Kang et al. 2010)
The SSU rDNA sequence of P. shiwhaense is 4% different from that of Gymnodinium aureolum, Lepidodinium viride and G. catenatum, which are the three closest species. The LSU rDNA differs 17-18% from G. catenatum, L. chlorophorum and G. nolleri. (From Kang et al. 2010)
P. shiwhaense is a mixotrophic dinoflagellate capable of photosynthesis and phagotrophy via a peduncle. It has been observed to feed on Amphidinium carterae and Rhodomonas salina in the lab. The main accessory pigment is perdinin, however, this species has not grown photosynthetically in the lab. (From Kang et al. 2010)
