Analyses
Samples from Viet Nam were examined under a Leica DMLB (Solms, Germany) microscope using phase-contrast (PC), differential interference contrast (DIC), and epifluorescence (Epi) optics. In order to visualize thecal plate patterns, dinoflagellate cells were stained with Calcofluor White M2R according to Fritz and Triemer (1985). The digital camera Olympus DP71 was used for light and epifluorescence microphotography. Microscopy study of the samples from the Persian Gulf was conducted at the Institute for Evolutionary Ecology of the NAS of Ukraine using an Olympus BX51 light microscope with UPlanFLN 40x/0.67 and UPlanFLN 100x/1.30 (Oil) lenses. Dinoflagellates were examined in transmitted light, DIC, and in an epifluorescence mode with preliminary staining of cells using Calcofluor White M2R (Fritz and Triemer, 1985). Pictures were taken with a Canon EOS 5D Mark II digital camera.
For scanning electron microscope (SEM) examination, cells ofProtoperidinium were isolated by Pasteur pipettes from preserved samples under a stereomicroscope and placed on a 5 µm carbon membrane filter, rinsed with distilled water, dehydrated through an ethanol series (15, 30, 50, 70, 90, 99, and 100) of absolute ethanol, and air-dried. The filter was mounted onto an aluminum stub with carbon tape and finally coated with gold. The stubs were studied under a Hitachi FE-SEM (Field Emission Scanning Electron Microscope) model S4800 at the Institute of Materials Science, Viet Nam Academy of Science and Technology (Ha Noi, Viet Nam).
Thecal plate terminology follows the Kofoid tabulation system (Kofoid 1909). The identification of Protoperidinium species, as well as the use of biometric terminology and abbreviations, was based on Schiller (1937), Graham (1942), Taylor (1976), Abé (1981), Balech (1974, 1988), Okolodkov (2008), and Phan-Tan et al. (2017). The taxonomic position was specified in accordance with the classification of dinoflagellates by Fensome et al. (1993), taking into account Balech (1988).