Morphology and taxonomy of three new marine sand-dwelling Amphidiniopsis species (Peridiniales, Dinophyceae) from the Sea of Japan, Russia

Abstract

:Three new thecate, heterotrophic sand-dwelling marine dinoflagellates of the genus Amphidiniopsis were collected in sublittoral sand of Peter the Great Bay of the Sea of Japan. The cell morphology was examined by light and scanning electron microscopy. All three species were dorsoventrally flattened and had three anterior intercalary plates. Amphidiniopsis ovalis sp. nov. was oval, 27.0–43.5 μm long and 24.0–38.1 μm wide. The length to width ratio was 1.1–1.2. The plate formula was apical pore complex (APC) 4′ 3a 7″ 3c 4(5)s 5′″ 2″″. The first apical plate was not in contact with the APC. The cingulum was slightly ascending less than half a cingular width. The sulcus was characteristically curved and slightly shifted to the left side of the cell. The theca was smooth or slightly reticulated. Amphidiniopsis elongata sp. nov. was almost rectangular, with a small apical hook and rounded posterior end, 42.0–64.0 μm long and 28.0–42.0 μm wide. The length to width ratio was 1.3–1.7. The cingulum was ascending about four cingular widths. The sulcus was characteristically curved and markedly shifted to the left cell side. The plate formula was APC 4′ 3a 6″ 5c 4(6)s 5′″ 2″″. The theca was smooth with large and small pores. Amphidiniopsis hoppenrathae sp. nov. was rounded with a small apical hook, 39.2–48.9 μm long and 35.4–42.8 μm wide. The length to width ratio was 1.1. The plate formula was APC 4′ 3a 6″ 3c 4s 5′″ 2″. The first apical plate was not in contact with the sulcus, and three anterior intercalary plates were located on the ventral side. The cingulum ascended about two cingular widths. The sulcus was located in the middle of the ventral side of the cell. The theca was ornamented with short spines.