Information on tintinnid horizontal distribution in the Antarctic Continental Zone is scarce. During the summer of 2019/2020, tintinnid diversity and horizontal distribution in surface waters were investigated in the Ross Sea and Amundsen Sea polynya.

Tintinnids (Ciliophora) are important microzooplankton grazers. In the Southern Ocean, they are found in the Antarctic Zone, Polar Front and Subantarctic Zone. The Antarctic Zone encompasses large gyres (Weddell Gyre and Ross Gyre) and the Antarctic Slope

Analyses of the morphometry of 630 loricae belonging to the described species Cymatocylis affinis and Cymatocylis convallaria retrieved from 21 samples collected in the Weddel Sea (6O–73�S) strongly suggest that both taxa, including the four formae into