Turrisphaera sp.

Thomsen, Helge A., Østergaard, Jette B. & Heldal, Mikal, 2016, Coccolithophores in Polar Waters: HOL Revisited Papposphaera sagittifera HET and, Acta Protozoologica 55 (1), pp. 33-50 : 44

Turrisphaera sp. ( Figs 33–37 )

Cells reminiscent of P. sagittifera HOL (syn. Turrisphaera borealis ) have been regularly encountered in Antarctic samples and were expected to eventually appear as the life cycle counterpart of Antarctic P. sagittifera cfr. The cells illustrated here originate from the Weddell Sea (EPOS) and display the typical cell coverage of symmetrical and tower-shaped holococcoliths that are flaring at both ends. Crystallographic features ( Figs 35–36 ) are also consistent with those of P. sagittifera HOL. Our main hesitation to up front identify the Antarctic material as P. sagittifera HOL is due to the fact that the individual holococcoliths are shorter (1.2–1.5 µm) and slightly more narrow (ca. 0.4 µm) and also accordingly have fewer hexagonal plates across the coccolith. The overall appearance of the Antarctic material is thus somewhat different from the Arctic P. sagittifera HOL (compare e.g. Figs 24 and 34 ). It should also be emphasized that we have at present no evidence from Antarctic waters of life cycle events that involves this particular form. We therefore prefer for the time being simply to refer to this material as Turrisphaera sp. Without molecular evidence it is hardly possible to take a different approach right now.

Figures

Figs 33–37. Turrisphaera sp. TEM whole mounts from the Antarctic (EPOS samples). 33 – complete cell with flagella and haptonema; 34 – whole cell at higher magnification showing the regular appearance of the tower-shaped holococcoliths; 35–36 – details of holococ- coliths showing the hexagonal crystallite plates; 37 – complete cell.

Figs 23–26. Papposphaera sagittifera HOL (TEM / Figs 23–25; SEM / Fig. 26) from the Arctic (NEW / Figs 23–25; Svalbard / Fig. 26). 23–25 – complete cells showing flagella, haptonema (Fig. 25, arrow) and large numbers of tower-shaped holococcoliths projecting in all directions; 26 – high magnification of the hexagonal crystallite plates.