Papposphaera sagittifera

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

P. sagittifera cfr. HET ( Figs 27–32 )

Material from the Weddell Sea EPOS cruise seems in all major details to match the appearance of northern hemisphere P. sagittifera . The two complete cells ( Figs 27, 30 ) are flagellated and both with a curled up haptonema. The coccospheres comprise the usual mixture of coccoliths with central processes clustered around the flagella and towards the antapical pole. Other coccoliths are devoid of processes and much reminiscent of P. sagittifera body coccoliths in terms of central area calcification ( Fig. 31 ) and the elaboration of the rim ( Fig. 32 ). The calyx ( Figs 28–29 ) is a flaring four-winged rosette similar to that described from Arctic P. sagittifera HET. Each wing has on the interior edge a marked step-wise reduction in size.

The identity of this material is still ascertained with some element of doubt. The Antarctic material is characterized by a large degree of coccosphere cohesiveness which means that the number of coccoliths that clearly display the central area calcification is rather limited. In those that are in fact exposed, such as Fig. 31 , there is an unfamiliar element of skewness in the overall design that is unknown in northern hemisphere P. sagittifera . The bars are obviously tilted with reference to the primary axes of the coccolith. There is also towards one end of the coccolith a ‘misplacement’ of elements that may at first sight appear random. However, these irregularities are in fact repeated also in the cell found earlier from the region ( Thomsen et al. 1988, loc. cit. Figs 35–37 ) which indicates that this may in fact be a typical feature of P. sagittifera from the southern hemisphere. A third reason for our hesitation to just right away identify this form as P. sagittifera is the fact the combination coccosphere also deviates from the northern hemisphere established standards (see further below).

Figures

Figs 27–32. Papposphaera sagittifera cfr. HET. TEM whole mounts from the Antarctic (EPOS samples). 27 – complete cell with flagella and a curled up haptonema; 28 – high magnification of calyces (four-winged rosettes) from Fig. 27; 29 – high magnification of calyx from Fig. 30; 30 – complete cell with flagella and a curled up haptonema; 31 – detail of central area calcification from the cell in Fig. 30; 32 – details of rim structure from the cell shown in Fig. 30.

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.