Papposphaera sagittifera Manton, Sutherland and McCully 1976 emend. Thomsen, Østergaard and Heldal

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 : 42-44

Papposphaera sagittifera Manton, Sutherland and McCully 1976 emend. Thomsen, Østergaard and Heldal

Syn.: Turrisphaera borealis Manton, Sutherland and Oates 1976

Diagnosis:

Heterococcolithophore phase: Cell oblong ca. 7 × 5 µm with two flagella and a haptonema. Coccoliths (1.1–1.3 × 0.6–0.7 µm) varimorphic to dimorphic muroliths. Circum-flagellar and antapical pole coccoliths carry a conspicuous calicate spine. The longest spines (up to 3.5 µm) are at the apical pole whereas those at the antapical pole tend to be somewhat shorter (ca. 1.5 µm). The calyx is typically constructed from four perpendicularly arranged elements forming a conspicuously flaring four-winged rosette. Each wing has parallel sides. The exterior edge is straight, whereas the interior edge has a variable number of steps that gradually decrease the width of the wing towards the distal end. In rare instances the rosette adopts a regular triangular outline where the individual wing is narrower, without a distal stepwise elaboration of the interior edge, and with a different angle between the exterior edge and the line that proximally connects the exterior and interior edges causing the rosette to be less flaring. The central area calcification comprises an axial cross that is continuous with the stem of the spine. There is additionally 5 (3–7) longitudinal bars evenly distributed across the coccolith. The rim is upright (ca. 0.25 µm in height) and slightly flaring and comprising two cycles of elements. The proximal cycle is formed by short rods (0.15 × 0.05 µm) joined end to end. The distal cycle comprises pentagonal elements that give the rim a characteristic serrate margin. The two cycles of elements are mutually and regularly shifted. Body coccoliths are similar to those described above with the exception of the central spine which is here often represented by a short knob-like structure equivalent to the proximal part of the stem. In other cases the coccolith centre is moundshaped caused by a slight upheaval of the arms of the axial cross where they meet. Unmineralized underlayer scales not observed.

Holotype: Manton, Sutherland and McCully 1976a loc. cit. Figs 1–4 . Material collected at Homer, South Alaska, 19 June 1975 (15 m depth / 6°C).

Epitype: Thomsen 1981, loc. cit. Figs 9 , 13 collected August 1977 in the vicinity of the Arctic Station, Disko, West Greenland (ca. 50 m depth / ca. 2°C).

Holococcolithophore phase: Cell mostly spherical and ca. 6 µm in diameter. The diameter of the entire coccosphere is ca. 12 µm. Cell flagellated and with a somewhat shorter haptonema. Coccosphere formed by holococcoliths of one type, each a symmetrical and lengthy tower-shaped structure (up to 3.5 µm in length) with a distinct flaring at both ends. The organic base plate measures ca. 1.2 × 1.5 µm. Underlayer scales (0.2–0.3 µm) are present most likely occupying the gaps between the coccolith base plates. There is typically a change in overall dimensions of the individual tower from one end of the cell to the other, with the longest holococcoliths encircling the flagellar pole of the cell. The holococcoliths carry a monolayer of hexagonal plates (ca. 0.15 µm across) of crystallites arranged in reticulate patterns or in lines that spiral the towers. Each hexagonal plate may have a central perforation.

Combination coccosphere ( Papposphaera sagittifera / Turrisphaera borealis )

With the characteristics of the heterococcolithophore and holococcolithophore phases yet with calyx features in the heterococcoliths that differ from those typically observed in P. sagittifera HET. The four-winged rosette comprises wings that are fairly narrow, hardly ever stepwise elaborated on the inside, and with an angle proximally between the exterior edge of the wing and the connecting line between the two edges of the wing that leads to little flaring of the rosette. Notice that this type of calyx is also infrequently observed in P. sagittifera HET.

New observations on P. sagittifera from Antarctic sites

Thomsen et al. (1988) reported P. sagittifera from the Weddell Sea based on the finding of a single specimen in the AMERIEZ material. It was concluded that there was a large degree of similarity between this cell and material previously examined from the northern hemisphere and there was no reservation at that time with regard to the identity of the material. We have during subsequent sampling campaigns (EPOS, ANT X/3) found a large number of cells reminiscent of P. sagittifera and T. borealis as well as combination coccospheres in Weddell Sea samples. This material is further described below and illustrated in Figs 27–48.

Figures

Figs 1–2. Maps of collection sites. 1 – northern hemisphere; 2 – southern hemisphere. Showing also the AMERIEZ sampling grid (Thomsen et al. 1988).

Fig. 3. Interpretational drawings of coccolith structure within species of Papposphaera. Intraspecific variation is shown where relevant. A – P. sagittifera; B – P. sagittifera cfr.; C – P. sarion; D – P. arctica; E – P. iugifera; F – P. heldalii; a – body coccolith central area calcification; b – calyx design; c – calicate coccolith central area calcification; d – holococcolith contour (flagellar pole coccolith); e – holococcolith contour (body coccolith). Notice the inclusion of schematic drawings of a rosette wing from each of the P. sagittifera types of calyces.

Figs 4–9. Papposphaera sagittifera HET (TEM / Figs 4–5, 7; SEM / Figs 6, 8–9) from the Arctic (West Greenland / Fig. 7; NEW / Figs 4–5; Svalbard / Figs 6, 8, 9). 4 – whole cell with curled up flagella and haptonema (arrow); 5 – detail of calyx; 6 – lateral view of coccolith displaying the two cycles of elements in the rim and details of the stem and the calyx; 7 – complete cell; notice the difference in length of coccolith processes from one end of the cell to the other; 8 – details of central area calcification; notice the short stub-like central proboscis and also possibly tilted pentagonal elements from the distal rim circle (arrows); 9 – detail of two coccoliths one with a short central process and the other with just a central upheaval of the arms of the crossbar.

Figs 10–16. Papposphaera sagittifera HET (TEM / Fig. 13; SEM / Figs 10–12, 14–16) from the Arctic (Svalbard / Figs 10–12, 14–16; NEW / Fig. 13). 10–12 – whole cells selected to show the limited occurrence of coccoliths with central processes and the obvious irregularities in size and placement of the body coccoliths; 13 – whole cell showing flagella and haptonema; 14 – cell selected to illustrate the variability in coccolith size, orientation and central area calcification; notice the presence of two types of calyces (encircled); 15 – calyx of the standard ‘flaring’ P. sagittifera HET type (enlargement from Fig. 14); 16 – ‘triangular’ calyx (enlargement from Fig. 14) similar to those found in P. sagittifera HET when forming part of a combination coccosphere.

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.

Figs 38–43. Papposphaera sagittifera cfr. TEM combination coccospheres from Antarctica (EPOS / Figs 39, 42–43; ANT X/3 / Figs 38, 40–41). 38 – complete cell with flagella and haptonema; 39 – cell with just a few P. sagittefera cfr. HET coccoliths and ‘Turrisphaera’ holococcoliths that are highly asymmetrical at the anterior pole; 40 – detail of holococcoliths from the cell shown in Fig. 38; 41 – higher magnification of anterior cell end of the cell shown in Fig. 38 to show details of the calyces and the central area calcification; 42–43 – details of coccoliths from the cell shown in Fig. 39.

Figs 44–48. Papposphaera sagittifera cfr. HOL. TEM whole mounts from the Antarctic (EPOS / Figs 45, 47–48; ANT X/3 / Figs 44, 46). 44 – details of highly asymmetrical flagellar pole holococcoliths; 45–47 – complete cells with flagella and haptonema; 48 – holococcoliths at high magnification.