Papposphaera heldalii, Thomsen & Egge, 2016

Thomsen, Helge Abildhauge & Egge, Jorun Karin, 2016, Papposphaera heldalii sp. nov. (Haptophyta, Papposphaeraceae) from Svalbard, Acta Protozoologica 55 (1), pp. 27-32 : 29

Papposphaera heldalii sp. nov.

Description of the heterococcolithophore phase: Coccosphere outer diameter ca. 10 µm; inner diameter 4 – 5 µm ( Figs 3–5 ). Dimorphic coccoliths. Body coc- coliths are narrowly elliptical and typically measure 0.9 – 1.0 × 0.5 – 0.6 µm. The coccolith rim ( Fig. 2 ) is formed by two cycles of elements. A proximal cycle of rod-shaped elements (0.1 – 0.2 × 0.04 µm) and a distal cycle of pentagonal elements that give the rim a regu- lar serrated appearance. Elements from the distal cycle are regularly shifted half the length of a rod-shaped ele- ment from the proximal cycle and an extension from the pentagonal elements separates the rod-like elements ( Figs 2, 7 ; arrows). The coccolith rim flares slightly rel- ative to the subtending organic base plate, and is vari- able in height (0.2 – 0.3 µm). There is no central area calcification. Clusters of coccoliths with calicate cen- tral spines occur at the apical and antapical poles of the cell ( Figs 3 – 5 ). These coccoliths are narrowly elliptical and measure 1.0 – 1.2 × 0.8 µm. The coccolith rim ( Fig. 7 ) is similar to that described above for the body coc- coliths. Central area calcification is in the shape of an axial cross ( Figs 3, 5 – 6 ) that leads into a central shaft (2.1 – 3.6 µm) which in turn carries a calyx 0.9 – 1.2 µm in height. The calyx ( Fig. 2 ) is formed by four triangu- lar wings arranged in a cross-shaped perpendicular pat- tern. Each wing is distally and laterally terminated by a prominent tooth and overlaps proximally for a short distance with the central stem.

Holotype: Figs 3, 6 (same cell).

Type locality: Collected March 2014 from St. B 2 ( Fig. 1 ) at 320 m depth (cold Atlantic water / <2°C /> 34.92 PSU) .

Type depository: The filter and the stub examined are maintained in the archives of the Bergen University Laboratory for Electron Microscopy which is affiliated with the Faculty of Mathematics and Natural Sciences.

Etymology: The species epithet ‘ heldalii ’ honours the contribution of Mikal Heldal, Univ. Bergen, to the recent exploration of lightly calcified coccolithophores from high Arctic sites.

There is little additional information required in sup- port of the details embedded in the formal species di- agnosis. We have not observed flagella and haptonema in association with any of the complete coccospheres examined. However, the occurrence of coccoliths with calicate spines in distinct clusters and with a notice- able difference in length of the central structure when comparing clusters within the same cell (see e.g. Fig. 4 ) clearly indicates that these cells have distinct polarity which is commonly linked to the presence in the living cell of flagella and haptonema. Since all other species of Papposphaera are flagellated there is every reason to believe that these cells are too.

In P. heldalii there is a large variability in size ( Figs 3 – 5 ) among body coccoliths within the same cocco- sphere exceeding what is typically observed within species of Papposphaera . Table 2 summarizes the vari- ability encountered, with the cell in Fig. 5 representing the most extreme case with mean values of 0.9 ± 0.14 × 0.6 ± 0.09 and overall size ranges between 0.5 – 1.2 and 0.4 – 0.7 µm respectively.

There is no evidence of unmineralized underlayer scales nor can we at this stage provide information with reference to a possible life history counterpart of P. heldalii .

The geographical distribution of P. heldalii is cur- rently almost exclusively limited to the Svalbard region ( Fig. 1 ). However , the species has also been found in ‘ MicroPolar’ samples from Young Sound (East Green- land / approx. 74°15N and 20°10W) (Heldal, Egge, Larsen and Paulsen, unpublished observations), and it is likely to have a panarctic distribution similar to what appears to be the case for many other lightly cal- cified coccolithophores from northern hemisphere high latitudes .

Figures

Figs 2–7. Papposphaera heldalii SEM images of cells from the Svalbard region collected during Jan. 2014 (Figs 4–5) and March 2014 (Figs 2–3, 6–7). 2 – cluster of coccoliths shown at high magnification. Notice in particular details of the calyx and coccolith rim calcification. The arrows point to extensions from the pentagonal elements separating the rod-like elements. See also ruptures in the organic base plates of body coccoliths; 3 – whole cell (type specimen) showing the general disposition of types of coccoliths within the coccosphere. A single coccolith (enlarged in Fig. 6) shows the central area calcification of a calicate coccolith; 4 – whole cell. Notice the difference in length of the central process among the two clusters of coccoliths carrying these. See also the conspicuous size differences between neighboring body coccoliths; 5 – body coccoliths showing large individual size differences; 6 – detail of central area calcification in a coccolith that carries a central process (broken away here); 7 – detail of coccolith rim from coccoliths that carry a central process. The arrows point to extensions from the pentagonal elements separating the rod-like elements.

Fig. 1. Svalbard sampling sites during MicroPolar cruises. The type locality of P. heldalii is marked by a square, and arrows point to ad- ditional sampling sites yielding P. heldalii material.