Mercedesia aspiphora, Thomsen & Østergaard, 2015

Thomsen, Helge A. & Østergaard, Jette B., 2015, Coccolithophorids in Polar Waters: Quaternariella and Porsildia gen. nov. Mercedesia gen. nov., Ericiolus,, Acta Protozoologica 54 (3), pp. 155-169 : 157

M. aspiphora sp. nov. ( Figs 3–8)

Syn.: ‘Coccolithophorid sp. 1’ in Thomsen et al. 1988 (loc. cit. Fig. 47).

Diagnosis: Cell quasispherical (diam. 3–5 µm) with two flagella (ca. 20 and ca. 25 µm long) and a somewhat shorter haptonema (10–15 µm). The coccosphere ( Fig. 5) consists of a dense layer of monomorphic triangular, slightly convex nannoliths. The nannoliths have three slightly concave sides (ca. 0.5 µm long) and a central three-armed rib pattern on the distal side ( Figs 3, 4, 7). Most cells have nannoliths with a small central nodule on the distal side ( Figs 3, 7).

Holotype: Figs 3, 6 (same cell) from the Weddell Sea , Antarctica ( EPOS st. #161 at 57°30.3 S / 47°00.6 W) occurring in a mixed sample from 10 and 20 meters depth and processed on 13 December 1988.

Etymology: ‘aspis’ (Gr.) shield and ‘phora’ (Gr.) carrying.

Numerical details of M. aspiphora have been accounted for in Table 1. The interpretation above of nannolith shape and form, in particular with respect to the distal convexity of the liths, remains questionable and can most likely only be fully ascertained from sectioned material studied in the TEM. The critical question is whether the nannoliths are in fact triangular and convex with the 3 ribs on top or if they are rather concave with 3 radial depressions. We have here assumed for geometrical reasons that the concave face of the triangular nannolith is most likely representing the proximal side. Figs 7–8 show both sides of the nannoliths. The arctic coccospheres originating from NEW deviates slightly from the antarctic EPOS material in having minutely serrate edges on the triangular nannoliths ( Figs 7–8). However, this could very well be an artefact caused by partly decalcification of the nannolith rims. There is no indication for presence of organic underlayer scales in this taxon, nor have we observed combination cells involving M. aspiphora .

Mercedesia aspiphora was abundant (> 25 specimens) in samples from Antarctica (AMERIEZ, EPOS) and rare (<5 specimens) in samples from the Arctic ( NEW, NOW) .