Pappomonas borealis ( Manton, Sutherland and McCully 1976a ) Thomsen and Østergaard 2014

Thomsen, Helge A. & Østergaard, Jette B., 2014, Coccolithophorids in Polar Waters: Pappomonas spp. Revisited, Acta Protozoologica 53 (3), pp. 235-256 : 241-243

Pappomonas borealis ( Manton, Sutherland and McCully 1976a) Thomsen and Østergaard stat. nov.

Basionym: Pappomonas flabellifera var. borealis Manton, Sutherland and McCully 1976a

The emended diagnosis below is building directly upon the original diagnosis of the former variety and only revised in places where additional precision is called for:

Differing from the type of the genus ( P. flabellifera ) by more nearly triangular blades to the flabelliform appendages, the distal edge dentate or fimbriate, the central cleft more distinct with the adjacent sides of the two half­blades not overlapping, the angle between outside edges of the blade as a whole approximately 90°, each half­blade attached laterally to the end of the columnar stalk for a longer distance (about half the blade length), than in the type. The base plate of a flagellar pole coccolith is almost circular, ca. 0.7 µm in diam. and with a cross­shaped calcification where elements merge into the central shaft. Mineralized plates without appendages somewhat wider relative to their length, commonly 0.9 × 1.4 µm excluding the rim. The number of rows of elements on the plate is typically within the range 5–9.

Type material: Homer, Alaska ( Manton et al. 1976a, loc.cit. Figs 12–14)

The body coccoliths of P. borealis are much reminiscent of those of P. flabellifera , however, clearly distinguishable based on size ( Table 1; Fig. 18 ) and in derived size-related features such as the number of rim elements and the complexity of the central area calcification. The height of a single pentagonal element from the rim is up to 0.3 µm. In large coccoliths ( Figs 19, 25, 27 ) there are usually two complete rings of elements and three to four rows of elements inside the inner oval that are arranged more or less in parallel with the longitudinal axis of the coccolith. The central area calcification in smaller coccoliths is much similar to that described for P. flabellifera .

Circumflagellar coccoliths ( Figs 24, 25) differ from those of P. flabellifera both with respect to shape (almost circular; ca. 0.7 µm in diam.) and calcification (cross shaped arrangement of elements that merge into the shaft of the central process), and with reference to the elaboration of the triangular structure that terminates the circumflagellar coccolith ( Figs 24–27). The triangle consists of two almost identical half blades in which the distal edge and the upper part of the ventral flanges are finely serrulate. The lateral edge of a triangle (straight line) measures in our material 1.25–1.5 µm while the upper edge from tip to tip measures 1.5–2 µm. The two half blades appear to be perfectly aligned forming a two-dimensional structure. The lower lateral edges are straight and adjoin at an angle that typically exceeds 90°. The central shaft (1.4–1.6 µm) is connected to the triangle for at least half the distance between the base of the triangle and the upper rim.

Deviant cells of P. borealis in which rim elements (1–2 on each coccolith) are hypertrophied have been observed in samples from both W. Greenland ( Fig. 28) and NEW ( Fig. 29). The aberrant element takes the shape of an oblique pointed triangle.

A combination cell with coccoliths belonging to P. borealis (HET) and Trigonaspis diskoensis (HOL) was discussed by Thomsen et al. (1991; loc.cit. Fig. 17). We are fortunate enough here to be able to present further cells ( Figs 30–32) that substantiate the life history relationship between these two taxa.

The currently known biogeographical range of P. borealis is summarized in Table 2.

Figures

Fig. 18. Pappomonas flabellifera (squares) and P. borealis (triangles) body scale dimensions.

Fig. 27. Pappomonas borealis (TEM whole mount) from the Arctic (West Greenland). Scatter of body and circumflagellar coccoliths il- lustrating differences in size and ornamentation among body cocco- liths and the highly dissimilar base of the circumflagellar coccoliths.