Pappomonas weddellensis Thomsen

Thomsen, Helge A. & Østergaard, Jette B., 2014, Coccolithophorids in Polar Waters: Pappomonas spp. Revisited, Acta Protozoologica 53 (3), pp. 235-256 : 243-245

Pappomonas weddellensis Thomsen in Thomsen et al. 1988

The original description of this taxon was based on only two specimens ( Thomsen et al. 1988). Additional sampling from the Weddell Sea, in particular during the ANT X/3 cruise, has provided a multitude of cells that renders possible a reexamination of the validity of morphological details emphasized in the original description. There is complete agreement between the original description and subsequent findings in almost all features; e.g. with regard to: 1) the central process of circumflagellar coccoliths which is terminated by two markedly differently sized half blades ( Fig. 34, arrows) one of which is drawn out into a pointed triangular blade, 2) the quasicircular base of a circumflagellar coccolith, and 3) the presence of reduced and non-stalked central processes on coccoliths at the antapical cell end. Whereas most of the body coccoliths observed display a cruciform central area calcification ( Fig. 37) in agreement with that of the type material, other cells ( Fig. 36) have a more elaborate central area calcification where each quadrant of the base plate scale has an additional line of rectangular elements organized along the long axis of the coccolith ( Fig. 35). However, it is worth emphasizing that the cell shown in Fig. 36 in addition to this deviant type of body coccolith also encompasses body coccoliths with the more typical arrangement of elements in a simple cross ( Fig. 36, arrow) plus the oc- casional irregularly positioned single element. The iso- lated body coccolith ( Fig. 35 from the cell shown in Fig. 36) shows a typical Pappomonas configuration of the rim with ca. 20 upright polygonal elements interspersed at the base by a sequence of rod-shaped elements ( Fig. 58C ).

Pappomonas weddellensis is similar to both the type species P. flabellifera and P. borealis in so many crucial morphological aspects that a shared generic affilia- tion still appears justified. Combination cells involving P. weddellensis and Trigonaspis sp. have not yet been encountered. Trigonaspis melvillea Thomsen 1988 is abundant in Antarctic waters and might thus be a possible candidate.

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

Figures

Fig. 58. Interpretation of rim calcification (body coccoliths) in spe- cies of Pappomonas and Papposphaera. A – Pappomonas flabellifera (NEW / micrograph 25036); B – Pappomonas borealis (NEW / micrograph 24879); C – Pappomonas weddellensis (ANT X/3 / mi- crograph 20549); D – Pappomonas garrisonii sp.nov. (ANT X/3 / micrograph 21149); E – Papposphaera sagittifera (NEW / micro- graph 24930); F–G – Balaniger virgulosa HET scale rim (F) and base plate calcification (G) (West Greenland / micrograph 10322).