Pappomonas flabellifera Manton and Oates 1975

Thomsen, Helge A. & Østergaard, Jette B., 2014, Coccolithophorids in Polar Waters: Pappomonas spp. Revisited, Acta Protozoologica 53 (3), pp. 235-256 : 237-239

Pappomonas flabellifera Manton and Oates 1975

When first described ( Manton and Oates 1975) the material examined comprised as also acknowledged by the authors three morphotypes that were basically dis- tinguished by differences in the appearance of the blades that terminate the circumflagellar coccoliths. While the West Greenland morphotype (loc.cit. Figs 9–12, 14, 20, 21) was later singled out as the variety ‘ borealis ’ ( Manton et al. 1976a), the two remaining morphotypes both of S. African origin were maintained within P. flabellifera var. flabellifera . The S.African type material ( Manton and Oates 1975; loc.cit. Figs 5, 6) which is further substantiated by additional micrographs (loc.cit. Figs 7, 8, 16, 17) represents a morphotype of P. flabellifera that is rarely encountered and to the best of our knowledge not illustrated in any subsequent publication. The feature that most clearly identifies the type material is the V-shaped circumflagellar coccolith appendage. The second S. African morphotype (loc.cit. Figs 13, 15, 18 , 19) has, however, become the de facto P. flabellifera var. flabellifera which has later been found and reported from a range of geographic sites. The inclusion of no less than three morphotypes in the original description of P. flabellifera has created confusion in as much as the diagnosis as it stands (and despite the precise identification of a type specimen) does in fact include morphological features and dimensions sampled across the whole range of morphotypes encountered.

The below reexamination of a substantially larger material of Pappomonas flabellifera var. flabellifera and P. flabellifera var. borealis (under the heading P. borealis stat. nov.) provides in our opinion the in- sight needed to set up a more robust future taxonomic framework.

The vast majority of the P. flabellifera cells examined in preparation for the current paper and also those illustrated in Figs 3–12 come from the North East Water Polynya ( NEW / Figs 3–8) and Svalbard ( Figs 9–12).

The P. flabellifera body coccolith is oval and dis- plays a fairly narrow variability in length and width in the material examined here (see Fig. 18 and Table 1). The rim is more or less perpendicular to the base plate scale ( Fig. 10) and comprises a distal cycle of 15–20 quasi-pentagonal and closely abutted elements ( Fig. 6) and interspersed between these a proximal/inner cycle of short rod-like elements (see Fig. 58A ). The central area calcification comprises rod-shaped elements joined end to end. In larger coccoliths ( Fig. 5) there is typically a ring of elements running roughly in parallel with the rim and with a number of more or less parallel lines of elements (3–4) occupying the interior and spanning the entire length of this oval. In smaller coccoliths the central area calcification is limited to 3–4 lines of elements arranged along the longitudinal axis of the coccolith ( Fig. 10). In most cases these patterns can be interpret- ed as a ring of elements arranged more or less parallel to the scale rim and with a single line of rods arranged along the longitudinal axis of the scale. Elements from the peripheral ring frequently come into contact with the rim calcification at either end of the coccolith.

The circumflagellar coccoliths, typically 10–15, are organized as a fairly compact ring at the anterior cell end ( Figs 3, 9, 11). The hollow process (0.8–10 µm) which is formed by a dense layer of minute rods ( Fig. 7) is proximally attached to an oval base plate scale ( Figs 7 and 8) that does not deviate markedly from an ordinary body coccolith in size, shape or central area calcification. However, the central process is supported also by lines of elements that run more or less perpendicular to the longitudinal axis of the coccolith forming a trans- verse bar. It is also apparent from Figs 7 and 8 that the rim in circumflagellar pole coccoliths is less elaborate in comparison with body coccoliths. The pentagonal elements are less abundant and more widely spaced. The central process distally carries a triangular structure formed in most cases by two slightly overlapping, asymmetrically sized and obtusely angled blades ( Figs 3 and 4) that are terminated distally by a jagged and irregular rim of crystalline facets, and often terminated on either side by a prominent tooth-like projection. The lateral edges of the triangle measure in our material 0.8–1.0 µm and the upper edge from tip to tip 1.0–1.2 µm. The overlap between the central shaft and the two terminal blades is fairly short ( Figs 7, 12). The angle formed by the two blades is at this point approximately 85 degrees.

It is obvious that Manton and Oates (1975) were very cautious when circumscribing P. flabellifera realizing that it summarizes features sampled across three acknowledged morphotypes. However, it will be evident when dealing with P. borealis below that substantial evidence exists in favour of treating P. borealis as a separate species and not merely as a variety of P. flabellifera . This obviously impacts on the formal circumscription of P. flabellifera and calls for an emended description of this taxon. The diagnosis is filtered for P. borealis effects in terms of size ranges provided and a lack of informative morphological details caused by the amalgamation of taxonomic units that were in fact too different to be handled at the subspecific level. The emended diagnosis below is building directly upon the original species diagnosis and only revised in places where additional precision is called for.

Figures

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

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).