Balaniger virgulosa ( Thomsen and Oates 1978 ) 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 : 247-249

Balaniger virgulosa ( Thomsen and Oates 1978) Thomsen and Østergaard comb. nov.

Syn. Pappomonas virgulosa Manton and Sutherland 1975

Balaniger balticus Thomsen and Oates 1978

Balaniger virgulosa HET ( Figs 46, 50 ) carries oval body coccoliths and circumflagellar coccoliths that terminate in a tuft of elongated elements. Body coccoliths measure 0.8 ± 0.10 × 0.5 ± 0.04 µm. The rim consists of erect and slightly tilted rectangular elements (0.1 µm) that are distinctly separated by small rod-shaped elements arranged along the base plate scale surface ( Figs 49 , 58F ). The central area calcification typically comprises a single oval ring arranged in parallel to the rim and a line of elements inside the oval. The calcification is formed by a sequence of upright larger elements distinctly separated by small adnate rod-shaped elements. This arrangement thus basically mirrors that of the coccolith rim with the exception that the upright elements are not inclined but appear to be positioned at right an- gles to the base plate scale ( Figs 49 , 58G ).

The circumflagellar coccolith is oval ( Fig. 48 ; material from Bergen, Norway). The rim and central area calcification mirrors that of the body coccoliths while also integrating a cruciform arrangement of elements that lead into the central shaft. The central shaft (ca. 1 µm) is terminated ( Fig. 47 ) by a characteristic tuft of four elongated elements (0.6–0.9 µm). Coccoliths with a reduced central appendage (shaft missing) are frequently observed at the posterior cell end ( Fig. 46 ).

We are here providing evidence ( Figs 52–57 ) that Pappomonas virgulosa and Balaniger balticus are part of the very same life history. The combination cells shown in Figs 54 and 57 thus comprise periplast areas where the characteristic pyramid-like structures of B. balticus occur mixed in between P. virgulosa coccoliths. The two morphotypes of B. balticus pyramids ( Figs 55–56 ) were introduced already when the species was originally described ( Thomsen and Oates 1978). In a single specimen from Svalbard ( Fig. 52 ) it is apparent that the body coccoliths are widely separated. When scrutinizing the area between the coccoliths ( Fig. 53 ) it was revealed that these areas comprised clusters of B. balticus pyramids. The Svalbard cell illustrated in Fig. 52 is thus yet another combination cell further strengthening the P. virgulosa and B. balticus life history case.

The finding of combination cells that link P. virgulosa to B. balticus in combination with: 1) an aberrant organization of rim and central area calcification in comparison with the generic type species P. flabellifera , and 2) a markedly different concept with regard to the termination of circumflagellar coccolith processes, renders impossible the continued inclusion of P. virgulosa within Pappomonas . The straightforward solution is to synonymise P. virgulosa with B. balticus (as B. virgulosa because ‘ virgulosa ’ takes precedence over ‘ balticus ’) and to refer in the future to the specific stages using the informal keyword HET for the heterococcolithophorid stage Pappomonas virgulosa and HOL for the holococcolithophorid stage Balaniger balticus .

The original diagnosis ( Manton and Sutherland 1975) is detailed enough to unequivocally circumscribe the heterococcolithophorid stage. The observations provided here basically corroborates the information in Manton and Sutherland 1975, however also adds information previously lacking with regard to the ex- act configuration of the circumflagellar coccolith and new knowledge with regard to life history stages of this taxon. As none of these features are crucial to species identification it is not considered relevant to emend the original description.

The currently known biogeographical range of B. virgulosa HET and HOL is summarized in Table 2.

Figures

Figs 46–53. Balaniger virgulosa HET from the Arctic (West Greenland / Figs 46–47, 49; NEW / Fig. 50; Spitsbergen / Figs 51–53; Bergen, Norway / Fig. 48); TEM (Figs 46–47, 49–50) and SEM (Figs 48, 51–53) whole mounts. 46 – complete cell with reduced central appendages on some coccoliths at the posterior cell end; 47 – detail of cirtcumflagellar coccolith central processes showing the shaft and the tuft of four elongate elements that terminate the structure; 48 – detail of specimen from western Norway showing central area features of a circumflag- ellar coccolith; 49 – detail of body coccoliths showing the rim and central area calcification; the arrows point to areas where the calcification is particularly evident; 50 – complete cell with flagella and a curled up haptonema; 51 – whole cell which shows the irregular arrangement of densely packed body coccoliths; 52 – combination cell comprising Pappomonas virgulosa and Balaniger balticus; interspersed between the widely separated body coccoliths is a layer of pyramidal appendages known from B. balticus; 53 – detail from Fig. 52 showing (arrows) the B. balticus pyramids.

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).

Figs 54–57. Balaniger balticus / Pappomonas virgulosa combination cells. TEM whole mounts from West Greenland. 54 – complete cell with flagella and a single haptonema; arrows point to areas of the periplast where B. balticus HOL elements occur; 55 – detail from Fig. 54 showing B. balticus HOL pyramids; 56 – detail from Fig. 57 showing a pointed variant of the B. balticus HOL pyramids; 57 – complete cell with the B. balticus HOL periplast elements pointed out.