Trigonaspis minutissima Thomsen 1980a

Thomsen, Helge A. & Østergaard, Jette B., 2015, Coccolithophorids in Polar Waters: Trigonaspis spp. Revisited, Acta Protozoologica 54 (2), pp. 85-96 : 90-91

Trigonaspis minutissima Thomsen 1980a

Trigonaspis minutissima was described alongside the type species of the genus from West Greenland coastal waters ( Thomsen 1980a). Subsequent sampling excursions to the same Disko Bay site has on more occasions yielded additional material of T. minutissima that allows a reexamination of the taxon .

The appearance of the whole cell including appendages and the overall distribution of coccoliths is accounted for in Figs 12 and 16 . Numerical facts have been assembled in Table 1. The tiny cell ( Fig. 12 ) carries a corona of slender and tower-shaped flagellar pole coccoliths while the remaining part of the cell appears to be covered by fairly identical disc-shaped and oval body coccoliths. Trigonaspis minutissima in contrast to T. diskoensis thus appears to be strictly dimorphic. The slender individual FPC is in principle still a double-flared tube ( Figs 13 and 15 ). The triangular groups of crystallites in this species also appear to be organized in a helical pattern. A single turn of the helix in the narrowest middle part of the FPC involves only 4–5 triangles.

The 2D-matrix of triangles on the individual body coccolith ( Fig. 14 ) appears in the undisturbed BC to be similarly well organized as previously reported for T. diskoensis .

In contrast to T. diskoensis there is in T. minutissima a slight difference in the size of triangles among flagellar pole and body coccoliths (see Table 1), with triangles from the body coccoliths being marginally larger.

A life cycle counterpart of T. minutiussima remains to be discovered. Considering the convincing similar- ity between T. diskoensis and T. minutissima in all crucial morphological features, the life cycle counterpart is likely to be a species of Pappomonas . Pappomonas flabellifera Manton and Oates 1975 which is also abun- dantly present in the Disko Bay area ( Thomsen and Østergaard 2014b) is from all perspectives a strong candidate.

Biogeographical data on T. minutissima is presented in Table 2.

Figures

Figs 12–16. Trigonaspis minutissima. TEM whole mounts from West Greenland (Arctic Station). 12 – whole cell with partly detached coccoliths; 13 – detail from Fig. 12 of flagellar pole coccoliths showing triangular crystallite groups and slender towers wreathed with 4–5 of these in a random transect; 14 – detail of body coccolith from the cell shown in Fig. 12; 15 – detail of coccoliths from the cell shown in Fig. 16; 16 – whole cell with flagella and curled up haptonema.