Sphaerodinium fimbriatum R.H.Thompson (1950: 296)

Bustamante-Gil, Carolina, Boltovskoy, Andrés, Rengefors, Karin, Tavera, Rosaluz, Amat, Eduardo & Ramírez-Restrepo, Jhon J., 2021, Checklist, new records, and taxonomic annotations of freshwater thecate dinoflagellate (Dinophyceae) in Colombia, Phytotaxa 509 (2), pp. 135-167 : 162

Sphaerodinium fimbriatum R.H.Thompson (1950: 296) . Figure 18

Dimensions: L: 43–45 µm, Td: 34–39 µm.

Cell shape: Rounded, oval, dorsoventrally slightly compressed. Plate margins very prominent as fimbriate lists, present in both the epithecal and the hypothecal plates ( Fig. 18C ). Prominent plate margins, both in the epitheca and the hypotheca, in the form of fimbriate lists.

Thecal characteristics: Tabulation, 4ʹ, 4a, 7ʹʹ, 7c, 6s, 6ʹʹʹ, 2ʹʹʹʹ ( Figs. 18C and 18D ), without apical pore. The plate 1ʹ narrow, elongated, flanked by 2ʹ and 4ʹ plates, and not contacting 1ʹʹ and 7ʹʹ plates ( Fig 18C ). This character does not appear in the order Peridiniales . The 3ʹ is hexagonal and the four anterior intercalary plates are almost isodiametrical.

Cingulum and sulcus: Equatorial cingulum. Narrow sulcus, the Sa plate enters into the epitheca and is in contact with the first and the last pre-cingular plates ( Fig. 18C ).

Ornamentation: The margins of the plates, very prominent, easily visible with light microscopy ( Fig. 18B ). The margin border present outstanding nodules, such as fimbriae ( Fig. 18C ). The epithecal plates have a rough texture, without any ornamentation, while each hypothecal plate has a central prominent strip, similar in appearance to the projections of the plate margins ( Figs. 18C, E ).

Localities: Ayapel and Zapatosa in North Colombia.

Commentaries: This is the first record of both the genus and the species Sphaerodinium fimbriatum in Colombia. The species is an easily recognizable, due to the shape of the theca and the curved edges when observed with LM. The specimens observed match the original description ( Thompson 1951) and are in the size range ( Table 10) mentioned in the literature ( Carty 2014; Moestrup & Calado 2018).

World distribution: Ivory Coast and USA ( Moestrup & Calado 2018).

Figures

FIGURE 18. Sphaerodinium fimbriatum. A Ventral view. B Dorsal view. C SEM ventral view. D. Epithecal plates. E. Hypothecal plates. Bar= 10 µm.