Naiadinium polonicum (Woloszynska) S. Carty (2014: 123

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 : 145

Naiadinium polonicum (Woloszynska) S. Carty (2014: 123 , 223). Figure 5

Basionym: Peridinium polonicum Woloszynska (1916: 271)

Synonyms:

Glenodinium gymnodinium in Penard (1891: 54)

Peridinium polonicum var. trilineatum in Er. Lindemann (1919: 223)

Glenodinium gymnodinium var. biscutelliforme in R. H. Thompson (1951: 293)

Peridiniopsis polonicum in Bourrelly (1968: 9)

Peridinium polonicum in Adachi (1965: 314)

Glenodinium gymnodinium in Sant´Anna et al. (1986: 100)

Peridinium polonicum in Fukuyo et al. (1990: 136)

Peridiniopsis polonicum in Hashimoto et al. (1996: 528)

Peridiniopsis polonicum in Roset et al. (2002: 141)

Naiadinium biscutelliforme in Carty (2014: 120)

Dimensions: LT: 49–56 µm, Td: 37–46 µm.

Cell shape: Oval, longer than wider, dorsoventrally compressed ( Figure 5A ). Epitheca bell-shaped, showing a little spine on the hypotheca ( Figure 5 ).

Thecal characteristics: Tabulation, Po, 4ʹ, 2a, 7ʹʹ, 5c, 6s, 5ʹʹʹ, 2ʹʹʹʹ. The plate 1ʹ is narrow on the base, widening fanshaped anteriorly ( Figs. 5B and 5D ). The 1a plate square and the 2a rectangular with the superior and inferior edges convex, almost twice as big as the 1a ( Fig. 5E ).

Cingulum and sulcus: Excavated and descending cingulum, formed by 5 plates. The sulcus, extending to the antapex, is formed by 6 plates, 4 external main plates and 2 internal platelets. The Sp plate is longitudinally elongated and concave, being the largest of the set. Its superior right side is staggered, joining Sd, Spa, Sm and Ss plates. ( Fig. 5G ). The plate Spa is very small and is not easily detectable by light microscopy ( Fig. 5B ). The sulcal ornamentation is very faint and shows a few pores on the Sp only ( Fig. 5G ).

Ecdysial opening: Dorsal epithecal, given by the detachment of the plates 3ʹ, 1a, 2a, 3ʹʹ,4ʹʹ and 5ʹʹ ( Figs. 5C and 5F ).

Ornamentation: The main plates are covered by a relief reticulum with rounded projections at the nodes of the mesh. The reticulum defines polygonal depressed alveoli, which are perforated by pores ( Fig. 5H ). The relief is smoother on the surface of the cingular and sulcal plates.

Locality: Guatapé reservoir North-west Colombia.

Comments: The shape of the cell and main thecal tabulation and cingular tabulation agrees with the original description and with modern studies ( Adachi 1965; Ascencio et al. 2018; Carty 2014; Craveiro et al. 2015; Woloszynska 1916). However, there is no uniformity regarding the number of plates in the sulcus and their nomenclature. Adachi (1965) erroneously divided the unusually long Sp plate in two, considering its anterior part as the Ss plate. Consequently, he named as transitional plate (T) the one that is in its immediately anterior position. Although Imamura & Fukuyo (1990), Craveiro et al. (2015) and Ascencio et al. (2018) do not subdivide the Sp plate in two, they maintain the Adachi’s T plate. Subsequently these authors consider the anterior of the two internal sulcal platelets as the left sulcal plate (Ss, our Sm).

Since in the Class Dinophyceae Sp plate never has been found in touch with the T plate nor Ss plate has been found as an internal plate, and considering plate homologies, we consider as Ss plate the one that other authors call T. If Naiadinium is compared with other representatives of the order Peridiniales where the sulcal structure is well known (e. g. Balech 1974; Boltovskoy 1999a), it can be noted that Naiadinium has the particularity that the Sa plate does not come into contact with the first cingular plate (1c), possibly due to the anterior migration of the Ss. This characteristic and the very long Sp is shared only with the genus Theleodinium, as illustrated in Moestrup & Calado (2018).

This is the first record of both the genus and the species N. polonicum in Colombia. The two internal sulcal plates, median sulcal plate (Sm), accessory posterior sulcal plate (Spa) and ecdysial opening are shown here for the first time with full definition ( Figs. 5F and 5G ).

World distribution: Naidinium polonicum is widely distributed in Europe, also found in USA, China, and Japan ( Moestrup & Calado 2018) and the Caribbean ( the Bahamas) ( Björnerås et al. 2020). In South America only in Chile ( Ascencio et al. 2018) and in Brazil as Glenodinium gymnodinium ( Sant’Anna et al. 1988).

Figures

FIGURE 5. Naiadinium polonicum. LM view. A. Ventral view. B. Empty theca, ventral view. C. Empty theca, ecdysis detachment of plates 3ʹ, 1a, 2a, 3ʹʹ, 4ʹʹʹ and 5ʹʹʹʹ. Bar=10µm. SEM view D. Ventral view. E. Dorsal view. F. Ecdysis. G. Sulcal plates. H. Ornamentation on theca surface.