Peridinium gatunense Nygaard

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 : 153-155

Peridinium gatunense Nygaard in Ostenfeld & Nygaard (1925: 206). Figures 12–13

Synonyms:

Peridinium cinctum var. gatunense in Nygaard (1932: 128)

Peridinium cinctum var. gibbosum in M. Lefèvre (1927: 121)

Dimensions: L: 51–68 µm, Td: 49–65 µm.

Cell shape: Basically spherical, contour of the epitheca, anteriorly dome-like shaped, widening to the cingulum with a slight concavity on the sides ( Fig. 12A and 12B ). Epitheca slightly taller than hypotheca. From apical or antapical view circular contour with a ventral sagging that corresponds to the sulcal area.

Thecal characteristics: Tabulation, 4ʹ, 3a, 7ʹʹ, 5c, 5s, 5ʹʹʹ, 2ʹʹʹʹ, there is no apical pore complex. The cases of anomalous tabulation are frequent ( Figs. 13C and 13D ). Cingular edges of the adcingular plates extend in lists sustained by radial ribs connected with the plates surface ornamentation network. Epitheca formed by 14 plates arranged in two concentrically rings around the 3ʹ plate, which is located in the most apical position. The first of them is formed by five plates: 2ʹ, 1a, 2a (penta), 3a and 4ʹ. The arrangement does not maintain a bilateral symmetry due to that plate 1a is half the size of the 3a, and the 2ʹ is smaller than 4ʹ ( Figs. 12D and 13A .). The second ring is formed by the remaining 8 plates where: the 1ʹ is the smallest of the epitheca. The 7ʹʹ is twice taller than the 1ʹʹ, which compensates the cingulum slope in the epitheca ( Fig. 12A ). The intercalary or growing bands are striated transversally ( Fig. 13B ).

Cingulum and sulcus: Cingulum, deeply excavated, bordered by the fins formed from the pre- and post-cingular plates ( Fig. 13C ). Descending helical path ( Fig. 12B ). Sulcus is surrounded by slightly prominent fins that originate from the surrounding plates and continue with the cingular lists, which barely penetrate the epitheca. The Sa plate is trapezoidal-shaped, and its minor base has an extension ( Fig. 12C ).

Ecdysial opening: Epithecal. The epitheca separates from the hypotheca along the pre-cingular suture, the cingular plates remaining attached to the hypotheca (as shown in squashed specimen in Fig. 12E ).

Ornamentation: The surface of the main plates is covered by a relief reticulum formed by solid cords and nodules, with one pore in each alveolus. Some tabular margins are bordered by well-marked marginal ridges and most specimens develop intercalary bands. ( Fig. 13 ).

Localities: Guatapé, La Fe, Porce II, and Porce III reservoirs in North-west Colombia.

Comments: Our specimens have a wider size range than the original description by Ostenfeld & Nygaard (1925), within the range of measures reported by Moestrup & Calado (2018), and exceeding in size those described by Cavalcante et al. (2017) and Hansen & Flaim (2007) ( Table 7). Teratological specimens with an atypical number, position, and shape of plates were frequent in our samples, just like what Boltovskoy (1973b) showed for populations of P. gatunense from Argentina. Two specimens from Porce and La Fe reservoirs displayed atypical tabulation as follows: one with the suture 1a/2a moved to the right, thus the 2a plate took a square shape ( Fig. 13C ); another specimen has the 1ʹʹʹʹ plate split in two ( Fig. 13D ).

World distribution: The species is widely distributed in temperate, subtropical, and tropical regions ( Moestrup & Calado 2018), Colombia ( Aguirre Ramírez et al. 2007; Björk & Gelin 1980; Montoya 2011).

Figures

FIGURE 12. LM view of Peridinium gatunense. A Dorsal view. B. Ventral view. C. Anterior sulcal plate D. Disposition of the epithecal plates. E Disposition of the hypothecal plates. Bar=10µm.

FIGURE 13. SEM view of Peridinium gatunense. A. Apical view. B. Antapical view. C. Teratological specimen: quadrangular 2a plate. D. Teratological specimen: splitted 1ʹʹʹʹ plate.