Peridinium limbatum ( ( Hedger et al. 2004 ) ) Lemmermann (1900: 120)

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 : 160

Peridinium limbatum ( ( Hedger et al. 2004) ) Lemmermann (1900: 120) . Figure 17

Basionym: Protoperidinium limbatum A. Stokes (1887: 246)

Synonyms:

Peridinium limbatum subsp. minnesotense Eisenack in Eisenack & Fries (1965: 141)

Dimensions: L: 88–96 µm, Td: 57–68 µm.

Cell shape: Pentagonal cells, dorsoventrally compressed ( Fig. 17A ).Triangular epitheca, longer than the hypotheca, with left bended apex ( Fig. 17B ). The hypotheca has short antapical horns separated by an antapical concavity. The cingulum descending, being its ends displaced no longer than one cingular height ( Figs. 17F ).

Thecal characteristics: Tabulation, Po,4ʹ, 3a, 7ʹʹ, 5c, 5s, 5ʹʹʹ, 2ʹʹʹʹ. The Po is surrounded by raised rim formed by the edges of the apical plates. Plate 1ʹ is big and extends in the short apical horn curved to the left ( Fig. 17F ). The 2ʹ and 4ʹ plates are elongated. The plate 2a is hexagonal, big, and located just above of the 4ʹʹ ( Fig. 17G ). Plate 7ʹʹ is wider than the 1ʹʹ. Hypotheca has two small appendices formed by the 1ʹʹʹ and 1ʹʹʹʹ, 5ʹʹʹ and 2ʹʹʹʹ plates (fig. 17G and 14F) with a small pair of spines at their edges.

Cingulum and sulcus: Narrow, descendant cingulum formed by 5 plates. Narrow sulcus, formed by 6 plates, penetrates slightly into the epitheca, and widens toward the antapex. The plate Sa is typical of the genus with a long body that slightly penetrates the epitheca and a lobe on its left side ( Figs. 17C and 17D ). The plate Sp is shaped like an isosceles triangle, laterally extended with its posterior margin concave and the left margin with a strong U-notch, corresponding to the insertion of the Spa ( Fig. 17E ).

Ornamentation: The surface ornamentation of the main plates is a relief reticulum formed by solid cords and nodules with 1-3 pores in each alveolus and presence of intercalary bands. Tabular margins bordered by well-marked marginal ridges. Lists, with radial ribs, rise from the margins of the cingulum and from the lateral sutures along the apical horn. ( Fig. 17 ).

Locality: Chuza reservoir in Central Colombia, deposited in Dr. Boltovskoy´s Collection.

Comments: this is a big and easily identified species due to its particular shape and it agree with the description by ( Stokes 1887). Our measures are similar to those given by Moestrup & Calado (2018) and bigger than those in Carty (2014). In our specimens, the plate 2a looks triangular, because three of its sides are very short, especially the one that borders 3ʹ plate ( Fig. 17G ). On the first sulcal description by Evitt & Wall (1968) they show six sulcal plates, however, in our samples the Sm plate was not observed, due to its small size it can often be lost.

World distribution: England, Ireland, Canada, and USA ( Moestrup & Calado 2018). In Colombia it was reported in Chuza reservoir ( Cárdenas-Torres & Florido-Mosquera 1998; Donato et al. 1996; León-López et al. 2012), Chingaza lake ( Donato-R 1991; Donato et al. 1996), Fuquene lake ( Canosa & Pinilla 2007), and La Tota lake ( Cardozo et al. 2005) in Central Colombia.

Figures

FIGURE 17. Peridinium limbatum. A. Ventral view. B. Dorsal view. C. Sulcal plates. D. Sa: anterior sulcal plate. E. Sp: posterior sulcal plate. F. Theca: ventral view. G. Theca: dorsal view. Bar in A, B=10µm.