Palatinus apiculatus (Ehrenberg) Craveiro et al. 2009

Ki, Taehee Kim and Jang-Seu, 2022, New record of the cold freshwater dinoflagellate Palatinus apiculatus (Dinophyceae) from the Paldang Reservoir, Korea, Journal of Species Research 11 (3), pp. 162-168 : 164-167

Palatinus apiculatus (Ehrenberg) Craveiro et al. 2009

( Figs. 2 and 3 )

Reference: Craveiro, S. C., Calado, A. J., Daugbjerg, N., & Moestrup, Ø, Journal of Phycology 45: 1178, figs. 1-13. 2009.

Basionym: Glenodinium apiculatum Ehrenberg, Infusionsthierchen , p. 258, pl. XXII, fig. XXIV. 1838.

Homotypic synonyms: Peridinium apiculatum (Ehrenberg) Claparède & Lachmann, Mémoires de l’Institut National Genevois 5: 404. 1859. Properidinium apiculatum (Ehrenberg) Meunier, Mémoires du Musée Royal d’Histoire Naturelle de Belgique 8: 60, pl. XVIII 47-52. 1919.

Description: Ovoid cell with a yellow-brownish color. 34.3 μm in length (25.8-39.5 μm) and 28.4 μm in width (21.5-34 μm). An eyespot is located near the sulcal region. The Kofoidian plates formula is 4′, 2a, 7″, 6c, 5s, 5‴, 2″″, with no apical pore complex (APC). The epitheca twisted to the left in ventral view. The apical plate and intercalary plate are asymmetrically arranged in apical view. Plate surfaces are smooth or finely granulated, and pore is evenly placed on the surface of thecal plates. Several small spines are present on the plate surface, and they are usually clustered in the hypotheca. The suture between the thecal plates expands to 4.5 μm. A vertical pattern is present on the suture.

Taxonomic remarks: Plate variations of Palatinus apciculatus are mainly present in the number of intercalary and precingular plates ( Craveiro et al., 2009; Kretschmann et al., 2018). In our study, new variations in cingular plates were the first to be observed. In specimens from Craveiro et al. (2009), plates 3C and 4C are in the down of the plates 3″ and 4″, respectively. However, present specimens showed a fusion of the 3C and 4C ( Fig. 3E ). The number of cingular plates is a key morphological feature that distinguishes the genus Palatinus and typical Peridinium [(e.g., Peridinium subg. Cleistoperidinium (Lemmermann) Lefèvre 1932 ] ( Craveiro et al., 2009). The six cingular plates in the genus Palatinus are different from the five in the typical Peridinium group ( Craveiro et al., 2009). Considering this, the variation of cingular plates should be carefully addressed. Therefore, detailed observation of cingular plates may be required in peridinioid species for clear classification. Compared to common variations described in the previous study ( Craveiro et al., 2009), variations of cingular plates were rare in the present specimen. Therefore, it can be ignored for the identification of the genus Palatinus .

Ecology: Korean Palatinus apiculatus was isolated from the cold water of a temperate reservoir. The water temperature of sampling site was 5.2℃. The bloom of this species was not observed.

Site of collection: Paldang Reservoir , Gyeonggi-do, Korea (GPS code: 37°39′15.63″N, 127°17′15.89″E; Fig. 1 ) .

Date of collection: 12 December 2021.

Gene sequences: Partial 18S rRNA, whole 18S-28S ITS, and partial 28S rRNA gene sequences under GenBank Accession number ON358395.

Figures

Fig. 2. Vegetative cells (A, C) and temporary cysts (B, D) of the Korean Palatinus apiculatus isolated from the Paldang Reservoir. An arrowhead represents an eyespot. Cell size is proportional to a given scale bar (10 μm).

Fig. 3. Scanning electron microscrope micrographs of Palatinus apiculatus isolated from the Paldang Reservoir, Korea. Plates of the theca are indicated, following to Kofoidian plate formula. A: ventral view showing sulcal region; B, C: apical view from the ventral side; D-F: dorsal view showing different wide of suture and variation of the cingular plate (v). Thick black bar in D-F represents each given length. Sa: anterior sulcal plate. Sd: right sulcal plate. Sp: posterior sulcal plate. Ss: left sulcal plate. Scale bar=10 μm.

Fig. 1.A map of the Paldang Reservoir, Korea.A black circle represents the sampling site. Black arrows represent direction of water flow.