Cymbella subturgidula Krammer, 2002

Silva, Weliton Jose da, Jahn, Regine, Ludwig, Thelma Alvim Veiga, Hinz, Friedel & Menezes, Mariangela, 2015, Typification and taxonomic status re-evaluation of 15 taxon names within the species complex Cymbella affinis / tumidula / turgidula (Cymbellaceae, Bacillariophyta), PhytoKeys 53, pp. 1-25 : 10-15

Cymbella subturgidula Krammer Figs 71-84 , 85-89 , 90-97

Cymbella subturgidula Krammer, Diatoms Europe 3: 166, Figs 44: 19-21, 2002.

Synonyms.

= Cymbella turgidula var. nipponica Skvortzov, Philipp. J. Sci. 61: 283, Figs 2:8, 4:4, 1936. (Figs 78 - 97 )

- Cymbella uenoi Skvortsov in Skvortsov & Noda, Sci. Rep. Niigata Univ., ser. D (Biol.) 8: 19, Pl. 3, Fig. 3, 1971. (nom. inval.)

= Cymbella rheophila Ohtsuka in Ohtsuka & Tuji, Phycol. Res. 50: 245, Figs 7, 8, 2002.

= Cymbella uenoi Skvortsov ex Tuji, Diatom 23: 50, Figs 20-25, 2007.

= Cymbella uenoi f. nipponica (Skvortsov) Tuji, Diatom 23: 54, Fig. 26, 2007.

Holotype.

Preparation 1046E IOK [not "1046c IOK"], in the Alfred-Wegener-Institut für Polar- und Meeresforschung (BRM), Bremerhaven, Germany.

Lectotype

(designated here). An individual on preparation 1046e IOK, in the Alfred-Wegener-Institut für Polar- und Meeresforschung (BRM), Bremerhaven, Germany, represented by Fig. 73 .

Type locality.

Korea, Ulchin County, Kyungsang Pukdo, Kwangchun River.

Valvae slightly lanceolate to lanceolate, dorsiventral, dorsal margin broadly convex and ventral margin straight to convex; ends barely protracted, subrostrate to broadly subcapitate; length 26.3-41.0 µm, breadth 9.0-13.5 µm, L/B ratio 2.3-3.6; axial area linear to linear-lanceolate, arched, central area indistinct to slightly rounded; striae 9-13 in 10 µm, becoming 12-15 toward ends, 1-3 isolated pores; 21-26 punctae in 10 µm. In SEM, the striae showed lineolate punctae externally and internally, the striae are composed by an alveolus internally, surrounded by thick costae; the isolated pores are rounded externally; internally, the alveoli of the isolated pores are irregularly obovate and connected to intercostae, the margins with tooth-like structures (brocca); one apical pore field (APF) not divided by the external terminal fissure of the raphe can be observed on each pole of the valvae; the terminal nodule extends to the dorsal side, under the APF and has a short branch that penetrates the APF apically; the helictoglossae lie under the terminal nodule and are deflected to the dorsal side.

Remarks.

Krammer (2002) described Cymbella subturgidula based on preparation 1046c, which he designated as the holotype. This preparation was sought in the Alfred-Wegener-Institut für Polar- und Meeresforschung (BRM), where the entire Krammer Collection was transferred. However, preparation 1046c IOK is from Argentina in South America, and not from the holotype designated from Korea. In the protologue of Cymbella subturgidula , Krammer (2002, p. 278 and 279) illustrated three specimens from preparation 1046E IOK, from Korea. Thus, the existence of slide 1046c IOK from Argentina, which is incongruent with the type locality, and the existence of slide 1046E which was used by Krammer to illustrate Cymbella subturgidula , led us to consider the indication of preparation 1046c IOK as a typographical error.

Cymbella subturgidula and Cymbella turgidula are closely related species. However, Cymbella turgidula is more lanceolate and has a higher degree of dorsiventrality than Cymbella subturgidula . Moreover, Cymbella turgidula is slightly broader than Cymbella subturgidula , with a more prominent ventral side of the valve. The ends in the two species are different, being subrostrate-rounded in Cymbella turgidula and slightly subrostrate-truncate in Cymbella subturgidula . The central area is more distinct in Cymbella turgidula than Cymbella subturgidula . Although the number of punctae in 10 µm is the same in both species, the striae in Cymbella subturgidula seem to be more coarsely punctuated than in Cymbella turgidula .

Cymbella turgidula var. nipponica was described by Skvortzow (1936). He considered that this taxon differed from the nominate variety due to the elongated valve, slightly undulate ventral margin, and broad rostrate ends. Ohtsuka and Tuji (2002) proposed that maintaining this taxon as a variety of Cymbella turgidula was not appropriate. They based their arguments on the co-occurrence of the nominate variety and the variety nipponica . Therefore, they proposed the name Cymbella rheophila T.Ohtsuka for this taxon at the specific rank.

Skvortsov and Noda (1971) described Cymbella uenoi Skvortsov, but did not indicate any type. According to Article 40.1 of the ICN, names of new genera or taxa of lower ranks published after 1958 are valid only when the type is indicated ( McNeill et al. 2012), and therefore Cymbella uenoi is invalid. Tuji (2007), however, indicated a type for Cymbella uenoi , fulfilling the conditions required by the ICN. Therefore, the author of the name becomes Cymbella uenoi Skvortsov ex Tuji. Tuji (2007) also transferred Cymbella turgidula var. nipponica [≡ Cymbella rheophila ] to that species, resulting in the name Cymbella uenoi f. nipponica , considering erroneously that the name Cymbella uenoi had priority under the name Cymbella rheophila .

Tuji (2007, p. 54) suggested the conspecificity of Cymbella subturgidula and Cymbella uenoi . The observations of the type material of Cymbella uenoi provided by Tuji (2007) and Cymbella uenoi f. nipponica [≡ Cymbella rheophila ], compared with the type material of Cymbella subturgidula (i.e. morphometric characteristics), led us to agree with Tuji (2007). Since Cymbella uenoi was validated only in 2007, the valid names of this species are either Cymbella rheophila or Cymbella subturgidula , both published in 2002, and not Cymbella uenoi as stated by Tuji (2007). Cymbella subturgidula was described in The Diatoms of Europe, volume 3, published by Kram mer on 28 January 2002 (Koeltz Scientific Books, pers. comm.), while Cymbella rheophila was not published before 29 July 2002, the date of acceptance of the paper. Therefore, the epithet subturgidula has priority over the epithet rheophila .

The re-analysis of the type material of Cymbella subturgidula allows us to broaden the metric data of this species compared to its original description. We observed a wider range of values for length (30.3-37.4 vs. 36-37 µm), breadth (9.0-12.8 vs. 10.0-11.0 µm), striae (9-11 vs. 10-11 in 10 µm) and punctae (21-24 vs. 24 in 10 µm) compared to Krammer’s (2002) description. Metric characteristics of the original material of Cymbella turgidula var. nipponica [≡ Cymbella reophila ; ≡ Cymbella uenoi f. nipponica , isolectotype designated here (Fig. 78 )] and Cymbella uenoi (Table 1 ) also agree with the characteristics of the type population of Cymbella subturgidula ( Skvortzov and Noda 1971, Ohtsuka and Tuji 2002, Tuji 2007).

Krammer (2002) described two isolated pores in Cymbella subturgidula . Similarly, Ohtsuka and Tuji (2002) and Tuji (2007) observed two isolated pores in the material of Cymbella turgidula var. nipponica [≡ Cymbella rheophila ; ≡ Cymbella uenoi f. nipponica ] and Cymbella uenoi . However, in the original sample of the lectotype of Cymbella turgidula var. nipponica we found some specimens with only one isolated pore (Fig. 88 ), and in recent material collected in Lake Biwa we found up to three isolated pores (Fig. 90 ).

Figures

Figures 71 - 84. Cymbella subturgidula Krammer 71 - 77 Specimens from Korea in preparation 1046 E IOK, holotype 73 Lectotype, designated here 78 - 80 Specimens from Japan in preparation R 214.928 78 Isolectotype, designated here, of Cymbella turgidula var. nipponica Skvortsov [≡ Cymbella rheophila Ohtsuka], heterotypic synonym of Cymbella subturgidula 81 Specimen from Japan in preparation R 214.930 82 - 84 Specimens from Japan in preparation R 214.932. Scale bar: 10 µm.

Figures 85 - 89. Cymbella subturgidula Krammer from Japan, in the original material of Cymbella tumidula var. nipponica Skvortsov [≡ Cymbella rheophila Ohtsuka], in sample 0983 85, 87 External valvar view 86, 88, 89 Internal valvar view.

Figures 90 - 97. Cymbella subturgidula Krammer from Japan in sample 1093 90, 91, 93, 97 External valvar view 92, 94, 95, 96 Internal valvar view.