Cymbella affinis var. excisa ( Kuetz .) Grunow, 1882

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 : 3-4

Cymbella affinis var. excisa ( Kuetz.) Grunow Figs 8-21

Cymbella affinis var. excisa ( Kütz.) Grunow, Beitr. Paläont. Österreich.-Ungarns Orients, 2: 142, Pl. 19(1), Fig. 26, 1882.

Basionym.

Cymbella excisa Kütz., Bacill., 80, Pl. 6, Fig. 17, 1844.

Lectotype

(designated here). An individual marked with blue ring on preparation BM 18543, from Hauck No. 72, 26.4.1837, in the Natural History Museum (BM), London, United Kingdom, represented by Fig. 11 .

Isolectotype

(designated here). An individual on preparation 1131G IOK, in the Alfred-Wegener-Institut für Polar- und Meeresforschung (BRM), Bremerhaven, Germany, represented by Fig. 16 .

Type locality.

"Unter Oscillatorien in Bächen bei Triest", Italy, 26.4.1837.

Valvae dorsiventral, dorsal margin broadly convex, ventral margin straight, usually with an excision in middle portion; ends subrostrate to rostrate; length 21.5-28.5 µm, breadth 7.0-9.5 µm, L/B ratio 2.6-3.9; axial area narrow, linear-arched, central area indistinct; striae 9-13 in 10 µm, becoming 11-17 toward ends, one isolated pore at end of central striae on ventral side; 21-26 punctae in 10 µm.

Remarks.

Similarly to Cymbella affinis , the lectotypification of Cymbella excisa designated by Krammer (2002, p. 26) cannot be considered according to Article 7.10 of the ICN ( McNeill et al. 2012), because the phrase "designated here" or equivalent is required from 1 January 2001 and it was not included by Krammer (2002). Therefore, the lectotype designated by us cannot be considered a replacement of Krammer’s (2002) “lectotype”; rather, it is the first lectotypification of this taxon.

The main difference between Cymbella affinis var. excisa and the nominate variety is the presence of an excision in the middle portion of the ventral side of the valve, a characteristic common to populations of this taxon around the world ( Krammer 2002). Therefore, we consider that the presence of excisions in all populations, not present in the type material of Cymbella affinis , constitutes sufficient grounds to consider Cymbella affinis var. excisa different from the nominate variety, which conforms to the statement by Grunow ( Schmidt 1875); and not a different species.

Krammer (2002) recorded populations in the isotype material of Cymbella affinis var. excisa with length 17-41 µm, and breadth 6.0-10.7 µm, which were higher than populations in the lectotype material. Krammer (2002) was able to observe initial and post initial cells which were similar to the minimum and maximum length and breadth of this taxon. However, Krammer (2002) included specimens of the variety excisa and the nominate variety in his description.

Figures

Figures 1 - 28. Cymbella affinis species complex 1 - 7 Cymbella affinis Kuetz. var. affinis 8 - 14 Cymbella affinis var. excisa (Kuetz.) Grunow, specimens from Trieste in preparation BM 18543 11 Lectotype, designated here 15 - 21 Cymbella affinis var. excisa [- Cymbella excisa sensu Krammer], specimens from Trieste in preparation 1131 IOK 16 Isolectotype, designated here 22 - 28 Cymbella affinis var. neoprocera W. Silva, specimens from Germany in preparation 212 A IOK, holotype 22 Lectotype, designated here. Scale bar: 10 µm.