Cymbella tumidula Grunow var. tumidula
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: 6
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|Cymbella tumidula Grunow var. tumidula|
Cymbella tumidula Grunow var. tumidula , in Schmidt, A. Schmidt’s Atlas Diatom.-Kunde, Pl. 9, Fig. 33, 1875.
(designated here). Plate 9, Fig. 33 from Schmidt (1875a) (Fig. 43 View Figures 43–63 ).
Italy, Trieste, 26.4.1837.
(designated here). An individual marked with a red ring on preparation BM 18543 from Hauck No. 72, 26.4.1837, in the Natural History Museum (BM), London, United Kingdom, represented by Fig. 49 View Figures 43–63 .
(designated here). An individual on preparation 1131G IOK, from Hauck No. 72, 26.4.1837, in the Alfred-Wegener-Institut für Polar- und Meeresforschung (BRM), Bremerhaven, Germany, represented by Fig. 54 View Figures 43–63 .
Italy, Trieste, 26.4.1837.
Valves lanceolate, dorsiventral, dorsal and ventral margins convex; subcapitate ends; length 25.4-34.7 µm, breadth 7.8-8.7 µm, L/B ratio 3.4-4.0; axial area linear-lanceolate, straight to arched, central area irregular to rounded; striae 10-15 in 10 µm, becoming 12-19 toward ends, 2-4 isolated pores at end of central striae on ventral side; 26-33 punctae in 10 µm.
The lectotypification of Cymbella affinis allowed us to consider Cymbella affinis and Cymbella tumidula [- Cymbella affinis sensu Krammer], lectotypified and epitypified here, as independent species. Cymbella tumidula has a more lanceolate outline, subcapitate ends, and a lower degree of dorsiventrality than Cymbella affinis . The striae in the middle part of the valve are shorter and unevenly distributed in Cymbella tumidula , forming a distinct central area (Figs 43-63 View Figures 43–63 ), in contrast to Cymbella affinis where the central area is indistinct and the striae are uniformly distributed. In addition, all specimens of the type material of Cymbella affinis have only one stigma, whereas in Cymbella tumidula 1-5 stigmata can be observed.
Specimens from the population of the holotype material of Cymbella affinis var. procera were very similar in outline but larger and wider than Cymbella tumidula var. tumidula , resulting in higher maximum length/breadth ratios. However, all metric characteristics of Cymbella affinis var. procera intergraded with Cymbella tumidula var. tumidula , and therefore this taxon was transferred to Cymbella tumidula var. procera .
The characteristics of Cymbella affinis sensu Krammer (2002, p. 41) were similar to the type population of Cymbella tumidula , but with a wider range of values. This includes length (17-34 vs. 25.4-34.7 µm, respectively) and breadth (7.5-9.5 vs. 7.8-8.7 µm). Cymbella affinis sensu Krammer (2002, p. 41) also presented narrower range of values of striae in 10 µm (10-13, becoming 13-15 toward ends vs. 10-15 in 10 µm, becoming 12-19 toward ends, respectively) and density of punctae (27-32 vs. 26-33 punctae in 10 µm) than Cymbella tumidula .
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