Cocconeis arenicola, Ryznik, 1973

Al-Handal, Adil Y., Riaux-Gobin, Catherine, Jahn, Regine, Wulff, Angela Katarina & Minerovic, Alison, 2019, Two new marine species of Cocconeis (Bacillariophyceae) from the west coast of Sweden, European Journal of Taxonomy 497, pp. 1-16 : 12

Comparison with Cocconeis arenicola

Cocconeis magnoareolata sp. nov. with its large areolae may be compared to C. arenicola Ryznik , described from tidal flats in the Yaquina Estuary, USA, but the later differs by having larger valves (22–27 × 17–20 µm) and by its striae density, almost one third of that in our new species (7 vs 21–22 in 10 µm). Although C. arenicola was abundant in Yaquina Estuary, it has not been observed at any other geographic location. The type slide of this species (ANSP, slide no. 62634) has been examined. R.Z. Riznyk made seven small circles on the cover slip, and only two of these contain valves of C. arenicola . New images have been taken and illustrated here ( Figs 8–9 ) to represent sternum and raphe valves. Sternum valve appears conforming to original description but the raphe valve does not seem to correspond to the description of the type by Riznyk (1973: pl. V, fig. 6). Striae density of both sternum and raphe valves described by the author is different from that observed in the type specimens. R.Z. Ryznyk gave seven striae in 10 µm on both valves, while the specimens in the type slide show 9–9.8 and 12–16 in 10 µm for sternum and raphe valves, respectively. Because of the very brief original description of this species, as well as of the varying of some features of the type specimens, an emended description is given below based on LM.

Figures

Figs 2–9. LM images. 2–4. RV of C. magnoareolata Al-Handal, Riaux-Gob., R.Jahn & A.K.Wulff sp. nov., showing variations in size and valve outline (BGBM, slide B 40 0043104). 5–7. SV of C. magnoareolata sp. nov. (BGBM, slide B 40 0043104). 8–9. SV and RV of C. arenicola Ryznik (ANSP, slide no. 62634). Scale bars: 10 µm.