Cyclotubicoalitus tonlesapensis (Tudesque, Le Cohu & Van de Vijver) K.Schultz, Tudesque & Van de Vijver, 2024

Schultz, Konrad & University, Bart Van de Vijver, 2024, Transfer of Stephanodiscus tonlesapensis Tudesque, Le Cohu & Van de Vijver to the genus Cyclotubicoalitus (Stephanodiscaceae, Mediophyceae), Notulae Algarum 316, pp. 1-4 : 3-4

Cyclotubicoalitus tonlesapensis (Tudesque, Le Cohu & Van de Vijver) K.Schultz, Tudesque & Van de Vijver , comb. nov.

Basionym: Stephanodiscus tonlesapensis Tudesque, Le Cohu & Van de Vijver, Diatom Research 36(3): 201, figs 143–192, 2021.

Holotype: BR -4606, Meise Botanical Garden , Belgium.

Registration: http://phycobank.org/104314

Type locality: Tonle Sap Lake, Kampong Thom province, Boeng Chhmar district, Cambodia (Lat. 12.816312; Long. 104.307535).

Notes: Regarding the differences between C. undatus and C. tonlesapensis, Tudesque & al. (2021) indicated, apart from the different interpretation of the cuculli, differences in the eccentricity of the central area as well as differences in areola and stria density. Following a comparison with the original description, some issues with the scale bars given by Stoermer & al. (1990) were noted, resulting in different values with, for example, areolar density of ca. 30–120. What appears to be a larger valve in Fig. 5 would be less than 3 µm in diameter ( Stoermer & al. 1990), which is well below the given minimum of 10.5 µm. There may be the need for a more detailed comparison of both taxa to determine and document the relevant differences.

The authors thank Wolf-Henning Kusber and Michael D. Guiry for their helpful remarks and corrections.

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S. tonlesapensis Cyclotubicoalitus Stephanodiscus Cyclostephanos Praestephanos Spines no no yes, no yes, no yes, no External opening RP simple pore simple pore spine-like simple pore spine-like,

complex Number of RP 1 1 one or more one or more 1 Number of

2 2 3 2 or 3 3 satellite pores of MFP

none none none or more none or more one or more Number of CFP

Cuculli yes yes no no no Eccentric undulation yes yes yes, no no no Costae raised no no no yes, no no