Lacuneolimna Tudesque, Le Cohu & Lange-Bertalot 2015, gen. nov.
Creators: name: Tudesque, Loïc
name: Cohu, René Le
name: Coste, Michel
name: Lange-Bertalot, Horst
Publisher: name: Zenodo
Year: 2015
Subjects: Biodiversity
Taxonomy
Chromista
Ochrophyta
Bacillariophyceae
Naviculales
Sellaphoraceae
Lacuneolimna

description: Lacuneolimna Tudesque, Le Cohu & Lange-Bertalot, gen. nov. (Figs 2–42)   
 Frustules isovalvar and isopolar (Figs 2–42). Valves rhomboid, broadly lanceolate to elliptic with a rectangular girdle view (Fig. 38). Small cells less than 20 μm in length with a mean size of 12 μm and less than 9 μm in breadth. Length/width ratio 1.7–2.9 (n=65). Transapical striae radiate, parallel near the apex in some cases, clearly resolvable with light microscopy. Striae pluriseriate consisting of 2–4 rows (Figs 35–37, 39–42) of small, circular areolae (ca. 120 in 10 μm) open externally and occluded by hymenes internally (Fig. 40). Striae lying externally between relief-like elevated virgae (system of transapical costae). Raphe sternum together with a transapically expanded central nodule forms a bolder relief above the system of virgae. This is due to deeper, approximately circular axial cavities separated by a step from the adjacent transapical depression (Figs 35–38, 41, 42). Virgae with an irregular network of cross-bars. Raphe straight internally and externally. In external view, proximal raphe endings drop-shaped, slightly deflected to the primary side of the valve, and terminal raphe fissures strongly bent towards the secondary side (Figs. 35–37, 41, 42). Internally, raphe structure is a simple slit (Figs 39, 40) lying in the slightly raised sternum, with weakly developed helictoglossae (Figs 39, 40).   
 Type:— Lacuneolimna zalokariae (Lange-Bertalot & Metzeltin) Tudesque, Le Cohu & LangeBertalot  comb. nov. et emend.  (Figs 2– 42).   
 Basionym: Eolimna zalokariae Metzeltin & Lange-Bertalot, Iconographia Diatomologica 5: 39–41, fig. 167: 1–2. 1998.   
 Amended diagnosis: length 7.6–15 μm, breath 4.2–5.9 μm, striae 18–21 in 10 μm, areolae ca. 120 in 10μm.   
 Etymology:— from the Latin lacuna, with reference to the depressions into the valve, and the genus Eolimna which is morphologically very close under light microscopy.   
 Distribution and ecology: the physicochemical measurements, summarized in Table 1, indicate that, at the place where it was sampled, the trophic status and the saprobic degree are very low, respectively oligotrophic and oligosabrobic. In addition, investigations and inventories of the diatom flora carried out in 2009 by the IRSTEA, in the framework of the French Guiana river bio-monitoring program, point out the widespread distribution of Lacuneolimna zalokariae (Fig. 1). It was recorded in the main river network from West (Maroni basin) to Est (Oyapock basin) in the French Guiana shield hydroecoregion; no specimens were recorded in the North plain close to the Atlantic ocean.
description: Published as part of Tudesque, Loïc, Cohu, René Le, Coste, Michel & Lange-Bertalot, Horst, 2015, Lacuneolimna gen. nov., Lacuneolimna zalokariae comb. nov. and Lacuneolimna novagallia spec. nov. (Bacillariophyceae) from the French Guiana diatom freshwater flora, pp. 19-30 in Phytotaxa 231 (1) on pages 21-24, DOI: 10.11646/phytotaxa.231.1.2, http://zenodo.org/record/13631569