Lacuneolimna novagallia Tudesque & Le Cohu, 2015

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, Phytotaxa 231 (1), pp. 19-30 : 24

Lacuneolimna novagallia Tudesque & Le Cohu , sp. nov. ( Figs 43–71 )

In LM ( Figs 43–54 , 57–66 ), valves rhombic-elliptical to elliptical with cuneately rounded apices. Length 9.8–18.2 μm; width 5.5–9.0 μm; length/width ratio 1.7–2.3. Striae radiate, 16–23 in 10 μm, evenly distributed throughout the whole valve (n=20). Narrow axial area. Central area transapically expanded and irregularly delimited by alternately shorter and longer striae around the central nodule. Isolated stigma-like dots occur frequently in the central area. Raphe slit straight, filiform. Raphe sternum delimited on either side by an apical row of dots. In SEM (external views: see Figs 55, 56 , 69–71 and internal views: Figs 67, 68 ), pluriseriate striae, consisting of small circular areolae externally opened and internally closed by hymenes, irregularly subdivided by a network of cross bars (diverticuli-like), stubs or struts. The stigma-like dots in LM are due to the expansion of the diverticuli-like bars, reducing the striae to a simple, isolated circular areola close to the central nodule. External virgae are of the same breath as the striae ( Figs 56 , 69–71 ) or sometimes wider ( Fig. 55 ). A row of deep, more or less rectangular, isolated cavities on either side of the raphe sternum limits the axial area. Externally, raphe straight with proximal ends hardly expanded and terminal fissures distinctly deflected towards the secondary side of the valve. Internally, raphe simple, slit-like, with weakly elevated helictoglossae.

Type:— FRENCH GUIANA. Nouvelle-France River : municipality of Saül , 3.572° N, 53.201° W, benthic periphyton, Loïc Tudesque , November 2011 (holotype: PC! 0534080, Muséum National d’Histoire Naturelle de Paris , Paris , France; isotype: ANSP! GC 26822 , the algae collection of the Academy of Natural Sciences, Philadelphia, U.S.A.).

Etymology: — from the Latin nova (new) and Gallia ( France) referring to the name of the river “Nouvelle France ”, type locality of this species.

Habitat: — freshwater periphyton from tropical and subtropical moist broadleaf forest.

Figures

FIGURES 43–54. LM micrographs of Lacuneolimna novagallia sp. nov. from the type locality, River Nouvelle France, French Guiana. Range of sizes. Transapical rows of dots alongside the raphe clearly visible. Scale bar = 10 μm.

FIGURES 55–56. SEM micrographs of the type material of Lacuneolimna novagallia sp. nov. External views showing multiseriate striae in grooves, the costae sometimes larger than the striae with cross-bar network whose expansion cover the striae and interrupt them close to the sternum. Deep cavities in line along the raphe sternum.

FIGURES 57–66. LM micrographs of Lacuneolimna novagallia sp. nov. population from the River Mana, French Guiana.Range of sizes. Scale bare = 10 μm.

FIGURES 67–71. SEM micrographs of Lacuneolimna novagallia sp. nov. from various rivers of French Guiana. 67–68. Internal view of frustules from the river Mana showing the simple structure of the raphe, the weakly elevated helictoglossae and the detail of the hymenes covering the areolae. 69–71. External views (epivalves) of frustules sampled respectively in the rivers Mana, Arataï (Approuague Basin) and Oyapock.