Mastogloia belaensis M.Voigt,

Vijver, Bart Van De, Fofana, Cheikh Abdoul Kader, Sow, El Hadji, Cocquyt, Christine, Blanco, Saúl & Ector, Luc, 2017, Morphology of two Mastogloia species (Bacillariophyta) from Lac de Guiers (Senegal) and comparison with the type material of M. braunii, European Journal of Taxonomy 374, pp. 1-23: 7-12

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Mastogloia belaensis M.Voigt


Mastogloia belaensis M.Voigt 

Figs 17–45View Figs 17–23View Figs 24–32View Figs 33–38View Figs 39–45

Journal of the Royal Microscopical Society ser. 3 75: 189, pl. 1 fig. 1, 5, 6, 7 ( Voigt 1956).

Description ( Senegal population)

Light microscopy ( Figs 17–32View Figs 17–23View Figs 24–32)

Valves lanceolate to elliptic-lanceolate with convex margins. Apices non-protracted, acutely rounded to slight protracted, subrostrate. Valve dimensions (n = 50): length 31–99 µm, width 11.5–20.0 µm. Axial area narrow, lanceolate, narrowing towards the apices. Lyre-shaped hyaline zone present close to the axial area, separating one row of pseudoloculi from the striae. Central area rather small, rectangular. Raphe lateral with clearly undulating branches. Proximal raphe endings indistinct, straight. Distal endings hooked towards the same direction. Striae radiate throughout, becoming less radiate and even parallel to slightly divergent ( Fig. 25View Figs 24–32) towards the apices, 13–15 in 10 µm. Pseudoloculi quite large, well visible in LM, 15–20 in 10 µm. Partectal ring clearly displaced towards the middle of the valve, composed of partecta of different size (6–8 in 10 µm): the middle 4–8 partecta (length 1.9–2.9 µm, width 1.8–3.9 µm) considerable larger than the outer partecta (length 0.9–1.4 µm, width 1.2–1.8 µm).

Scanning electron microscopy ( Figs 33–45View Figs 33–38View Figs 39–45)

External raphe branches clearly undulating ( Fig. 34View Figs 33–38). Proximal raphe endings simple, very weakly expanding, slightly deflected ( Figs 34–35View Figs 33–38). Distal raphe fissures centrally crossing the terminal nodule, elongated, hooked towards the same direction, continuing onto the valve mantle, terminating almost near the mantle edge ( Fig. 36View Figs 33–38). Very low, slightly thickened marginal crest visible on the valve face/ mantle junction separating the striae on the valve face from the mantle areolae by a hyaline line ( Fig. 34View Figs 33–38). Mantle striae entirely uniseriate, composed of several, usually transapically elongated to slit-like pseudoloculi ( Figs 33–34, 36, 38View Figs 33–38). First pseudoloculi near the junction rounded ( Figs 36, 38View Figs 33–38). Valve face almost flat, subdivided into two zones: outer zone composed of uniseriate striae, with up to four rounded pseudoloculi, central zone formed by one row of rounded pseudoloculi close to the axial area and one row of transapically elongated rectangular pseudoloculi ( Figs 34–35View Figs 33–38). Near the central area, rectangular pseudoloculi replaced by 1–2 small, rounded ones whereas near the apices, central transapically elongated pseudoloculi absent, outer zone with rounded pseudoloculi reaching the axial area ( Fig. 36View Figs 33–38). Shallow depressions sometimes visible in the axial area ( Figs 34–36View Figs 33–38). Hyaline areas present on each valve apex ( Fig. 36View Figs 33–38). Internally, raphe sternum lyriform, slightly raised ( Figs 39, 42View Figs 39–45). Raised thickened costa-like interstriae interrupted by the raphe-sternum extending from the axial area towards the valve margins, separating the areolae ( Figs 42–43View Figs 39–45). Inner areolae arranged in groups of 4–8 per pseudoloculus ( Fig. 45View Figs 39–45). Raphe branches straight with indistinct, coaxial proximal endings, terminating on a raised central nodule ( Figs 39, 42View Figs 39–45). Valve apices with clear pseudosepta covering the distal raphe endings ( Fig. 43View Figs 39–45).

Girdle composed of the valvocopulae and one open, non-perforated copula ( Figs 33, 37View Figs 33–38). Small siliceous papillae present on the copula ( Fig. 37View Figs 33–38). Valvocopulae with typical partectal ring, opening near the apices through a series of elongated partectal pores ( Figs 33, 37–38View Figs 33–38). Partectal ring open, one end closed but with a cleft forming a narrow lacuna ( Fig. 40View Figs 39–45), other split with a cleft ( Fig. 41View Figs 39–45), covering entirely the pseudosepta. Partecta extending to almost ¼ to 1/6 from the valve apex, clearly separated from the valve margin by a siliceous flange ( Fig. 39View Figs 39–45). Partecta subequal in size with the large ones grouped in the middle, the smaller ones closer to the apices ( Fig. 39View Figs 39–45). Partecta ornamented with several series of small, rounded areolae, loosely aggregated in very unclear plaques and arranged inwardly ( Fig. 44View Figs 39–45).