Encyonema candangense W.J.Silva & M.G.M.Souza, 2015

Silva, Weliton José Da & Souza, Maria Das Graças Machado De, 2015, New species of the genus Encyonema (Cymbellales, Bacillariophyta) from the Descoberto River Basin, Central-western Brazil, Phytotaxa 195 (2), pp. 154-162 : 158-159

Encyonema candangense W.J.Silva & M.G.M.Souza sp. nov. ( Figs 17–24 )

Type:— BRAZIL. Distrito Federal / Goiás: Descoberto River, “pesque-pague” (fee-fishing site) (15º52’07”S; 48º16’42”W), rocky substrate, 23 June 2003, Souza (without number) [holotype: a specimen marked on slide UB 01496 in Herbário da Universidade de Brasília ( UB) ( Fig. 18 )] .

Diagnosis:— Differs from E. indistinctum Krammer and E. caronianum in the outline, narrower valves and more densely areolate striae.

Description:— Valves slightly dorsiventral, linear, dorsal margin slightly convex, ventral margin straight to slightly convex; rounded ends, indistinct from valve; length: 19–24 μm; breadth: 2–4 μm; length/breadth ratio: 4.0– 8.9; axial area narrow, linear-lanceolate, smooth externally and internally; raphe filiform; external fissures of raphe irregular, external proximal fissure slightly expanded, pore-like, deflected to dorsal side; external terminal fissures hooked, deflected to ventral side; internal fissures of raphe straight, internal proximal fissures hooked to dorsal side, merged, forming very narrow intermissio, internal terminal fissures ending in helictoglossae slightly deflected to ventral side; striae with deep alveoli, parallel, larger close to margins, 8–13 striae in 10 μm; small stubs under intercostal ribs; areolae with linear foramina externally and internally, foramen lips inconspicuous or absent; 47–51 areolae in 10 μm; isolated pores absent.

Etymology:— The epithet candangense derivate from “candango” (Portuguese), designation given to the people that came in 1950s from Northeastern Brazil to Central-western Brazil to build the city of Brasília.

Material analyzed:— UB 01496, UB 01497.

Ecology:— The taxon occurred in two samples, and only during the dry season. The pH of the water was 6.37– 6.48, turbidity 2.8–3.6 μT and conductivity 27.5–38.9 mS. cm-1. Dissolved oxygen was 7.68–7.90 mg.L- 1 and COD 5.6–10.8 mg.L- 1. E. candangense occurred in environments with low concentrations of ammonium (0.07–0.17 mg.L- 1), nitrate (0.2 mg.L- 1) and nitrite (0.001 –0.004 mg.L- 1).

Figures

FIGURES 17–24. Encyonema candangense sp. nov. 17–21. Valve view, LM. 22, 23. External valve view, SEM. 24. Broken frustule, showing external and internal valve surfaces and the arrangement of alveolae of the hypovalve. Scale bars: Figs 17–21 = 10 μm; Figs 22, 23 = 2 μm; Figs 24 = 1μm.