Fragilaria neotropica P.D.Almeida, E.Morales & C.E.Wetzel, 2016

Almeida, Pryscilla D., Morales, Eduardo A., Wetzel, Carlos E., Ector, Luc & Bicudo, Denise C., 2016, Two new diatoms in the genus Fragilaria Lyngbye (Fragilariophyceae) from tropical reservoirs in Brazil and comparison with type material of F. tenera, Phytotaxa 246 (3), pp. 163-183 : 171

Fragilaria neotropica P.D.Almeida, E.Morales & C.E.Wetzel , sp. nov. ( Figs 23–53 )

Frustules narrowly rectangular in girdle view. Valves linear-lanceolate, conspicuously inflated at the center, gradually narrowing towards the poles, frequently broken towards ends ( Figs 23–34 ).Apices capitated, sometimes deflected without obvious pattern ( Figs 35–40 ). Central area broader, with ghost striae and delimited by adjacent shortened striae ( Figs 47, 48, 50 ), sometimes deformed in a zig-zag fashion ( Figs 31, 32, 39, 40 , 50 ). Sternum linear, narrow, inconspicuous ( Figs 28, 35, 39 ). Striae alternate, short and interrupted by spines, with indistinct areolae; difficult to observe in LM ( Figs 25–27 ). Pyramidal spines throughout entire margin, including the poles, where 3–4 spines are present ( Figs 41, 43, 44 ). Spines on valve face located at junction between valve face/mantle ( Figs 41, 51–53 ). Striae composed of 1–3 areolae on valve face and 1–3 areolae on mantle ( Figs 47, 52 ). Areolae rounded indistinct in LM ( Figs 26, 27 ), covered with rotae ( Figs 43, 47, 49, 50 ). Apical pore fields of the ocellulimbus type with 2–3 rows of poroids ( Figs 43–46 ). Plaques present on abvalvar margin of mantle ( Figs 52, 53 ). One small rimoportula present at one of the valve ends ( Figs 41–43, 46 ). Cingulum composed of 2–3 copulae. Girdle bands open with two rows of unoccluded perforations ( Figs 51–53 ). Colonies not observed. Plastids unknown. Length: 52.0–72.0 μm, width: 1.7–2.0 μm, stria density 28–32 in 10 μm.

Type:— BRAZIL. São Paulo: Cotia, Pedro Beicht Reservoir, 23° 44’00.5” S, 46° 57’ 24.5” W, 921 m a.s.l., P. D. Almeida & D. C. Bicudo, 18 June 2010 ( Table 1) (holotype SP!, population on slide SP 427579, illustrated here in LM as Figs 23–40 and SEM as Figs 41–53 . Isotype: BR! slide 4432).

Etymology:—The specific epithet refers to the Neotropic ecoregion where it was found.

Ecology:—Found in surface sediments, as epiphytic on Nymphoides sp. and also as planktonic. Acidophilous, mesotraphentic, living in reservoirs with low nutrient concentrations and low pH ( Table 3).

Figures

FIGURES 23–40. LM. Fragilaria neotropica P.D.Almeida, E.Morales & C.E.Wetzel, sp. nov. 23–34. Population from type material SP427579 (surface sediments). 35–40. Population from periphyton. Scale bar = 10 μm.

FIGURES 41–53. SEM. Fragilaria neotropica P.D.Almeida, E.Morales &C.E.Wetzel, sp. nov. Population fromtype material (SP427579). 41. Valve in external view. 42. Valve in internal view. 43. Apex in external view with rimoportula. 44. Apex in external view without rimoportula showing the apical pore field. 45.Apex in internal view without rimoportula. 46. Apex in internal view with rimoportula and showing the apical pore fields 47. Central area in external view showing spines and ghost striae. 48. Central area in internal view. 49. External view of striae with areolae covered with rotae. 50. Central area deformed. 51–53 Frustule showing details of the girdle bands ornamentation. Black arrow indicates open bands. Scale bar = 20 μm in Figs 41, 42. Scale bar = 3 μm in Figs 50, 52. Scale bar = 2 μm in Figs 44, 47, 48, 51, 53. Scale bar = 1 μm in Figs 43, 45, 46. Scale bar = 500 nm in Fig. 49.