Fragilaria rinoi Almeida & C.Delgado

Cristina Delgado, M. Helena Novais, Saúl Blanco & Salomé F. P. Almeida, 2016, Fragilaria rinoi sp. nov. (Fragilariales, Fragilariophyceae) from periphytic river samples in Central Portugal, European Journal of Taxonomy 248, pp. 1-16 : 5-9

Fragilaria rinoi Almeida & C.Delgado sp. nov.

Figs 1 , 3–82

Diagnosis

Valvae linearis lanceolatae ad rhombicae. Longitudo valvae 8.8–24.1 µm, latitudo valvae 4.2–5.6 µm. Striae uniseriate, alternantes, punctatae, 14–16 in 10 µm, parallelae in media parte, ad apices radiatae. Striae ex areolis rotundis, 13–14 in 1 μm, externe occlusae. Rimoportula una pro valva.

Etymology

The new species is dedicated to Prof. Jorge Rino (Aveiro, Portugal) who carried out valuable research on the ecology and biology of freshwater algae during the second half of the twentieth century. His passionate and unique way of teaching encouraged students to pursue this study area.

Type material

Holotype

Slide BM 101 794, prepared with material from the sample collected in Mogofores, housed in the Natural History Museum, London (UK), illustrated in Figs 3–62 . The valve representing the holotype is illustrated in Fig. 9 .

Isotype

Slide ZU10/14, prepared from the sample Mogofores, housed at the Friedrich Hustedt Diatom Collection, Alfred-Wegener- Institut für Polar- und Meeresforschung, Bremerhaven, Germany (BRM).

Type locality

PORTUGAL: Cértima River, Vouga Basin, Mogofores, municipality of Coimbra, district of Coimbra, Coimbra subregion, Centro Region, Portugal, coordinates 40°27.17´N, 8°27.575´W, river epilithon, 21 Mar. 2012, Carmen L. Elias and Cristina Delgado.

Description

LM observations ( Figs 3–77 ). Fragilaria rinoi sp. nov. is characterized by the presence of solitary cells with lanceolate valves and slightly rostrate apices in larger specimens to rhombic lanceolate in smaller specimens. Frustules rectangular in girdle view with interruption of striation in the middle portion. Axial area narrow, linear, central area larger, unilateral in all specimens. Valve dimensions (n = 30): length 8.8–24.1 µm and width 4.2–5.6 µm. Sternum narrow, slightly widening towards the central area ( Figs 3–77 ). Striae parallel to the transapical axis becoming slightly radiate at the poles, 14–16 in 10 μm.

SEM observations ( Figs 78–82 ). External valve face without spines. A single rimoportula is present at one pole and might vary from apically oriented ( Fig. 79 ) to almost transapical orientation ( Figs 80, 82 ). Striae uniseriate, composed of round areolae (13–14 areolae in 1 μm) on both valves (Figs 78–80). Each valve has two apical pore fields (APF) composed of simple fine porelli arranged in regular rows parallel to the apical axis ( Fig. 78 ) and made up of 4 rows, each composed of 10 to 11 poroids ( Fig. 81 ). Outer and inner areolar openings without siliceous depositions ( Figs 78–82 ).

Distribution and ecology

Fragilaria rinoi sp. nov. was found in the epilithon, but always in low relative abundances. From a total of 51 samples collected in the river basins of Vouga, Mondego and Lis, F. rinoi sp. nov. was identified in 8 samples (Fig. 1), but only in two of them with abundance above 1%. These two samples were located in Estarreja (Antuã river; Mar. 2012, with relative abundance – r.a. – of about 1.6%) and Mogofores (Cértima river; Mar. 2012, r.a. of about 2.8%) ( Fig. 1 ), in the Vouga watershed. The rest of the localities where F. rinoi sp. nov. occurred were: Chãs (Lis basin, 0.9%), Carvalhal (Vouga basin, 0.7%), Foz do Ceira (Mondego basin, 0.5%), Lousã Piscinas (Mondego basin, 0.5%), Casal do Ermio (Mondego basin, 0.2%) and Botão (Mondego basin, 0.2%). The averages, the maximum and minimum values of the 14 physical and chemical variables are presented in Table 1 , indicating that the optimal temperature for this new taxon is 14.5°C. Fragilaria rinoi sp. nov. was present in rivers with medium to high conductivity (43–765 µS.cm–1), neutral to slightly alkaline pH (7.0–7.8) and relatively high nitrate-nitrogen (3.7 mg.l-1), ammonium (0.2–3.8 mg.l-1) and phosphorus (0.2–1.4 mg P.l-1). This diatom occurs under high dissolved oxygen concentrations (between 82% and 103%) and silica concentrations between 2.4 and 8.5 mg.l-1 ( Table 1 ).

Associated diatoms

Theassemblageofthetypelocality(Mogofores)wasdominatedby Planothidiumfrequentissimum (Lange- Bert.) Lange-Bert. (26.2%), Sellaphora seminulum (Grunow) D.G.Mann (15.9%) and Gomphonema saprophilum (Lange-Bert. & E.Reichardt) Abarca et al. (11.1%). Species with abundances higher than 3% were Amphora pediculus (Kütz.) Grunow (5.3%), Encyonema ventricosum (C.Agardh) Grunow (5.3%), Eolimna subminuscula (Manguin) Gerd Moser, Lange-Bert. & Metzeltin (5.1%), Geissleria ignota (Krasske) Lange-Bert. & Metzeltin (4.6%), Cyclotella meneghiniana Kütz. (4.4%), Nitzschia amphibia Grunow (4.4%) and Navicula veneta Kütz. (3.9%). Other diatom taxa with abundance lower than 3% were Fragilaria rinoi sp. nov. (2.8%), Navicula reichardtiana Lange-Bert. (2.1%), Nitzschia palea (Kütz.) W.Sm. (1.9%), and Cocconeis euglypta Ehrenb. (1.6%).

The diversity value of this diatom community was high (Shannon-Wiener Index = 3.6).

Figures

Fig. 1. Geographic locations of the sampling sites where Fragilaria rinoi Almeida & C. Delgado sp. nov. was found. The type locality is represented by a black circle in the Vouga river basin followed south by river Mondego and Lis basins.

Figs 3 – 77. Light microscope images of Fragilaria rinoi Almeida & C. Delgado sp. nov. 3 – 62. Mogofores (Cértima river, Vouga river basin, 21 Mar. 2012) type material (BM 101 794; Fig. 9 is from the holotype). 63 – 72. Estarreja (Antuã river, Vouga river basin, 22 Mar. 2012). 73 – 77. Foz do Ceira (river Ceira, Mondego river basin, 20 Mar. 2012). Scale bar = 10 µm.

Figs 78 - 82. Scanning electron microscope images of Fragilaria rinoi Almeida & C. Delgado sp. nov. from Mogofores (river Cértima, Vouga river basin), 21 Mar. 2012 (Holotype BM 101 794). 78. Complete valve in external view. 79 – 80. Complete valves in internal view. 81. Detail of an apex in external view, with  the  apical  pore  field  and  rimoportula.   82. Detail of an apex in internal view, with the rimoportula clearly visible. Scale bars: 78 – 80, 82 = 2 µm; 81 = 1 µm.

Tables

Table 1. Minimum (Min), maximum (Max) and averages (Avg) of 14 physical and chemical variables and water velocity (n = 8 samples) corresponding to the ecological spectrum of the presence of Fragilaria rinoi Almeida & C. Delgado sp. nov. in Portugal.

Variable	Min	Max	Avg
Water temperature (ºC)	7.4	21.5	14.5
pH	7.0	7.8	7.4
Conductivity (µS.cm-1)	43	765	418
TDS (mg.l-1)	20.0	355.0	202.6
Dissolved oxygen (%)	82	103	88
Dissolved oxygen (mg.l-1)	2.1	11.7	7.9
Water velocity (m.s-1)	0.1	0.4	0.3
N-NH + (mg N.l-1) 4	0.2	3.8	1.7
N-NO - (mg.l-1) 3	0.2	7.8	3.7
P-PO 3- (mg PO 3-.l-1) 4 4	0.3	2.9	1.8
Total-P (mg P.l-1)	0.2	1.4	0.9
Alkalinity (mg CaCO.l-1) 3	15.2	350.0	165.2
Chlorides (mg Cl.l-1)	7.6	47.8	31.4
Hardness (mg CaCO.l-1) 3	16.7	301.7	148.1
Silica (mg SiO.l-1) 2	2.4	8.5	6.3