Fragilaria candidagilae Almeida, C. Delgado, Novais & S. Blanco, 2015

Delgado, Cristina, Novais, M. Helena, Blanco, Saúl & Almeida, Salomé F. P., 2015, Examination and comparison of Fragilaria candidagilae sp. nov. with type material of Fragilaria recapitellata, F. capucina, F. perminuta, F. intermedia and F. neointermedia (Fragilariales, Bacillariophyceae), Phytotaxa 231 (1), pp. 1-18 : 4-8

publication ID	https://doi.org/ 10.11646/phytotaxa.231.1.1
persistent identifier	https://treatment.plazi.org/id/FA6A87C4-CE45-0C28-DDCB-2963FB35F975
treatment provided by	Felipe
scientific name	Fragilaria candidagilae Almeida, C. Delgado, Novais & S. Blanco
status	sp. nov.

Treatment

Fragilaria candidagilae Almeida, C. Delgado, Novais & S. Blanco , sp. nov. ( Figs 2–33 View FIGURES 2–33 , LM; Figs 34–39 View FIGURES 34–39 SEM)

Valvae linearis lanceolatae ad ellipticae, 13.0–25.8 μm longae, 4.5–5.0 μm latae, apicibus valde capitatis. Striae alternantes, punctatae, 12–14 in 10 μm, parallelae in media parte, ad apices radiatae. Area centralis unilateraliter expansa ex sterno ad marginem valvae. Sternum axialis angustum. Striae ex areolis rotundis, 7 in 1 μm, externe occlusae.

Type:— PORTUGAL, Beira Litoral, municipality of Coimbra, subregion Baixo Mondego, Mondego river basin, Ribeira do Botão , 40º 18.910’ N, 8º 23.043’ W, river epilithon, Coll. Carmen L. Elias, 13 February 2012 (holotype: Museum of Natural History , London, UK; BM! 101 793) GoogleMaps , partially illustrated in Figs 111–128 View FIGURES 40–122 View FIGURES 123–149 , isotype: Hustedt Collection, Bremerhaven, Germany; ZU10/13).

Description:— Valves linear-lanceolate to elliptical, with strongly capitate apices ( Figs 2–17 View FIGURES 2–33 ). Frustules rectangular in girdle view with interruption of striation in the middle portion due to absence of striae ( Figs 18, 19 View FIGURES 2–33 , 37 View FIGURES 34–39 ). Valve dimensions (n=30): Length 13.0–25.8, width 4.5–5.0, striae density 12–14 in 10 μm. Striae alternate, punctuate and parallel in the central part to slightly radiate near the ends ( Figs 34–39 View FIGURES 34–39 ). Striae are continuous from the valve face onto the mantle ( Figs 37 and 39 View FIGURES 34–39 ). Central area unilaterally expanded from the axial area to the valve face margin. Siliceous plaques are present along the valve mantle edge ( Figs 37, 39 View FIGURES 34–39 ). Narrow axial area ( Figs 2–33 View FIGURES 2–33 ). Striae uniseriate, composed of round areolae (7 areolae in 1 μm) on both valves ( Figs 34–39 View FIGURES 34–39 ). Each valve has two apical pore fields (APF) that are of the ocellulimbus type and made up of 6 to 7 rows, each composed of 8 to 14 poroids ( Fig. 39 View FIGURES 34–39 ). Frequently isolated, cells without spines and rimoportulae occur near the poles, one per valve ( Fig. 34–36, 38 View FIGURES 34–39 ). Girdle bands open with perforations ( Figs 36, 37 View FIGURES 34–39 ). A rimoportula is present and might vary from apically oriented ( Fig. 34 View FIGURES 34–39 ) to almost transapical orientation ( Figs 35–36 View FIGURES 34–39 ). Siliceous depositions on outer areolar openings in the form of rounded floating disks cover almost all the areolae openings ( Figs 34, 38 View FIGURES 34–39 ). Inner areolar openings without siliceous depositions ( Figs 35, 36 View FIGURES 34–39 ).

Etymology:— The new species is dedicated to Prof. Cândida Gil (Aveiro, Portugal) who enthusiastically taught and carried out studies on the ecology and biology of freshwater diatoms in Portugal especially in the last two decades of the twentieth century.

Distribution and ecology:— Fragilaria candidagilae was found in the epilithon but always in low relative abundances. From a total of 70 samples from the river basins of Douro, Mondego and Ribeiras do Algarve watersheds, Fragilaria candidagilae was identified in 23 samples, but only in 10 samples (9 sampling sites) the abundance of this Fragilaria was above 1% (3 of them>5%) ( Table 1). Fragilaria candidagilae was found in the Mondego (2 sites), Douro (1 site) and Ribeiras do Algarve (6 sites) watersheds ( Fig. 1 View FIGURE 1 ). Two of these samples were from the type locality Ribeira do Botão in April 2011 and February 2012. The physico-chemical parameters from the nine sites are presented in supplementary material. In Mondego basin this taxon appeared in Brasfemes (Rio Resmungão; February 2012, with relative abundance – r. a. – of about 2.3%), Ribeira do Botão (April 2011, 1.5% and February 2012, r.a. ca. 7.8%) and Ribeira de Seixe (r.a. ca. 13.1%). ( Fig. 1 View FIGURE 1 ). These are all permanent rivers, with mean values of water temperature between 3.8–20.4 ºC. Fragilaria candidagilae was present in poor mineralized rivers with low to medium conductivity (89.9–457.0 μS cm –1), neutral-alkaline pH (7.0–8.3) and low nitrates (<1.5 mg L- 1), nitrites (0.1 mg L- 1) and ammonium (0.1 mg L- 1) concentrations (see supplementary material). This diatom occurs under dissolved oxygen concentrations between 66.1% to 105.7 % and silica concentrations between 0.2 to 8.2 mg L- 1 (see Supplementary material).

Detailed microhabitat observations took place at two of the sampling sites in the Mondego basin, where the new species was found. In the type locality (Ribeira do Botão, February 2012), the relative abundance of the new Fragilaria candidagilae was 7.76% and the associated diatoms co-occuring with this new taxon were Achnanthidium minutissimum (Kütz. 1833: 578) Czarn. (1994: 157) (49.54%), Encyonema minutum (Hilse in Rabenhorst 1862: 1261) D.G.Mann in Round et al. (1990: 667) (6.62%), Fragilaria aff. rumpens (Kütz. 1844: 69) G.W.F. Carlson (1913: 29) (5.93%), Reimeria sinuata (W.Greg. 1856: 4) Kociolek & Stoermer (1987: 457) (5.71%), Achnanthidium pyrenaicum (Hust. 1939: 554–555) H. Kobayasi (1997: 148) (3.42%), Cocconeis pseudolineata ( Geitler 1927: 515) Lange-Bertalot in Werum & Lange-Bertalot (2004: 133) (2.96%), Ulnaria biceps (Kützing 1884: 66) Compère in Jahn et al. (2001:100) (2.51%), Cocconeis lineata Ehrenb. (1854: 8) (2.28%), Gomphonema rhombicum M.Schmidt in Schmidt et al. (1904: pl. 248, fig. 1) (1.83%), Ulnaria ulna ( Nitzsch 1817: 99) Compère in Jahn et al. (2001: 100) (1.60%), Navicula cryptotenelloides Lange-Bertalot (1993: 105) (1.37%), Karayevia oblongella ( Østrup 1902: 252) Aboal in Aboal et al. (2003: 159) (1.37%) and Gomphonema gracile Ehrenberg (1838: 217) (1.14%).

Differential diagnosis:— Fragilaria candidagilae from Ribeira do Botão type locality with LM ( Figs 2–19 View FIGURES 2–33 ) and SEM micrographs ( Figs 34–39 View FIGURES 34–39 ) and Brasfemes stream ( Figs 20–33 View FIGURES 2–33 with LM) were photographed in this study. Morphometric data were obtained from these populations and from two other sampling sites: Ribeira de Seixe (Foz do Carvalhoso) and Ribeira de Algibre (Tôr), and were compared with type material of Fragilaria recapitellata , F. perminuta , F. neointermedia , F. capucina and with data from a publication containing micrographs from type material for F. intermedia ( Tuji & Williams 2013) .

Fragilaria candidagilae may be confused, in the first instance, with F. recapitellata or F. perminuta in terms of size and shape ( Table 3). The comparison with the type material photographed in this study of F. recapitellata revealed that F. candidagilae is wider (4.5–5.0 μm vs. 2.8–4.2 μm) and it is smaller (13.0–25.8 μm vs. 21.4–30.4 μm) although there is a certain overlap. The striae density is higher in F. recapitellata than in F. candidagilae (17–19/10 μm vs. 12–14/10 μm). The type material photographed in other studies of F. perminuta indicated also that F. candidagilae is wider than F. perminuta (4.5–5.0 μm vs. 3–4 μm) but F. perminuta is only slightly smaller (13.0–25.8 μm vs. 8–25 μm). The striae density is higher in F. perminuta than in F. candidagilae (17–19/10 μm vs. 12–14/10 μm).

The striae density of F. candidagilae (12–14 μm) is similar to the type material of other taxa such as F. intermedia (11–14 μm), F. neointermedia (10–14 μm) and F. capucina (13–17 μm) but F. candidagilae is wider than F. intermedia and F. neointermedia (4.5–5.0 μm vs. 3.0–4.0 μm). On the contrary, the valve outline, size, and width are different from the new taxon, only F. capucina has an overlap with F. candidagilae considering width (3–5 μm vs. 4.5–5.0 μm).

According to the geometric morphometric analysis ( Fig. 150 View FIGURE 150 ), valve shape of the type population of F. candidagilae overlaps partially with that of F. intermedia and F. perminuta (including the epitype drawing), although statistically different (p = 0.0015, Table 2). Despite the similarity of width and striae density between F. candidagilae and F. intermedia , the new taxon here described has significantly shorter valves (p = 0.0015, Tables 2, 3).

SEM pictures of Portuguese populations were also compared with SEM pictures of F. capitellata in Tuji & Williams (2008) and similar ultrastructural characters were observed (one rimoportula, two rectangular apical pore fields per valve and no spines).

Other similar taxa include the Baikal endemisms F. capucina f. lanceolata-baikali R.J. Flower & D.M. Williams in R.J. Flower et al. (2004: 92) and F. capucina f. sublanceolata-baikali R.J. Flower & D.M. Williams in R.J. Flower et al. (2004: 92) as well as F. sandellii which were also compared with Fragilaria candidagilae . The first two taxa have narrower valves and a different outline from F. candidagilae , and F. sandellii Van de Vijver & Jarlman in Van de Vijver et al. (2012: 242), showed denser striae and rostrated apices different from F. candidagilae too.