Fragilaria vaucheriae (Kütz.) J.B.Petersen

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 : 9

Fragilaria vaucheriae (Kütz.) J.B.Petersen

Figs 2 , 83–90

Exilaria vaucheriae Kütz., Linnaea 8: 560 (1833a). – Type: Alg. Dec. III. No. 24 (syntypes: BM 78023, BM 78024).

The type material of Fragilaria vaucheriae ( Kützing 1833b) was published in Kützing’s exiccata set Algarum Aquae Dulcis Germanicarum (Decas III, No. 24) without either description or figure. This material was observed by Lange-Bertalot (1980, pl. 4, figs 82–94, 97–102) with a broader concept that was later narrowed in Krammer & Lange-Bertalot (2004: pl. 108, figs 10–15). In the present study, the type material from the Natural History Museum of London was photographed with a scanning electron microscope ( Figs 83–90 ). Micrographs from the recently published paper by Wetzel & Ector (2015), which were acquired from Van Heurck’s collection housed at the Botanic Garden Meise, Belgium (BR) were also used for the morphometrical measurements of F. vaucheriae .

Description

Fragilaria vaucheriae is characterized by the presence solitary cells with valves linear and narrow and rostrate to subcapitate ends ( Fig. 83 ). Frustules rectangular in girdle view with interruption of striation in the middle portion ( Figs 84–85 ). Axial area narrow, linear, central area larger than F. rinoi sp. nov., unilateral in all specimens. Striae coarse, uniseriate, parallel to the transapical axis and slightly radiate at the poles ( Figs 83, 88 ). External valve face presents small spines in some specimens ( Figs 83, 88 ). A single rimoportula is present at one pole, aligned with the first stria at the valve face apex (Figs 83, 88). Girdle bands are open ( Figs 84, 85, 87 ), with small, unoccluded perforations. Striae composed of round areolae (12–13 areolae in 1 μm) on both valves ( Figs83 , 89). Each valve has two apical pore fields (APF) composed of simple fine porelli arranged in regular rows parallel to the apical axis (Fig. 83) and made up of 6 rows, each composed of 10 to 11 poroids ( Figs 85–88 ). Outer areolar are closed with siliceous depositions ( Figs 83–90 ). Siliceous plaques are present along the valve mantle edge ( Figs 85, 87, 90 ).

The photographs of the other Fragilaria species ( Fragilaria candidagilae , F. recapitellata , F. perminuta , F. neointermedia , F. intermedia , F. capucina and F. microvaucheriae ) were further digitally measured and included in comparative boxplots and scatterplots here discussed ( Figs 91–92 ). Whenever possible (i.e., when valves were more than 20 µm long) four measures of striae density were taken from each valve.

Figures

Fig. 2. Type material of Fragilaria vaucheriae deposited in the Natural History Museum of London (BM 78023, BM 78024).

Fig. 91. Comparison of the type population of Fragilaria rinoi Almeida & C. Delgado sp. nov. with the  type  material  of  related  taxa.   Data  fitted  to  95 %   confidence  ellipses.   NMDS  plot  of  Booksteintransformed valve outline pseudolandmark coordinates. Black: F. rinoi sp. nov. Red: F. candidagilae Almeida, C. Delgado, Novais & S. Blanco. Blue: F. capucina Desm. Pink: F. intermedia Grunow in Van Heurck. Olive green: F. microvaucheriae C. E. Wetzel & Ector. Purple: F. neointermedia Tuji & D. M. Williams. Green: F. perminuta (Grunow) Lange-Bert. Dark blue: F. recapitellata Lange-Bert. & Metzeltin. Sky blue: F. vaucheriae (Kütz.) J. B. Petersen.

Fig. 92.  Boxplot  of  measurements  of  different  Fragilaria species. Variation in valve length (a), width (b) and  striae  in  10  μm  (c)  measured  in  the  type  populations.  The  boxes  represent  the  25 – 75 %   quartiles,  the  median is shown with a horizontal line inside the box, and minimum and maximum values are shown with short horizontal lines (whiskers). Outliers are plotted as individual points.

Figs 83 - 90. SEM micrographs of the type material of Fragilaria vaucheriae (Kütz.) J. B. Petersen. 83. Complete valve in external view. 84. Complete frustule in external view. 85 – 86. Frustule in girdle view. 87, 90 .  Detail  of  the  apex  in  girdle  view,  with  the  girdle  bands  and  fimbriae  clearly  visible  (indicated  by  the arrows). 88 – 89. Detail of the apex in external view (arrow indicates the rimoportula). Scale bars = 2 µm.