Synedra vaucheriae var. deformis Grunow

De, Bart Van, Vijver, Mertens, Adrienne & Ector, Luc, 2020, Analysis of the type material of Synedra deformis W. Sm. and Synedra vaucheriae var. deformis Grunow (Fragilariaceae, Bacillariophyta), Cryptogamie, Algologie 20 (13), pp. 137-149 : 141-142

Synedra vaucheriae var. deformis Grunow , type population

( Fig. 2 )

Fragilaria intermedia f. deformis (Grunow) A.Cleve. — Basionym: Synedra vaucheriae var. deformis Grunow in Van Heurck, Synopsis des Diatomées de Belgique. Atlas, pl. XL, fig. 18 (1881) (original drawing and note in Fig. 2R ). — Lectotype (designated inTuji & Williams 2013): Grunow sample 907 (W).

MORPHOLOGY

LM ( Fig. 2 A-Q)

Frustules in girdle view rectangular, solitary or linked to short chains of maximum eight cells ( Fig. 2A ). Valve outline linear in longer valves with convex to occasionally parallel margins, often irregularly shaped, gradually narrowing towards the apices. Shoulders never clearly developed. Smaller valves becoming more elliptic ( Fig. 2 O-Q). Apices clearly protracted, capitate to rostrate in smaller specimens, often deformed. Valve dimensions (n = 20): valve length 16-28 µm, valve width 4.0-4.5 µm. Axial area narrow but distinct, linear to weakly lanceolate, gradually but weakly widening towards the central area. Central area small to often asymmetrical due to irregular shortening of striae on one side. Ghost striae never present. Striae parallel throughout, becoming weakly radiate near the apices, 13-15 in 10 µm, occasionally irregularly spaced. Areolae not discernible in LM.

SEM ( Fig. 2 S-V)

Girdle composed of several open, perforated copulae ( Fig. 2S ). Mantle edge covered by irregularly shaped, large mantle plaques ( Fig. 2S ). Mantle composed of broad hyaline edge. Mantle striae restricted to the upper part of the mantle ( Fig. 2S ). Striae uniseriate, composed of very small, rounded areolae ( Fig. 2T, U ), covered by individual external hymenes ( Fig. 2U ). Virgae between the striae weakly raised ( Fig. 2U ). One rimoportula present at one apex, in line with the last stria at the apex ( Fig. 2 T-U). Apical pore field present at both apices, relatively large, composed of up to six rows of relatively large, rounded to squarish pores ( Fig. 2S ). Spines never present. Internally, rimoportula distinctly present at one apex ( Fig. 2V ), superimposed on one of the final striae at the apex, weakly oblique.

Figures

FIG. 2. — Synedra vaucheriae var. deformis Grunow. Images taken from the type material (Grunow sample 907): A, LM view of four frustules connected in girdle view; B-Q, LM views of the population arranged in decreasing length; R, original drawing and notes made by Grunow (Naturhistorisches Museum Wien, Austria); S, SEM external detail of the apex of a frustule girdle view showing the girdle bands and the apical pore fields; T, SEM external view of an entire valve; U, SEM external detail of a valve apex with the rimoportula; V, SEM internal view of an entire valve showing the slightly eccentric position of the rimoportula at one apex. Scale bars: A-Q, T, V, 10 µm; S, U, 1 µm.