Fragilaria joachimii Kahlert, 2019

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 : 144

Fragilaria joachimii Kahlert , type population

( Fig. 4 )

Basionym: Fragilaria joachimii Kahlert in Kahlert et al., Journal of Phycology 55: 963, fig. 5 (2019).

MORPHOLOGY

LM ( Fig. 4 A-T)

Frustules in girdle view rectangular, in culture linked forming long chains of up to several tens of cells ( Fig. 4 S-T). Valves linear with parallel margins and broadly rounded, protracted, rostrate, never capitate apices. Shoulders poorly developed, gradually tapering into the apices. Centrally, valves often slightly inflated. Valve dimensions (n = 40): valve length 14-28 µm, valve width 3.5-4.5 µm (length 5-31 µm, width 3.3-4.6 µm in the protologue, Kahlert et al. 2019). Axial area very narrow linear, not widening towards the central area. Central area large, forming a broad, often asymmetrical, inflated fascia, due to several shortened striae on one side. Striae parallel throughout, becoming weakly radiate near the apices, 14-16 in 10 µm, often irregularly spaced. Areolae not discernible in LM.

SEM ( Fig. 4 U-X)

Girdle composed of several open, perforated copulae ( Fig. 4 U-V). Frustules not linked using linking spines but by mucus ( Fig. 4U , arrows). Large, irregularly shaped mantle plaques present on the mantle edge ( Fig. 4V ). Mantle striae continuing from the valve face till halfway or 1/3 of the mantle edge ( Fig. 4V ). Striae uniseriate, composed of small, rimmed, rounded areolae ( Fig. 4 W-X), individually covered by external hymenes ( Fig. 4X ). Virgae between the striae weakly raised ( Fig. 4W ). One rimoportula present at one apex, in line with the last stria at the apex ( Fig. 4X ). Apical pore field present at both apices ( Fig. 4X ). Small spines and granules scattered throughout the entire valve face and mantle ( Fig. 4 W-X).

Figures

FIG. 4. — Fragilaria joachimii Kahlert. Images taken from the type material (Strain TCC887 isolated from BrostrÖmmen near Norrtälje, Sweden): A-R, LM views of the population arranged in decreasing length; S, T, LM views of several frustules connected to form long chains in girdle view; U, SEM external view of several frustules in girdle view connected via mucus (indicated by the arrows); V, SEM external view of a frustule in girdle view showing the girdle bands and the mantle plaques. Note the small spines and granules near the valve face/mantle junction; W, SEM external view of an entire valve with scattered small spines on the margin; X, SEM external detail of a valve apex with the rimoportula and the apical pore field. Scale bars: A-W, 10 µm; X, 1 µm.