Stricosus blumbergii Theriot and Ashworth, 2018

Sabir, J. S. M., Theriot, E. C., Lobban, C. S., Alhebshi, A. M., Al-Malki, A. L., Hajrah, N. H., Khiyami, M. A., Obaid, A. Y., Jansen, R. K. & Ashworth, M. A., 2018, Systematics of araphid diatoms with asymmetric rimoportulae or densely packed virgae, with particular attention to Hyalosynedra (Ulnariaceae, Bacillariophyta), Phytotaxa 347 (1), pp. 1-49 : 42

Stricosus blumbergii Theriot and Ashworth sp. nov. ( Figs 112–117 )

Synonym: Reported previously as Hyalosynedra laevigata HK 362 in Lobban (2013), Nakov et al. (2014), Lobban and Ashworth (2014a,b), Theriot et al. (2015).

Holotype:— ANSP G.C. 65322

Isotype: — ECT 3915.

Type locality: —Baffin Bay, Texas, USA (27° 15.24’ N, 97° 29.85’ W).

Material studied: —Wild and cultured ( HK 362) material isolated from the type locality: ECT 3915, collected by plankton tow in Baffin Bay, Texas, USA (27° 15.24’ N, 97° 29.85’ W).

Description: —Valve lengths were 288.3–393.6 μm and widths were 6.5–8.9 μm ( Figs 112–115 ). The center and flanking regions were weakly convex, tapering linearly to the apex in most specimens. The last third of the margin became weakly convex in a few specimens. The ends were relatively broad and blunt in appearance. The sternum was weakly lanceolate being about twice to three times as thick in the center of the valve as at the apices. Specimens were coarse with about 37–41 virgae per 10 μm. The bilayer wall was open to the inside by a single pore between each pair of virgae. Externally, the wall consisted of biseriate striae ( Fig. 117 ). At each end of the valve was a rimoportula, the interior part of which was composed of a large pair of symmetrical coverings, the slit between them being weakly oblique to the transapical axis ( Fig 116 ). The exterior expression of the rimoportula was an elongate depression located about 2.8–3.1 μm from the end of the valve. The deeply sunken ocellulimbi were each overhung with 2–4 spines, and were about 12–14 pores wide and 7–10 pores tall with 4.3–6.8 pores per 1 μm ( Fig. 117 ). Girdle bands were open and without pores.

Remarks:— This is the largest diatom in this study. It resembles S. gracilis in length and shape, but is much wider for the same length than S. gracilis , which also had more densely spaced virgae, with 44–52 in 10 μm.

Etymology: —Named in honor of the late Mrs. Jane and Dr. Roland Blumberg, UT benefactors, business persons and community supporters.

Figures

FIGURES 112–115. Stricosus blumbergii from wild (ECT3915; 112, 113) and cultured material (HK362; 114, 115). 112. LM of wild specimen with margin at end more nearly parallel and ends blunt. 113. LM of wild specimen with margin at end subcapitate. 114. SEM of cultured specimen with ends converging and more pointed, weakly subcapitate. 115. SEM of cultured specimen with end margins more nearly parallel and ends blunt.

FIGURES 116–117. Stricosus blumbergii specimens from culture (HK362). 116. Interior apex. 117. Exterior apex.