Divergita, Sabir and Theriot, 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 : 21

Divergita al-ghamdii Sabir and Theriot sp. nov. ( Figs 44–48 )

Holotype:— ANSP G.C. 38100

Isotypes: — KSA 2015- 37 in the Theriot Collection at UT Austin.

Type locality: —sand at 20 m depth off Rabigh, Kingdom of Saudi Arabia (22 o 49.91’ N, 38 o 54.68’ E).

Material studied: —Wild and cultured ( UTKSA 0237) material isolated from the type locality: KSA 2015-37, sand collected by turkey baster at 20 m depth off Rabigh, Kingdom of Saudi Arabia (22 o 49.91’ N, 38 o 54.68’ E).

Description: —Specimens were 63.8–76.8 μm in length and 4.3–5.6 μm wide, convex in the middle, then weakly concave to linear to the apices. Apices were tapered or weakly capitate ( Figs 44–46 ). The striae were uniseriate at the sternum, with external pores forming a decussate pattern ( Fig 48 ). Virga densities were about 29–37 in 10 μm at the sternum ( Figs 44, 48 ), as indicated by the row of areolae along the sternum and the density of pores on the internal membrane. The sternum was lanceolate in shape. The rimoportula at each end of the valve was asymmetric as it was in Hyalosynedra species ( Fig. 47 ). The ocellulimbi were very weakly sunken ( Fig. 48 ), if at all, and were about 12–14 pores wide and 3 pores tall, with pore densities of 6–8 per 1 μm. There were no spines above the ocellulimbus. Girdle bands were disassociated in the cleaned cultured material, but all bands observed were without pores ( Fig. 48 ) and open.

Remarks:— Unlike the following two species, observed valves were straight, rather than curved, and virgae tended to be more densely packed.

Etymology: —This species was named in honor of Prof.Dr.Khalid Mohammad Al-Ghamdi, Chairman, Department of Biological Sciences, Faculty of Science, King Abdulaziz University (KAU), Jeddah 2158, Saudi Arabia.

Figures

FIGURES 44–48. Divergita al-ghamdii from wild material (KSA2015-37; 44, 45) and culture (UTKSA0237; 46–48). 44. LM of longer specimen with capitate ends. 45. LM of shorter specimens with convergent (non-capitate) ends. 46. Dissociated valves and girdle bands. 47. SEM interior detail of apex. 48. SEM exterior detail of apex. Note disassociated smooth girdle band in upper left of image.