Family: Thalassiosiraceae Lebour
Genus: Thalassiosira Cleve
Scientific name: Thalassiosira oestrupii (Ostenfeld) Hasle
Coscinosira oestrupii Ostenfeld; Thalassiosira antiqua var. septata Proschkina-Lavrenko
Allen and Cupp, 1935: p. 113, Fig. 4 (as Coscinosiraoestrupii); Hustedt, 1930: p. 318, Fig. 155 (asCoscinosira oestrupii); Hendey, 1964: p. 89 (asCoscinosira oestrupii); Simonsen, 1974: p. 10, Pl. 1:3-5; Scott and Marchant, 2005: p. 108, Fig. 2.56: ad.
Cells chain-forming, united by chitinous threads from the off-central strutted process, discoid to rectangular in girdle view; pervalvar axis 0.5-2 times valve diameter. Valves circular, 7-60 µm diameter, flat to slightly convex. Areolation eccentric, coarse; areolae 5-10 in 10 µm in the center, 6-12 in 10 µm nearer the margin. Strutted processes trifultate and operculate, with internal extensions; 1 process in an off-center position and 1 marginal ring of processes 6-8 in 10 µm (not visible by LM). Labiate process solitary, not marginal, internally flattened and parallel to margin (Scott and Marchant, 2005).
Valve diameter 18-30 µm.
Sites of occurrence in RSA:
In Winter 2006 Cruise, this species was observed at various sites (refer sites map), usually in small numbers; however, it was rather abundant at some localities; maximum abundance (1.9 10 4 cells/l) was associated with the northwestern part of the inner RSA off Saudi Arabia (St. 23). It has been previously reported from the inner RSA (Simonsen, 1974) and Kuwaiti waters (Al-Kandari et al., 2009).