Family: Thalassionemataceae Round in Round et al.
Genus: Thalassiothrix Cleve et Grunow
Scientific name: Thalassiothrix longissima Cleve et Grunow
Pavillard, 1925: p. 60, Fig. 106 B; Cupp, 1943: p. 184, Fig. 134; Hendey, 1964: p. 165;
Simonsen, 1974: p. 38; Throndsen et al., 2007: p. 186.
Cells four-sided, very long and more or less curved, threadlike, usually living singly; valves very narrow linear, ends slightly narrowed, more so on one end than on the other. Length 1 -4 mm, width 3-6 µm; corners of the valves beset with delicate spines, about 3 in 10 µm in the middle part of the cell, fewer toward the ends or entirely absent. Sometimes the entire cell is without marginal spines. Membrane is with short marginal ribs, 14-16 in 10 µm. Mucilage pore near the ends (Cupp, 1943).
Cells length 740-920 µm; width 3-4 µm.
Cosmopolitan oceanic species.
Sites of occurrence in RSA:
In Winter 2006 Cruise, this species occurred at different sites (refer sites map), usually in small numbers; maximum abundance (9.9*10^2 cells/l) was associated with the Sea of Oman (St. 26a). It has been previously reported from the inner RSA (Simonsen, 1974) and from Kuwaiti waters of the inner RSA (Al-Yamani et al., 2004; Al-Kandari et al., 2009).