Family: Naviculaceae Kützing
Genus: Trachyneis Cleve
Scientific name: Trachyneis antillarum (Cleve et Grunow) Cleve
Cells solitary, free; valves lanceolate, elliptic-lanceolate to elliptical. Axial area narrow,raphe straight, central area dilated to form an extanding stauros which may or may not reach the valve margin. Valve surface areolate, complex, with an outer lamina bearing fine perforations superimposed upon an inner loculate layer. Alveoli oblique, radiate. Girdle is composed of a plan unstriated bands. Chromatophores: two elongated plates, lying along the girdle (Hendey, 1964).
Alloioneis antillarum Cleve et Grunow
Hendey, 1970: p. 149, Pl. 4: 44; Simonsen, 1974: p. 43.
Valve linear-lanceolate with obtuse apices. Raphe eccentric, axial area broad, irregularly linear and unilateral. Central area rounded, unilateral, developed as a rounded area on the narrow side opposite the central nodule. Valve surface coarsely alveolate. Alveoli in longitudinal flexuose or irregular oblique rows. Length 100-120 µm, breadth 29 µm (Hendey, 1970).
Cells length 76-110 µm; width 20-27 µm.
Mainly littoral tropical species, but is frequently found in the plankton.
Sites of occurrence in RSA:
In Winter 2006 Cruise, this species was commonly observed at various sites (refer sites map), often in large numbers; maximum abundance (1.1*10^3 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 from Kuwaiti shore (Hendey, 1970) and coastal waters (Al-Kandari et al., 2009).