Family: Chaetocerotaceae Ralfs in Pritchard
Genus: Chaetoceros Ehrenberg
Scientific name: Chaetoceros lorenzianus Grunow
Chaetoceros cellulosum Lauder
Pavillard, 1925: p. 45, Fig. 70 B; Hustedt, 1930: p. 680, Fig. 385; Allen and Cupp, 1935: p.136, Fig. 58; Cupp, 1943: p. 117, Fig. 71; Crosby and Wood, 1958: p. 517, Pl. 38: 52;Hendey, 1964: p. 124, Pl. XVI: 1; Simonsen, 1974: p. 31; Ricard, 1987: p. 203, Figs. 452,453; Throndsen et al., 2007: p. 169.
Cells 7-48 µm wide, rectangular in broad girdle view; chains straight, stiff; apertures elliptical to oval. Valve surface flat or slightly elevated in center. Girdle zone usually short except in cells containing resting spores. Setae fused only at point of exit from margin; with very distinct transverse striae; terminal setae, diverging for their entire length. Chromatophores are large, platelike, 4-10 per cell. Resting spores with primary valve bearing two conical protuberances, each of which terminates in a solid dichotomously branched process.Secondary valve smooth (Cupp, 1943).
Apical axis 10-33 µm; pervalvar axis 17-22 µm.
Neritic, tropical and temperate species.
Sites of occurrence in RSA:
In Winter 2006 Cruise, it was one of the commonest species occurred at varous sites in the RSA (refer sites map) and was encountered in 63.4% of the samples. Species was observed often in large numbers; maximum abundance (2.3*10^5 cells/l) was associated with the Iranian coast in the central part of the inner RSA (St. 27). Species has been previously reported from the inner RSA (Simonsen, 1974) and from Kuwaiti waters (Al-Yamani et al., 2004; AlKandari et al., 2009).