NEW ARAPHID DIATOM SPECIES OF THE GENUS TRACHYSPHENIA PETIT FROM RECENT COASTAL SEDIMENTS OF THE EASTERN SIDE OF THE GULF OF SUEZ, EGYPT

Abstract

The taxonomy and ultrastructure of three new diatom species of the genus Trachysphenia Petit are described from recent coastal sediments from the eastern side of the Gulf of Suez, Egypt. These species are Trachysphenia lanceolatum, T. rhombica and T. noweirii. SEM observations reveal that the morphological features of the described species have some similarities, in particular under LM, with certain fragilarioid genera such as Opephora, Staurosira, Staurosirella, Pseudostaurosira, Punctastriata and Stauroforma, but have sufficient dissimilarities from these to warrant the erection of new taxa. The most diagnostic or distinguishing characters of the new taxa are: 1) Consistently small valves; 2) Shape of the valve; 3) Areolae of uniform size on the valve face, quadratic to subcircular in shape and arranged in transverse rows, continuous on to the mantle; 4) Very narrow sternum; 5) The type of velum structure covering the areolae; 6) Absence of both rimoportulae and linking spines, 7) Apical pore fields represented by a few small openings.