Species Description: This species somewhat resembles Nitzschia ventricosa, but is much larger and has different ultrastructure. As in N. ventricosa, the valves are lanceolate with very long slender rostrate apices that may be unequal in length (Fig. 1, entire valve, SEM). The raphe is excentric; the striae are transverse. The fibulae subtending the raphe vary somewhat in size and density, and a larger central space is present (Fig. 2, detail of Fig. 1). The prominent irregularly spaced ribs seen in N. ventricosa are lacking in N. longissima. The few cells seen in the IRL were 310-330µm long and 7µm wide, with 40-42 striae in 10µm. The fibulae number 6-7 in 10µm. These measurements are consistent with the dimensions given in various literature sources. The species is widely distributed; it was rare in the IRL system, as was also observed by Navarro (1982).
Navarro JN. 1982. Marine diatoms associated with mangrove prop roots in the Indian River, Florida, U.S.A. Biblio Phycol 61: 1-151.