MORPHOLOGY AND ULTRASTRUCTURE OF GOMPHONEIS RHOMBICA (FRICKE) COMB. NOV.

Abstract

The morphology and ultrastructure of the diatom Gomphonema rhombicum Fricke is described from epilithic samples from Arinsal stream (Andorra) using LM, SEM and TEM. Ultrastructural features include striae composed of two rows of unoccluded puncta internally positioned in pronounced alveoli, apical pore fields separated from striae by a smooth strip of silica, and a stigma that is rounded externally but slit-like internally. Although this diatom lacks an axial plate and marginal laminae, it shows many ultrastructural affinities with previously studied species included in the genus Gomphoneis. A transfer of Gomphonema rhombicum to Gomphoneis is proposed. Autoecological data of this diatom are presented.