VALVE ULTRASTRUCTURE AND SYSTEMATIC POSITION OF GOMPHONEMA KAZNAKOWI MERESCHKOWSKY

Abstract

Ultrastructure of the diatom Gomphonema kaznakowi Mereschkowsky is described from recent Chinese material. SEM observations indicate this species has unoccluded puncta both internally and externally and, contrary to previous reports, condensed striae at the headpole. Unoccluded puncta and external raphe ends lacking strong deflections found in G. kaznakowi are reminiscent of Gomphoneis species of the Elegans subgroup; however, lack of marginal laminae and doubly-punctate striae preclude assignment in Gomphoneis. Structure of the headpole striae is similar to species found in the Intricatum group of Gomphonema; G. kaznakowi may represent a branch within Gomphonema near the split with Gomphoneis.