Naviculadicta langebertalotii sp. nov. (Bacillariophyta) from streams in Galicia (N-W Spain)

A new benthic freshwater diatom, Naviculadicta langebertalotii sp. nov., is described on the basis of light and scanning electron microscope observations as well as on its ecological preferences as reconstructed from data collected in the fi eld. The most characteristic morphological features are the valve outline (elliptical, but with lateral margins that are frequently concave causing the outline to tend to a panduriform shape), longitudinal lines due to more marked and/or transapically elongated areolae on both sides of the raphe, and the hooked terminal raphe endings confi ned on the valve face (SEM). The new species so far was found on stones in meso- /eutrophic, slightly acidic (but not acidifi ed) soft-water streams of Galicia (north-western Spain). Since its morphological characteristic did not correspond to any of the genera defi ned within Navicula sensu lato, the new species had provisionally to be assigned to the genus Naviculadicta Lange-Bertalot.