2025 Volume 100 Issue 1 Pages 61-77
A new species of Gomphonemopsis, G. costata, was discovered from the surface of some Japanese seaweeds and seagrasses. Its morphology was examined by light and scanning electron microscopy; the details are described herein. This new species is morphologically similar to G. novozelandicum, G. pseudexigua and G. sieminskae in having a rectangular to bow-tie-shaped (pandurate) central area and a non-perforated valvocopula, but differs from these known taxa in its rough striae, thickened interstriae, short trapezoidal to circular areolae, many bands comprising the cingulum. The results of our molecular phylogeny indicated the monophyly of G. costata, G. cf. exigua and G. novozelandicum with high interspecific rbcL differences. These Gomphonemopsis species were sister to Phaeodactylum tricornutum and not found to be related to the clades containing taxa of the family Rhoicospheniaceae and the order Cymbellales to which Gomphonemopsis currently included, and any other orders of the raphid diatoms.
