A strew labelled as Skeletonema costatum (and other species such as Bacteriastrum furcatum) mounted in Styrax. Prepared by Dingley P Fuge. Olympus BHB microscope using 450nm LED light. As well as the image of the strew I imaged one with the 63x Leitz Pl Apo NA 1.4 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 30 images stacked in Zerene (Pmax).
Skeletonema costatum (Greville) Cleve, 1873. Published in: Cleve, P.T. (1873). Examination of diatoms found on the surface of the Sea of Java. Bihang till Kongliga Svenska Vetenskaps-Akademiens Handlingar 1(11): 1-13, 3 plates. Page 7. Homotypic synonyms: Stephanopyxis costata (Greville) Hustedt, Melosira costata Greville 1866.
EDIT – I have been told these are likely Skeletonema tropicum Cleve, 1900 rather than S. costatum. Apparently this is one of the few species in Skeletonema distinguishable in light microscopy. Cells are bigger and have many more fultoportulae processes than S. costatum. Skeletonema tropicum Cleve, 1900. Published in: Cleve, P.T. (1900). Notes on some Atlantic plankton-organisms. Kongl. Svenska Vetenskaps Academiens Handlingar 34(1): 1-22, 8 pls. Page 22.
I have updated the name accordingly.