An arrangement of Cocconeis heteroidea. Prepared by Flatters and Garnett Ltd. Olympus BHB microscope using 450nm LED light. As well as the arrangement I imaged two diatoms using the 63x Leitz Pl Apo 1.4 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. Images stacked in Zerene (Pmax).
I imaged the upper/middle and right hand one at higher resolution. Cocconeis heteroidea Hantzsch 1863. Published in: [Hantzsch, C.A.] (1863). Ueber einige Diatomaceen aus dem ostindischen Archipel. In: Beiträge zur näheren Kenntniss und Verbreitung der Algen. Herausgegeben von Dr. L. Rabenhorst. Heft I. (Rabenhorst, L. Eds), pp. 17-30. Leipzig: Verlag von Eduard Kummer. Page 21, Plate VI A [6 A], Figure 10. This name is currently regarded as a synonym of Monoalveoneis heteroidea (Hantzsch) Yurchak, Gogorev, Kezlya & Kulikovskiy 2025. Published in: Yurchak, M., Gogorev, R., Sokolova, I., Kezlya, E., Doan-Nhu, H. & Kulikovskiy, M. (2025). Morphology of alveolate species of the genus Cocconeis (Cocconeidaceae, Bacillariophyta) with the description of Monoalveoneis gen. nov.. Phytotaxa 721(3): 201-217, 41 figures, 1 table. Page 2010.
The upper/middle one is what I would think of as C. heteroidea. The one on the right is different to the others and looks a bit like Schmidt’s Atlas Plate 192, Figure 2; “Mauritius (Grove), subradiale Streifung nur als Atlasschimmer gesehen. C. heteroidea Hantzsch.”. Translation “Subradial striation visible only as a silky sheen.”. However I remain to be convinced that this one is part of the ‘Cocconeis heteroidea’ family as it looks very different. Not seen anything quite like it before though, and the ‘S’ shaped raphe (which is reminiscent of C. heteroidea) is really unusual given the rest of the structure of that diatom. I will leave the name with a question mark for now.