A strew slide labelled as Cocconeis ceticola from the epidermis of Antarctic whales (more on the name in a minute). Prepared by JA Long. Olympus BHB microscope using 450nm LED light. Higher resolution images using a 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. Image stacks prepared in Zerene (Pmax). Mianly looks to be one species, but with a few other diatoms present. Also, there were some large polygonal structures in with the diatoms. I think given the size and shape that these could well be corneocytes from the whale epidermis (cells from the outermost layer of the skin).
Back to name. Cocconeis ceticola E.W.Nelson 1920. Published in: Bennet, A.G. (1920). On the occurrence of diatoms on the skin of whales. Proceedings of the Royal Society of London. Series B, Containing Papers of a Biological Character 91(641): 352-357. Page 355, Figures 1,2. This name is currently regarded as a synonym of Bennettella ceticola (E.W.Nelson) R.W.Holmes 1985. Published in: Holmes, R.W. (1985). The morphology of diatoms epizoic on cetaceans and their transfer from Cocconeis to two new genera, Bennettella and Epipellis. British Phycological Journal 20(1): 43-57, 49 figs. Page 51, Figures 1-11, 14-17, 18-23.
However, I’m not 100% convinced (based on appearance and comparison with articles I’ve looked at) that these are what would be described as C. ceticola. I think they might be Cocconeis wheeleri Hart 1935. Published in: Hart, T.J. (1935). On the diatoms of the skin film of whales and their possible bearing on problems of whales movements. Discovery Reports 10: 247-282. Page 260, Plate XI, Figures 5-7. This name is currently regarded as a synonym of Bennettella wheeleri (Hart) R.W.Holmes 1985. Published in: Holmes, R.W. (1985). The morphology of diatoms epizoic on cetaceans and their transfer from Cocconeis to two new genera, Bennettella and Epipellis. British Phycological Journal 20(1): 43-57, 49 figs. Page 52, Figures 27-39. There seems to be some overlap between B. ceticola and B. wheeleri however they do look to be different species. The ones on the slide look more like B. wheeleri to me, give the more ‘pointy’ ends, however for now I will stick with the slide label name.
Also, a Whale skin reference: Spearman RI. The epidermal stratum corneum of the whale. J Anat. 1972 Dec;113(Pt 3):373-81. PMID: 4663387; PMCID: PMC1271409.