Asteromphalus humboldtii from Commonwealth Bay, Antarctic. Single example on the slide. Prepared by Samuel Henry Meakin. Mounted in Sirax and dated September 1943. Olympus BHB microscope using 450nm LED light. 63x Leitz Pl Apo NA 1.40 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 14 images stacked in Zerene (Pmax).
A. humboldtii is mentioned in a recently article – Hallegraeff, G.M., Leblanc, K. New observations on the Antarctic Asteromphalus darwinii/hookeri diatom species-complex (Asterolampraceae). Polar Biol 46, 759–772 (2023). https://doi.org/10.1007/s00300-023-03160-6, available for download here. I reached out to one of the authors (Prof Gustaaf Hallegraeff) with a copy of this image in case it was of interest. He commented that he remains doubtful that A. humboldtii is a species that is distinct from A. hookeri and that this likely a large form of A. hookeri. Indeed, the WoRMS database also has A. humboldtii as a synonymized name for A. hookeri.