A strew slide of soundings RRS Discovery, 19th February 1926, 52Deg54Min S, 34Deg5Min W, 1897 Fathoms, Slide No. 7. Mounted in Naphrax, and with some issues with the mountant. Prepared by Brian Darnton. Olympus BHB microscope using 450nm LED light. As well as the strew I imaged an example of Actinocyclus actinochilus (I still love one alternative name Charcotia decrescens) 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. 24 images stacked in Zerene (Pmax). Some debris overlaying. Pseudonodule visible at the 11 o’clock position, just inside the rim. There were about 12 of these (intact or partial) across the slide.
Actinocyclus actinochilus / Charcotia decrescens
Charcotia decrescens M.Peragallo, 1921. Published in: Peragallo, M. (1921). Diatomées d’eau douce et Diatomées d’eau salée. In: Deuxième Expedition Antactique Française (1908-1910) commandée par le Dr. Jean Charcot, Sciences Naturelles: Documents Scientifiques, Botanique. (Anon. Eds), pp. 1-38, 1 pl.; pp. 6-96, 5 pl. Masson et Cie, Paris. Page 78, Plate V, Figure 3. This name is currently regarded as a synonym of Charcotiella decrescens (M.Peragallo) S.Blanco & C.E.Wetzel.
Now referred to as Actinocyclus actinochilus (Ehrenberg) Simonsen, 1982. Published in: Simonsen, R. (1982). Note on the diatom genus Charcotia M. Peragallo. Bacillaria 5: 101-116, 4 plates. Page 105, Figures 1-9.
Also see: Al-Handal, Adil Y., Torstensson, Anders and Wulff, Angela. “Revisiting Potter Cove, King George Island, Antarctica, 12 years later: new observations of marine benthic diatoms” Botanica Marina, vol. 65, no. 2, 2022, pp. 81-103. https://doi.org/10.1515/bot-2021-0066
Quote; “In his work on the Antarctic diatoms, Peragallo (1921) described Actinocyclus actinochilus under various new species names including Charcotia janus, C. bifrons, C. australis, C. valdiviae, C. castracanae, C. chromaradiatus, C. decrescens, C. irregularis, C. irregularis, C. disperses, C. micropunctatus, C. ornatus, and C. minor. These are in addition to several other names in other geographical locations (Simonsen 1982). Common in Potter Cove.”.
Given its unusual appearance, this is one of my wish list diatoms. Although there was some debris over it, it still stacked quite well.