Coscinodiscus hauckii Cleve

Lobban, Christopher S. & Witkowski, Andrzej, 2023, Marine benthic diatoms of Guam: new records, Dictyoneis apapae sp. nov., and updates to the checklist, Micronesica 2023 (2), pp. 1-75 : 8

Coscinodiscus hauckii Cleve Figs 42, 43

Ref. illus.: Hustedt 1927 –1930, p. 388, fig. 200b

Samples: GU52O-4, inter alia

Dimensions: Diam. 27–30 µm, stria density at margin 21-22 in 10 µm.

Diagnosis: Ring of short striae surrounding flat central zone with or without short spines.

Comments: The stria density given by Hustedt is ca. 18 in 10 µm. Hein et al. (2008, p. 18, pl. 2, fig. 2) reported C. hauckii var. mesoleia , which has a clear center, with 28 striae in 10 µm. It is not clear from Hustedt’s text about the nominate variety whether he thought the unregelmässig punktiertem Mittelfeld was perforated, because he also used punktiert in reference to the short striae. The variety may not be justified, given that the difference in the central zone of the nominate variety comprises only small papillae, and there is only a slight difference in stria densities between the forms (20 in the variety). Our stria density is higher, and Hein et al.’s still higher. Our SEM shows that this species lacks rimoportulae, so it does not belong in Coscinodiscus (see Round et al. 1990).

Figures

Figures 39–43. Figs. 39–41. Cocconeis carinata. Fig. 39. Cluster of cells in LM. Fig. 40. Sternum valve. Fig. 41. Raphe valve. Figs. 42, 43. Coscinodiscus hauckii in LM and SEM. Scale bars: Figs 39, 42 = 10 µm, Fig. 43 = 5 µm, Figs 40, 41 = 1 µm.