Bacillaria, J.F.Gmelin, 1788

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 : 4

“ Bacillaria Group B” sensu Schmid var. tumidula Figs 10–14

Previous Micronesian record: J.S. Park et al. 2022, p. 45, figs 144, 145

Samples: GU21AM-2, GU21AN-1; GU52J-3, GU52K-4, GU52S-2; GU58G-4D

Diagnostics: Colonial, as in B. paxillifera , the “slide rule” diatom, but inflated in the middle. Uniseriate striae with external costae.

Comment: As noted by Lobban et al. (2012) for the nominate form, marine forms were orphaned when Jahn & Schmid (2007) redefined B. paxillifera as freshwater/brackish, naming several new species, but excluding three marine groups distinguished by Schmid (2007). Our assignment of this variety to Group B, based on the nominate form, has not been verified and remains in limbo until Jahn completes her analysis. The short cristae at the central area are characteristic but we have images of specimens without them and without costae; further progress awaits completion of work on this group.

Figures

Figures 8–14. Auricula and “Bacillaria.” Figs 8, 9. Auricula densistriata. Figs. 10–14. “Bacillaria Group B” sensu Schmidt, var. tumidula. Fig. 10. Acid cleaned frustules in LM. Fig. 11. Live cell. Fig. 12. Internal valve surface, SEM. Fig. 13. Wider central part of cell in SEM, showing external short cristae (arrow). Fig. 14. Apex of frustule in SEM showing the raphe flap (arrow) that links cells together and girdle bands. Scale bars: Fig. 11 = 25 µm, Fig. 10 = 10 µm, Figs 8, 9, 12–14 = 5 µm.