Mastogloia ovata Grunow, 1860

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 : 10

Mastogloia ovata Grunow Figs 65, 66

Ref. illus.: Hustedt 1931 –1959, p. 476, fig. 895

Lobban et al. 2012, p. 281, pl. 35, figs 1, 2 (as “ M. pseudolatecostata ”)

Lobban et al. 2012, p. 279, pl. 33, figs 7, 8 (as “ M. ovata ”)

Samples: GU44T-1, GU44 AJ, GU44AU-1; GU52P-7; GU70A-2A

Our specimen published as voucher for M. pseudolatecostata must be rejected because the stria density is too high (21–24 vs 12–14 in 10 µm). It is a better match for M. ovata than the voucher specimen cited in the same paper. SEM images of such specimens are shown in Figs 65, 66. A specimen from Bikar Atoll, Marshall Islands that matches M. pseudolatecostata is shown in Fig 67 ; this species not yet identified in Guam. The specimen claimed as a voucher for M. ovata in Lobban et al. 2012 less clearly matches the description in Hustedt (1931 –1959) and close to Hein et al. (2008, pl. 40, fig. 3) “ Mastogloia cf. ovata . ”

Comments: The inner margin of M. ovata has indentations at each cross wall ( Fig. 66 ), that of M. pseudolatecostata in the middle of each partectum ( Fig. 67 ).

Figures

Figures 65–70. Mastogloia. Figs 65, 66. Mastogloia ovata exterior and interior valve faces. Fig. 67. Mastogloia pseudolatecostata (Bikar Atoll, Marshall Is.), external valve face with part of valvocopula showing partecta. Figs. 68–70. Mastogloia cf. pisciculus. Fig.68. LM (DIC) with foci on valve face and partecta Arrows on this and next image point to longitudinal rib bisecting the inner zone. Fig. 69. External surface, SEM. Fig. 70. Internal valve face and partecta, also showing partly double row of areolae (arrow). Scale bars: Figs 67, 68 = 10 µm, Figs 65, 66, 69, 70 = 5 µm.