Mastogloia emarginata Hustedt, 1925

Lobban, Christopher S., 2015, Benthic marine diatom flora of Guam: new records, redescription of Psammodictyon pustulatum n. comb., n. stat., and three new species (Colliculoamphora gabgabensis, Lauderia excentrica, and Rhoiconeis pagoensis), Micronesica 2015 (2), pp. 1-49 : 7

Mastogloia emarginata Hustedt Figs 51–55

Section: Ellipticae

Ref. illus.: Hustedt 1931 –1959, fig. 896; Pennesi et al. 2013, figs 65, 66 (lectotype specimen) Samples: GU44R-2, GU44AU-1; GU53E-2; GU66F-4; GU55B-4

Dimensions: Length 18–20 µm; width 9–13 µm; striae 20–23 in 10 µm; partecta 2 in 10 µm.

Diagnostics: Small oval valves with 3–4 concave partecta on each side, reaching the apex, pore on the outer side of each partectum distinctively visible in LM ( Fig. 54 , arrows). Longitudinal striae nearly straight, coarser than the transapical striae, resulting in rectangular areolae.

Comments: Differs from M. ovulum Hustedt , which has finer, circular areolae, and partectal pores that are not evident in LM. As noted in the errata to Lobban et al. (2012), the specimen given there in pl. 33, figs 9, 10 for M. ovulum was misidentified and is given here correctly as M. emarginata ; the specimen of M. ovulum posted on the web in its place is printed here as Figs 56, 57 ; see Jordan et al. 2009 –2015, /taxa_id/585541, for SEM images of M. ovulum . Besides the unique pores, M. emarginata differs from M. ovalis A. Schmidt in having partecta reaching the apex and from M. matthaei (see below) and M. stellae (Pennesi et al. 2013, figs 45–52, 57–60) in the number of partecta as well as characters of the areolae.

Figures

Figures 51–70. Figs. 51–55. Mastogloia emarginata. Figs 51-54. LM views of two specimens focused on valve face and valvocopula, arrowhead indicates one of the prominent exit pores of the partecta (GU44AR-2) (DIC). Fig. 55. Internal view of valve and valvocopula (GU55B-4) (SEM). Figs 56, 57. Mastogloia ovulum specimen at two focal planes (GU44K-6) (DIC). Figs 58-61. Mastogloia matthaei, two specimens at two focal planes (GU52P-2) (DIC). Figs. 62, 63. Mastogloia obliqua, valve at two focal planes (GU66F-4) (DIC). Figs. 64–67. Mastogloia peracuta (GU44AP-9). Figs 64, 65. Specimen at two focal planes (DIC). Figs 65, 66, External views of two specimens in SEM. Figs 68–71. Mastogloia pumila. Figs 68, 69. Specimen in DIC at two focal planes (GU52P-1; catalog # GUD002950). Fig. 70. Internal aspect of valve and valvocopula (GU52P-9) (SEM). Fig. 71. Frustule showing both internal and external valve faces. Scale bars: Figs 51–69 = 5 µm, Figs 70, 71 = 3 µm.