Proschkinia complanata (Grunow) D.G.Mann

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 : 13

Proschkinia complanata (Grunow) D.G.Mann Figs 87–90

Ref. illus.: Lobban et al. 2012, p. 296, pl. 1, figs 4–6 and pl. 53, figs 1–4 [as P. complanatoides (Hustedt) Karayeva ]; Kim et al. 2020, p. 960, figs 2, S2

Samples: GU44Z-15, GU52Q-10a, GU62A-7, GU66G-5, GU68F-8

Dimensions: Length 32–48 μm, width 6–8 μm; striae 30–32 in 10 μm

Comments: Majewska et al. (2019, p. 625), working on Proschkinia spp. epizoic on sea turtles, described a new species P. torquata Bosak, Van de Vijver & Majewska , which they compared with P. complanatoides . They suggested that our Guam specimens might be a new species because they saw no widening of the central area (GU44Z-15: Fig. 90 ) and the internal fistula was not like P. complanatoides . However, Kim et al. (2020) studied Grunow’s specimens of P. complanata with SEM and showed a fistula matching ours, also matching in the presence of a flap over the external fistula opening ( Figs 87, 88 ) and a raised rib on the raphe internally for some distance from the central nodule ( Fig. 90 ). One short stria on the side with the fistula ( Fig. 88 ), and a silica flap over the fistula opening; central striae on opposite sometimes further apart ( Figs 87, 88 vs. 90). Comparing our specimens to P. torquata , the fistula has a similar series of spheres, and the external opening is also covered by a flap, but P. torquata has longitudinal silica strips over the central part of the valve face and the apices are rounded rather than acute. Kim et al. (2020, table 4) listed Guam specimens with P. complanata not P. complanatoides and their images of authentic (including type) material convince us that there are no differences that would warrant a new species. We have seen this species across Micronesia, and it seems so far to be the only species present. We remove P. complanatoides from the Guam flora.

Figures

Figures 87–90. Proschkinia complanata, SEM. Fig. 87. Entire recently divided frustule showing two external valve faces and one internal, along with numerous girdle bands. Fig. 88. Detail of central area showing short stria on side with fistula (arrow) and flap covering fistula opening (arrowhead). Figs. 89, 90. Central area internal views showing fistula and accessory pores (arrows, Fig. 89); elevated raphe rib (arrow, Fig. 90). (Fig. 89 is detail of frustule in Fig. 87.) Scale bars: Fig. 87 = 5 µm, Figs 88, 90 = 2 µm, Fig. 89 = 1 µm.