Protokeelia cholnokyi (Giffen) F.E. Round & P.W. Basson

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 : 12

Protokeelia cholnokyi (Giffen) F.E. Round & P.W. Basson Figs 114–117

RHOPALODIALES D.G. Mann : Rhopalodiaceae (Karsten) Topachevs'kyj & Oksiyuk

Ref. illus.: Giffen 1963, figs 27–29 (as Auricula cholnokyi Giffen ); Round & Basson 1995a, figs 1– 9.

Samples: GU44I-1, GU44J-2, GU44Z-15

Dimensions: Length 16–19 µm, depth (from ventral corners to apex of dorsal curve) 10–14 µm; striae ca. 18 in 10 µm, measured transversally across striae near the ventral margin.

Diagnostics: Dorsal (convex) margin nearly circular to weakly reniform; two distinct indentations on the dorsal side of the valve. A ridge (or fold) on the ventral side of the valve arises from points that are not clearly indented and curves closer to the dorsal than the ventral margin. Spines absent.

Comments: The genus Protokeelia was established by Reimer & Lee (1984) for an endosymbiotic diatom isolated from a foram, and subsequently three new free-living species were described by Round (1993) and Round & Basson (1994, 1995b), all from Bahrain and neighboring Saudi Arabia. The literature was reviewed by Round & Basson (1995a), who re-examined Auricula cholnokyi and transferred it and A. quinquelobata Voigt to Protokeelia , so there are now six species. Although Round & Basson (1995b) wrote that “each new site visited seems to yield a new species,” no further reports of new species have been published in the last 20 years; however, it seems unlikely that the biodiversity of Protokeelia has been exhausted, particularly elsewhere in warm waters. The known species have all been epipelic; the specimens we have seen were collected in algal turfs but these samples typically contain sediment.

The terminology is somewhat confusing, because the valve shows only one side as usually lying with the raphe on a ridge along the convex (dorsal) margin and the ventral margin more or less concave. The side thus showing is the ventral part of the valve, while the dorsal part is narrower and has the indentations (clearly seen in the whole frustule SEM, Fig. 117 ). The distinction between P. cholnokyi and P. quinquelobata has not been examined in SEM, but Round & Basson (1995a) assert that “the shape of the valve and of the ridge on the ventral face” suggest the two species are distinct. Voigt’s (1960, pl. 2, figs 8, 9, 10) taxon is more reniform and the ventral ridge arises and curves closer to the ventral margin than is the case in P. cholnokyi . Reexamination of Voigt’s material is needed to verify the distinction. The taxon given in Witkowski et al. (2000, p. 410, pl. 215, figs 11, 12) as “ Protokeelia cholnokyana (Giffen) Round et Basson ” is described as “narrowly reniform” and is much shallower than specimens illustrated by Giffen and Round & Basson.

Figures

Figures 114–126. Figs 114–117. Protokeelia cholnokyi. Fig. 114. Valve in LM (GU44I-1) (DIC). Fig. 115. External view of valve (GU44J-2 / ECT3569), SEM; image courtesy of Elizabeth Ruck. Fig. 116. Internal view of valve (GU44Z-15) (SEM). Fig. 117. External, dorsal view of whole frustule showing girdle bands and dorsal faces of valves (SEM); courtesy of Elizabeth Ruck. Figs 118–126. Psammodictyon pustulatum. Figs 118, 119. Frustule at two focal planes (GU66F-7A) (DIC). Fig. 120. Valve from GU66A-3 (DIC). Fig. 121. Specimen from Nagasaki on Meister’s slide 3509092. Fig. 122. Valve from Hustedt collection, slide W1/18, specimen from Vera Cruz, Mexico, image courtesy of Friedel Hinz. Fig. 123. External view of valve face (GU52Q-10a) (SEM). Fig. 124. Internal view of valve and part of the valvocopula. Arrows indicate where the valvocopula is broken. Inset shows full-resolution detail of valve margin and valvocopula, with the row of pores on the latter. Fig. 125. Frustule in oblique view showing the valves and girdle components. The ventral part of the valvocopula (vc) of the epivalve (ev) is visible at the front, and at the back the distal part of the valvocopula for the hypovalve (hv). Arrow indicates row of pores on the first pleura (p). Fig. 126. External detail of valve, showing the loculate character; arrow indicates row of pores on valvocopula. Scale bars: Figs 114–117, 123, 124 = 5 µm, Figs 118–122 = 10 µm, Figs 125, 126 = 2 µm.