Cyclotella utahensis Graeff, Kociolek & S.R. Rushforth, 2013

GRAEFF, C. L., KOCIOLEK, J. P. & RUSHFORTH, S. R., 2013, New and Interesting Diatoms (Bacillariophyta) from Blue Lake Warm Springs, Tooele County, Utah, Phytotaxa 153 (1), pp. 1-38 : 2-3

Cyclotella utahensis Graeff, Kociolek & S.R. Rushforth , sp. nov. ( Figs 1–18 ; figure 5 = holotype)

Valve face circular, 5–13 µm in diameter, strongly tangentially undulate ( Figs 2–6 ). Costa-like ornamentation restricted to the outer ⅓ of the valve face, appearing dichotomously branched near the margin in most valves ( Figs 2–4 ) except on the largest and smallest specimens. Fascicles number 10–13/ 10 µm. Each fascicle contains 3–5 striae ( Figs 9, 10 ). Undulations in the center of the valve appear mottled ( Figs 2–5 ) and possess 1–2 central strutted processes (fultoportulae) ( Figs 13–15 ). Fultoportulae are evident around the margin of the valve, 4–6/ 10 µm ( Figs 12–13 ).

In the SEM, the mottled appearance of the valve center is conspicuous ( Figs 9–10 ). The external opening of the central fultoportula sometimes has a narrow rim about it ( Fig. 10 , white arrow). Siliceous conical nodules form one ring on the very margin of the valve and one ring about ½ the way down the striae ( Figs 10, 12 ). The striae are sometimes pushed together into 2–3 striae within a fascicle separated from other fascicles by hyaline strips, but each stria is composed of two rows of areolae that terminate about ¼–⅓ from the margin ( Figs 9–10 ). Prominent elevations are present ( Figs 11–12 ). Between the elevations with striae, unornamented ribs occur that have the external openings of the marginal fultoportulae ( Fig. 12 , white arrows). These openings can also be surrounded by a slightly thickened rim. The external opening for the rimoportula is round and smaller than the openings of the marginal fultoportulae, with a noticeable thickening around the rim ( Figs 9, 12 , black arrows). The cingulum is composed of at least several, narrow open bands with one or more rows of small pores along the pars exterior ( Fig. 11 ).

Internally the central fultoportulae each have three satellite pores ( Figs 13–15 ). There are primary ribs that are thicker, and between them are thinner, more recessed secondary ribs ( Figs 13, 15, 17 ). A single, sessile rimoportula is present on one of the primary ribs ( Fig. 13 , black arrow, Figs 17–18 ). Marginal fultoportulae are present on the secondary ribs, each with three satellite pores ( Figs 13, 15, 17 ). Areolae are evident between the ribs and seen to possess flat cribra ( Figs 13, 16 ).

Type: — USA. Blue Lake , Tooele Co., Utah ( COLO 439031 , holotype! (= Fig. 5 ), designated here; COLO 8504 , BM 101675, isotypes) .

Etymology:—Named for the state in which it was found.

Distribution: — Cyclotella utahensis is abundant in the plankton of the main basin of Blue Lake (COLO 8504).

Observations: — This taxon resembles others in the genus that have strongly tangentially undulate valves, both fossil and recent. For example, Khursevich & Kociolek (2008) and Kociolek & Khursevich (2013) described several species attributed to Cyclotella , such as C. idahica Khursevich & Kociolek (in Kociolek & Khursevich 2103: 83) and C. oregonica Kociolek & Khursevich (in Khursevich & Kociolek 2008: 44) that are similar to this new species, differing mostly in the structure of the punctate portion of the outer part of the valve exterior. This new species differs from C. scaldensis Muylaert & Sabbe (1996: 336) and C. striata (Kütz.) Grunow (in Cleve & Grunow 1880: 119; basionym: Coscinodiscus striatus Kützing 1844: 131 ), two estuarine species, in the structure of the striae. In addition, C. scaldensis has a very long rimoportula ( Muylaert & Sabbe 1996) that is absent in C. utahensis , while C. striata has finer striae and fascicles as well as a different pattern of ornamentation in the center of the valve ( Häkansson 1996). Houk et al. (2010) listed three morphological groups within Cyclotella , and C. utahensis would be included in their group 1, which includes the generitype of Cyclotella . Other Recent Cyclotella species with tangentially undulate valve faces and lacking areolae in the center of the valve usually have smooth (not bumpy) central areas, similar to the generitype, C. distinguenda Hustedt (1927: 320) (e.g. Krammer & Lange-Bertalot 1991).

Figures

FIGURES 1–8. LM. Cyclotella utahensis. Valve views showing the size diminution series. Figure 5 is the holotype. Scale bar: 10 µm.

FIGURES 9–12. SEM. Cyclotella utahensis. External and girdle views. Fig. 9, Full valve view showing undulate and mottled valve face. Fig. 10, Full valve view showing external opening of the central fultoportula (white arrow). Fig. 11, Girdle view showing open girdle bands. Fig. 12, External view with nodules and external openings of the marginal fultoportulae (white arrows) and the rimoportula (black arrow). Scale bars: 1 µm.

FIGURES 13–18. SEM. Cyclotella utahensis. Internal views. Fig. 13, Full valve showing relative positions of the central fultoportula and the rimoportula (black arrow). Fig. 14, Full valve of a small specimen lacking obviously recessed ribs. Fig. 15, A large specimen with two central fultoportulae and two recessed ribs between some primary ribs. Fig. 16, Areolae with cribra visible between ribs. Fig. 17, View of the sessile rimoportula and two recessed ribs between a pair of primary ribs. Fig. 18, Marginal fultoportulae with three satellite pores. Scale bars: Figs 13–15: 1 µm; Fig. 16: 0.1 µm; Figs. 17–18: 0.5 µm.