Ulnaria tooelensis 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 : 9-12

Ulnaria tooelensis Graeff, Kociolek & S.R. Rushforth , sp. nov. ( Figs 38–55 ; figure 40 = holotype)

Valves linear to linear-elliptical in smaller specimens, tumid on one side of the central area, with apices subcapitate in larger specimens and protracted in smaller specimens ( Figs 38–46 ). Length 14.0– 97.5 µm, breadth 3.5–5.5 µm. Central sternum very narrow, straight, widening unilaterally at the center to form a rectangular central area on one side ( Figs 40, 43 ). Striae punctate, more or less opposite and parallel, infrequently with a stray stria without a corresponding stria on the opposite side of the central sternum ( Figs 41, 44 ). Striae number 11–15/ 10 µm in the center of the valve, 13–16/ 10 µm at the ends. A labiate process (rimoportula) is positioned at each end of the valve ( Figs 40–41 ). A pore field is present at the very terminus of the valve on each end ( Figs 39–41, 45–46 ). The cingulum is comprised of at least two closed girdle bands each with a single row of poroids ( Figs 47–48 ).

In the SEM, the valve has small, rounded, unoccluded areolae comprising the striae ( Figs 51–52, 54–55 ). The striae are more or less aligned, though that arrangement breaks down in places along the valve ( Figs 49–50 ). The rimoportula opening is round, similar in size to the areolae, but located within a small depression ( Fig. 51 ). The unilateral central area has some thickened interstriae present ( Fig. 52 ). Ocellimbi are evident on the margin at the poles ( Figs 49–51 ). Internally, the unornamented central area is evident, and the central sternum is narrow ( Figs 53, 55 ). The rimoportula is small, elliptical and bordered by narrow “lips” ( Fig. 54 ). Internally, the ocellimbi are distinct with a fine grid pattern positioned at the valve terminus on the mantle ( Fig. 54 ).

Type:— USA. Blue Lake , Tooele Co., Utah. ( COLO 439033 , holotype! (= Fig. 40 ), designated here; COLO 8505 , BM 101677, isotypes)

Etymology:—Named for the county in which it is found.

Distribution:— Ulnaria tooelensis is common in the main basin of Blue Lake and the surrounding marsh.

Observations:—This diatom was identified by Kaczmarska and Rushforth (1983) as Fragilaria vaucheriae (Kützing) Petersen (1938: 167) . These two diatoms are morphologically distinct, as illustrated by Krammer & Lange-Bertalot (1991: pl. 108, figs 10–15). They examined the type material of Exilaria vaucheriae Kützing (1833: 32) , the basionym of F. vaucheriae . The valve margins of Ulnaria tooelensis taper gradually toward the apices while they are relatively parallel in F. vaucheriae . The apices of U. tooelensis are broader than those in in F. vaucheriae . However, the valve breadths and stria densities of the two taxa are congruent (Krammer & Lange–Bertalot 1991: 124).

Other species that appear similar to U. tooelensis include Synedra capitellata Grunow in Van Heurck (1881: plate 40, fig. 26), S. familiaris f. major Grunow in Van Heurck (1881: plate 40, fig. 16), S. rumpens var. scotica Grunow in Van Heurck (1881: plate 40, fig. 11) and S. rumpens var. meneghiniana Grunow in Van Heurck (1881: plate 40, fig. 13). All of these taxa are linear, with barely to distinctly capitate headpoles and coarse striae. They are all much smaller (Grunow in Van Heurck 1881, Patrick & Reimer 1966, also see Krammer & Lange-Bertalot 1991 under names within the genus Fragilaria ) than what we have observed for U. tooelensis , and the valves of our new taxon that are in the same size range as these are shaped differently and have striae that are much more disorganized. A review of the nomenclature, types and ultrastructure of these species is presented in Tuji & Williams (2006, 2013). Further work on the ultrastructure and systematics of this complex of species, including the S. delicatissima W. Smith (1853: 72) group ( Tuji & Williams 2007) and F. gracilis Østrup (1910: 190) (Tuji 2007) , will go far to help elucidate circumscription of these two genera and the placement of these species within them.

Smaller specimens of this species also bear a superficial resemblance to Staurosirella micra Levkov & Williams (2011: 8) , described recently from Lake Ohrid ( Levkov & Williams 2011). This Ohrid species has a tumid central area that is has one side without ornamentation. Like U. tooelensis , Staurosirella mica also has pore fields at both apices and striae composed of uniseriate rows of round to elliptical areolae ( Levkov & Williams 2011: figs 39–56). The two species differ in the structure of the pore fields (an ocellimbus in U. tooelensis ) and areolae (simple rounded pores both internally and externally in U. tooelensis ), and the presence of two rimoportulae, one at each end, in U. tooelensis .

Because U. tooelensis has a rimoportula and ocellulimbus at each apex ( Round et al. 1990) and closed girdle bands with a row of poroids, the taxon is excluded from the genus Fragilaria (Williams 1986; Williams & Round 1986). Our species lacks the external areolar occlusions of Catacombas Williams & Round (1986: 314) , leaving us with placement of this species in Ulnaria (Kützing) Compére (2001: 100) . This taxon and its interesting suite of character states provides additional information for a future review of the phylogenetic relationships of this interesting group of diatoms, and the taxonomic implications such a review and analysis would yield.

Figures

FIGURES 38–48. LM. Ulnaria tooelensis. Figs 38–46, Valve views showing the size diminution series. Figure 40 is the holotype. Fig. 47, Girdle view showing a cingulum with at least two closed bands, each with a single row of poroids. Fig. 48, Closed girdle band. Scale bars: 10 µm.

FIGURES 49–55. SEM. Ulnaria tooelensis. Internal and external valve views of five specimens. Fig. 49, Full external valve view showing rimoportula openings at each end. Fig. 50, Full external valve showing unpaired striae. Fig. 51, Apex showing small, round, depressed external opening of the rimoportula and the ocellimbus. Fig. 52, Large external central area with slightly thickened interstriae and small, unoccluded areolae. Fig. 53, Full internal view showing rimoportulae at each apex. Fig. 54, Small, rounded rimoportula and well-defined apical pore field which extends over a larger area than the external ocellimbus. Fig. 55, Internal view of the central area with unoccluded areolae. Scale bars: Figs 49–50, 53: 10 µm; Figs. 51–52, 54–55: 1 µm.