Cavinula maculata Potapova, Cvetkoska, Hamilton & Levkov, 2014

Cvetkoska, Aleksandra, Levkov, Zlatko, Hamilton, Paul B. & Potapova, Marina, 2014, The biogeographic distribution of Cavinula (Bacillariophyceae) in North America with the descriptions of two new species, Phytotaxa 184 (4), pp. 181-207 : 203

Cavinula maculata Potapova, Cvetkoska, Hamilton & Levkov sp. nov. ( Figs 193 –204)

Valves elliptic-lanceolate with rounded apices. Valve face flat, sharply bent (not gradually curved) at margin onto mantle. Valve length 25–41 µm, width 15–20 µm with 20–25 stria in 10 µm. Striae radiate throughout; a few shortened striae may be present around central area. Striae uniseriate, composed of fine, rounded to elliptic areolae, 20–25 in 10 µm. Internally, interstriae slightly elevated and areolae covered with hymenes. Axial area narrow, linear. Central area large circular or transversely elliptic. Central nodule elevated internally. Raphe linear; externally, proximal and the distal raphe ends pinhole-shaped; distal raphe ends do not extend onto valve mantle (i.e. terminate on the valve face). Internally, raphe positioned on elevated sternum; distal raphe fissures terminate with a helictoglossa. Copulae open, with one row of pores.

Type: — SOUTH CAROLINA, USA: Toms Creek near Gadsden, collection date: May 8, 1997, collected by B.L. Porter (holotype! slide ANSP GC59003 , holotype! designated here, holotype specimen = Fig. 198 ; isotypes CANA 93669 ) .

Etymology: —The specific epithet ( maculata ) refers to the thickened central nodule that often appears as a dark spot in LM.

Differential diagnosis:–– Cavinula maculata most resembles C. scutiformis in size, striae orientation, and enlarged and thickened central nodule. The valve outline of C. maculata is, however, elliptic-lanceolate rather than elliptic as in C. scutiformis , striae are much denser, and central area is conspicuously larger. The axial area is also narrower and linear. Areolae around central area in C. scutiformis are usually transversely elongated, while they are small and circular in C. maculata .

Distribution:–– C. maculata is so far known from its type locality, Toms Creek, South Carolina, from Meyers Creek near Hopkins, South Carolina (ANSP sample GC024185, slide ANSP GC103271a), and from Perkins Branch, Delaware (ANSP sample DE000158, slide ANSP GC 115038b). Water chemistry data are available for two South Carolina sites. In 1997, when samples were collected, pH in these creeks ranged from 4.4–5.6, conductivity from 28–68 µS/cm, and nutrient concentrations were low.

Figures

FIGURES 193–198. LM micrographs of Cavinula maculata Potapova, Cvetkoska, Hamilton & Levkov sp. nov. Figs 199–204. SEM micrographs of Cavinula maculata Potapova, Cvetkoska, Hamilton & Levkov sp. nov. Figs 199, 201, 203. External valve views. Figs. 200, 202, 204. Internal valve views. LM Scale bar: 10 µm in Figs 193–198. SEM Scale bars: 5µm in Figs 199, 200; 2 µm in Figs 201–203; 1 µm in Fig. 204. Fig. 198 = holotype.