Placoneis itamoemae Straube, Tremarin & Ludwig, 2013

Straube, Arielli, Tremarin, Priscila Izabel, Castro-Pires, Emanuela Cristina De, Marquardt, Gisele Carolina & Ludwig, Thelma Alvim Veiga, 2013, Morphology, ultrastructure and distribution of Placoneis itamoemae sp. nov. (Cymbellaceae) from Brazil, Phytotaxa 76 (3), pp. 55-62 : 56-57

Placoneis itamoemae Straube, Tremarin & Ludwig sp. nov. ( Figs 1–24 )

Type:— BRAZIL. Paraná: Balsa Nova County, Papagaios river , 25°27'55"S, 49°45'58"W, January/2001, UPCB 44567 - diatom collection of the Botany Department, Universidade Federal do Parana; holotype slide UPCB 44567 , designated here in Fig. 3 ; isotype slide ANSP GC 26818 ( Academy of Natural Sciences , Philadelphia) .

Valves elliptic-lanceolate, length 26.0– 37.9 µm and breadth 10.0– 13.4 µm (n=47), with rostrate ends. Raphe sternum straight and narrow, central area slightly expanded, formed by 5–6 irregularly shortened median striae on either side of the raphe, 1–3 (usually 2) rounded isolated pores on one side of the central area. Central pores more expanded internally, located on the prominent central nodule. Raphe straight with proximal ends externally slightly expanded, rounded and internally deflected to the side of central pores; distal ends turned into opposite directions and each one with distinct morphology, hooked-like at one end of the valve and gradually curved at the other. Internally, the distal raphe ends terminate in small helictoglossae. Striae radiate, arched in the middle portion of valve, becoming parallel to convergent at the apices, 17–21 in 10 µm, extending onto the valve mantle, formed by one row of rounded to elliptical areolae, 36–39 in 10 µm. Etymology: —This species is named in honor of Dr. Ita Moema Valente-Moreira, a retired diatom researcher from Universidade Federal do Paraná.

Ecological data:— The collected sample from Papagaios river showed high temperature (22.5ºC), slightly acid conditions (pH 6.7), 102.8 µS.cm -1 of conductivity and 1.52 mg /L of dissolved oxygen ( Visinoni 2002).

Figures

FIGURE 1–14. Morphological variation of Placoneis itamoemae, LM, scale = 10 µm. Note the exemplars with different numbers of pores in the central area (Figs 8–10).

FIGURES 15–19. Placoneis itamoemae, SEM. Fig. 15. Overview of the valve, scale = 5 µm. Figs 16, 17. External view of central area showing the proximal raphe ends and central pores, scale = 1 µm. Figs 18, 19. Internal view of central area showing the proximal raphe ends and central pores, scale = 2 µm and 1 µm, respectively.

FIGURES 20–24. Placoneis itamoemae, SEM. Fig. 20. Inside view of the valve, scale = 2 µm. Figs 21, 22. External detail of valve apices showing the distal ends of the raphe, scales = 2 µm. Fig. 23. Striae extending to the mantle, scale = 2 µm. Fig. 24. Internal detail of valve apice showing the helictoglossa, scale = 1 µm.