Haslea sigma Talgatti, Sar & Torgan, 2014

Talgatti, Dávia, Sar, Eugenia A. & Torgan, Lezilda C., 2014, Haslea sigma (Naviculaceae, Bacillariophyta) a new sigmoid benthic species from salt marshes of Southern Brazil, Phytotaxa 177 (4), pp. 231-238 : 233

Haslea sigma Talgatti, Sar & Torgan sp. nov. ( Figs. 2–35 )

Description in LM: —The cells have two apically elongated chloroplasts (in valvar view) with pyrenoids axially located ( Figs. 2–8 ). The frustule is delicate, the striation is inconspicuous and it is possible to visualize only the raphe sternum, the pseudostauros and the valve sides ( Figs. 9–23 ). The valves are sigmoid, lanceolate, with almost parallel sides in the middle ( Figs. 2–23 ). The ends are curved towards opposite sides with cuneate apices. Raphe and raphe sternum are sigmoid.

Description in SEM: — External view: The central raphe fissures are almost straight, slightly bent towards primary side of the valve and drop-shaped ( Figs. 32, 33 ). The terminal raphe fissures are slightly curved to opposite sides towards the concave side of the valve and expanded slightly ( Figs. 26 ˗28). Valve surface has straight, parallel and longitudinal strips of silica ( Figs. 24, 27, 32, 33 ), which cover the striae and are separated by narrow slits (arrows in Fig. 27 ). Two of these slits go to the end of valve and come together at the far tip of the pole ( Fig. 26 ). The cingulum appears to be composed by two open, plain bands: valvocopula and copula ( Figs. 25, 28 ).

Internal view: The central raphe endings are coaxial, simple, straight and not expanded ( Figs. 29, 31 ), whereas each polar raphe ending is expanded and terminates in a raised and straight helictoglossa ( Figs. 34, 35 ). On the primary side there is an accessory rib that accompanies the raphe close to the helictoglossa, which is raised and overlaps the raphe sternum (black arrow in Fig. 30 , black arrow-head in Fig. 34 ). In the center, this rib merges with one thickened virga that almost reaches to the valve margin ( Figs. 25, 29–31 ). On the secondary side there is also an accessory rib, however it is shorter than that of the primary side, it is raised, but does not overlap the raphe sternum, and in the center this rib merges with one or two thickened virgae ( Figs. 29–31 ). These thickened virgae form a pseudostauros that is visible in LM ( Figs. 9–23 ). Striae uniseriate, parallel, formed by quadrate areolae occluded by hymenes ( Figs. 31 , white arrow in 34) and crossed at a right angle by a longitudinal pattern.

Valve dimensions (n = 26): 55.8–70 µm long, 5.8–7.2 µm wide, 30–40 transapical striae in 10 µm, and 35–40 longitudinal striae in 10 µm.

Holotype: — BRAZIL. Rio Grande do Sul State, Rio Grande city, Pólvora Island (32º01’14.424’’S – 52º05’59.095’’W), benthic sample, collected by D. Talgatti and L. Bertolli, May 17, 2013. Circled specimen on slide HAS 6699 ( Museu de Ciências Naturais-Fundação Zoobotânica do Rio Grande do Sul, Porto Alegre, Brazil), here designated. Figure 12 corresponds to the holotype specimen.

Isotype: — BRAZIL. Rio Grande do Sul State, Rio Grande city, Pólvora Island (32º01’14.424’’S – 52º05’59.095’’W), benthic sample, collected by D.Talgatti and L. Bertolli, May 17, 2013. Circled specimen on slide LPC 13001 (Herbarium of the División Ficologia “ Dr. Sebastián A. Guarrera ”, Faculdad de Ciencias Naturales y Museo, Argentina), here designated .

Etymology: —The specific epithet refers to the valve shape that resembles an “S” (σίγμα in Greek).

Ecology: — Haslea sigma was found as the second most abundant species (14.79%) and the only unique representative of the genus on the sediment surface on Pólvora Island. Other abundant taxa were Nitzschia rautenbachiae Cholnoky (1957: 76) , Nitzschia spp. and Navicula spp. This sediment was composed mainly by clay (79%) and silt (13%). The taxon was found alive in oligohaline zone (salinity 3.0 ‰), at temperature 20 ºC and pH 7.1.

Diagnosis: — Haslea sigma differs from Haslea nipkowii (Meister) Poulin & Massé by having thickened virgae forming a pseudostauros, central raphe fissures almost straight (not overlapping), and terminal raphe fissures slightly curved (not T-shaped).

Figures

FIGURES 2–23. LM: Haslea sigma sp. nov.. Figs. 2–8. Live material under DIC. Cells in valve view showing two apically elongated chloroplasts (in valvar view) with pyrenoids axially located (arrow). Figs. 9–16. Acid cleaned valves in DIC. Figs. 17–23. Acid cleaned valves in brightfield. Fig. 12. Holotype. Scale bar = 10 μm.

FIGURES 24–35. SEM: Haslea sigma sp. nov. Figs. 24, 26–28, 32, 33. External view. Fig. 24. General view showing the outline of the valve. Fig. 26. Detail of two slits forming a wedge-like structure and detail of slightly curved terminal raphe. Fig. 27. Apice of valve showing the valve surface with straight, parallel and longitudinal strips (black arrow) separated by narrow slits (white arrow). Fig. 28. Detail of open valve showing cingulum composed by valvocopula (black arrow) and one copula (white arrow). Figs. 25, 29–31, 34, 35. Internal view. Fig. 25. General view showing the outline of the valve. Fig. 29. Valve center presenting raphe ending (black arrow), and a pseudostauros formed on primary side (ps) by one thickened virga (black arrow-head) and on secondary side (ss) by two thickened virgae (white arrow-head). Fig. 30. Center of valve showing on primary side part of accessory rib (black arrow), on secondary side the short accessory rib (white arrow) and the pseudostauros (black arrow-head). Fig. 31. Center of valve with pseudostauros, note that on primary and secondary sides the pseudostauros is formed by only one thickened virga. Figs. 32, 33. Longitudinal strips and slits, and central raphe fissures drop-like, bent to primary side. Figs. 34, 35. Apices showing helictoglossa (black arrow), quadrate areolae (white arrow) and end of accessory rib (arrow-head) on the primary side. Scale bars = 10 μm (Figs. 24, 25), 5 μm (Fig. 30), 2 μm (Fig. 27), 1 μm (Figs. 28, 29, 31–34), 0.5 μm (Figs. 26, 35).