inventory The genus Pinnularia ( Bacillariophyta , Pinnulariaceae ) from Lago dos Tigres , Britânia , Goiás , Brazil

Studies of the genus Pinnularia Ehrenb. are only incipient in central-western Brazil, especially in Goiás. Only 20 of the 170 taxa known from Brazil were recorded in this state until now. A taxonomic study of Pinnularia from Lago dos Tigres (Tocantins-Araguaia River Basin) recorded 20 specific and infraspecific taxa, distributed in 17 species, including P. instabilis whose lectotype is designated here. Only P. meridiana var. meridianawas previously recorded in aquatic systems of the state. Eighteen taxa are newly recorded for Goiás, and one is the first record in Brazil. The Pinnularia flora from Lago dos Tigres contains nine taxa in common with the Amazon River Basin flora, and seven other taxa that occur elsewhere in the Paraná River Basin.


Introduction
The taxon name Pinnularia was proposed by Ehrenberg (1840aEhrenberg ( , 1840b) as a subgenus of Navicula Bory. Later, Ehrenberg (1843aEhrenberg ( , 1843b used the name at generic level. However, the name Pinnularia was earlier used by Lindley & Hutton (1835) for a genus of fossil high plants. Pinnularia Lindley & Hutton was lesser used than Pinnularia Ehrenb., which was conserved against the first one and it is the correct name to generic level according the International Code for Nomenclature of algae, fungi and plants (ICN, McNeill et al. 2012).
Pinnularia is a genus of naviculoid diatoms characterized by valves linear, lanceolate or elliptic, with plane or undulate surfaces (Krammer 2000). Members of this genus usually presented different courses of the internal and external fissure of the raphe; transapically, the valves bear alveolated costal systems, which are simple or partially recovered (Krammer 2000). This genus occurs predominantly in oligotrophic continental waters, with low electrolyte concentration and low pH values (Uherkovich 1984, Metzeltin & Lange-Bertalot 1998, Krammer 2000.
The genus Pinnularia comprises more than 2,700 species specific and infraspecific combinations, of which about 674 are currently accepted (Guiry & Guiry 2015). In Brazil, studies about Pinnularia recorded approximately 215 taxa (Pereira et al. 2014, Eskinazi-Lec¸a et al. 2016. These studies were mainly concentrated in the regions South (Torgan et al. 1999, Tremarin et al. 2009, Southeast (Menezes & Dias 2001, Rocha & Bicudo 2008 and North , Metzeltin & Lange-Bertalot 1998, 2007, 2014. In Central-West Region only 20 taxa were registered until now (Delgado & Souza 2007). These studies comprised small areas, such as Distrito Federal, the This Lago dos Tigres System has acid to neutral waters, which reach temperatures higher than 21°C. These waters are characterized as oligomesotrophic to mesotrophic, with high oxygen concentration (Nabout & Nogueira 2007). Physical and chemical variables were measured and values of averages and standard deviations (n ¼ 11) are provided in Table 1. Depth and water transparency were measured by means measuring tape and Secchi disk, respectively. Water temperature, conductivity, oxygen saturation and pH were determined through a water multi-analyzer (HORIBA U-21). Total nitrogen (TN) and total phosphorus (TP) were inferred according to APHA (2005).
Phytoplankton samples were obtained using 25 mm plankton net. Periphytic material was scraped from artificial substrates (rocks) using toothbrush. These substrates were sampled after the 21 st day of colonization. The material examined was collected from the 11 sites along Lago dos Tigres system (Britâ nia, Goiá s), monthly, from June 2004 to November 2004, and from June 2008 and January 2009, totalizing 178 samples ( Table 2). All the samples were fixed with Transeau solution (Bicudo & Menezes 2006) and deposited in the Herbarium of the Universidade Federal de Goiá s (UFG), with numbers between UFG29864 and UFG29973, and between UFG43636 and UFG43724 ( Table 2).
The samples were oxidized according to Simonsen (1974), modified by Moreira-Filho & Valente-Moreira (1981) and permanent slides were mounted using Naphrax s . The material was examined with Zeiss Axioscop 40 microscope and images were captured with an Axiovison system for observation of morphological characteristics of each taxa. A part of oxidized material was deposited under stubs and sputtered with a layer of 150-200 A°of gold in Sputter Coater Desk V (Denton Vacuum, LLC). The preparations were analyzed in a Jeol Pinnularia acrosphaeria var. tumidula Krammer, Diatoms of Europe, vol. 1, p. 55, 214, Fig. 21: 8, 9, 2000 Valves linear, tumid at the middle part; broadly rounded apices; length: 79-82 mm, breadth: 12.5-12.66 mm, length/ breadth ratio: 6.32-6.57; axial area broad, linear, presenting granulations; raphe lateral, one terminal end abruptly curve and other sickle-shaped, proximal ends slightly curved to the same direction; striae parallel, becoming slightly radiate towards to the ends of the valves; striae: 12/10 mm.            Krammer 2000, p. 55, 214). Because the agreement with the type and type locality and with the original description of the taxa, we concluded that the description of the legend is, actually, a typographic error that can be corrected. In contrast, if it was not accepted as typographic error, the taxon would not be valid because was published without an illustration as required by Art. 44.2 of the ICN (McNeill et al., 2012). Similarly, other authors seem to consider the legend of the Krammer (2000, figures 21: 8, 9) as a typographical error since has adopted the name as validly proposed (e.g., Rocha & Bicudo 2008, Montoya-Moreno et al. 2013. The diacritical characteristic of this taxon from the nominated variety is the prominent intumescence at the middle part of the valve (Krammer 2000). The specimens found in Lago dos Tigres agreed with the original description and is very similar to the type material illustrated by Krammer (2000, figure 21: 9). Rocha & Bicudo (2008) also found P. acrosphaeria var. tumidula in the State of São Paulo, which the specimens of the Lagos dos Tigres were similar.
The outline of the individuals found in Lago dos Tigres was similar to P. certa. However, some of these representatives were longer (48-60 mm against 43-54 mm) and or narrower (7-9 mm against 8.4-9.4 mm) than the type population characterized by Metzeltin & Lange-Bertalot (1998).
Valves linear, sometimes with slightly concave margins at the middle part; cuneate apices; length: 45-61 mm, breadth: 10.5-12 mm, length/breadth ratio: 4.01-5.79; axial area wide, linear-lanceolate, reaching 1 2 of the breadth of the valvae; central area with thin fascia, reaching the valves margins; raphe lateral, proximal ends slightly curved to the same side; striae short, parallel, becoming slightly convergent towards to the ends of the valves; striae: 10-11/10 mm.  ; Pioneer citation for the State of Goiás. Remarks. P. acuminata and P. inconstans Mayer presents similar outlines, but the first one has acuminate apices, wider axial area and an inconspicuous to small fascia (Krammer 2000, figures 144: 7-9). On the other hand, the neotype specimens of P. inconstans have more rounded ends of the valvae, narrower axial area, and a conspicuous fascia (Krammer 2000, figures 143:3-5, 11, 12). Such similarities lead to confusions concerning the identification of the two taxa in some studies of diatom flora.
The representatives of Pinnularia cf. acuminata from Lago dos Tigres were similar to P. inconstans sensu Krammer (2000, Fig 143: 10) and P. inconstans sensu Tremarin et al. (2010), and, concomitantly, to P. acuminata var. guyanensis, but presented breadth values intergrading with those of the nominated variety. The densities of striae of the specimens from Lago dos Tigres were slightly higher than P. acuminata var. acuminata but agreed with P. acuminata var. guyanensis. However, Pinnularia cf. acuminata presented a wider axial area and more cuneated valvar ends than the type of P. acuminata.
The individuals from Lago dos Tigres present outline to P. subacuminata Krammer & Metzeltin, but still here the axial area of Pinnularia cf. acuminata was slightly narrower, the valvar ends were cuneate instead cuneate-rounded, as observed in P. subacuminata. Moreover, P. subacuminata is larger (45-61 mm against 95-115 mm) than the specimens from Lago dos Tigres.
Since Lago dos Tigres presented intermediate specimens between several taxa compared here, we identified the taxon as Pinnularia cf. acuminata, the oldest epithet and the most similar taxon of this complex. More accurate studies should be carried out in order to verify the limits and circumscription among the taxa of this complex.

Pinnularia mayeri
The outline and measures of the specimens from Lago dos Tigres are also similar to Pinnularia pisciculus var. angusta Metzeltin & Krammer in Metzeltin & Lange-Bertalot (1998, figures 175: 6-12, 194: 5, 6), and those illustrated in Metzeltin & Lange-Bertalot (2007, figures 267: 8-12, 273: 1-8), except by the more prominent valvar ends, as well as in P. mayeri. P. pisciculus var. angusta also presents specimens with outline more linear, such as in the Lago dos Tigres material, to lanceolate specimens such as in P. mayeri. This variance can suggest a possible conspecificity of these two taxa. Remarks. Pinnularia microstauron var. rostrata distinguish from the nominate variety because is narrower (6-7 mm against 10-12.4 mm) and presents rostrate apices (Krammer 2000). This taxon is somewhat similar to P. microstauron var. brasiliensis considering the dimensions, the valvar outline and axial and central areas, but presents clear differences respect to the shape of the apices, which is narrower in the variety brasiliensis than in the variety rostrata (Figures 13-17).
The specimens observed in Lago dos Tigres were very similar to the material type of P. microstauron var. rostrata described by Krammer (2000), with some individuals more densely striated than the type population (10-13/10 mm against 10-11/10 mm). The representatives from Lago dos Tigres were also similar to the specimens illustrated by Metzeltin et al. (2005, Figures 164: 7, 8, 23), which, however, presented less prominent apices compared to those.
The specimens of the Lago dos Tigres were also similar to Pinnularia cf. microstauron var. rostrata observed by Canani et al. (2011), from Minas Gerais. Nevertheless, the only one specimen recorded by Canani et al. (2011) was larger than the type of P. microstauron var. rostrata and our specimens (9.8 mm against 6-8 mm), and it can belong to another taxa, closed to this group.
Live specimens of P. perumbrosa were recorded by . These specimens presented similar outlines compared to the Metzeltin & Lange-Bertalot's (1998, 2007 material. Although the P. perumbrosa sensu Pereira et al. (2012) was larger than the type population, this agreed with those specimens illustrated by Metzeltin & Lange-Bertalot (2007).
The material observed in Lago dos Tigres presented larger specimens than any material of P. perumbrosa but it could metrically agree with P. diandae. Nevertheless, the smallest length values of our material interbreed with measures of P. perumbrosa (Metzeltin & Lange-Bertalot 2007). Moreover, our material presented also a decrease of the breadth values from Remarks. The material observed in Lago dos Tigres was larger than the type material of P. superpaulensis (111 mm against 123.2-126.7 mm) (Simonsen 1987, figure 754: 4). On the other hand, Metzeltin & Lange-Bertalot (2007, figures 257: 1-3) presented specimens of this taxon larger than the type and our material (122.30-131.54 mm length).
Pinnularia superpaulensis was recorded in Tupé Lake, Amazonas, Brazil . The metric range of the specimens described in this study is wide and match with the type, P. superpaulensis sensu Metzeltin & Lange-Bertalot (2007) and our material (89.3-144 mm). However, the illustrated material in Pereira et al. (2013) had distinct outline compared to these others.
The diversity of Pinnularia in central-western Brazil is still incipiently known. From twenty taxa recorded in this study, 18 were new occurrences in State of Goiás. This demonstrates the potential of aquatic environments of this region to encompass biological diversity still not known. Because tributaries of the main Hydrographic River Basin from Brazil are present in Goiás and the importance of aquatic biological communities to the maintenance of the quality of this systems, studies about the flora of diatom and other algae groups should be carried out urgently in this State. Thus, these studies could provide important data to the management of aquatic resources of the Country.