The genus Euastrum Ehrenberg ex Ralfs ( Desmidiaceae ) in a subtropical stream adjacent to the Parque Nacional do Iguaçu , Paraná State , Brazil

(The genus Euastrum Ehrenberg ex Ralfs (Desmidiaceae) in a subtropical stream adjacent to the Parque Nacional do Iguaçu, Paraná State, Brazil). This study aimed to document the species of Euastrum (Desmidiaceae) in a subtropical stream adjacent to an important environmental protection area, the Parque Nacional do Iguaçu, in the extreme west of Paraná State, Brazil. For this purpose, monthly samplings of periphytic material associated to Eleocharis minima Kunth were performed in the period between August 2012 and July 2013. This taxonomic inventory allowed the identification of 12 taxa at specific and infraespecific level. Eight new occurrences were recorded for Paraná State: Euastrum attenuatum var. splendens, E. bidentatum var. bidentatum, E. cornubiense var. cornubiense, E. croasdaleae var. croasdaleae, E. denticulatum var. quadrifarium, E. didelta var. quadriceps, E. elegans var. elegans and E. evolutum var. incudiforme.


Introduction
Euastrum Ehrenberg ex Ralfs (1848) comprises a cosmopolitan distribution genus, belonging to the Desmidiaceae (Zygnematophyceae) family.It has isolated cells, about 2 times longer than wide, or about as long as wide, divided in two semicells.The semicells can be divided into 3 lobes, being 2 basal lobes and one polar lobe (or apical lobe).Many species can present lateral lobes among the basal lobes and the polar lobe.
An important characteristic of the genus is the presence of a median apical incision in most of its representatives, which can be deep or shallow, narrow or open, U-shaped or V-shaped.In lateral view the cells are usually oval, rarely elliptic and subretangular, with narrow or acute spines and truncate poles.In apical view the cells are elliptic, oval, or quadratic, mainly with rounded poles, and showing lateral protuberances.The cell wall can be smooth, punctuated or scrobiculated.It occurs one chloroplastid in each semicell, with usually 1 pyrenoid, in some cases, two or several pyrenoids (Prescott et al. 1977, Bicudo & Menezes 2006, Franceschini et al. 2010).
This study, although in a qualitative character, highlights the importance of the Brazilian phycological flora knowledge.This also emphasizes the need of knowing the taxa biogeography, once known species number is probably much lower than the real number of existent species, since many habitats and regions have not been sampled yet.Besides, the phycological flora knowledge is extremely necessary as a comparative base for ecological studies in continental aquatic environments, as well to propose biodiversity protection and conservation measures.In face of that, this study aimed to document taxonomically the occurrence of the taxa belonging to the Euastrum genus in a subtropical stream, adjacent to Parque Nacional do Iguaçu, an important environmental protection area located in the further western of Paraná State, Brazil.

Material and methods
The study was conducted at Tenente João Gualberto stream, an important tributary of the lower Iguaçu River hydrographic basin, located in São Miguel do Iguaçu municipality (25º20'S and 54º14'W), further western of Paraná State, Brazil.This stream is situated in an area adjacent to the Parque Nacional do Iguaçu, the first Brazilian Conservation Unit to be instituted as World Natural Heritage Site by UNESCO.This region has a mesothermal-humid subtropical climate, with well-defined summer and winter periods, and rainfalls regularly well distributed all over the year (Alvares et al. 2014).The sampling station (figure 1) is a small watercourse, approximately 3.4 m large between margins, about 20 cm deep.The area presents approximately 2 m of riparian vegetation in its surroundings.
The biological material samplings were performed in the period between August 2012 and July 2013, totalizing 12 months of samplings.The periphytic material was collected from the aquatic macrophyte Eleocharis minima Kunth, being removed with the help of a brush and distilled water jets.Samples were preserved in Transeau solution, in the proportion of 1:1, according to Bicudo & Menezes (2006).The biological material is deposited in the State University of West Paraná (UNIOESTE) Herbarium, Cascavel campus (UNOP-Algae).
For the qualitative analysis an average of 15 slides per sample were prepared.The microalgae morphometric and photographic analysis was performed in a trinocular microscopic with infinite correction optical, Olympus model CX31, with camera attached.The systematic and taxonomic framework for the identified taxa was performed based on the classic literature of Prescott et al. (1977), as well as in specialized scientific papers.
The measures (in μm) are represented by the symbols: L -length, W-width and I -isthmus, and the morphometric data were recorded for all the taxa.The taxa geographic distribution was obtained in Guiry & Guiry (2016).It was also verified the occurrence of taxa for Paraná State.Comments were elaborated when deemed necessary.

Results and Discussion
The    Cells longer than wide.L: 50-52.5 µm; W: 29.0-33 µm; I: 6-9.9 µm.Deep median constriction, sinus open, semicell subquadrate, without median incision, with a protrusion surrounded by large granules, concave margins forming a polar lobe with subparallel margins, the apex slightly inflated.Face of the semicell with a median inflation surrounded by large granules and with a large inflation on both sides of the basal lobes.Lateral view elliptic.Apical view not observed.Cell wall smooth.Chloroplastid with two pyrenoids per semicell.The individuals found presented inferior sized than the ones cited by Prescott et al. (1977), being close to cited by Silva e Felisberto (2015) which the length would be 31-34 μm; width 19-21 μm and isthmus of 4-5 μm, although all the other characteristics are in accordance with the description.Euastrum denticulatum (Kirchner) Gay var.denticulatum, Bull. Soc. Bot. Fr. 31: 335. 1884. Figures 12-13 Cells longer than wide.L: 13.3-24.6µm; W: 10.5-18.4µm; I: 2.9-5.7 µm.Deep median constriction, sinus closed, semicell subtrapeziform, basal lobes rectangular, lateral margins undulated, notch between the basal and apical lobes open and shallow, apical lobe with deep median notch, short spine at each of the angles.Apical view elliptic with a protuberance.Lateral view not observed.Cell wall ornamented with granules.Chloroplastid with one pyrenoid per semicell.Occurrence in the Paraná State : Felisberto & Rodrigues (2005a, b, 2008, 2010), Bortolini et al. (2010), Aquino et al. (2014).
Euastrum elegans (Bréb.)Kütz.ex Ralfs var.elegans, Brit. Desmid.: 89, pl. 14, fig. 7a-c. 1848. Figure 18-19 Cells longer than wide.L: 18.3-20.8µm; W: 12.8-15.5µm; I: 3.3-3.6µm.Deep median constriction, sinus narrow and closed.Semicell subretangular, lateral margins bilobed and retuse ending in a subapical spine, apical margin of the polar lobe elevated with a deep median incision, face of the The individuals found presented inferior sized than the ones cited by Prescott et al. (1977), which the length would be 26.6-39μm; width 14-30 μm and isthmus of 4-8 μm, although all the other characteristics are in accordance with the description.According to Prescot et al. (1977) E. evolutum var.incudiforme (Börges) West & West differs from the typical variety by presenting smaller measures, two minute teeth on either side of the median incision and by not having intramarginal granules in the polar lobes.The individuals found presented inferior size than the ones cited by Prescott et al. (1977), which the length would be 50-60 μm; width 36-39 μm and isthmus of 7.5-10 μm, although all the other characteristics are in accordance with the description.