New records of Cosmarium Corda ex Ralfs in lotic environment , adjacent to the Iguaçu National Park , Paraná State , Brazil

(New records of Cosmarium Corda ex Ralfs in lotic environment, area adjacent to the Iguaçu National Park, Paraná State, Brazil). This study aimed to document the Cosmarium (Desmiadiales, Zygnematophyceae) taxa at a subtropical stream located in an area adjacent to the Iguaçu National Park, an important environmental protection area in the further west of Paraná State. For this purpose, monthly samplings of periphytic material associated to Eleocharis minima Kunth were performed in the period of August 2012 to July 2013. This taxonomic inventory allowed the identification of 37 taxa at specific and infra-specific levels. There were 15 new records for Paraná State: Cosmarium bipunctatum Börgensen, C. clepsydra Nordstedt var. bicardia (Reinsch) Croasdale, C. crenatum var. crenatum Ralfs, C. difficile Lütkemüller var. dilatatum Borge, C. isthmochondrum var. isthmochondrum Nordstedt, C.obsoletum (Hantzsch) Reinsch var. obsoletum, C. ordinatum (Borge) West & West var. ordinatum, C.ornatum Ralfs var. ornatum f. ornatum, C. pseudoconnatum Nordstedt var. pluriradians Scott & Grönblad, C. pseudoretusum F. Ducell. var. pseudoretusum Krieger et Gerlof, C. pyramidatum var. borgei Krieger & Gerloff, C. regnellii var. minimum Eichler & Gutwinski, C. repandum var. minus (West & West) Krieger & Gerloff, C. securiforme Borge var. brasiliense Grönblad and C. variolatum var. variolatum Lundell.


Introduction
The Zygnematophyceae Class is the biggest and most diverse algae group of the Streptophyta lineage (Gontcharov & Melkonian 2005), encompassing organisms characterized by the absence of flagellated cells in its life cycle, besides presenting sexual reproduction through conjugation.It comprehends two Orders: Zygnematales and Desmidiales (Hoek et al.1995, Bicudo et al. 2014).
Desmidiales, popularly known as desmids, are microscopic green algae, which stand out mainly by its specific richness, distributed in a cosmopolitan way, so they can be found in plankton, periphyton or metaphyton (Coesel 1982, Margalef 1983, Felisberto & Rodrigues 2002, Felisberto & Rodrigues 2008, Menezes et al. 2011b).They comprehend a group of high morphological diversity and great ecological importance in the continental aquatic ecosystems, acting as biological indicators (Coesel 2001(Coesel , Šťastný 2009)).They present as mainly characteristics two identical semi cells formed by a median constriction and the isthmus, with cell wall morphologically diverse, rich in ornamentations, such as granules, spinules, pores or processes (Hoek et al. 1995).The Cosmarium Corda ex Ralfs genus is one of the oldest and largest in number of taxa described (ca.1500 species) to the Desmidiales Order, its representatives having preference by environments with acid oligo-to eutrophic waters (Bicudo & Menezes 2006).
Thus, due the importance of floristic studies about the Paranaense desmid flora, and the knowledge about the biogeographic distribution of the taxon in continental aquatic environments, besides the great species diversity within Cosmarium, this study aimed to taxonomically document the occurrence of the taxa belonging to this genus in a subtropical stream, area adjacent to the Iguaçu National Park, an important environmental protection area located in the further west of Paraná State.

Material and methods
The study was carried out in the Tenente João Gualberto stream, an important tributary of the lower Iguaçu River hydrographic basin, located at São Miguel do Iguaçu municipality (25º20'S and 54º14'W), further west of Paraná.This stream is situated in an area adjacent to the Iguaçu National Park Conservation Unit.This region has Cfa climate (humid temperate with hot summer), humid-mesothermal subtropical, with welldefined summer and winter periods, besides having rainfalls well distributed during the year (Álvares et al. 2014).The sampling station (figure 1) has a narrow stretch, approximately 3.4 m wide between margins, about 20 cm depth.The area presents approximately 2 m of riparian vegetation in its surroundings.
The biological material was collected in the period between August 2012 and July 2013, comprehending 12 samplings.The periphytic material was collected from the aquatic macrophyte Eleocharis minima Kunth, and removed with the help of a brush and distilled water jets.Samples were preserved in 1:1 Transeau solution, according to Bicudo & Menezes (2006).The biological material is deposited in the State University of West Paraná Herbarium, Cascavel campus (UNOP-Algae).
For the qualitative analysis, an average of 15 slides per sample were prepared.Morphometric and photographic analysis of microalgae were performed in a trinocular microscope with infinite correction optics, Olympus model CX31, with camera attached.Systematic and taxonomic framework for identified taxa was performed based in the classic literature (e.g., Prescott et al. 1981), as well as in specialized scientific papers of the area.
The measures (in μm) are represented by the symbols L -length, W-width and I -isthmus.The geographic distribution for the Paraná State and morphometric data were recorded to all taxa.Descriptions were made just for the first taxa cited for the State.Comments were elaborated when deemed necessary.

Results and Discussion
The taxonomic assessment of the genus Cosmarium allowed the identification of 37 taxa.These, 15 taxa are new records for the State of Paraná.

Cosmarium regnellii var. minimum
Of This study, although of qualitative character, highlights the importance of the knowledge regarding the phycological flora of Paraná, due the high number of taxa recorded.Such findings emphasize the need to know the taxa biogeography, in order to serve as a comparative base for ecological studies in continental aquatic environments, as well as to proposed preservation and biological conservation measures.

Figure 1 .
Figure 1.Location of the sampling station in the Tenente João Gualberto stream, Paraná, Brazil.