New records of Cosmarium Corda ex Ralfs (Desmidiaceae, Zygnematophyceae) in a tributary of the Itaipu Reservoir, Paraná, Brazil

ARTICLES

New records of Cosmarium Corda ex Ralfs (Desmidiaceae, Zygnematophyceae) in a tributary of the Itaipu Reservoir, Paraná, Brazil

Stefania Biolo^I,*; Norma Catarina Bueno^II; Natália Silveira Siqueira^I; Carina Moresco^I

^IUniversidade Estadual de Maringá, Programa de Pós-graduação em Ecologia de Ambientes Aquáticos Continentais, Departamento de Biologia, Maringá, Paraná, Brazil

^IIUniversidade Estadual do Oeste do Paraná, Programa de Mestrado em Conservação e Manejo de Recursos Naturais, Centro de Ciências Biológicas e da Saúde, Cascavel, PR, Brazil

ABSTRACT

This work is part of a survey of the desmid flora in a tributary of the Itaipu Reservoir, in the state of Paraná, Brazil. The objective was to expand the knowledge base regarding the genus Cosmarium (Desmidiaceae, Zygnematophyceae). We conducted a qualitative analysis of 60 samples of phytoplankton, which were collected from along the banks of the São Francisco Falso River between July of 2003 and June of 2004. We identified, drew, and described 18 taxa of Cosmarium. Of those 18 taxa, 8 represent new records for the state of Paraná: C. angulosum Bréb. var. angulosum, C. bireme Nordst. var. bireme, C. clepsydra Nordst. var. clepsydra, C. cf. galeritum Nordst. var. borgei, C. ginzbergeri, C. norimbergense Reinsch var. norimbergense, C. protractum (Nägeli) De Bary var. protractum, and C. rectangulare var. hexagonum (Elfving) G.S. West & West.

Key words: algae, desmids, phytoplankton, taxonomy

Introduction

Cosmarium Corda ex Ralfs is one of the oldest and most species-rich genera of the family Desmidiaceae (Croasdale & Flint 1988). It is estimated that more than 1500 freshwater species have been described. These species can be cosmopolitan or have a very limited distribution, covering a wide range of taxonomic forms (Bicudo & Menezes 2006; Franceschini et al. 2010).

To date, eight taxonomic studies have shown the presence of Cosmarium Corda ex Ralfs in the state of Paraná, Brazil. Bittencourt-Oliveira (1993) inventoried the phytoplankton community in the Tibagi River and identified 14 taxa of Cosmarium. Cecy et al. (1997) and Picelli-Vicentim et al. (2001) inventoried the phytoplankton community in the Passaúna River Dam area and identified 15 and 4 Cosmarium taxa, respectively. When inventorying the desmids in the Salto Caxias Reservoir Hydroelectric Power Plant, Silva & Cecy (2004) identified 20 Cosmarium taxa, 13 of which were new records for the state. Felisberto & Rodrigues (2008) identified 17 Cosmarium taxa among the periphyton community in the Salto do Vau Reservoir. Those authors also identified 48 taxa of Cosmarium in three areas near the Rosana Reservoir Hydroelectric Power Plant. Bortolini et al. (2010) surveyed the Cascavel Municipal Lake and identified 21 Cosmarium taxa, 10 of which were new records for the state. Finally, Menezes et al. (2011) found 23 taxa of Cosmarium in the São Francisco Falso River.

The objective of the present study was to gain a deeper understanding of the taxonomy and geographic distribution of Cosmarium in the São Francisco Falso River, thereby increasing our knowledge of and disseminating information on the diversity of algae in the state of Paraná. To that end, we conducted a geospecific taxonomic study of the genus.

Material and methods

The São Francisco Falso River is one of the main tributaries of the Itaipu Reservoir (24º05'-25º33'S; 54º00'-54º37'W) on the Brazilian side of the border with Paraguay, the creation of the reservoir having flooded an area of the city of Santa Helena, in the state of Paraná. Although it is affected by agricultural activities in the surrounding areas, as well as by tourism and leisure activities (artificial beaches), the São Francisco Falso River does not receive urban or industrial effluents (Silva et al. 2010).

The study samples were collected monthly in the 2003-2004 period from five sampling stations along the São Francisco Falso River:

Station 1-24º52'41"S; 54º13'35"W

Station 2-24º52'28"S; 54º15'17"W

Station 3-24º51'52"S; 54º16'02"W

Station 4-24º51'30"S; 54º17'11"W

Station 5-24º51'14"S; 54º17'11"W

The samples were collected with a 25-mm mesh plankton net and were preserved in Transeau's solution (1:1), having been placed in the solution immediately after collection (Bicudo & Menezes 2006).

For qualitative analysis, we prepared temporary slides (20 slides per sample, on average, or as many slides as needed until no different taxa were observed). The slides were examined with a binocular microscope at magnifications of ×400 and ×1000, and camera lucida drawings were made at those same magnifications. The specimens were added to the Herbário da Universidade Estadual de Maringá (HUM, State University at Maringá Herbarium; Accession nos. 12,612-12,671), located in the city of Maringá, Brazil, and the Herbário da Universidade Estadual do Oeste do Paraná (UNOP, State University of Western Paraná Herbarium; Accession nos. 1824-2267), located in the city of Cascavel, Brazil. Measurements (length and width) are expressed in µm.

For each Cosmarium species, we calculated the constancy index, modified from the method proposed by Dajoz (1978) and expressed as a percentage, using the following equation: C = (p × 100)/P, where p = number of samples containing a given species and P = total number of samples. On the basis of the results obtained, we determined the constancy of Cosmarium spp.: C > = 70, constant species; 30 < C < 70 = common species; 10 < C < 30 = sporadic species; and C < 10 = rare species. The taxonomic distribution was based on taxonomic studies conducted in the state of Paraná up until 2011, including descriptions and illustrations.

Material and methods

Our taxonomic survey of the genus Cosmarium Corda ex Ralfs in the São Francisco Falso River allowed us to identify 41 taxa. Of those, 23 had been previously described by Menezes et al. (2011). Therefore, we registered and described 18 new taxa. Of those, 1 was identified down to the genus level, 2 were identified down to the species level, and 15 were described as variants. Of those 15 variants, 10 were typical and 5 were atypical (of their species). The distribution of the Cosmarium taxa inventoried is shown in Table 1.

Of the 18 taxa that we registered and described, 8 were new records for the state of Paraná: Cosmarium angulosum Bréb. var. angulosum, C. bireme Nordst. var. bireme, C. clepsydra Nordstedt var. clepsydra, C. galeritum Nordst. var. borgei W. Krieg. & Gerloff, C. ginzbergeri Grönblad, C, norimbergense Reinsch var. norimbergense, C. protractum (Nägeli) De Bary var. protractum, and C. rectangulare var. hexagonum (Elfving) G.S. West & W. West.

The Cosmarium algae found among the phytoplankton community in the São Francisco Falso River between 2003 and 2004 in the present study were predominantly rare or sporadic. Only Cosmarium reniforme var. reniforme was common during sampling, and none of the taxa were constant.

Cosmarium Corda ex Ralfs

Cosmarium Corda ex Ralfs are single, free-living cells that are usually deeply constricted medially. The median sinus ranges from shallow to fully dilated. In terms of shape, the semicells can range from nearly spherical to subpyramidal or conical. The lateral margins can be smooth, wavy, granular, dentate, or serrated, or they can have shallow incisions. The cell wall can be smooth, punctate, granular, scrobiculate, spiculate, or variously ornamented, having no angular or lateral spinules. The chloroplasts can be axial or, more rarely, parietal, each chloroplast containing one, two, four, or, more rarely, numerous pyrenoids (Bicudo & Menezes 2006; Francheschini et al. 2010).

Artificial key to identify the taxa of Cosmarium Corda ex Ralfs in the São Francisco Falso River:

1. Smooth or punctate cell wall 2. Smooth cell wall 3. Open median sinus ..............................11. C.moniliforme var. moniliforme 3. Closed median sinus 5. Lateral margins with one concavity .................................................. .........................................12. C. norimbergense var. norimbergense 5. Straight to convex lateral margins 6. Convex lateral margins, oblong to trapeziform semicell with 2 pyrenoids and apical thickening ..........................8. Cosmarium sp. 6.

Straight to slightly convex lateral margins, semicell of shapes other than those described above, with 1 pyrenoid and without apical thickening

7.

Obtusely conical or generally convex apical margin, subsemicircular to subtriangular semicell ................................. ................................................5. C.clepsydra var. clepsydra

7. Truncate apical margin, semicell of shapes other than those described above 8. Subtrapeziform semicell ..............1. C.abbreviatum var. minus 8. Angular-elliptical semicell 9.

Cell that is wider than it is long ......4. C.bireme var. huzelii

9. Cell that is as long as it is wide or that is longer than it is wide ........................................3. C.bireme var. bireme 2. Punctate cell wall 10. Open median sinus, subquadratic to subrectangular semicell ................ ........................................................2.C.angulosum var. angulosum 10. Closed median sinus, semicell of shapes other than those described above 11. Narrow, slightly retuse to notched apical margin, semielliptical, slightly angular to subpyramidal semicell ........10. C. laeve var. laeve 11. Wide apical margin, semicell of shapes other than those described above 12.

Divergent lateral margins in the first part (converging to the apex), subhexagonal semicell ................................................ ........................................15. C.rectangulare var. hexagonum

12.

Lateral margins converging directly to the apex, pyramidal-trapezoidal semicell .....................8. C. cf. galeritum var. borgei

1. Granular cell wall 13. Open median sinus 14. Shallow median constriction 15. Subcircular semicell ......................7. C.excavatum var. excavatum 15. Subrectangular semicell ..........................16. C.regnesi var. regnesi 14. Deep median constriction, semicell of shapes other than those described above 16. Three-lobed semicell, granules arranged in oblique, decussate series and becoming smaller as they reach the central bulge, where they are arranged in rings .................14. C. protractum var. protractum 16.

Semicell of shapes other than those described above, granules arranged in ways other than those described above

17. Reniform to rectangular semicell, granules arranged in longitudinal series ...................................13. C. portianum var. portianum 17. Semicircular to truncate pyramidal semicell, granules arranged .... .....densely and hexagonally ..........................6. C. decoratum 13. Closed median sinus 18. Elliptical semicell, single series of intramarginal granules arranged apically and laterally, series of granules in the region of the isthmus ................. ...........................................................................9. C. ginzbergeri 18.

Oblong-elliptical semicell, granules distributed throughout the cell ......... ........................................................17. C.reniforme var. reniforme

Table 1 - Click to enlarge

1. Cosmarium abbreviatum var. minus (West & G.S. West) Willi Krieger & Gerloff, Die Gattung Cosmarium 3-4: 242.1965; 2: pl. 42, fig. 18. 1965. 1969.

Cosmarium abbreviatum f. minor West & G.S. West, Trans. Yorkshire Nat. Union 5(23): 92. 1900.

A cell that is as wide as it is long, deep median constriction, closed median sinus; subtrapeziform semicell, rounded basal angles, slightly retuse lateral margins medially, truncate apical margin; smooth cell wall, chloroplast = 1, pyrenoid = 1. Dimensions: 10.0-14.3 µm in length; 10.0-14.3 µm in width; isthmus, 3.0-4.2 µm.

Constancy: sporadic.

Distribution in the state of Paraná: Rosana Reservoir Hydroelectric Power Plan (Felisberto & Rodrigues 2010).

Material examined: BRAZIL. Paraná: Santa Helena, São Francisco Falso River, 01/VII/2003, Bueno 855 (HUM, UNOP), 28/VII/2003, Bueno 861 (HUM, UNOP), 01/IX/2003, Bueno 871, 874 (HUM, UNOP), 06/X/2003, Bueno 883 (HUM, UNOP), 04/XI/2003, Bueno 888 (HUM, UNOP), 08/XII/2003, Bueno 904, 906 (HUM, UNOP), 10/III/2004, Bueno 921 (HUM, UNOP), 05/IV/2004, Bueno 926 (HUM, UNOP), 17/VI/2004, Bueno 938 (HUM, UNOP).

Because C.abbreviatum var. minus shows considerable polymorphism, Bicudo (1988) and Bicudo (1996) proposed a list of synonyms, which was employed by Felisberto & Rodrigues (2004; 2008). The variety minus can be distinguished from the typical variety of the species by its smaller size and its lateral angles, which are not as rounded or pronounced. Our cell measurements yielded values that were lower than were those initially reported by Felisberto & Rodrigues (2004) but consistent with those later reported by the same authors (Felisberto & Rodrigues 2008).

2. Cosmarium angulosum Bréb. var. angulosum, Mém. Soc. Impér. Nat. Cherbourg 4: 127. pl. 1, fig. 17. 1856.

A cell that is 1.5 times as long as it is wide, deep median constriction, open median sinus; subquadratic to subrectangular semicell, smooth, straight, or slightly convex lateral margins, rounded, truncate apical margin; punctate cell wall, chloroplast = 1, pyrenoid = 1; angular-elliptical apical view, subcircular lateral view. Dimensions: 18.4-24.5 µm in length; 12.2-16.3 µm in width; isthmus, 2.0-4.4 µm.

Constancy: sporadic.

Distribution in the state of Paraná: First record of the taxon.

Material examined: BRAZIL. Paraná: Santa Helena, São Francisco Falso River, 28/VII/2003, Bueno 861 (HUM, UNOP), 01/IX/2003, Bueno 872 (HUM, UNOP), 06/X/2003, Bueno 883 (HUM, UNOP), 04/XI/2003, Bueno 888 (HUM, UNOP), 08/XII/2003, Bueno 904 (HUM, UNOP), 05/IV/2004, Bueno 926, 928 (HUM, UNOP).

When describing taxa of C. angulosum var. angulosum, Prescott et al. (1981) reported an open median sinus; however, the illustrations clearly show a linear median sinus. In the present study, we found individuals whose characteristics were consistent with those described by Prescott et al. (1981), some specimens having shown a slightly linear sinus. We chose to identify C. angulosum var. angulosum in accordance with the description provided by Prescott et al. (1981). Therefore, our description and our pictorial representation show an open median sinus.

3. Cosmarium bireme Nordst. var. bireme, Vidensk. Medd. Naturh. Foren. Kjöbenhavn 1869(14/15): 212, pl. 3, fig. 33. 1870.

A cell that is 1.1 times as long as it is wide or that is as long as it is wide, deep median constriction, closed median sinus dilated at the apex; angular-elliptical semicell, rounded lateral margins, truncate apical margin; smooth cell wall, chloroplast = 1, pyrenoid = 1; an apical view with a central papilla on the semicell surface. Dimensions: 10.0-22.0 µm in length; 9.0-20.0 µm in width; isthmus, 4.0-8.0 µm.

Constancy: sporadic.

Distribution in the state of Paraná: First record of the taxon.

Material examined: BRAZIL. Paraná: Santa Helena, São Francisco Falso River, 01/VII/2003, Bueno 885 (HUM, UNOP), 08/VII/2003, Bueno 904 (HUM, UNOP), 19/I/2004, Bueno 911 (HUM, UNOP), 05/IV/2004, Bueno 928 (HUM, UNOP), 04/V/2004, Bueno 931, 932 (HUM, UNOP), 17/VI/2004, Bueno 940 (HUM, UNOP).

The apical view was suggestive of C.bireme Nordst. var. bireme; however, it was impossible to draw the apical view. Our cell measurements yielded values that were higher than were those reported in the literature (6.0-19.0 µm in length; 6.0-12.0 µm in width; isthmus, 3.0-5.0 µm; Prescott et al. 1981).

4. Cosmarium bireme Nordst. var. huzelii Kurt Först., Amazoniana, 2(1/2): 45, pl.14, fig. 11-12. 1969.

A cell that is 1.1 times as wide as it is long, deep median constriction, closed median sinus dilated at the apex; angular-elliptical semicell, rounded lateral margins, rounded, truncate apical margin; smooth cell wall, chloroplast = 1, pyrenoid = 1. Dimensions: 10.0-20.0 µm in length; 9.0-22.0 µm in width; isthmus, 3.0-8.2 µm.

Constancy: rare.

Distribution in the state of Paraná: Salto Caxias Reservoir Hydroelectric Power Plant (Silva & Cecy 2004); Rosana Reservoir Hydroelectric Power Plant (Felisberto & Rodrigues 2010).

Material examined: BRAZIL. Paraná: Santa Helena, São Francisco Falso River, 04/XI/2003, Bueno 888 (HUM, UNOP), 04/V/2004, Bueno 931, 936 (HUM, UNOP), 17/VI/2004, Bueno 940 (HUM, UNOP).

The apical view was suggestive of C.bireme var. huzelii; however, it was impossible to draw the apical view. The variety in question (huzelii) differs from the typical variety in that it has cells that are wider than they are long, resembling C.polygonum (Näg.) Archer var. polygonum f. rectum C. Bicudo, which has straight lateral margins. Our cell measurements yielded values that were higher than were those previously reported for C.bireme var. huzelii in the São Francisco Falso River (Silva & Cecy 2004; Felisberto & Rodrigues 2010).

5. Cosmarium clepsydra Nordst. var. clepsydra, Vidensk. Medd. Naturh Foren. Kjoibenhavn (14/15) 212. 1869.

Cells that are 1.1 times as long as they are wide or that are as long as they are wide, deep median constriction, narrow, closed median sinus dilated at the apex; subsemicircular to subtriangular semicell, slightly convex or nearly straight lateral margins; obtusely conical or generally convex apical margin; smooth cell wall, no chloroplasts, no pyrenoids; rhomboid apical view, concave lateral margins, obtuse angles. Dimensions: 20.0 µm in length; 18.3-20.0 µm in width; isthmus, 4.0-5.0 µm.

Constancy: rare.

Distribution in the state of Paraná: First record of the taxon.

Material examined: BRAZIL. Paraná: Santa Helena, São Francisco Falso River, 08/XII/2003, Bueno 906 (HUM, UNOP), 05/IV/2004, Bueno 928 (HUM, UNOP).

6. Cosmarium decoratum West & G.S. West, Trans. Linn. Soc. London, Bot., II, 5(2): 61, pl.7, fig.21. 1895.

A cell that is 1.4-1.6 times as long as it is wide, deep median constriction, slightly open sinus, tapering toward the apex and dilated at the apex; semicircular to truncate pyramidal semicell, rounded basal and apical angles, convex lateral margins, rounded apical margin; granular cell wall, hexagonally arranged series of dense granules, no chloroplasts, no pyrenoids. Dimensions: 74.0-84.0 µm in length; 48.0-58.8 µm in width; isthmus, 16.8-20.0 µm.

Constancy: rare.

Distribution in the state of Paraná: Rosana Reservoir Hydroelectric Power Plant (Felisberto & Rodrigues 2010).

Material examined: BRAZIL. Paraná: Santa Helena, São Francisco Falso River, 28/VII/03, Bueno 860 (HUM, UNOP), 04/V/2004, Bueno 935 (HUM, UNOP).

According to Felisberto & Rodrigues (2010), C.decoratum is very similar to C. logiense Bisset. However, the former is larger in length and width, features that are consistent with our findings. In addition, C. logiense can be distinguished from C.decoratum by its elliptical cells, subquadrangular shape, retuse lateral margins, and apical margin with one concavity (Prescott et al. 1981).

7. Cosmarium excavatum Nordst. var. excavatum, Vidensk. Medd. Naturh. Foren. 1869(14/15): 214. 1869(1870); 1887: pl. 3, fig. 25. 1887.

A cell that is 1.7-1.9 times as long as it is wide, shallow median constriction, excavated median sinus, rounded apex; subcircular semicell, convex, wavy apical and lateral margins; granular cell wall, granules arranged in 4-5 vertical series in the front view, chloroplast = 1, pyrenoid = 1; circular apical view. Dimensions: 26.4-30.4 µm in length, 14.0-18.4 µm in width; isthmus, 7.2-9.6 µm.

Constancy: rare.

Distribution in the state of Paraná: Rosana Reservoir Hydroelectric Power Plant (Felisberto & Rodrigues 2010).

Material examined: BRAZIL. Paraná: Santa Helena, São Francisco Falso River, 05/IV/2004, Bueno 928 (HUM, UNOP).

C.excavatum Nordst. var. excavatum is similar to C. isthmium West in terms of how the granules are arranged on the cell wall. However, the latter taxon shows larger cell size, higher density granules on the cell wall, and a deeper, more tightly closed median sinus. Our cell measurements yielded values higher than those reported by Ramos et al. (2011).

8. Cosmarium cf. galeritum Nordst. var. borgei W. Krieg. & Gerloff, Die Gattung Cosmarium 1: 108, pl. 23, fig. 2. 1962.

A cell that is 1.2 times as wide as it is long or that is as long as it is wide, deep median constriction, closed median sinus; pyramidal to trapezoidal semicell, convex lateral margins, truncate apical margin; punctate cell wall with apical thickening, chloroplast = 1, pyrenoid = 1. Dimensions: 30.0-46.7 µm in length; 26.0-45.9 µm in width; isthmus, 6.0-14.3 µm.

Constancy: rare.

Distribution in the state of Paraná: First record of the taxon.

Material examined: BRAZIL. Paraná: Santa Helena, São Francisco Falso River, 28/VII/2003, Bueno 860 (HUM, UNOP), 01/IX/2003, Bueno 871 (HUM, UNOP), 08/XII/2003, Bueno 906 (HUM, UNOP), 05/IV/2004, Bueno 926, 928 (HUM, UNOP).

Prescott et al. (1981) described C. galeritum as having chloroplasts with approximately 10 radial plates containing 2 pyrenoids or, more rarely, 1 pyrenoid, whereas Bortolini et al. (2010) described C. galeritum as having axial chloroplasts containing 2 pyrenoids. Felisberto & Rodrigues (2004) described C.galeritum var. borgei as having 2 pyrenoids but provided no information on chloroplast shape. Bicudo & Ungaretti (1986) provided no written or pictorial information on the pyrenoids in C.galeritum var. borgei. Because the remaining characteristics of the semicells in the individuals found in the present study were consistent with those described in the literature, those individuals were provisionally identified as C. galeritum var. borgei, despite having only 1 pyrenoid.

Other varieties of C.galeritum were recorded in the state: C.galeritum var. triangulare, in the Tibagi River (Bittencourt-Oliveira 1993); C.galeritum var. galeritum, in the Cascavel Municipal Lake (Bortolini et al. 2010); and C.galeritum var. subtumidum Borge, in the Rosana Reservoir Hydroelectric Power Plant (Felisberto & Rodrigues 2010). C.galeritum var. borgei is characterized by an apex that is wider than is that seen in the typical variety of the species (Bicudo & Ungaretti 1986).

Figure 2 - Click to enlarge

9. Cosmarium ginzbergeri Grönblad, Acta Societatis Scientiarum Fennicae, new series B II(6): 18, pl. VI, fig. 112. 1945.

A cell that is 1.5 times as long as it is wide, deep median constriction, linear, closed median sinus dilated at the apex; uniformly rounded, semielliptical semicell, rounded basal angles; granular cell wall, isthmus ornamented with a single series of granules, intramarginal granules arranged in a single series laterally and apically, chloroplast = 1, pyrenoid = 1. Dimensions: 122.4 µm in length; 83.6 µm in width; isthmus, 30.6 µm.

Constancy: rare.

Distribution in the state of Paraná: First record of the taxon.

Material examined: BRAZIL. Paraná: Santa Helena, São Francisco Falso River, 28/VII/2003, Bueno 860 (HUM, UNOP)

When describing C.ginzbergeri for the first time, Grönblad (1945) highlighted the great beauty of the species, which was found among material collected in the Brazilian Amazon. The author also described the lateral view as showing four series of intramarginal granules and parietal chloroplast with numerous pyrenoids. In our specimen, we found only 1 pyrenoid in one of the semicells.

10. Cosmarium laeve Rabenh. Flor. Europ. Alg. III, p. 161. 1868.; Nordst., in Nordstedt & Wittrock, Öfv. Kongl. Vet-Akad. Förhandl. 6: 29, pl. 12, fig. 4. 1876. var. laeve.

Cosmarium laeve Rabenh. var. septentrionale Wille, in Miller, Univ. Wyoming Publ. Sci. Bot. 2(6): 90, pl. 4, figs. 10-12. 1936.

A cell that is 1.5 times as long as it is wide, deep median constriction, linear, closed median sinus dilated at the apex; slightly angular, semielliptical to subpyramidal semicell, flat, narrow apex that can range in shape from slightly retuse to notched; finely punctate cell wall, chloroplast = 1, pyrenoid = 1. Dimensions: 17.8-24.5 µm in length; 12.0-16.3 µm in width; isthmus, 4.1-8.0 µm.

Constancy: sporadic.

Distribution in the state of Paraná: Salto Caxias Reservoir Hydroelectric Power Plant (Silva & Cecy 2004); Salto do Vau Reservoir Hydroelectric Power Plant (Felisberto & Rodrigues 2008); Rosana Reservoir Hydroelectric Power Plant (Felisberto & Rodrigues 2010).

Material examined: BRAZIL. Paraná: Santa Helena, São Francisco Falso River, 28/VII/2003, Bueno 861 (HUM, UNOP), 01/IX/2003, Bueno 870, 872 (HUM, UNOP), 06/X/2003, Bueno 883, 885 (HUM, UNOP) 4/XI/2003, Bueno 888 (HUM, UNOP), 08/XII/2003, Bueno 904, 905 (HUM, UNOP), 03-II-2004, Bueno 912, 913 (HUM, UNOP), 10/III/2004, Bueno 920 (HUM, UNOP), 05/IV/2004, Bueno 924 (HUM, UNOP), 17/VI/2004, Bueno 938 (HUM, UNOP)

C.laeve Rabenhorst resembles C. montrealense Croasdale, which was first described by Croasdale and which can be distinguished from C.laeve Rabenhorst by its widely rounded apex and smooth cell wall (Silva & Cecy 2004). Although the length-to-width ratio found in the present study was higher than was that found by Silva & Cecy (2004), it is consistent with that found by Prescott et al. (1981). Felisberto & Rodrigues (2004) found wider individuals.

11. Cosmarium moniliforme (Turpin) Ralfs, Brit. Desm., 107, pl. 17, fig. 6. 1848. var. moniliforme.

Tessarthronia moniliformis Turpin, Dic. Sci. Nat., pl. 7, fig. 1. 1820.

A cell that is 1.4-1.8 times as long as it is wide, deep median constriction, acute, open median sinus; circular semicell, convex and smooth lateral and apical margins; smooth cell wall with apical thickening, chloroplast = 1 (with 6-7 lobes), pyrenoid = 1; circular apical view. Dimensions: 23.1-32.0 µm in length; 16.8-18 µm in width; isthmus, 6.3-8.0 µm.

Constancy: rare.

Distribution in the state of Paraná: Tibagi River (Bittencourt-Oliveira 1993);Salto Caxias Reservoir Hydroelectric Power Plant (Silva & Cecy 2004)

Material examined: BRAZIL. Paraná: Santa Helena, São Francisco Falso River, 28/VII/2003, Bueno 859 (HUM, UNOP), 01/IX/2003, Bueno 871 (HUM, UNOP), 06/X/2003, Bueno 882 (HUM, UNOP), 04/XI/2003, Bueno 890 (HUM, UNOP), 19/I/2004, Bueno 908 (HUM, UNOP).

C.moniliforme Ralfs closely resembles C. contractum Kirchner. The latter can be distinguished from the former by its widely elliptical cell and elliptical apical view (Prescott et al. 1981).

12. Cosmarium norimbergense Reinsch var. norimbergense, Acta Societatis Senckenbergensis, 6: 117, pl. 22-A-IV, fig. 1-11. 1867.

A cell that is 1.1 times as long as it is wide, deep median constriction, narrow, closed median sinus dilated at the apex; vertically rectangular semicell, rounded, rectangular basal angles, lateral margin with one concavity, retuse to slightly convex apical margin; smooth cell wall, chloroplast = 1, pyrenoid = 1. Dimensions: 14.0 µm in length; 12.7 µm in width; isthmus, 6.3 µm.

Constancy: rare.

Distribution in the state of Paraná: First record of the taxon.

Material examined: BRAZIL. Paraná: Santa Helena, São Francisco Falso River, 28/VII/2003, Bueno 859 (HUM, UNOP).

In the state of Paraná, C.norimbergense var. depressum has been found in the Rosana Reservoir Hydroelectric Power Plant (Felisberto & Rodrigues 2010).

13. Cosmarium portianum Archer, Proc. Dubl. Nat. Hist. Soc. 3: 49, pl. 1, figs. 8, 9; Quart. Jour. Microsc. Sci. 8: 235. pl. 11. 1860. var. portianum

A cell that is 1.2-1.3 times as long as it is wide, deep median constriction, open median sinus; reniform to rectangular semicell; granular cell wall (20-23 granules being visible at the edge of the semicell), granules arranged in longitudinal series, chloroplast = 1, pyrenoids = 2; oblong lateral view. Dimensions: 39.0-49.0 µm in length; 33.0-38.8 µm in width; isthmus, 11.2-16.8 µm.

Constancy: sporadic.

Distribution in the state of Paraná: Rosana Reservoir Hydroelectric Power Plant (Felisberto & Rodrigues 2010).

Material examined: BRAZIL. Paraná: Santa Helena, São Francisco Falso River, 01-VII-2003, Bueno 858 (HUM, UNOP), 28/VII/2003, Bueno 861, 863 (HUM, UNOP), 01/IX/2003, Bueno 871, 873, 874 (HUM, UNOP), 04/XI/2003, Bueno 888, 890 (HUM, UNOP), 08/XII/2003, Bueno 903, 904 (HUM, UNOP), 05/IV/2004, Bueno 925 (HUM, UNOP).

Our cell measurements yielded values that were higher than were those reported in the literature (Prescott et al. 1981; Rodrigues & Bicudo 2004).

14. Cosmarium protractum (Nägeli) De Bary var. protractum, Untersuch. Conjugaten: 72. 1858.; G. West & W. West, Monogr. III, p. 181, pl. 82, fig. 8; pl. 94, figs. 4-5.

Euastrum protractum Nägeli, Gatt. Einzell. Alg.: 119, pl. VII, A, fig. 4. 1849.

A cell that is 1.1 times as wide as it is long, deep median constriction, open median sinus that is slightly closed in the first portion and dilated at the apex; 3-lobed semicell, subrectangular incision between the apical lobe and each lateral lobe, rounded and narrow lateral lobes, prominent apical lobe, rounded apical angles, retuse apical margin; granular cell wall, granules arranged in oblique, decussate series and becoming smaller as they reach the central bulge, where they are arranged in rings; chloroplast = 1, pyrenoids = 2. Dimensions: 56.0 µm in length; 50.0 µm in width; isthmus, 12.0 µm.

Constancy: rare.

Distribution in the state of Paraná: First record of the taxon.

Material examined: BRAZIL. Paraná: Santa Helena, São Francisco Falso River, 10/III/2004, Bueno 919 (HUM, UNOP).

Prescott et al. (1981) and Felisberto & Rodrigues (2004) discussed the differences between C.protractum and C. ornatum, the former showing a markedly prominent apex in which an apical lobe is formed and the latter being reniform to subreniform and similar to C. protractum in terms of cell wall ornamentation, with a slightly elevated but little prominent apex. Cell measurements performed by Cecy et al. (1997) and Felisberto & Rodrigues (2004) yielded values that were lower than were those found in the present study.

15. Cosmarium rectangulare var. hexagonum (Elfving) West & G.S. West, Monogr. III, 56, pl. 70, fig. 4. 1908.

Cosmarium hexagonum Elfving, Acta Soc. Fauna Flora Fennica 2(2): 12, pl. 1, fig. 8. 1881.

A cell that is 1.1-1.2 times as long as it is wide, deep median constriction, closed median sinus dilated at the apex; subhexagonal semicell, straight, truncate apex; finely punctate cell wall, chloroplast = 1, pyrenoid = 1. Dimensions: 15.2-26.5 µm in length; 14.3-22.4 µm in width; isthmus, 4.0-8.0 µm.

Constancy: sporadic.

Distribution in the state of Paraná: First record of the taxon.

Material examined: BRAZIL. Paraná: Santa Helena, São Francisco Falso River, 01/VII/2003, Bueno 855 (HUM, UNOP), 28/VII/2003, Bueno 863 (HUM, UNOP), 01/IX/2003, Bueno 870, 871, 874 (HUM, UNOP), 04/XI/2003, Bueno 888, 932 (HUM, UNOP), 17/VI/2004, Bueno 938, 940 (HUM, UNOP).

C.rectangulare var. hexagonum differs from the typical variety in that the cells are smaller in size and nearly as long as they are wide, as well as being slightly flattened. Our cell measurements yielded values that were lower than were those found by Prescott et al. (1981) and slightly higher than were those found by Sophia et al. (2005) but consistent with most of those reported by Lopes & Bicudo (2003; 16-21.2 µm in length; 14.0-20 µm in width; isthmus, 5.6 µm).

16. Cosmarium regnesi Reinsch var.regnesi, Act. Soc. Senckenberg 6: 116. 1867.

A cell that is 1.1 times as wide as it is long, deep median constriction, excavated, open median sinus, rounded apex; subrectangular semicell, jagged lateral and apical margins; smooth cell wall, no chloroplasts, no pyrenoids. Dimensions: 12.8 µm in length; 14.4 µm in width; isthmus, 4.0 µm.

Constancy: rare.

Distribution in the state of Paraná: Salto do Vau Reservoir (Felisberto & Rodrigues 2008); Cascavel Municipal Lake (Bortolini et al. 2010); Rosana Reservoir Hydroelectric Power Plant (Felisberto & Rodrigues 2010).

Material examined: BRAZIL. Paraná: Santa Helena, São Francisco Falso River, 05/IV/2004, Bueno 928 (HUM, UNOP).

Prescott et al. (1981) identified as C.regnesi var. montanum those individuals that were larger in size than were those of the typical variety (6.0-10.0 µm in length; 6.2-9.5 µm in width; isthmus, 3.0-5.5 µm). We found only one such specimen in the present study. Because the remaining characteristics of that specimen were consistent with those of the typical variety, we chose to identify it as C.regnesi var. regnesi.

17. Cosmarium reniforme (Ralfs) W. Archer, J. Bot. 12: 92. 1874.

Cosmarium margaritiferum Menegh. var. reniformis Ralfs, Brit. Desm., 100, pl. 16, fig. 2a. 1848.

A cell that is 1.1-1.3 times as long as it is wide, deep median constriction, closed median sinus dilated at the apex; reniform semicell, convex lateral margins, straight or slightly convex apical margins; granular cell wall, 33 visible granules at the edge of the semicell, chloroplast = 1, pyrenoids = 2; oblong-elliptical apical view. Dimensions: 32-51 µm in length; 30.0-40.8 µm in width; isthmus 8.0-12.0 µm.

Constancy: common.

Distribution in the state of Paraná: Rosana Reservoir Hydroelectric Power Plant (Felisberto & Rodrigues 2010).

Material examined: BRAZIL. Paraná: Santa Helena, São Francisco Falso River, 01/VII/2003, Bueno 858 (HUM, UNOP), 28/VII/2003, Bueno 859, 861, 863 (HUM, UNOP), 01/IX/2003, Bueno 872, 873, 874 (HUM, UNOP), 06/X/2003, Bueno 882, 883 (HUM, UNOP), 08/XII/2003, Bueno 904, 906 (HUM, UNOP), 19/I/2004, Bueno 911 (HUM, UNOP), 03/II/2004, Bueno 912 (HUM, UNOP), 10/III/2004, Bueno 921 (HUM, UNOP), 05/IV/2004, Bueno 924, 925, 926 (HUM, UNOP), 04/V/2004, Bueno 932 (HUM, UNOP), 17/VI/2004, Bueno 936, 940 (HUM, UNOP).

Our cell measurements yielded values that were lower than were those reported by Bicudo et al. (1992) but comparable to those reported by Sophia et al. (2005).

18. Cosmarium sp.

A cell that is 1.1 times as long as it is wide, deep median constriction, narrow, closed median sinus dilated at the apex; oblong and trapeziform semicell, smooth, convex lateral margins, retuse apical margin; smooth cell wall with apical thickening, chloroplast = 1, pyrenoids = 2. Dimensions: 12.8-23.2 µm in length; 11.2-21.6 µm in width; isthmus 3.2-4.4 µm.

Constancy: rare.

Distribution in the state of Paraná: First record of the taxon.

Material examined: BRAZIL. Paraná: Santa Helena, São Francisco Falso River, 01/VII/2003, Bueno 855 (HUM, UNOP), 03/II/2004, Bueno 916 (HUM, UNOP), 10/III/2004, Bueno 921 (HUM, UNOP), 04/V/2004, Bueno 932 (HUM, UNOP).

Those individuals that showed well-defined angular margins, 2 pyrenoids, and apical cell wall thickening (and that were therefore similar to C.bireme) were separated and were provisionally identified at the genus level as Cosmarium sp.

July of 2003 was the month that was richest in Cosmarium spp. (91.7%). The period between January and March of 2004 was the least rich in Cosmarium spp. (25-41.7%). However, April of 2004 was a month that was again rich in Cosmarium spp. (83.3%). Regarding the sampling stations along the São Francisco Falso River, Stations 5 and 2 were the richest in Cosmarium spp. (Cosmarium spp. having accounted for 83.3% and 66.7%, respectively, of all taxa found), whereas Station 4 was the least rich in Cosmarium spp. (16.6%). C.laeve var. laeve e C. reniforme var. reniforme were the only taxa that were found at all sampling stations.

Those spatiotemporal variations in the proportion of Cosmarium spp. among the phytoplankton community in the São Francisco Falso River were probably related to certain environmental characteristics, which contributed to the presence of those algae (and desmids in general) in certain places (Biolo et al. 2008; Menezes et al. 2011). Such characteristics possibly consist of variations in the following limnological parameters: the trophic status of the environment, which can range from oligotrophic to mesotrophic (Silva et al. 2010); water transparency and luminosity, which were found to be particularly high at Stations 2, 3, and 5 in the present study; and the presence of aquatic macrophytes (Brook 1981; Coesel 1982; Bicudo & Ungaretti 1986; Felisberto & Rodrigues 2005; Melo et al. 2005), metaphytic and periphytic forms breaking off the substrate contributing to an increase in the amount of desmids in the phytoplankton community (Taniguchi et al. 2000; Rodrigues et al. 2003). Despite the characteristics of the lotic environment, including greater water flow, unidirectional flow, and allochthonous influence (especially from the Itaipu Reservoir and the region around the river, due to agricultural activities and tourism), the characteristics of the river shore provided a variable environment that allowed the development of desmids, principally Cosmarium spp., which are tolerant to variations in limnological conditions (Gough & Woelkerling 1976).

Cosmarium are algae that have a cosmopolitan distribution, specifically in tropical regions (Bicudo & Menezes 2006). Biolo et al. (2008) inventoried the desmids in the same tributary of the Itaipu Reservoir and found Cosmarium to be the most species-rich genus, the authors having identified a total of 41 species and 12 genera. The finding of Biolo et al. (2008) is consistent with those of Bicudo & Ungaretti (1986), Bicudo et al. (1992), Cecy et al. (1997), Lopes & Bicudo (2003), Silva & Cecy (2004), Felisberto & Rodrigues (2004), Felisberto & Rodrigues (2008), Ramos et al. (2011), and Menezes et al. (2011).

A total of 23 taxa found in the São Francisco Falso River between 2003 and 2004 were provisionally identified as Cosmarium spp. (Menezes et al. 2011). A new analysis resulted in a substantial number of species being identified, the present study having contributed to the addition of 18 Cosmarium taxa to the Paraná state desmid flora database.

Of the 18 Cosmarium taxa identified in the present study-1 taxon not having been identified at the species level-8 were new records for the state of Paraná. This underscores the importance of surveying the biodiversity of algae in the state. Despite the studies conducted so far, taxonomic and ecological data on the desmid flora in the state of Paraná remain scarce. Further studies investigating algal communities (particularly desmids) in various aquatic environments and habitats are needed in order to increase our understanding of the biodiversity in the state and therefore contribute to biodiversity conservation.

Figure 3 - Click to enlarge

Acknowledgments

This study received financial support from the Programa Institucional de Bolsas de Iniciação Científica (PIBIC, Institutional Program for Scientific Initiation Scholarships) of the Brazilian Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, National Council for Scientific and Technological Development) and the Universidade Estadual do Oeste do Paraná (UNIOESTE, State University of Western Paraná), located in the city of Cascavel, Brazil. We would like to thank the Periphyton Laboratory of the State University at Maringá Núcleo de Pesquisas em Limnologia, Ictiologia e Aquicultura (NUPELIA, Center for Research on Limnology, Ichthyology, and Aquaculture), located in the city of Maringá, Brazil, for the technical and scientific support.

Submitted: 6 April, 2011

Accepted: 13 August, 2012

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Publication Dates

• Publication in this collection
  08 May 2013
• Date of issue
  Mar 2013

History

• Received
  06 Apr 2011
• Accepted
  13 Aug 2012