*Dirección para correspondencia:

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Abstract

The genus Nupela comprises ca. 50 species that generally have a distribution restricted by bioclimatic frontiers. As part of an integrated analysis of the diatom flora of Colombia, in this study we focused our interest on the genus Nupela from lowland waters. Periphyton samples were collected from 150 sites of lotic water bodies in Colombia, taking into account hidrogeomorfological variability. In each sampling station, periphyton samples were obtained by scraping, and temperature, pH, dissolved oxygen and conductivity variables were measured. Samples were processed by both light microscopy (LM; Carl Zeiss Axio Scope.A1) and scanning electron microscopy (SEM; FEI-Quanta 450 and a Jeol JSM-6360 LV). The genus Nupela was found in 28 sites. Five taxa were identified, described and illustrated from tropical or subtropical environments: N. lesothensis, N. praecipua y N. subpallavicinii; these were new records for Colombia, and N. acaciensis and N. catatumbensis two new species for science. N. acaciensis is characterized by raphe branches of both valves equally long combined with cymbelloid symmetry, striae built by 2 transapically elongated areolae that delimit a longitudinal line at each hemivalve. N. catatumbensis is characterized by the presence of a well developed raphe in both valves; valves lanceolate with subcapitated to capitated ends and cymbelloid symmetry, striae built by 3-4 transapically elongated areolae, interestriae elevated as transapical ribs and internal proximal raphe ends hook-shaped. The genus Nupela was widely distributed in the studied basins but showed different distribution patterns: N. acaciensis and N. subpallavicini had a restricted distribution, while N. catatumbensis, N. lesothensis and N. praecipua had a wider distribution, and were collected in sites with significant variations in their ecomorphology, altitude, temperature, pH and electrolyte content.

Key words: Nupela, Nupela acaciensis, Nupela catatumbensis, diatoms, Bacillariophyceae, neotropics, Colombia.

Resumen

El género Nupela comprende alrededor de 50 especies que tienen en general una distribución restringida por fronteras bioclimáticas. Como parte de un estudio integral de la flora diatomológica de Colombia, en este trabajo focalizamos nuestro interés en el género Nupela en cuerpos de agua de tierras bajas. Muestras de perifiton fueron recolectadas en 150 sitios en cuerpos de agua lóticos seleccionados por su variabilidad hidrogeomorfológica. En cada estación de muestreo se obtuvieron muestras por raspado de varios sustratos,  y  adicionalmente  se  registraron:  temperatura, pH, oxígeno disuelto y conductividad. Las muestras fueron procesadas para su análisis con microscopio óptico (MO, Carl  Zeiss Axio  Scope. A1)  y  de  barrido  (MEB;  FEI- Quanta 450 and a Jeol JSM-6360 LV). El género Nupela fue hallado en 28 sitios. Cinco especies fueron identificadas, descritas e ilustradas, tres de ellas: N. lesothensis, N. praecipua y N. subpallavicinii fueron descritas para ambientes tropicales y subtropicales y representan nuevas citas para Colombia. Además fueron descritas N. acaciensis y N. catatumbensis, dos especies nuevas para la ciencia. N. acaciensis se caracteriza por poseer rafe desarrollado en ambas valvas, simetría cymbelloide, estrías formadas por dos aréolas transapicalmente alargadas que definen una línea  longitudinal  en  cada  hemivalva.  N.  catatumbensis se caracteriza poseer rafe desarrollado en ambas valvas. Valvas lanceoladas con extremos subcapitados a capitados y simetría cymbelloide. Estrías formadas por 3-4 aréolas transapicalmente alargadas, interestrías elevadas a modo de costillas transapicales y extremos proximales internos del rafe en forma de gancho. El género Nupela estuvo ampliamente representado en el área de estudio, sin embargo, las especies  mostraron  diferentes  patrones  de  distribución. N.  acaciensis  y  N.  subpallavicini  estuvieron  presentes en una única cuenca, mientras que N. catatumbensis, N. lesothensis y N. praecipua presentaron una distribución más amplia, y fueron recolectadas en sitios con variaciones significativas en ecomorfología, altitud, temperatura, pH y contenido electrolítico.

Palabras clave: Nupela, Nupela acaciensis, Nupela catatumbensis, diatomeas, Bacillariophyceae, neotropical, Colombia.

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The genus Nupela was erected by Vyverman & Compère in 1991, based on materials collected in acid waters at Mont Giluwe, New Guinea. The most important character that defines the genus is the areolae structure, transapically elongated, with external big foramina and internal hymen perforated at the centre. Each stria is built by few areolae and presents a hyaline marginal area. Valves are sometimes transapically curved (cymbelloid frustules) and sometimes they are curved on the pervalvaraxis combined with the presence of rudimentary or shortened raphe in one valve (achnanthoid frustules).

Although the genus was erected on the basis of N. giluwensis Vyverman & Compère, after-wards Lange-Bertalot (1993) and Lange-Bertalot & Moser (1994) described new species and transferred other taxa from the genera Achnanthes, Anomoeoneis, Navicula, Rhoicosphenia and Stauroneis to Nupela. Later other authors studied the genus, transfered more species and described new taxa (Monnier, Lange-Bertalot, & Bertrand, 2003; Potapova, Ponader, Lowe, Clason, & Bahls, 2003; Siver, Hamilton, & Morales, 2007; Kulikovskiy, Lange-Bertalot, & Witkowski, 2009; Wojtal, 2009; Siver, Wolfe, & Edlund, 2010; Potapova, 2013). In the original description heterovalvar frustules are not mentioned.  Lange-Bertalot  &  Moser  (1994) and Potapova et al. (2003) described heterovalvar species, but did not redefine the genus. Monnier et al. (2003) considered that the presence of one valve with reduced raphe is a character of Nupela and pointed out that it is a character defined by practice.

At present, the genus Nupela comprises around 50 species (Wotjal, 2009; Siver et al., 2010; Fourtanier & Kociolek, 2011; Potapova, 2013). Since its initial discovery in high elevation ponds of New Guinea, Nupela has been reported in neutral pH, low conductivity waters across Europe, South America, North America, Asia and Africa (Spaulding & Edlund, 2008).

In Colombia, three species of the genus were mentioned (Montoya-Moreno, pers. com.): Nupela pallavicinii (Krasske) Lange- Bertalot in Lange-Bertalot & Moser (1994) described at El Boquerón (Bogotá); Donato (2001) mentioned N. paludigena Lange-Berta- lot at Lago Buitrago (Cundinamarca) and Lago Santiago (Cauca) and Vélez & Hooghiemstra (2005) mentioned N. tenuistriata (Hustedt) Metzeltin & Lange-Bertalot at Lago Las Margaritas, Lago Carimagua (Meta).

The aim of this paper is to describe and illustrate Nupela species collected in lowland waters of the Eastern part of the country, as part of the study of benthic diatoms from different Colombian basins held by the Laboratorio de Biotecnología del Instituto Colombiano del Petróleo.

Material and Methods

Samples were collected from the sampling sites where Ecopetrol S.A. helds physical, chemical and biological assessments, according to requirements of the environmental authorities  in  each  region.  A  total  of  150 samples were collected from selected sites, taking into account hidrogeomorphological variability. The study area comprised the Amazon region, the interandean valleys, the Andean region,  the  “Llanos  Orientales”,  high  plains and the Catatumbo. These regions are contrasting in their hydrogeomorphology. The rivers in the foothills of the Andes (Magdalena Alto) have beds of blocks, stones, and gravel. The water flow is turbulent and forms cascades and rapids. In lowlands of Catatumbo and the interandean valleys (Magdalena Medio) the streams are broad and beds have soft sediments, silt and/or  clay;  accumulations  of  woody  debris are frequent and the water flow is smooth. For the high plains rivers (Meta and Cravo Sur and Tomo basins), the stream bed consists of soft sediments, sand and/or fine organic matter, leaf packs are formed frequently. The streams of the Putumayo and Caquetá basins here studied are small, with rocky substrates and coverage dominated by trees, well preserved (Ovalle, Plata-Díaz, Reyes, Pimienta, & Riss, 2013).

For each site, information about water temperature, pH, conductivity and dissolved oxygen was also obtained. Phytoplankton samples were collected by brushing the surface of a variable number of substrates delimited with a 25cm² acrylic frame, and were preserved with 1:1 Transeau solution. Samples were treated to eliminate organic matter following the method described  in  CEN/TC  230  (2003).  Posteriorly, they were analysed using two microscopic techniques. Samples for light microscopy (LM) were mounted in Naphrax®, and for scanning electron  microscopy  (SEM)  on  glass  stubs and then coated with gold-palladium in a FEI-Quanta  450  microscope  of  the  Laboratorio de Microscopía of Instituto Colombiano del Petróleo. Analyses were held with a LM Carl Zeiss Axio Scope.A1 and with FEI-Quanta 450 SEM and a Jeol JSM-6360 LV SEM at the Servicio de Microscopía Electrónica de la Facultad de Ciencias Naturales y Museo de La Plata. Uncleaned and cleaned subsamples and permanent slides were deposited at the Laboratorio de Biotecnología of Instituto Colombiano del Petróleo (Piedecuesta, Colombia).

The terminology used is the one proposed by Anonymous (1975), Ross et al. (1979) and Barber & Haworth (1981).

The samples for in Nupela species were found are listed bellow:

200418858: Abejas Stream. 04/27/2009. Collector: Guillermo Alemán.

200420431: Bilibil Stream. 05/06/2009. Collector: Guillermo Alemán.

200527650: Bilibil Stream. 05/14/2010. Collector: Guillermo Alemán.

200468182: Bilibil Stream. 10/26/2009. Collector: Guillermo Alemán.

200423382: La Pita Stream .05/19/2009. Collector: Guillermo Alemán.

200424905: La Hormiga Stream. 05/20/2009. Collector: Guillermo Alemán.

200432427: Zancudo Stream. Upstream. 06/25/2009. Collector: Guillermo Alemán.

200432428: Zancudo Stream. Downstream. 06/25/2009. Collector: Guillermo Alemán.

200476086: Zancudo Stream. 11/25/2009. Collector: Guillermo Alemán.

200436356: Fortalecillas River. 07/08/2009. Collector: Giovani Espinel.

200436357: Fortalecillas River. Downstream. 07/08/2009. Collector: Giovani Espinel.

200436532. El Aceite Stream. 07/09/2009. Collector: Giovani Espinel.

200438022: La Azul Stream, upstream. 07/17/2009. Collector: Giovani Espinel.

200438023: La Azul Stream. downstream. 07/17/2009. Collector: Giovani Espinel.

200439228: Veradita Stream. 07/20/2009. Collector: Giovani Espinel.

200439233: El Boral Stream. 07/23/2009. Collector: Jaime Orejarena.

200440779: Agua Clara River. 07/28/2009. Collector: Giovani Espinel.

200441028: Tate River. 07/30/2009. Collector: Hernando Ovalle.

200446180: Cravo Norte River. 08/13/2009. Collector: Giovani Espinel.

200454443: La Cortezana Stream. 09/09/2009. Collector: Hernando Ovalle.

200461115: Grande Stream. 09/26/2009. Collector: Guillermo Alemán.

200476922: Grande Stream. 11/26/2009. Collector: Guillermo Alemán.

200462477: La Cira Stream. 09/29/2009. Collector: Hernando Ovalle.

200463448: El Zarzal Stream. 10/07/2009. Collector: Fredy Yepes.

200465803: Palagua Stream. 10/14/2009. Collector: Fredy Yepes.

200469503: Pamplonita Stream (San Rafael Bridge). 10/29/2009. Collector: Guillermo Alemán.

200470667: Magdalena River, downstream. 11/05/2009. Collector: Fredy Yepes.

200473754: Gavilan Stream after confluence with Negro Stream. 11/16/2009. Collector: Jaime Orejarena.

200476490: Agua Blanca Stream. 11/21/2009. Collector: Giovani Espinel.

200476494: No1 Stream. 11/21/2009. Collector: Giovani Espinel.

200484429: El Diamante Stream. 12/19/2009. Collector: Fredy Yepes.

200568525: Santa Rita Stream. 0/10/2021: Collector: Fredy Yepes.

200570641: Venado Stream. 10/11/2003. Collector: Guillermo Alemán.

200640901: Blanca stream. 11/07/2001. Collector: Giovani Espinel.

200642952: Jarama Stream 11/07/2007. Collector: Hernando Ovalle.

Results

The genus Nupela was present at 28 sites located in streams and rivers from eight basins of  different  regions  of  the  country:  Magda- lena Alto and Medio, Catatumbo, Cravo Sur, Putumayo, Caquetá, Tomo and Meta (Table 1). In this paper five species were described and illustrated:  two  of  them  are  reported  here as  new  species  and  three  are  new  records for Colombia.


Description: Valves lanceolated with subrostrated to subcapitated ends, slightly asymmetric with respect to the apical axis (cymbelloid symmetry). Voigt Fault evident at the dorsal side of the valve. Striae built by two transapically elongated areolae that delimit a hyaline longitudinal line, to the ends the striae are composed only by one areola. Striae parallel to slightly radial at valve centre, parallel to the apices. Valve mantle with a row of are-olae continuous at the valve poles. Raphe well developed  at both  valves. External  proximal raphe ends pore like, slightly expanded; terminal fissures hook-like and bent to the secondary valve side. Internal proximal raphe ends also hooked to the secondary side, central nodule notorious; distal ends straight finishing in small helictoglossae. Central area irregular, quadrangular at the primary valve side, missing the most internal areolae of the 2-3 central striae, at the secondary side more rounded due to the smaller internal areolae of the 2-3 central striae, sometimes one is missing.

Morphometric data: length: 5-12.5µm; width: 3-3.5µm; l/w: 3.9-5.6; 44-54 striae/10µm; 2 areolae/stria.

Type   material:   Holotype   (Iconotype): specimen  illustrated  in  Fig.  1C;  Isotype: 200640901.

Type  locality:  04°  10’ 57.00’’N-73°  37’ 31.70’’  W,  Blanca  Stream,  Acacias,  Meta Department, Llanos Orientales, Colombia.

Etymology: the specific epithet refers to the name of municipality of the type locality.

Distribution: only collected at the type locality.

Remaks: the closest taxon is N. schoemaniana Lange-Bertalot, from which it differs in having striae composed by 3-4 areolae, the shape of the central area and internal straight proximal raphe ends (Table 2). Other similar taxon is N. florideana Metzeltin & Lange- Bertalot that differs in striae composed by 3-4 areolae, stauroid central area and straight internal proximal raphe ends. N. acaciensis also resembles N. giluwensis Vyverman & Compére that differs in valve outline thinner with broadly capitated ends. Besides, at the dorsal side the latter has 2 hyaline longitudinal lines at valve centre that are reduced to one towards the ends and internal proximal raphe ends T-shaped.

This species was collected in samples with DO 7.4mg/L, conductivity 10.3µS/cm, pH 5, temperature 21.3ºC and altitude 370m.a.s.l.


Description: Valves lanceolate with sub- capitated to capitated ends, slightly asymmetrical in relation to the apical axis (cymbelloid symmetry). Voigt Fault conspicuous, on the dorsal side of the valve. Raphe filiform straight, external proximal ends simple, terminal fis- sures question mark-like, curved to the dorsal side. Striae radial and parallel towards the api- ces. Striae uniseriate; areolae with external big foramina and internal hymen perforated at the centre, interestriae rib-like. Axial area narrow to the apices, broaden and with irregular limits to the valve centre, central area wide, irregular, more developed on the dorsal side, where the striae are composed of 1-2 areolae less and sometimes 1-2 striae are missing and the central area reaches the valve margin. Axial and central area more silicified. In internal view, the raphe is filiform and straight, proximal ends hook-like, curved to the dorsal side; distal ends finish in small helictoglossae. Valve mantle with a row of elongated areolae interrupted at the poles at the level of the terminal fissure.

Morphometric data: length: 12-20µm; width: 3.5-4.5µm; l/w: 3-4.6; 44-51 striae/10µm; 3-4 areolae/stria.

Type material: Holotype (Iconotype): specimen illustrated in fig. 2D. Isotype: 200432427.

Type locality: 08° 12’ 47.30’’ N-72° 26’ 50.1’’ W. Zancudo Stream, Río Zulia Basin, Catatumbo, Colombia.

Etymology:  the  specific  epithet  refers to  Catatumbo,  the  region  were  the  species was found.

Distribution: the species is widely distributed  in  the  study  area,  at  the  Catatumbo,  Meta  River,  Caquetá  River,  Magdalena Alto and Medio River and Tomo River basins.  200432427, 200432428,  200476086, 200570641,       200439228,       200438022, 200454443,       200476494,       200476922, 200473754, 200484429 (Table 2).

Remarks: the closest species is Nupela encyonopsis Metzeltin & Lange-Bertalot, both species have costa like interstriae. Nevertheless, this species differs from N. catatumbensis in the shape of the central and axial areas, poorly  developed  and  with  regular  bounderies, in the number of areolae per striae and in the shape of the external proximal raphe ends pore-like (Table 3). Other similar species is N. brachysiroides  Lange-Bertalot  that  differs  in the presence of a sinuous line sunken at both sides of the central and axial areas, besides it differs in the straight external proximal raphe ends and in the lower striae density and number of areolae per striae (Table 3).

This species was collected in samples with DO 5.1-7.6mg/L, conductivity 3.6-748µS/cm, pH 5.2-7.9, temperature 21.1-29.1ºC and altitude 97-575m.a.s.l.


Basionym: Rhoicosphenia lesothensis Schoeman (Schoeman & Archibald, 1976-1980).

Type locality: Spring in the Berea district of Lesotho.

Valves lanceolate with rostrate ends, slightly transapically asymmetrical. One valve has a well-developed raphe (DRV) and the other with reduced raphe branches to approximately half of its full length (VRR). Voigt Fault conspicuous. DRV: raphe filiform sligthly sinuous, internal proximal  ends  straight,  distal  ends  finish  in small helictoglosae. Striae radial at most of the valve extension, parallel and convergent at the ends. Axial area narrow at the ends widening to the valve centre where it merges with the wide irregular central area. VRR: it differs from the other valve in the short raphe fissures, externally it presents irregular depressions at the hyaline central area. One row of elongated areolae at valve mantle, interrupted at the apices.

Morphometric data: length: 9-12µm; width: 3-3.5µm;  l/w:  3-3.6µm;  38-46  striae/10µm; 50-74 areolae/10µm.

Distribution  in  Colombia:  it  is  recorded  for  the  first  time  in  the  country  in  different  basins  with  significant  variations  in their ecomorphology and electrolyte content. Samples 200570641, 200527650, 200418858, 200469503,       200436532,       200438023, 200440779,       200446180,       200454443, 200465803, 200463448, 200441028 (Table 2).

Remarks: this species was collected in samples   with   DO   1-8.6mg/L,   conductiv- ity 13.5-302.5µS/cm, pH 6.0-8.3, temperature 21.1-30.6ºC and altitude 70-542m.a.s.l.


Basionym: Achnanthes praecipua Reichardt (Reichardt, 1988)

Type locality: Custepec River, México.

Valves  broadly  lanceolate  with  obtuse ends. Achnanthoid  frustules,  heterovalvar. A valve  with  complete  raphe  (VDR)  and  the other with rudimentary raphe branches (VRR). Voigt Fault inconspicuous. VDR: raphe filiform straight, internally proximal ends simple and the distal ends terminated in small helictoglossae. Axial area in internal view and central nodule prominent. Striae radial throughout the valve. Central area unmarked, wide axial area with irregular boundaries. VRR, raphe reduced to a small helictoglossa, “ghost” full raphe, sternum internally elevated. A row of elongated areolae on the mantle interrupted at the apices.

Morphometric data: length: 8-13.5µm; width: 4-5µm; l/w: 2-2.8µm; 30-39 striae/10µm; 35-43 areolas/10µm.

Distribution in Colombia: it is recorded for the first time in the country in a high variety of habitats from an ecomorphological point of view. Found in samples

200468182, 200568525, 200642952, 200424905 200527650, 200420431, 200423382, 200424905, 200436357, 200436356, 200436532, 200438023,  200438022, 200439228, 200461115, 200462477, 200476490, 200476494, 200470667, 200439233 (Table 2).

Remarks: this species was collected in samples  with  DO  3.6-8.6mg/L,  conductivity
3.7-649µS/cm, pH 5.1-8.3, temperature 22.6- 30.1ºC and altitude 69-575m.a.s.l.


Type  locality:  river  of  black  waters  in Tepui Avayan, Venezuela.

Valves broadly lanceolate with capitate ends. Both valves with developed raphe, slightly asymmetric with respect to the transapical axis, frustules curved in girdle view. Achnanthoid symmetry, one valve face concave and the  other  convexe. Voigt  Fault  sligthly  conspicuous. Secondary valve margin more con- vex than the primary margin. Raphe filiform straight, external proximal raphe ends pore- like, slightly expanded, distal ends curved towards the secondary valve side; internally proximal raphe ends hook-shaped bent towards the  secondary  side  of  the  valve  and  distal ends terminated in small helictoglossae. Striae radial throughout the valve. Axial area tapers towards the apex, and gently broadens towards the centre; central area asymmetric rounded at the primary side bounded by shorter striae, at the secondary side it extends up to the margin. Interstriae prominent in external view. A row of elongated areolae on the valve mantle, interrupted at the apices and at the fascia on the secondary margin.

Morphometric data: length: 10-17µm; width: 4-5.5µm; l/w: 2.5-3µm; 37-48 striae/10µm; 28-37 areolae/10µm.

Distribution  in  Colombia:  it  is  recorded for the first time in the country. Found only in sample 200640901 (Table 2).

Remarks:   this   species   was   collected in  samples  with  DO  7.4mg/L,  conductivity 10.3µS/cm, pH 5, temperature 21.3ºC and altitude 370m.a.s.l.

Discussion

Colombia is considered the second most biodiverse  country  in  the  world  (Anónimo, 2010) and this may be due to its geographical location and topography. Diatom studies conducted  to  date,  showed  that  this  group has high diversity the same as other groups of organisms and many new taxa for science have been recently described (Vouilloud, Sala, Núñez-Avellaneda, & Duque, 2010; Montoya- Moreno, Sala, Vouilloud & Aguirre, 2012).

In  the  framework  of  a  project  to  con- struct an index for water quality evaluation for Colombia and through the analyses undertaken with LM and SEM of 150 benthic diatom samples collected in lotic waterbodies from low-lands, we have identified approximatly 2 000 morphotypes. In the study area the genus Nupela was well represented and five species were identified: N. acaciensis and N. catatumbensis are new for science and N. lesothensis, N. prae- cipua and N. subpallavicinii are recorded for the first time in Colombia. Nupela acaciensis is  characterized  by  having  developed  raphe in both valves, cymbelloid symmetry, striae built by two elongated areolae that delimit a longitudinal line at each hemivalve. The closest taxa are N. schoemaniana Lange-Bertalot (Lange-Bertalot, 1993) and N. florideana Metzeltin & Lange-Bertalot (Metzeltin & Lange-Bertalot, 2007) from which it differs in striae, central area and internal proximal raphe ends. N. acaciensis also resembles N. giluwensis Vyverman & Compère (Vyverman & Compère, 1991) that differs in valve outline, presence of hyaline longitudinal lines on the valve face, internal proximal raphe ends, and distribution of the mantle areolae, continuous or interrupted at valve apices. Nupela catatumbensis is characterized by having developed raphe in both valves, cymbelloid symmetry, striae built by 3-4 transapically elongated areolae, interstriae elevated conforming transapical ribs and internal proximal raphe ends hook-shaped. Its closest species is N. encyonopsis Metzeltin & Lange-Bertalot  (Metzeltin  &  Lange-Bertalot, 1998) which differs in the shape of the central and axial areas, in the number of areolae per striae, and in the shape of the external proximal raphe ends. Another similar species is N. brachysiroides Lange-Bertalot (Lange- Bertalot, 1993) that differs in the presence of a sinuous line sunken at both sides of the central and axial areas, in the external proximal raphe ends, and in striae density and number of are-olae per stria.

The genus Nupela was originally described from high elevation ponds of Papua, New Guinea. Since its initial discovery, several species have been reported across Europe, South America, North America, Asia and Africa in neutral pH and low conductivity waters (Spaulding & Edlund, 2008). In the studied area, the genus was present in 28 sites located in  22  streams  and  rivers,  and  eight  basins of different regions of the country, with low conductivity but a medium range of variation in other environmental characteristics. The Caquetá, Tomo, Cravo Sur and Meta River Basins, placed at the Eastern lowlands were characterized by waters with acid to neutral pH. On the other hand, rivers from the Putumayo River basin had neutral pH. The streams from the Upper Magdalena River Basin were characterized by high temporal variation of water flows, a high coverage of hard substrates and a relatively basic pH, while those of the Catatumbo Basin comprise mountain rivers with predominantly hard substrates (like gravel and rocks) and also lowland water bodies with soft substrates (clay); pH sligthly acid to neutral, with exception of the Pamplonita River (San Rafael Bridge) a hipereutrophic site with frequent algal blooms.

Although the genus was widely distributed in these basins, the studied species showed different distribution patterns. N. acaciensis and N. subpallavicini have a restricted distribution, while N. catatumbensis, N. lesothensis and N. praecipua have a wider distribution and were collected  in  sites  with  significant  variations in their ecomorphology, altitude, temperature, pH and electrolyte content. N. acaciensis was only recorded in Meta River basin, placed at the Eastern lowlands, characterized by waters with very low electrolithic content, and acid to neutral pH. N. subpallavicini was originally described from a river of black waters in Tepui Avayan, Venezuela  (Metzeltin  &  Lange-Bertalot, 1998), and in Colombia it was collected only in a site with very low conductivity and pH, and at a medium altitude. N. catatumbensis was found both in small rough streams (with beds of gravel and stones) with turbulent flow as well as in rivers with beds with soft sediments (silt and clay). N. lesothensis, originally described from South Africa (Schoeman & Archibald, 1976-1980), and N. praecipua, described from the Custepec River, México (Reichardt,  1988),  were  collected  in  different basins with significant variations in their ecomorphology, altitude, temperature, pH and electrolyte content.

Acknowledgments

The authors want to thanks to the biologists of the Biotechnology Laboratory of ECO- PETROL, S.A. who participated in the field work and especially to Hernando Ovalle who facilitate the historical inquiry of the variables in the database.

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References


*Correspondencia: Silvia Sala: Departamento Científico Ficología, Universidad Nacional de La Plata, Argentina; sesala@fcnym.unlp.edu.ar
Amelia Alejandra Vouilloud: Departamento Científico Ficología, Universidad Nacional de La Plata, Argentina; avouilloud@fcnym.unlp.edu.ar
Yasmin Plata-Díaz: TIP LTDA. Instituto Colombiano del Petróleo. Ecopetrol. Piedecuesta/Santander/Colombia; _labbiohidro@ecopetrol.com.co
Edna Pedraza: TIP LTDA. Instituto Colombiano del Petróleo. Ecopetrol. Piedecuesta/Santander/Colombia; _labbiohidro@ecopetrol.com.co
Astrid Pimienta: Instituto Colombiano del Petróleo. Ecopetrol. Piedecuesta/Santander/Colombia; Astrid.Pimienta@ecopetrol.com.co
1. Departamento Científico Ficología, Universidad Nacional de La Plata, Argentina; sesala@fcnym.unlp.edu.ar, avouilloud@fcnym.unlp.edu.ar
2. TIP LTDA. Instituto Colombiano del Petróleo. Ecopetrol. Piedecuesta/Santander/Colombia;_labbiohidro@ecopetrol.com.co
3. Instituto Colombiano del Petróleo. Ecopetrol. Piedecuesta/Santander/Colombia; Astrid.Pimienta@ecopetrol.com.co

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