valve morPhology of didymoSPhenia geminata  
(
bacillarioPhyceae) from Santa cruz and tierra del  
fuego ProvinceS, Patagonia, argentina  
morfología valvar de didymoSPhenia geminata (bacillarioPhyceae)  
de laS ProvinciaS de Santa cruz y tierra del fuego, Patagonia,  
argentina  
1
2
1
1
Noelia M. Uyua * , Silvia E. Sala , Norma H. Santinelli , Alicia V. Sastre  
,
3
4
5
and Pedro De Carli  
Juan I. Cortes , Bibiana Rogel  
Summary  
1
. Instituto de Investigación de  
Background and aims: In 2013, blooms similar to those produced by Didymosphenia  
geminata (Lyngbye) M. Schmidt around the world, were detected in the Grande River  
basin, Tierra del Fuego province, and in 2014 in de las Vueltas River in Santa Cruz  
province. The aim of this paper is to analyze the valve morphology and morphometry  
of these materials to establish if they correspond to D. geminata or to other species  
of the genus that is producing the massive growth in southern Patagonia.  
M&M: Samples were collected at Grande River in 2013 and 2015 and, in de las Vueltas  
River in 2015 and 2016. Samples were analyzed with light and electron microscopy.  
For morphometric analyses 100 specimens from each sample were measured and  
statistical analyses were carried out using the R statistical package.  
Results: The studied populations have the same fine morphology described for other  
populations collected in Patagonia. Nevertheless, in some sampling sites from Santa  
Cruz province, we found a morphotype with a markedly smaller size, subcapitated  
poles, little marked constrictions of the poles, a broad central area (relative to cell  
size) and 1 to 3 stigmata, that was never reported in South America.  
Hidrobiología, Facultad de Ciencias  
Naturales y Ciencias de la Salud,  
Universidad Nacional de la Patagonia  
San Juan Bosco. Gales 48. Trelew,  
Chubut, Argentina.  
2
. División Ficología, Facultad  
de Ciencias Naturales y Museo,  
Universidad Nacional de La Plata.  
Paseo del Bosque s/n. La Plata,  
Buenos Aires, Argentina.  
3
. Centro para el Estudio de Sistemas  
Marinos (CESIMAR). Centro Nacional  
Patagónico. CONICET. Boulevard  
Brown 2915. Puerto Madryn, Chubut,  
Argentina.  
Conclusions: The studied populations correspond to D. geminata ssp. geminata  
Metzeltin & Lange-Bertalot. From a morphological point of view the smaller  
morphotype present in Santa Cruz belongs to the same subspecies but can be  
easily misidentified during the routine monitoring programs carried out with light  
microscope due its size and valve outline.  
4
. Secretaría de Estado de Ambiente  
de Santa Cruz. Sebastián Elcano 260.  
Río Gallegos, Santa Cruz, Argentina.  
5
. Instituto de Ciencias del Ambiente,  
Sustentabilidad y Recursos Naturales  
ICASUR) Universidad Nacional de  
(
Key wordS  
la Patagonia Austral (UNPA). Av.  
Lisandro de la Torre 860. Río Gallegos.  
Santa Cruz. Argentina.  
Diatoms, Didymosphenia geminata, southern Patagonia, morphology, invasion.  
reSumen  
Introducción y objetivos: En 2013 floraciones similares a las producidas por  
Didymosphenia geminata (Lyngbye) M. Schmidt en distintos lugares del mundo  
fueron detectadas en la Cuenca del Río Grande, provincia de Tierra del Fuego y, en  
*
noeliauyua@gmail.com  
Citar este artículo  
2014 en el río de las Vueltas en la provincia de Santa Cruz. El objetivo del trabajo  
UꢀUA, N. M., S. E. SALA, N.  
H. SANTINELLI, A. V. SASTRE,  
J. I. CORTES, B. ROGEl and P. DE  
CARLI. 2020. Valve morphology  
of Didymosphenia geminata  
fue analizar la morfología y morfometría valvar de estos materiales para establecer  
si corresponden a D. geminata o a otra especie del género que está produciendo  
floraciones masivas en la Patagonia sur.  
M&M: Las muestras fueron colectadas en el Río Grande en 2013 y 2015 y en el Río  
de las Vueltas en 2015 y 2016. El material fue analizado con microscopía óptica  
y electrónica. Para los análisis morfométricos fueron medidos 100 especímenes  
por muestra y los análisis estadísticos fueron llevados a cabo con el programa  
estadístico R.  
Resultados: Las poblaciones estudiadas presentan las mismas características  
morfológicas descriptas para poblaciones de distintos lugares de Patagonia. Sin  
embargo, en Santa Cruz observamos un morfotipo marcadamente más pequeño,  
con polos subcapitados, constricción suavemente marcada, un área central amplia  
con 1 a 3 estigmas, que no había sido descripto antes para Sudamérica.  
Conclusiones: Las poblaciones estudiadas corresponden a D. geminata ssp.  
geminata Metzeltin & Lange-Bertalot. Desde un punto de vista morfológico, los  
especímenespequeñospresentesenSantaCruzpertenecenalamismasubespecie  
pero por su tamaño y contorno valvar pueden ser confundidos con otros taxones  
durante los programas de monitoreo llevados a cabo con microscopía óptica.  
(Bacillariophyceae) from Santa Cruz  
and Tierra del Fuego provinces,  
Patagonia, Argentina. Bol. Soc. Argent.  
Bot. 55: 535-545.  
DOI: https://doi.  
org/10.31055/1851.2372.v55.  
n4.29634  
Recibido: 24 Jul. 2020  
Aceptado: 23 Oct. 2020  
Publicado en línea: 13 Nov. 2020  
Publicado impreso: 20 Dic. 2020  
Editora: Luz Allende  
PalabraS claveS  
Diatomeas, Didymosphenia geminata, Patagonia sur, morfología, invasión.  
ISSN versión impresa 0373-580X  
ISSN versión on-line 1851-2372  
535  
Bol. Soc. Argent. Bot. 55 (4) 2020  
introduction  
other regions of the world. At the same time this fact is  
worrisome because, this site could function as a center  
Didymosphenia geminata (Lyngbye) Schmidt of anthropic dispersion. On the other hand, in March  
has been extensively studied in the last years due to 2015 a monitoring program by the Subsecretaría  
its invasive behavior. D. geminata is a freshwater de Pesca of Santa Cruz Province to evaluate the  
diatom that forms dense soggy carpet-like layers, situation of the species in the province was held. In  
several inches thick, lining the bottom of the the framework of this program, 217 samples from 48  
aquatic environments where it lives. During the water bodies (rivers, streams and lakes) from different  
last fifteen years, blooming reports increased and basins were analyzed. Didymosphenia was recorded  
called the attention not only of scientists but also of only in de las Vueltas River. Samples collected in  
governments all around the world, due to the serious different sections of the de las Vueltas River were  
ecological damage they caused -e.g. changes in food studied with electron microscopy to analyze the fine  
chain structure and rivers and streams hydraulic morphology of these populations.  
characteristics- and economic losses that affected  
Uyua (2017) held morphological and molecular  
tourism, fisheries and hydroelectric industries (Kilroy, analyzes from the first populations of the species  
2
2
004; Spaulding & Elwell, 2007; Brand & Grech, that produced big blooms in rivers and streams  
020). of Argentina. These analyses made it possible to  
Although there are some early records of the corroborate that the blooms reports from Patagonia  
species in Chile (Asprey, 1964; Rivera & Gebauer, are produced by D. geminata. Besides, comparisons  
989), the first record of D. geminata forming blooms among Argentinean populations showed the same  
in South America was in Chile and Argentina in 2010 genetic variability than those populations from others  
Segura, 2011; Reid et al., 2012; Sastre et al., 2013). sites around the world. Similar results were obtained  
1
(
Valve morphology of the genus Didymosphenia when fine morphology was analyzed. These results  
has been well documented (Dawson 1973a, b;Antoine support the idea that D. geminata is an invasive  
&
Benson-Evans, 1983; Stoermer et al., 1986; species that recently has spread worldwide, but there  
Metzeltin & Lange-Bertalot, 1995, 2014) but there is are studies that show the presence of the species in  
still no agreement among authors about the number Patagonia since long time ago (Asprey, 1964; Rivera  
of species (Guiry & Guiry, 2017; Metzeltin & Lange- & Gebauer, 1989; Jones et. al., 2019). In fact, Rivera  
Bertalot, 2014). Uyua and collaborators (2016a) gave and Gebauer (1989) analyzed materials collected by  
the first morphological description of Didymosphenia Boyer in Chile in the earlier XX century deposited  
populations from Argentina –located in Chubut at the Academy of Natural Science of Philadelphia  
province- and compare these materials with others confirming the presence of the species in the northern  
aroundtheworld.Althoughtheauthorsdeterminedthat region of the country.  
these populations morphologically correspond to D.  
The aim of this paper is to establish if the massive  
geminata, they considered that species differentiation growths detected in Tierra del Fuego and Santa Cruz  
merely by means of morphological characteristics is correspond to Didymosphenia geminata or to other  
difficult. Besides, Metzeltin & Lange-Bertalot (2014) species of the genus based on fine valve morphology  
pointed out that identifications are more difficult if a and morphometry.  
small stage of the cell cycle is available. Moreover, it  
is also very difficult if local morphotypes of the same  
species are variable depending of the region of the material and methodS  
world where they are (Stoermer et al., 1986).  
Since 2010, D. geminata has spread throughout Study area  
Patagonia (Lamaro et al., 2019). In the Grande River  
The study area comprises Santa Cruz and Tierra del  
basin, Tierra del Fuego, a fisherman detected blooms Fuego provinces, Argentina (Fig. 1). Samples were  
similar to those produced by Didymosphenia in collected at de las Vueltas and Grande Rivers. De  
February 2013. This river is one of the most famous las Vueltas River belongs to Lake Viedma sub-basin  
international fishing centers of salmonids and its within Santa Cruz River basin. Source waters for this  
presence near a “fishing lodge” suggested that it could river originate on the southern bank of the Desierto  
have reached the island transported by fishermen from Lake and flows into Viedma Lake. The river flow  
536  
N. M. Uyua et al. - Didymosphenia geminata in southern Patagonia  
Fig. 1. Map of study area. A: Map of sample locations in south Patagonia Argentina. B: Map of sample sites  
of de las Vueltas River in Santa Cruz province. C: Map of sample sites of Grande River from Tierra del Fuego  
province.  
3
average is between 47-86 m /s in spring-summer and del Fuego, were analyzed from Grande River. Four  
3
between 19-40 m /s in autumn-winter (Díaz, 2005). samples collected in March 2015 and another one in  
The rivers Toro, Cóndor, Eléctrico, Milodón and Fitz September 2016 by the Subsecretaría de Pesca de la  
Roy are tributaries on the right margin and del Bosque Provincia de Santa Cruz were analyzed from de las  
River is tributary on the left margin.  
Vueltas River (Fig. 1). Samplings were carried out  
The Grande River belongs to Grande River basin. following international security recommendations  
This river has its springs in Chilean territory and carries (Duncan et al. 2007). The six sampling sites were  
the waters of various courses. Some tributary rivers in located with GPS. Periphyton was collected by  
Argentine territory are Bella Vista and Herminita brushing a variable surface from different rocks and  
rivers on the right and left margin respectively and, from submerged and emergent plants and macroalgae.  
Turba and Mac Lennan Rivers downstream. The Samples were preserved in 4% formaldehyde or  
2
Grande River basin has 8580 km , corresponding to alcohol 70%.  
2
the Argentine territory 3780 Km , and its average flow  
Materials were treated to eliminate organic matter  
following the method described in Hasle and Fryxell  
(1970). For light microscopy (LM) analyses samples  
3
is 40-45 m /s (Urciuolo et al., 2009).  
Methods  
Sampling was held at Grande River in Tierra del were mounted in Naphrax® and, for scanning electron  
2
Fuego province and de las Vueltas River in Santa Cruz microscopy (SEM) they were deposited on 1 cm  
province. Two samples collected in December 2013 pieces of glass mounted on metal stubs and then  
by Ben Pascal and in March 2015 by the Secretaría coated with gold. LM analyses were held with an  
de Desarrollo Sustentable de la Provincia de Tierra Olympus CKX41 microscope and photographed using  
537  
Bol. Soc. Argent. Bot. 55 (4) 2020  
an Olympus Evolt E-330 camera. SEM analyses were  
A non-parametric Kruskal-Wallis test was  
held with a Jeol JSM-6360 LV SEM at the Electron performed to verify the significance of possible  
Microscopy Service of the Facultad de Ciencias differences in length and width of D. geminata  
Naturales y Museo, Universidad Nacional de La among the different rivers (populations) analyzed in  
Plata, Argentina. Uncleaned, cleaned subsamples and this study and with others previously studied from  
permanent slides were deposited at the Herbario of Chubut province (Uyua et al., 2016b). To evaluate  
the División Ficología, Museo de La Plata under the the differences between the groups, a post hoc Dunn  
following numbers:  
(1964) multiple comparisons test (dunn.test) was  
ARGENTINA. Provincia de Tierra del Fuego. Río performed using the Bonferroni adjustment. Statistical  
Grande, Estancia Menéndez, Latitud. 53° 50’ S y analyses were carried out using the R statistical  
Longitud 67° 47’ O. Enero 2013. Colector: Ben package version 2.15.1 (R development Core Team,  
Pascal. 13420 (LPC).  
ARGENTINA. Provincia de Santa Cruz. Río de las  
2013).  
In de las Vueltas River, it was possible to measure  
Vueltas, Latitud 49° 05’46.1” S y Longitud 72° 53’ in situ parameters as temperature, pH, dissolved  
6.2” O. Marzo 2015. Colector: Subsecretaría de oxygen (DO), electrical conductivity and turbidity in  
5
Pesca de la provincia de Santa Cruz.13421 (LPC).  
ARGENTINA. Provincia de Santa Cruz. Río de las  
Vueltas, Latitud 49° 06’ 43.9” S, Longitud 72° 54’  
March 2015 with Horiba U10 equipment.  
4
4.3” O. Marzo 2015 Colector: Subsecretaría de reSultS  
Pesca de la provincia de Santa Cruz. 13422 (LPC).  
ARGENTINA. Provincia de Santa Cruz. Río de las  
Light microscopy analyses of untreated materials  
Vueltas, Latitud 49º 05’ 50.1’’ S, Longitud 72º 53’ producing large masses of stalks, brown dense soggy  
5.3’’ O. Marzo 2015. Colector: Subsecretaría de carpet-like layers confirmed the presence of the  
5
Pesca de la provincia de Santa Cruz. 13423 (LPC). species Didymosphenia geminata in Tierra del Fuego  
ARGENTINA. Provincia de Santa Cruz. Río de las and Santa Cruz (Fig. 2).  
Vueltas, Latitud 49º 06’ 15.2’’ S, Longitud 72º 54’  
23.8’’ O. Marzo 2015. Colector: Subsecretaría de Didymosphenia geminata from Tierra del Fuego  
Pesca de la provincia de Santa Cruz. 13424 (LPC). The cells have heavily silicified and slightly  
ARGENTINA. Provincia de Santa Cruz. Río de las cuneate frustules (Fig. 2A-F). Valves are strongly  
Vueltas, Latitud 49º 05’ 46.1’’ S, Longitud 72º 53’ heteropolar, symmetric or slightly asymmetric respect  
5
6.2’’ O. Septiembre 2016. Colector: Subsecretaría the apical plane with capitate apical and basal poles.  
de Pesca de la provincia de Santa Cruz. 13425 Valve face is flat, with a marginal rib at the junction  
LPC). of the valve face and mantle that ends in spines at  
ARGENTINA. Provincia de Tierra del Fuego, Latitud the apical pole (Figs. 3B, C). Some specimens show  
(
5
2
3° 48’ 51.6’’ S, Longitud 67° 55’ 01.5’’ O. Marzo a smooth spine while others have a serrated spine.  
015. Colector: Dirección General de Recursos Uniseriate striae are strongly radial all alongside and  
Hídricos 13425 (LPC).  
near the apical pole the striae are parallel (Figs. 3A-E).  
Internally, the valve face presents branched transapical  
The terminology used to describe the morphology ribs at valve center and at apical pole. Areolae are  
of the studied materials is that proposed inAnonymous externally surrounded by small papillae. The basal  
(1975), Ross et al. (1979) and Barber & Haworth pole presents a wide pore field, with small pores  
(1981). For morphometric analyses 100 specimens aligned in longitudinal rows. The raphe-sternum that  
from each sample were measured considering presents “ghost areolae” is narrow, widening abruptly  
maximum length and maximum width, and in 30 to an elliptic central area that shows 2-5 stigmas with  
of the 100 also were measured apical pole width, an oval external opening and globular and spongy  
foot pole width, apical pole constriction, foot pole occlusion in the internal side (Fig. 3A, D, F-G).  
constriction, maximum width/head-pole width ratio, Raphe is lateral, slightly curved; terminal fissures are  
number of striae in 10 µm, number of areolae in 10 differently curved at each pole. Internal distal ends  
µm, and number of stigmata, features considered as slightly bent towards the same side, ending in small  
diagnostic characters.  
helictoglossae (Figs. 3F-H). External proximal raphe  
538  
N. M. Uyua et al. - Didymosphenia geminata in southern Patagonia  
Fig. 2. LM. Didymosphenia geminata from de las Vueltas River (Santa Cruz province) and Grande River  
(Tierra del Fuego province). A-F: Río Grande River, Tierra del Fuego. G-L: de las Vueltas River, Santa Cruz.  
Scale bars = 20 µm.  
endings simple teardrop shaped. Internal proximal rounded to elongated transversely (Fig. 3D). Raphe  
raphe endings are located below the central nodule lateral with expanded central areas ends, distal raphe  
that presents a medium depression (Figs. 3F-H).  
ends long and abruptly bent –in some cases slightly  
Morphometric parameters: length: 125-146 μm; obtuse- to the opposite side of the stigmata (Fig. 3A-  
width 37-42.5 μm; l/w: 2.9-3.5; striae: 8-11 in 10 μm; C, E). Radial striae alternating longer and shorter in  
areolae: 10-12 in 10 μm; stigmas: 2-5; 40-44 rows of the central area becoming slightly divergent towards  
areolae in the pore fields in 10 μm and 14 areoles in 10 poles, almost parallel at basal pole and radial at the  
μm in the girdle bands.  
apical pole (Fig. 3). The striae are extended over  
the valve surface reaching the middle of the mantle,  
leaving a hyaline area on the edge of the valve mantle.  
Morphometric parameters: length: 126.8-133.6  
Didymosphenia geminata from Santa Cruz  
Morphotype #1: Specimens with similar  
characteristics to those from Tierra del Fuego. µm; width: 36.6-39.6 µm; l/w: 3.3-3.5; striae: 9-11 in  
Frustules are slightly cuneate. Apical and basal poles 10 µm; areolae: 10-12 in 10 µm; stigma: 2-4.  
capitate; apical pole larger than basal pole (Fig. 2A-  
F). Central area almost elliptical, asymmetric with specimens is similar to that of the specimens above  
to 4 stigmata (Fig. 3D). External stigma openings described (Fig. 4E-H). This morphotype differs from  
Morphotype #2: The fine morphology of these  
2
539  
Bol. Soc. Argent. Bot. 55 (4) 2020  
Fig. 3. SEM. Didymosphenia geminata from Grande River. A-E: Valves in external view. A: general valve  
view. B-C: detail of the apical pole. D: Valve center. E: Detail of the basal pole. F-H: Valves in internal view.  
F: general valve view. G: Detail of the central area. H: Detail of the basal pole. Scale bars= A, F: 20 µm; B-E;  
G-H: 5 µm.  
morphotype #1 in the markedly smaller size and in the much less marked, and the morphology of spines  
valve outline (Figs. 2; 4) with subcapitate poles and with three points in some specimens and very  
slightly marked constriction (2I-L). Central area poorly developed in others.  
wide with 1 to 3 stigmata on the primary side (Figs.  
G-L; 4).  
Statistical analyses of morphometric parameters  
show that specimens from Grande River are larger  
2
Morphometric parameters: length: 54.9-74.4 than those at de las Vueltas River (p<0.05, Kruskal  
µm; width: 26.2-32.3 µm; l/w: 1.92-2.67; striae: Wallis test). Besides, a comparison of the length of  
9
1
-11 in 10 µm; areolae: 10-12 in 10 µm; stigma: the cells with different populations from Patagonia  
-3. previously studied (Uyua et al., 2016b) shows  
Comparisons among specimens within each that Grande y Chubut rivers present the largest  
population (rivers) show morphological variations specimens from Patagonia (p<0.05, Kruskal Wallis  
in the raphe terminal fissures of the apical pole, test) and de las Vueltas River has the greatest range  
being in some cases abruptly bent and in others of size variation (Fig.5; Table 1). On the other  
Fig. 4. SEM. External valvar morphology of the two morphotypes found in de las Vueltas River, Santa Cruz  
province. A, E: Valve view. B, F: Detail of apical pole. C, G: Detail of the central area. D-H: Detail of the basal  
pole. Scale bars = A: 20 μm; E: 10 μm; B-D, F-H: 5 μm.  
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N. M. Uyua et al. - Didymosphenia geminata in southern Patagonia  
Fig. 5. Boxplot of maximum length of populations from different rivers from Patagonia. Azul, Chubut,  
Futaleufú and Rivadavia rivers belong to Chubut province (data by Uyua et al., 2016b), Grande River  
belongs to Tierra del Fuego province and de las Vueltas River belongs to Santa Cruz province.  
hand, only one sample collected in March 2015 las Vueltas River showed differences between the  
(LPC 13422) showed a similar proportion of the proportions of morphotypes present (Fig. 6).  
two morphotypes while the others showed a high On the other hand, physicochemical parameters  
proportion (94 %) of cells with 54-74 µm length measured in de las Vueltas River showed that the  
range (morphotype #2). A comparison between water body had low temperature (6.5 °C), high  
samples collected in different seasons (March 2015 DO concentrations (16.18 mg/l), low conductivity  
and September 2016) but in the same site in de (0.094 mS /cm), low turbidity (3 ppm) and pH 8.86.  
Table 1. Comparison of morphometric data of D. geminata from Patagonia Argentina  
Length  
µm)  
Width  
(µm)  
Striae/  
10 µm  
Areolae/  
10 µm  
Author  
Stigma  
(
D. geminata from  
Chubut (Argentina)  
Uyua et al., 2016b  
109-147  
30-42  
34-41  
8-11  
2-5  
10-12  
D. geminata from Río  
Negro (Argentina)  
Beamud et  
al.,2013  
107-133  
D. geminata from  
Santa Cruz (Argentina).  
Morphotype #1  
This study  
126-134  
36-39  
10-12  
2-4  
10-12  
D. geminata from  
Santa Cruz (Argentina).  
Morphotype #2  
This study  
This study  
54-75  
26-33  
9-11  
8-11  
1-3  
2-5  
10-12  
10-12  
D. geminata from Tierra  
del Fuego (Argentina)  
125-146  
37-42.5  
541  
Bol. Soc. Argent. Bot. 55 (4) 2020  
morphologic and morphometric features described  
for the species Didymosphenia hulli (Khan-Bureau et  
al. 2016) from Farmington River in United States of  
America. The authors show that the main differences  
between D. geminata and D. hulli are at genetic  
level. Previous genetic studies from Argentinean  
populations from Chubut and Tierra del Fuego  
provinces were carried out using three different  
molecular markers (Uyua, 2017). The results showed  
that the same genetic variability exists among the  
Argentinian populations studied as observed globally  
(Uyua, 2017). Based on these and results obtained  
by different authors (Kelly, 2009; Cardenas pers.  
comm.) we considered that it is possible that the  
variability found by Khan-Bureau et al. (2016) is  
the same that we found for the species D. geminata.  
More studies are necessary to resolve the presence  
or not of new species around the world and their  
phylogenetic relationship.  
It is possible that these two morphotypes represent  
different stages of the life cycle of the species but  
until now the life cycle of D. geminata is undescribed.  
Bishop (2014) showed that restoration dynamics and  
size distribution depend on habitat demonstrating  
the importance of spatial variability, although he  
could not describe the specific mechanism of  
D. geminata cell cycle. This could explain the  
morphometric differences observed among the rivers  
Fig. 6. Histograms of length variation of  
Didymosphenia geminata cells from the same  
location in de las Vueltas River in different seasons  
of the year.  
diScuSSion  
The specimens from South Patagonia here studied from Patagonia. Besides, the results obtained by  
show the same fine valve morphology of the Stoermer et al. (1986), evidenced that D. geminata  
specimens from Chubut and Río Negro provinces comprises several geographically differentiated  
(Beamud et al., 2013, Uyua et al., 2016b). The morphotypes.  
size variation of Santa Cruz populations agrees De las Vueltas River does not have easy public  
with the length range of D. geminata reported for accesses and belongs to a basin shared between  
different populations around the world (Krammer Argentina and Chile, like Futaleufú River (Chubut  
&
Lange-Bertalot, 1986; Whitton et al., 2009; province) and Grande River (Tierra del Fuego  
Metzeltin & Lange-Bertalot, 2014; Bishop, 2014; province). The river is characterized by shallow  
Khan-Bureau et al., 2016) although is the only river waters, with rapids, rocky bottoms and dense  
with the presence of cells smaller than 100 µm in riparian vegetation (Notophagus antartica forest).  
length in south Patagonia Argentina. The smaller The parameters measured in this river and others  
specimens (morphotype #2) from de las Vueltas from Patagonia such as Grande River (Urciuolo &  
River are similar to those described from Isar River Taier, 2011), Futaleufú River (Uyua, 2017), Limay  
in Germany, Sachalin Island in Russia (Metzeltin & River and in the Lake Nahuel Huapi among others  
Lange-Bertalot, 2014) and the Himalayan rivers in (Beamud et al., 2013; Beamud et al., 2016) and  
India (Bhatt et al., 2008). Bhatt et al. (2008) found where Didymosphenia form dense blooms, show that  
that in India cell size varied in a continuum while in the species has a wide tolerance range. Historically,  
de las Vueltas River we found two different groups D. geminata was considered to be restricted to  
of cells size: cells with length from 54 to 74 μm and oligotrophic (low nutrient) and low temperature  
cells from 120 to 140 μm. On the other hand, our waters, and a broad range of conductivity in the  
small specimens (morphotype #2) present the same European Alps (Krammer & Lange-Bertalot, 1986).  
542  
N. M. Uyua et al. - Didymosphenia geminata in southern Patagonia  
However, Spaulding & Elwell (2007) showed that geminata from Argentina is from 54 µm to 147 µm.  
D. geminata is present in waters from 4 to 27 °C. These results show the phenotypic plasticity of the  
Besides, the relationship of the presence of D. species.  
geminata and pH is narrow: Kilroy et al. (2005)  
pointed out that most part of the literature stated a  
pH between 7 and 8.5 as the optimal range. Although author contributionS  
the pH value in de las Vueltas River is higher  
than the optimal, it is near to the maximum and,  
NMU, SES, NHS and AVS conceived the  
besides, the value is within the range established by study. BR and PDC collected samples. NMU and  
Kawecka & Sanecki (2003). D. geminata requires SES prepared and analyzed the field material. JIC  
high light intensity (Kilroy et al., 2005) that is one collaborated in statistical analysis. NMU prepared  
of the characteristics of this river in terms of water the first manuscript draft. NMU, SES, NHS y AVS  
turbidity. Chemical parameters of de las Vueltas finished the last manuscript version.  
River are close to the “optimal” characteristics to be  
susceptible to be invaded by D. geminata.  
On the other hand, an important observation in acKnowledgmentS  
this study was the presence of different proportions  
of small specimens (morphotype #2) in different  
Authors wish to thank Dirección General de  
seasons and in different places of the same river. Recursos Hídricos of Tierra del Fuego province  
We consider that this is related to the life cycle and the Subsecretaría de Pesca of Santa Cruz  
but we still have not been able to solve it. Periodic province for the collaboration in obtaining the  
samplings over time are necessary to understand samples. NMU was a Doctoral Fellow cofinanced  
the population’s behavior. Besides, it is necessary by the National Council of Scientific and Technical  
to study the possible interactions with others Research (CONICET, Argentina) and the Chubut  
parameters (phosphate, nitrate, calcium, etc.) as Province’s Science, Technology and Productive  
possible phenotypic response of the species to Innovation Secretariat (SCTeIP, Chubut Province,  
environmental characteristics.  
Argentina, VIII99-ANEXO-A) during part of this  
Recently D. geminata was detected in the middle the research. We appreciate constructive reviews of  
stretch of the Santa Cruz River (Sturlese comm. the manuscript by two anonymous referees.  
pers.). This river crosses the Santa Cruz province  
from the Andes to the Atlantic Ocean. Preliminary  
analyses show populations similar to those of bibliograPhy  
Patagonia but the small specimens observed in de las  
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