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INTRODUCTION
Diatoms have been reported from marine coastal
waters of Buenos Aires and Río Negro Provinces since the
beginning of the twentieth century. The first comprehen-
sive studies on the phytoplankton of the marine coastal
waters of this area were made by Frenguelli (1928, 1930,
1938, 1939). Frenguelli’s vast work, that includes 521
new taxa (see Sar et al. 2009), and his collections about
fossil and extant diatoms have been of great value for fur-
ther research.
Recent studies including ultrastructural analysis
focused on members of the Order Thalassiosirales Glezer
& Makarova in this area have been done by Lange et
al. (1983), Gayoso (1988, 1989), Sar (1996), Sar et al.
(2001, 2002), Sunesen & Sar (2004), and Sunesen et
al. (2009). However, genera Cymatotheca Hendey, Try-
blioptychus Hendey and Cyclotella (Kützing) Brébisson,
which appeared in our sampling, have not been previ-
ously treated.
As far as we can determine the two former genera
were poorly known until the recent study carried out by
Tremarin et al. (2008) who analysed the fine structure of
Cymatotheca in external view and by Prasad et al. (2002)
who elucidated the fine structure, taxonomy, systematics
and distribution of Tryblioptychus and compared it with
other genera of the Thalassiosirales having radial, tangen-
tial, or both undulate valves.
Skeletonema Greville was recently reinvestigated by
Zingone et al. (2005) and the description of the conserved
generitype, Skeletonema costatum (Greville) Cleve, was
emended by Zingone & Sarno in Zingone et al. (2005).
Simultaneously, Sarno et al. (2005) conducted morpho-
logical investigations coupled with molecular analysis of
several strains determined as S. costatum and described
four new species. The mentioned papers and a subsequent
one, Sarno et al. (2007), allow determination of striking
features of the genus and understanding the specific lim-
its. Based on this knowledge our determination of Skel-
etonema costatum (Sar et al. 2001) must be reconsidered.
Cyclotella is a large and complex genus primarily of
freshwater that presents a few species from brackish and
marine coastal waters (Prasad et al. 1990). Håkansson
(2002) in her comprehensive revision of the genus pointed
out that the knowledge of the latter group is very limited
and there is uncertainty about the identity of small-sized
species. Despite this opinion, several papers published by
Lange & Syvertsen (1989), Prasad et al. (1990), Håkans-
son et al. (1993), Håkansson (1996), Håkansson & Clarke
(1997), Håkansson (2002), and Prasad & Nienow (2006),
allow the limits of this group to be clarified.
In the framework of a monitoring project of poten-
tially toxic species, we have prepared a series of papers
devoted to the diatom flora from Buenos Aires and Rio
Negro coastal waters. The purpose of the present paper is
to study the species of the genera Cymatotheca, Trybliop-
VIE ET MILIEU - LIFE AND ENVIRONMENT, 2010, 60 (2): 133-154
Copy proofs, 22 pages - 16.09.2010
CYMATOTHECA, TRYBLIOPTYCHUS, SKELETONEMA
AND CYCLOTELLA (THALASSIOSIRALES) FROM ARGENTINIAN
COASTAL WATERS. DESCRIPTION OF CYCLOTELLA
CUBICULATA SP. NOV.
E. A. SAR1*, I. SUNESEN1, A. S. LAVIGNE1
1 Consejo Nacional de Investigaciones Científicas y Técnicas, Departamento Científico Ficología, Facultad de Ciencias
Naturales y Museo, Universidad Nacional de La Plata, Paseo del Bosque s/n, 1900 La Plata, Argentina
* Correspondence author: easar@fcnym.unlp.edu.ar
ABSTRACT. – This study is devoted to analyze the fine structure of Cymatotheca weissflogii,
Tryblioptychus cocconeiformis, Skeletonema grethae, S. tropicum, Cyclotella atomus, C. choc-
tawhatcheeana and C. litoralis (Thalassiosirales). Net samples were collected from the surface
layer of the water column at several coastal stations in Buenos Aires and Río Negro Provinces,
Argentina. A new marine planktonic fultoportuloid diatom, Cyclotella cubiculata sp. nov., is
described using light and scanning electron microscopy. This species resembles Cyclotella lito-
ralis in general external aspect of the valve except for a minor difference in the position of the
opening of the rimoportulae. Nevertheless, Cyclotella cubiculata clearly differs from C. litoralis
by presenting marginal chambers easily visible with light microscopy and visible with scanning
electron microscopy only in internal view. Comparisons between the new species and some
allied brackish and marine species with marginal chambers as Cyclotella striata and C. stylorum
are conducted. Cyclotella atomus and C. choctawhatcheeana are recorded for the first time from
Argentinian coastal waters, Cymatotheca weissflogii, Tryblioptychus cocconeiformis, Skeletone-
ma tropicum and Cyclotella litoralis are recorded for the first time from Argentina, and Skele-
tonema grethae is recorded for first time from the South Atlantic Ocean.
FULTOPORTULOID DIATOMS
FINE MORPHOLOGY
DISTRIBUTION
ARGENTINA
The legend of Table I is missing
(see page 147)
134 E. A. SAR, I. SUNESEN, A. S. LAVIGNE
Vie Milieu, 2010, 60 (2)
tychus, Skeletonema and Cyclotella found in the area, to
report novelties about their morphology and distribution,
and to create a new species of Cyclotella providing com-
parison with allied taxa.
MATERIALS AND METHODS
The material analysed was collected in three areas (Fig. 1):
at several locations along the northern coast of Buenos •
Aires Province: San Clemente del Tuyú, Santa Teresita, La
Lucila del Mar, Mar de Ajó, Nueva Atlantis, Pinamar and
Villa Gesell, from November 1994 to September 2000 and
from March 2008 to May 2009
at several locations along the southern coast of Buenos •
Aires Province: Los Pocitos, Ría del Jabalí and San Blas,
from May 2008 to May 2009 and;
at several stations in the northern area of San Matías Gulf •
(Río Negro Province): Punta Orengo, Las Garzas, Banco
Reparo, San Antonio Oeste, Los Álamos, Las Grutas, El
Sótano and El Fuerte, from April 1998 to May 2000 and
from March 2006 to April 2007
In Buenos Aires Province, seawater temperature ranges from
8-24 °C and the salinity from 31-34.1 psu (unpublished data);
and in the northern area of San Matías Gulf from 7-23.5 °C, with
salinity ranging from 34-36 psu (Pascual et al. 2001). Qualitative
samples were taken from the surface layer of the water column
(between 0 and 5 m) with 30 µm net hauls and fixed with 4%
formalin. In the laboratory, the preserved samples were rinsed
with distilled water to remove salt and preservatives, and then
the organic matter was oxydized accord-
ing to Hasle & Fryxell (1970) and Prygiel
& Coste (2000). The cleaned material was
mounted for light (LM) and scanning elec-
tron microscopy (SEM) according to Fer-
rario et al. (1995). Permanent mounts were
made with Hyrax or Naphrax.
The materials were deposited in the
Colección de Diatomeas Argentinas,
Departamento Científico Ficología, Fac-
ultad de Ciencias Naturales y Museo, Uni-
versidad Nacional de La Plata under the
numbers LPC 4250 to 4495, LPC 4550 to
4643, LPC 11001 to 11137, LPC 11601 to
11672, LPC 13648 to 13685.
Observations were made with microscopes under phase
contrast Wild M20 and Nikon Microphot-FX. The microphoto-
graphs were obtained using Nikon Microphot-FX microscope
and scanning electron microscopes Jeol JSMT 100 and Jeol
JSM 6360 LV.
The terminology followed is that recommended by von
Stosch (1975), Ross et al. (1979), Lange & Syvertsen (1989),
Round et al. (1990), Theriot & Serieyssol (1994), Julius & Tan-
imura (2001) and Håkansson (2002). The classification scheme
follows Round et al. (1990) due to the fact that it better reflects
the phylogenetic reconstruction of the Thalassiosirales given by
Kaczmarska et al. (2005) and Sims et al. (2006).
RESULTS
Family Thalassiosiraceae Lebour
Cymatotheca Hendey
Cymatotheca weissflogii (Grunow) Hendey, Figs 2-9
Hendey 1958: 48, pl 5, Fig. 9; Tremarin et al. 2008:
1103, figs 3, 4, 60.
Basyonym: Euodia weissflogii Grunow in Van Heurck
1883, pl 126, Fig. 13.
Valves are circular or slightly elliptical in outline,
11-12 µm diameter in circular forms (Figs 2, 3), or 13.7-
16.8 µm long and 11.6-15.2 µm wide in elliptical forms
(Figs 4, 5). The valve is tangentially undulate (Figs
2-9). The raised sector presents a deeper mantle and the
Fig. 1. – Map of Buenos Aires and Río
Negro Provinces, showing sampling sta-
tions and location of the area in Argentina.
1: San Clemente del Tuyú, 2: Santa Teresi-
ta, 3: Mar del Tuyú, 4: La Lucila del Mar;
5: Mar de Ajó, 6: Nueva Atlantis, 7: Pina-
mar, 8: Villa Gesell, 9: Mar Azul, 10: Los
Pocitos, 11: Ría del Jabalí, 12: San Blas,
13: Punta Orengo, 14: Las Garzas, 15: San
Antonio Oeste, 16: Banco Reparo, 17: Los
Alamos, 18: Las Grutas, 19: Piedras Colo-
radas, 20: El Sótano, 21: El Fuerte.
THALASSIOSIRALES FROM ARGENTINIAN COASTAL WATERS 135
Vie Milieu, 2010, 60 (2)
depressed sector is associated to a hyaline area free of
areolation and presents a shallower mantle (Figs 6-8). The
striae are spaced with wider interstriae in the raised sector
of the valve surface, 5-8 in 10 µm, and denser with nar-
rower interstriae in the depressed sector, 10-12 in 10 µm
(Figs 6, 7). The areolae are smaller on the valve mantle
than on the valve surface and form striae more densely
arranged, 18-24 in 10 µm (Figs 6, 7). Areolae, 1.0-1.5
in 1 µm, are loculate with external foramen and internal
slightly domed-shaped cribra (Figs 6-9). The fultopor-
tulae form a marginal ring placed on the valve mantle,
3-4 in 10 µm (Figs 6, 9 arrowheads). A single valve face
fultoportula with no outwards extension lies at the raised
area off the valve centre (Figs 6-9 arrowheads). The mar-
ginal fultoportulae present a short tube surrounded by
three operculate satellite pores internally, with no out-
wards extensions. There is a single rimoportula, inter-
nally sessile and tangentially oriented, located next to the
depressed area (Fig. 9 arrow) and included in the mar-
ginal ring of fultoportulae in front of the valve face fulto-
portula, with no outwards extension. External opening of
the portulae is conspicuous in the depressed sector of the
valve and inconspicuous in the raised sector (Figs 6-8).
Distribution in Argentina: Cymatotheca weissflogii
mentioned by Simonsen (1974) as “a tropical benthic spe-
cies, allochthonous in the plankton sample” was found
during the present study in plankton net samples from San
Clemente del Tuyú, Santa Teresita, La Lucila del Mar,
Mar de Ajó and Villa Gesell, rare all year round. This spe-
cies is recorded for the first time from Argentinian coastal
waters.
Photographed material: LPC 4297 11/03/1996, LPC
4338 01/08/1998, LPC 4449 08/29/2000, San Clemente
Figs 2-9. – Cymatotheca weissflogii. Figs 2-5, LM. Figs 6-9, SEM. Figs 2, 3, Same circular valve at different focuses. Figs 4, 5, Same
elliptical valve at different focuses. Figs 6-8, External view. Fig. 6, Valve showing subcentral and marginal fultoportulae (arrowheads).
Fig. 7, Tilted frustule showing valve with subcentral fultoportula (arrowhead) and girdle. Fig. 8, Tilted valve showing hyaline area free
of areolation and shallow valve mantle. Fig. 9. Valve in internal view showing marginal ring of fultoportulae, subcentral fultoportula
(arrowheads) and sessile rimoportula (arrow).
136 E. A. SAR, I. SUNESEN, A. S. LAVIGNE
Vie Milieu, 2010, 60 (2)
del Tuyú; LPC 4375 01/13/1999, Santa Teresita; LPC
4393 11/10/1999, La Lucila del Mar.
Remarks: Simonsen (1987) pointed out that Euodia
Bailey ex Ralfs in Pritchard (1861), a genus in which the
analysed species was created by Grunow in Van Heurck
(1883, pl 126, Fig. 13) as E. weissflogii, is a later syn-
onym of Hemidiscus Wallich and a later homonym of
Euodia J. R. Forster & G. Forster (Rutaceae). Hendey
(1958) created the genus Cymatotheca and transferred
Grunow’s species as Cymatotheca weissflogii. Subse-
quently, Woodhead & Tweed (1960: 248) pointed out that
the transference of E. weissflogii Grunow to the genus
Cymatotheca Hendey (1958) “seems preferable to merg-
ing the West African material under Hemidiscus Wallich”
as proposed by Hustedt (1955). The taxonomic position
of the genus Cymatotheca Hendey was controversial.
Simonsen (1974) firstly placed it in the family Coscino-
discaceae Kützing but Simonsen (1979) assigned it to the
family Thalassiosiraceae Lebour emend. Hasle (1973a).
The genus was not included by Round et al. (1990) in
their classification scheme, but it was rightly included by
Nikolaev et al. (2001) within the Order Thalassiosirales,
Family Thalassiosiraceae.
Tryblioptychus Hendey
Tryblioptychus cocconeiformis (Grunow ex Cleve)
Hendey, Figs 10-13
Hendey 1958: 46, pl 2, Fig. 10; Prasad et al. 2002: 291,
figs 1-44; Tremarin et al. 2008: 1108, Fig. 41.
Basyonym: Campylodiscus (?) cocconeiformis Grunow
ex Cleve 1883, pl 38, Fig. 78.
Frustules are drum-shaped, 5.4-7.0 µm in height
(Fig. 12). Valves are circular in outline, 12.5-17.0 µm
in diameter, tangentially undulate with a raised and a
depressed sector (Figs 10-13). Valve surface is radially
undulated with areas slightly depressed occupied by fas-
cicles of 2-4 striae and areas slightly raised, hyaline, the
inter-fascicles, 2.8 in 10 µm. Junction between valve sur-
face and valve mantle is surrounded by a hyaline area free
of areolation. Valve mantle abruptly sloped, deep, with a
ring of larger areolae, 8.5 in 10 µm (Figs 12, 13). Areolae
are loculate with external foramen and internal cribra. A
single valve face fultoportula, with no outwards exten-
sion, lies at the raised area off the valve centre on the cen-
tral inter-fascicle (Fig. 13 arrowhead). Marginal fultopor-
tulae with no outwards extensions are placed on the inter-
fascicles and form a ring at the junction of the valve face/
mantle (Fig. 12 arrowheads). A single rimoportula with
external tube is located in the hyaline ring of the fascicle
contiguous to the central inter-fascicle, in the depressed
part of the valve, in front of the subcentral fultoportula
(Fig. 12 arrow).
Distribution in Argentina: Tryblioptychus cocconei-
formis, mentioned by Prasad et al. (2002) as “distributed
in bays, estuaries and other shallow coastal waters envi-
ronments between 15º S and 35º N” was found during the
present study only in plankton net samples from Ría del
Jabalí (40º32’ S-62º19’ W), rare in spring. This species
was previously registered by Ferrario et al. (2006) from
the Argentinian coastal waters and it is formally recorded
for the first time from Argentinian coastal waters in this
study.
Photographed material: LPC 11620, 09/29/2008, Ría
del Jabalí.
Remarks: Cleve (1883) created a new taxon under the
name Campylodiscus (?) cocconeiformis with doubts
about the genus and Hendey (1958) transferred it to the
genus Tryblioptychus Hendey as Tryblioptychus coc-
coneiformis (Grunow ex Cleve) Hendey. A comprehen-
sive analysis of the morphology, distribution, taxonomic
relationships and systematic position of the species was
made by Prasad et al. (2002). Simonsen (1979) assigned
the genus Tryblioptychus Hendey to the family Thalas-
Figs 10-13. – Tryblioptychus cocconeiformis. Figs 10, 11, LM. Figs 12, 13, SEM. Fig. 10, Valve showing radial undulation. Fig. 11,
Same valve as in Fig. 10 at different focus showing tangential undulation. Fig. 12, Tilted frustule showing marginal fultoportulae
(arrowheads) and broken rimoportula (arrow). Fig. 13, Detail of Fig. 12 showing the subcentral fultoportula (arrowhead).
THALASSIOSIRALES FROM ARGENTINIAN COASTAL WATERS 137
Vie Milieu, 2010, 60 (2)
siosiraceae Lebour emend. Hasle (1973a), criterion sub-
sequently followed by Prasad et al. (2002). Round et al.
(1990) and Nikolaev et al. (2001) did not include Try-
blioptychus in their classification schemes.
Family Skeletonemataceae Lebour emend. Round
Skeletonema Greville emend. Sarno & Zingone
Skeletonema grethae Zingone & Sarno, Figs 14-21
Sarno et al. 2005: 156, Fig. 3, A-I.
Cells with one or two parietal chloroplasts, forming
short and straight chains (Fig. 14). The valves are circular
in outline, 3.2 to 8.8 µm in diameter. The valve surface
is flat or slightly convex, and the valve mantle slightly
oblique (Figs 15-17, 19). Areolae pseudoloculate, 35
to 39 in 10 µm, radiating from the central annulus with
external openings (Fig. 21). Spinulae sometimes present
on the valve mantle (Figs 15-19). Valves with a ring of
fultoportulae placed on the junction of the valve surface/
mantle (Figs 15-17, 19, 21). The intercalary fultoportulae
present long and narrow tubes, open along their length, 8
to 11 in 10 µm, generally aligned and joined in 1:1 type to
those of the sibling valve, with interlocking like a knuckle
(Figs 16-18), and very short tubes internally (Figs 20-21
arrowheads). Fultoportulae are 4.5 to 7.0 µm in length,
and 0.4 to 0.5 µm in width. The terminal fultoportulae
present long, open tubes, and distal ends truncated with
irregular margins (Fig. 15). Single rimoportula per valve.
The intercalary rimoportula is located in the marginal
area of the valve surface, near the ring of fultoportulae,
with external tube short and cylindrical, and sessile inter-
nal lip obliquely placed (Figs 16-20 arrows). Terminal
rimoportula adjacent to the central annulus, with external
tube flared towards the apical opening, as long as or lon-
ger than the external tubes of the fultoportulae, internally
sessile (Figs 15, 21 arrows).
Figs 14-21. – Skeletonema grethae. Fig. 14, LM. Figs 15-21, SEM. Fig. 14, Colony. Cells with one chloroplast. Fig. 15, Terminal valve
showing a ring of fultoportulae with open tubes and subcentral rimoportula (arrow). Figs 16, 17, Sibling valves with intercalary fulto-
portulae joined in 1:1 type. Note the rimoportulae (arrows). Fig. 18, Detail of the 1:1, knuckle-like junction of the intercalary fultopor-
tulae. Arrow shows rimoportula. Fig. 19, Valve mantle with spinulae. Fig. 20, Broken valve showing internal view of marginal rimo-
portula (arrow) and fultoportulae (arrowheads). Fig. 21, Terminal valve in internal view showing rimoportula (arrow) adjacent to the
central annulus and marginal ring of fultoportulae (arrowheads).
138 E. A. SAR, I. SUNESEN, A. S. LAVIGNE
Vie Milieu, 2010, 60 (2)
Figs 22-34. – Skeletonema tropicum. Figs 22-29, LM. Figs 30-34, SEM. Figs 22-24, Colonies with several chloroplasts in each cell.
Figs 25, 26, Terminal cells with long rimoportula (arrows). Figs 27-29, Details of the junction of the intercalary fultoportulae of the
sibling cells. Note junctions 1:1 and 1:2 in the same colony in Figs 28 and 29, Fig. 30, Complete colony with a long rimoportula on
each terminal valve (arrows). Fig. 31, Colony with intercalary fultoportulae straight or slightly curved and with junction 1:1 and 1:2.
Fig. 32, Colony with terminal cell in valve view showing rimoportula half-way between central annulus and marginal ring of fultopor-
tulae (arrow). Fig. 33, Wide colony with terminal cell showing the rimoportula (arrow). Note variability in intercalary fultoportulae
junctions. Fig. 34, Terminal part of the colony of Fig. 30, note terminal and intercalary rimoportulae (arrows).
THALASSIOSIRALES FROM ARGENTINIAN COASTAL WATERS 139
Vie Milieu, 2010, 60 (2)
Distribution in Argentina: Skeletonema grethae, men-
tioned by Kooistra et al. (2008) as “a warm water species”
was found during the present study in plankton net sam-
ples from San Clemente del Tuyú, Mar Azul, Los Pocitos
and Ría del Jabalí, very rare in autumn and spring. This
species is recorded for the first time from South Atlantic
marine coastal waters in this study; previously Kooistra et
al. (2008) pointed out that it was only found in US waters,
thus the present report extends its geographical range.
Photographed material: LPC 11124, 04/08/2009, San
Clemente del Tuyú; LPC 11619, 09/29/2008, Los Pocitos;
LPC 11620, 09/29/2008, Ría del Jabalí.
Remarks: Recently, Skeletonema grethae was created
based on the analysis of the morphology of several strains
from the North Atlantic Ocean labelled as Skeletonema
costatum (Greville) Cleve (Sarno et al. 2005). Our mate-
rial of S. grethae showed some morphometric differences
from the forms described by Sarno et al. (2005) in the
length of the external tubes of the intercalary fultoportu-
lae (4.5 to 7.1 µm in the former, 2.0 to 4.5 µm in the lat-
ter), in the distance between fultoportula (0.6 to 1.3 µm
in the former, 0.2 to 1.0 µm in the latter), in the length
of the external tube of the terminal rimoportulae (5.5 to
6.5 µm in the former, 1.8 to 3.6 µm in the latter) and in
cell number per colony (few in the former and many in
latter). These differences could be explained because we
only examined sampled material, while the mentioned
authors only examined cultured material.
Skeletonema tropicum Cleve, Figs 22-40
Cleve 1900, pl. 7, figs 30, 31; Sarno et al. 2005: 166,
Fig. 9 A-F; Sar et al. 2001: 221, Figs 73, 75, 76 (as Skel-
etonema costatum).
Cells with several parietal chloroplasts (Figs
22-25), forming long and straight chains (Figs 22-24,
27-33). The valves are circular in outline, 8.5 to 28.0
(32.0) µm in diameter. The valve surface is slightly con-
vex, and the valve mantle is vertical, varying from shallow
to deep (Figs 33, 34). Areolae pseudoloculate, 22 to 30 in
10 µm, radiating from the central annulus with external
openings generally regular in size and ordered in rows in
the valve mantle (Figs 34, 36, 40). Sometimes in the same
colony a sibling cell presents areola openings disordered
and spinulae scattered on the valve mantle (Figs 38, 39).
Valves with a ring of fultoportulae, placed on the junction
Figs 35-40. – Skeletonema tropicum. SEM. Fig. 35, Fragment of a wide colony showing intercalary rimoportula (arrow). Figs 36, 37,
Tilted fragments of colonies showing terminal valves with rimoportula (arrows) and marginal ring of fultoportulae. Figs 38, 39, Sibling
valves showing intercalary rimoportulae (arrows) and different kinds of junction. Fig. 40, Intercalary valve in internal view showing
the sessile rimoportula (arrow) placed in the marginal ring of fultoportulae (arrowheads).
140 E. A. SAR, I. SUNESEN, A. S. LAVIGNE
Vie Milieu, 2010, 60 (2)
of the valve surface and valve mantle, 0.6 to 1.3 µm apart.
The intercalary fultoportulae present long tubes, 5 to 9 in
10 µm, straight or slightly curved, open along their length,
commonly aligned and joined in 1:1 type to those of the
sibling valve (Figs 31, 35-39). Sometimes in the same
colony a sibling cell presents fultoportulae with junc-
tion 1:2 type (Figs 28, 29, 33, 39). Interlockings among
intercalary fultoportulae are like knuckles (Figs 38, 39).
The terminal fultoportulae present long, open tubes and
distal ends truncated with stout spines (Figs 34, 36, 37).
Single rimoportula per valve. The intercalary rimoportula
is located in the marginal area of the valve surface, near
the ring of fultoportulae, with external tube slightly flat-
tened and sometimes split at the end, and sessile internal
lip obliquely arranged (Figs 34, 35, 37-40 arrows). Ter-
minal rimoportula placed half-way between the central
annulus and the ring of fultoportulae, with external tube
flared towards the apical opening as a trumpet, as long as
or longer than the external tubes of the fultoportulae (Figs
25, 26, 30, 32-34, 36, 37 arrows).
Distribution in Argentina: Skeletonema tropicum,
considered by Kooistra et al. (2008) as a warm water
to temperate species which appears where winter sea-
water surface temperatures are as low as 12-14 °C, was
found during the present study in plankton net samples
from San Clemente del Tuyú, Santa Teresita, La Lucila
del Mar, Mar de Ajó, Nueva Atlantis, Pinamar and Villa
Gesell, common all year round, with occasional blooms
in spring and fall, and from Punta Orengo, San Antonio
Oeste, Banco Reparo, Las Grutas and Piedras Coloradas,
rare all year round.
Photographed material: LPC 11124, 04/08/2009, San
Clemente del Tuyú. We chose microphotographs from the
mentioned sample, where the species was very abundant
(5.38 105 cel·l-1), because they are better than all the oth-
ers obtained.
Remarks: Our material of Skeletonema tropicum
showed some differences with the material analysed
by Sarno et al. (2005) in the cell diameter (8.5 to 28.0
[32.0] µm in the former, 5.3 to 10.0 µm in the latter), in the
length of the external tubes of the intercalary and terminal
fultoportulae (4.5 to 6.1 and 5.7 to 6.1 µm in the former,
1.2 to 4.1 and 2.1 to 3.5 µm in the latter respectively), in
the width of external tubes of the intercalary and terminal
fultoportulae (0.4 to 0.7 and 0.5 to 0.6 µm in the former,
0.1 to 0.5 and 0.2 to 0.6 µm in the latter respectively), in
the length of the external tube of the terminal rimoportula
(4 to 7 µm in the former, 2.8 to 5.3 µm in the latter). These
differences could be explained because we only examined
sampled material while mentioned authors only examined
cultured material.
Figs 41-46. – Cyclotella atomus. SEM. Figs 41-43, External view. Figs 44-46, Internal view. Fig. 41, Valve showing fultoportula
(arrowhead) in the raised sector of the tangential undulation. Fig. 42, Valve showing central fultoportula (arrowhead) and marginal
rimoportula (arrow). Fig. 43, Same valve of Fig. 42 tilted. Note the rimmed pores of the marginal fultoportulae, the rimoportula (arrow)
and central fultoportula (arrowhead). Figs 44, 45, Valves showing central and marginal fultoportulae with two satellite pores and single
rimoportula (arrows). Fig. 46, Same valve of Fig. 45 showing detail of marginal fultoportulae.
THALASSIOSIRALES FROM ARGENTINIAN COASTAL WATERS 141
Vie Milieu, 2010, 60 (2)
Family Stephanodiscaceae Glezer & Makarova
Cyclotella (Kützing) Brébisson
Cyclotella atomus Hustedt, Figs 41-46
Genkal & Kiss 1993: 39, figs 1-9; Håkansson & Clarke
1997: 207, Figs 1-16, 18-21; Håkansson 2002: 106, Figs
381-388.
Cells solitary. Valves circular in outline, 4.3 to 7.4 µm
in diameter, externally divided in two concentric zones, a
central field and a marginal area (Figs 41, 42). The cen-
tral field is tangentially undulate to almost flat, internally
and externally smooth, occupying about two thirds to half
of the valve surface (Figs 43, 44-46). The marginal area
presents raised striae and depressed interstriae extending
to the edge of the valve mantle (Figs 41, 43). The striae, 8
to 14 in 10 µm, are formed by several rows of minute are-
olae, internally dug out in the vicinity of the central field
(Figs 41-46). A marginal ring of fultoportulae is placed in
the mantle just below the valve face/valve mantle junc-
tion (Fig. 43). Fultoportulae are arranged on every third
to fifth interstria, opening outwards by a rimed pore and
internally by a tube surrounded by two radial satellite
pores (Figs 43-46). A single rimoportula is located on an
interstria, between two fultoportulae, slightly above of
the fultoportulae ring, in front of the raised central field.
Externally the rimoportula opens by an elliptical pore
with slightly thickened rim, smaller than fultoportula
pores, and internally by a lip tangentially oriented (Figs
42-45 arrows). A ring of spinulae in the valve face/valve
mantle junction is present in some specimens (Fig. 43).
There is one fultoportula on the raised sector of the cen-
tral field, externally opened by a pore (Figs 41-43 arrow-
heads) and internally by a short tube surrounded by two
satellite pores (Figs 44, 45).
Distribution in Argentina: Cyclotella atomus, men-
tioned by Håkansson & Clarke (1997) as “a cosmopoli-
tan, fresh- to brackish water species” was found during
the present study in plankton net samples from San Cle-
mente de Tuyú, La Lucila del Mar and Pinamar, very rare
all year round. This species was previously reported from
Argentinian continental waters (see Vouilloud 2003) and
it is recorded for the first time from the marine coastal
waters of Argentina in this study.
Photographed material: LPC 4304, 08/01/1997, La
Lucila del Mar; LPC 4361, 07/31/1998, LPC 4390,
11/10 /199 9, San Clemente del Tuyú; LPC 442 8,
04/27/2000, Pinamar.
Remarks: Our specimens present central fultopor-
tula with two satellite pores and resemble some shown
by Hasle (1962), Sabater & Klee (1990), Håkansson &
Clarke (1997), Håkansson (2002) in external and internal
general aspect, morphology of marginal fultoportulae,
internally with two satellite pores and externally with a
rimmed pore, and arrangement of the rimoportula. How-
ever, the material from Argentinian coastal waters dif-
fers by the stria density, 9-14 striae in 10 µm, lower than
reported in the literature for the species.
Cyclotella choctawhatcheeana Prasad, Figs 47-54
Prasad et al. 1990: 419, Figs 2-26; Wendker 1991: 359,
Figs 1-7, Håkansson et al. 1993: 337, Figs 1-10; Prasad
& Nienow 2006: 133, Figs 47-55; Melo et al. 2006: 295,
Figs 2-7.
Cells solitary. Frustules are drum-shaped, in girdle
view (Fig. 47). Valves are circular in outline, 4.5-10 µm
in diameter, externally divided in two concentric zones, a
central field and a marginal area (Figs 48, 51). The central
field is tangentially undulate having variable elevation,
externally colliculate or slightly colliculate and internal-
ly smooth, occupying about two thirds of the valve sur-
face (Figs 47, 48, 51, 54). The marginal area restricted to
about a third of the valve surface, presents radial striae
and interstriae extending to the edge of the valve mantle
(Fig. 51). The striae are alveolate, 20-30 in 10 µm. The
outside areolate layer can be formed of three or more
rows of areolae (Figs 49, 51). Interstriae are wide or nar-
row in external view, and more or less raised of the valve
surface. Internally, alveola open at the margin by ellipti-
cal apertures, marginal chambers are absent (Figs 52-54).
A marginal ring of fultoportulae is present on the mantle,
near the margin. Fultoportulae are placed on every forth
to ninth interstriae (Figs 47, 52-54) or less commonly on
every second to third (Figs 48, 49), opening outwards
by a circular pore with a thickened rim and internally
by a tube surrounded by two radial satellite pores (Figs
47-49, 51-54). A single rimoportula is placed on an inter-
stria, slightly over of the marginal fultoportulae horizon,
between two fultoportulae, in front of the raised central
field (Figs 48, 49 arrows). Externally, rimoportula opens
by a circular to oval pore with a thickened rim, smaller
than those of the fultoportulae (Figs 48, 49 arrows), and
internally by a lip almost radially arranged (Figs 52-54
arrows). There are one to six fultoportulae on the raised
sector of the valve surface, they externally open by a pore
and internally by a short tube surrounded by three satel-
lite pores. The cingulum is composed by four open, non
porous bands, with the openings aligned in pervalvar
direction. The valvocopula is wide, first copula reduced
to a long and prominent ligula at the pars exterior, second
copula wide, shortly ligulate (not illustrated) and third
copula narrow, largely ligulate (Figs 47, 49 v, c).
Distribution in Argentina: Cyclotella choctawhatchee-
ana, mentioned by Prasad & Nienow (2006) as “cosmo-
politan inhabitant of coastal brackish waters and saline
lakes” was found during the present study in plankton
net samples from San Clemente de Tuyú, Mar de Ajó, La
Lucila del Mar, Nueva Atlantis and Villa Gesell, rare in
spring and summer; and from Banco Reparo and Bahía
San Antonio, rare in summer. This species was previous-
142 E. A. SAR, I. SUNESEN, A. S. LAVIGNE
Vie Milieu, 2010, 60 (2)
Figs 47-54. – Cyclotella choctawhatcheeana. Fig. 50, LM. Figs 47-49, 51-54, SEM. Figs 47-49, 51, External view. Figs 52-54, Internal
view. Fig. 47, Frustule drum-shaped. Note the cingulum composed of a valvocopula (v), a first copula reduced to a long ligula at pars
exterior (c), second and third copulae (c). Fig. 48, Valve showing several fultoportulae on the raised sector of the undulation and a
rimoportula (arrow). Fig. 49, Detail of Fig. 48, Tilted valve showing valvocopula (v) and first copula (c) with reduced pars exterior.
Fig. 50, Valve showing marginal fultoportulae placed every fourth or fifth interstriae and central fultoportula. Fig. 51, Valve showing
marginal fultoportulae with thickened rim. Figs 52-54, Valves showing marginal elliptical apertures of the alveola, central fultoportula,
ring of fultoportulae and rimoportula (arrows). Note central fultoportulae with three satellite pores and marginal fultoportulae with two
satellite pores.
THALASSIOSIRALES FROM ARGENTINIAN COASTAL WATERS 143
Vie Milieu, 2010, 60 (2)
ly reported by Maidana & Romero (1995) and González
& Maidana (1998) from Argentinian hypersaline lakes
and in this study it is recorded for the first time from the
Argentinian coastal waters.
Photographed material: LPC 4250, 11/02/1994, Nueva
Atlantis; LPC 4304, 01/11/1997, La Lucila del Mar; LPC
4310, 03/15/1997, San Clemente del Tuyú; LPC 4315,
03/16/1997, Villa Gesell; LPC 4374, 01/16/1997, Mar de
Ajó; LPC 4607, 04/29/1999, Banco Reparo; LPC 4635,
02/29/2000, San Antonio Oeste.
Remarks: Prasad et al. (1990) created this brackish
water, chain-forming taxon under the name of Cyclotel-
la choctawhatcheeana and compared it with euryhaline
species of Cyclotella. Almost simultaneously, Wendker
(1991) also created a brackish-water, solitary taxon under
the name of Cyclotella hakanssoniae. Håkansson et al.
(1993) compared and discussed C. choctawhatcheeana
Prasad, C. hakanssoniae Wendker and other related taxa
as C. caspia, and C. striata var. baltica Grunow and C.
litoralis Lange & Syvertsen. Authors analysed the type
material of C. caspia from the Grunow Collection, estab-
lished its taxonomic limits and pointed out that this spe-
cies is quite different from the other treated taxa. Besides,
based on their analysis of C. choctawhatcheeana and C.
hakanssoniae they determined that both taxa are conspe-
cific, thus C. hakanssoniae is a heterotypic synonym of C.
choctawhatcheeana. Recently, Prasad & Nienow (2006)
pointed out that C. choctawhatcheeana also appeared
as single cells in the Florida Bay populations. This spe-
cies was previously misidentified as C. caspia by Hasle
(1962) and Bérard-Therriault et al. (1987).
Cyclotella litoralis Lange & Syvertsen, Figs 55-70
Lange & Syvertsen 1989: 343, Figs 1-30.
Cells solitary or joined in colonies by mucilaginous
thread (Figs 55-57, 63, 64). Frustules drum-shaped, cylin-
drical or rectangular in girdle view, 9-16 µm in height.
Valves are circular in outline, 10.0-62.8 µm in diameter,
tangentially undulate, and externally divided in two con-
centric zones, a central field and a marginal area (Figs
59, 61, 62). The central field presents variable elevation,
higher in the larger specimens and lower in the smaller
specimens (Figs 63, 64 and 56 respectively). It is exter-
nally colliculate and internally smooth, occupying almost
a half of the valve surface (Figs 56-59, 61-64). The mar-
ginal region restricted to a half of the valve surface, pres-
ents radial depressed striae, 9-14 in 10 µm, and interstriae
(Figs 56, 59, 63, 64), extending from the vertical part of
central area to the edge of the valve mantle (Figs 58, 63
asterisks). Interstriae are wider in the smaller specimens
and narrower in the larger specimens (Figs 59, 68), and
sometimes furnished with granules (Figs 65, 66). The
striae are alveolate, the outside areolate layer presents
two or three rows of areolae near the central field, four
to six near the valve surface margin and sometimes more
in the mantle (Figs 56, 58, 59, 65-68). Valve mantle with
inserted interstriae close to the margin (Figs 58, 67, 68).
Internally, alveola open at the margin by elliptical aper-
tures, marginal chambers are absent (Figs 60, 69, 70). A
marginal ring of fultoportulae is present on the mantle.
Fultoportulae are placed on every second, less frequently
on every or every third interstriae, opening outwards by
a circular pore with a thickened rim (Figs 56, 59, 65, 66),
and internally by a tube surrounded by two radial satel-
lite pores (Fig. 70). A single rimoportula is placed on
an interstria, slightly below the marginal fultoportulae
horizon, between two fultoportula, in front of the raised
central field (Figs 56, 59, 65-67 arrows). Externally, the
rimoportula opens by a circular, oval or drop-shaped pore
with a slightly thickened rim, smaller than those of the
fultoportulae (Figs 56, 65-67 arrows), and internally by
a lip, flat and radially arranged (Figs 60, 69, 70 arrows).
There are one to many fultoportulae on the raised sector
of the valve surface, they externally open by a pore (Figs
59, 61 arrowheads, 63, 64) and internally by a short tube
surrounded by three satellite pores (Figs 60, 69). The cin-
gulum is composed of four open, ligulate, unornamented
bands with the openings arranged in dextral spiral (Figs
67, 68). The valvocopula, second and third copulae, are
approximately of the same breadth and the first copula
is narrow. The first and third copulae are largely ligulate
and the second one –is shortly ligulate (Figs 56-58, 67,
68 v, c).
Distribution in Argentina: Cyclotella litoralis, men-
tioned by Hasle & Syvertsen (1996) as inhabiting “south-
ern and northern temperate region, coastal, marine” was
found during the present study in plankton net samples
from San Clemente del Tuyú, Santa Teresita, La Lucila
del Mar, Mar de Ajó, Nueva Atlantis, Pinamar and Villa
Gesell, rare all year around; and from Punta Orengo and
Piedras Coloradas, rare all year around. This species
is recorded for the first time from Argentinian coastal
waters.
Photographed material: LPC 4262, 03/27/1995, Nueva
Atlantis; LPC 4263, 03/28/1995, Pinamar; LPC 4303,
01/11/1997, Santa Teresita; LPC 4305, 01/11/97, Mar
de Ajó; LPC 4367, 19/09/1998, LPC 4389, 10/06/1999,
Villa Gesell; LPC 4610, 07/05/1999, Punta Orengo; LPC
13667, 06/14/2006, LPC 13669, 07/25/2006, LPC 13671,
08/05/2006, Piedras Coloradas.
Remarks: Lange & Syvertsen (1989) created Cyclo-
tella litoralis and compared it with C. striata (Kützing)
Grunow and C. stylorum Brightwell. Håkansson (1996)
analysed C. striata complex, lectotypified C. striata (Küt-
zing) Grunow, and concluded that C. striata var. baltica
Grunow in Van Heurck is conspecific with C. litoralis.
Subsequently, Håkansson (2002) transferred, raised in
rank and lectotypified C.striata var. baltica Grunow as C.
baltica (Grunow) Håkansson considering some minor dif-
ferences in the position of the valve mantle fultoportulae
and of the rimoportula.
144 E. A. SAR, I. SUNESEN, A. S. LAVIGNE
Vie Milieu, 2010, 60 (2)
Cyclotella cubiculata sp. nov.
Descriptio: Cellulae solitariae. Frustula typaniformia
in facie connectivali visa. Valvae circulares, 23-63 µm
diametro. Frons tangente valde undulata, in partibus con-
centricas duabus morphologia distincte differenti concen-
trice divisa. Area centralis ex exteriore parte colliculata,
ex interiore parte levis. Area marginalis radiantibus striis
depressis, 11-13 in 10 µm, et interstriis instructa, ad mar-
ginem valvae prolongatis. Interstriae interdum granulis
instructae. Striae alveolatae, tegumento areolato exteriore
serierum 2-6. Limbus intestriiis brevibus insertis prae-
ditus. Cubicula marginalia ex interiore parte posita, 4-6
in 10 µm, crassiore interstria 1 (2) disjuncta. Cubicula
omnia alveolis 2 (3) et interstriis 1 (2) recessis costatis
fultoportulis duobus poris satellitariis radialibus instruc-
ta. Cubiculum rimoportulae maximum. Rimoportula in
interstria recessa posita, oblique oriens. Fultoportulae
in recessis interstriis positae, poro extrinseci aperientes
in omnibus interstriis alteris, raro in ommibus interstriis
primis vel tertiis, annulum in limbo valvae formantes.
Rimoportula unica, in circulo fultoportularum vel supra
circulum fultoportularum locata. Pars elevata areae cen-
tralis fultoportulis 5-15 seriem semicircularem formanti-
Figs 55-60. – Cyclotella litoralis. SEM. Fig. 55, Cells joined in a colony by mucilaginous threats. Fig. 56, Cell on the right of the colo-
ny of Fig. 55 showing marginal ring of fultoportulae, a rimoportula (arrow) and cingulum formed by a valvocopula (v) and three open
copulae (c). Fig. 57, Lower cell shows the openings of the valvocopula (v) and second copula (c), first and third copulae ligulate (c).
Upper cell shows the cingulum from the opposite side. Rimoportula is arrowed. Fig. 58, Frustule showing striae extending from the
vertical part of the central area to the edge of the valve mantle (asterisks). Note inserted interstriae on the valve mantle. Fig. 59, Valve
in external view showing the ring of fultoportulae and a rimoportula (arrow). Fig. 60, Valve surface in internal view showing the open-
ings of the alveola, ring of fultoportulae and a rimoportula (arrow).
THALASSIOSIRALES FROM ARGENTINIAN COASTAL WATERS 145
Vie Milieu, 2010, 60 (2)
Figs 61-70.- Cyclotella litoralis. Figs 61, 62, LM. Figs 63-70. SEM. Fig. 61, Valve showing many fultoportulae on the raised sector
(arrowhead). Fig. 62, Same valve of Fig. 61 in different focus showing the rimoportula (arrow). Fig. 63, Cell with long mucilaginous
threats secreted by the fultoportulae. Note position of the rimoportula (arrow). Fig. 64, Tilted frustule showing high elevation. Note
position of the rimoportula (arrow). Fig. 65, Detail of Fig. 63 showing the circular aperture of the rimoportula (arrow). Fig. 66, Detail
of a drop-shaped opening of the rimoportula (arrow). Figs 67, 68, Details of Fig. 64 from opposite sides. Fig. 67, Note cingulum com-
posed of four bands, one valvocopula (v) and three copulae (c), with the openings in dextral spiral. Fig. 68, Note the narrow first copula
and the shortly ligulate second copula. Fig. 69, Valve in internal view. Rimoportula is arrowed. Fig. 70, Detail of Fig. 69 showing the
marginal openings of the alveola, fultoportulae placed on the interstriae with two satellite pores and rimoportula (arrow).
146 E. A. SAR, I. SUNESEN, A. S. LAVIGNE
Vie Milieu, 2010, 60 (2)
bus instructa. Fultoportulae in fronte interne poris stelli-
tariis tribus. Limbus interstriis brevibus insertis praeditus.
Cingulum taeniis 4 vel 5 apertis in cochleam dextrorsum
retortis instructum.
Species planctonica, marina.
Holotypus: Praeparatio LPC 4260 (1) hic designatus
(holotypus Cyclotella cubiculata), in Collectio diatomar-
um Departamento Científico Ficología, Facultad de Cien-
cias Naturales y Museo, Argentina.
Isotypus: Praeparatio LPC 4260 (2) hic designatus
(isotypus Cyclotella cubiculata), in Collectio diatomarum
Departamento Científico Ficología, Facultad de Ciencias
Naturales y Museo, Argentina.
Locus typicus: Nueva Atlantis, 36º 45’ 81’’S-56º 40’
04’’W, Prov de Buenos Aires, Argentina.
Figs 71-91, Table I.
The cells are solitary. Frustules are drum-shaped in
girdle view (Figs 77, 78). Valves are circular in outline,
23-63 µm in diameter. The valve surface is tangentially
undulate, having pronounced elevation, and it is exter-
nally divided in two concentric areas, a central field and a
marginal area (Figs 77-79). The central field is externally
colliculate, occupying almost a half of the valve surface
(Figs 71-79), and internally smooth (Figs 85-87). The
marginal area is restricted to a half of the valve surface,
and presents radial depressed striae (11-13 in 10 µm) and
interstriae, extending from the vertical part of central area
to the edge of the valve mantle (Figs 78, 79 asterisks).
Interstriae are wide, and frequently furnished with gran-
ules towards the junction valve face/mantle (Figs 77-84).
The striae are alveolate, the outside areolate layer presents
two or three rows of areolae near the central field, four to
six near the valve surface margin and sometimes more in
the mantle (Figs 80-84). Valve mantle with inserted inter-
striae close the margin (Figs 80-84). Internally, the valve
presents marginal chambers, 4-6 in 10 µm, often separat-
ed by one coarse interstriae, less frequently by two (Figs
85-91). When seen in LM, the marginal chambers are
evident (Figs 71-76) while this feature is not appreciated
when the external view of the valve is observed in SEM.
Each chamber contains commonly two (three) alveolus
openings and one (two) recessed costate interstriae (Figs
85-91). The chamber that contains the rimoportula shows
four to six alveolus openings (Figs 88, 90). The fultopor-
tulae are located on every recessed costate interstria and
bear two radial satellite pores (Figs 88-91). The single
rimoportula is short and pedicellate, flat, with obliquely
oriented lip (Figs 85, 87, 88, 90 arrows). The fultopor-
tulae open outwards by a circular pore with a thickened
rim and are placed on every second, less frequently on
Figs 71-76. – Cyclotella cubiculata sp. nov. LM. Figs 71, 72, Same valve in different focuses showing marginal chambers, arc of fulto-
portulae (arrowheads) and rimoportula (arrows). Figs 73-76, From holotype, slide LPC 4260 (1). Fig. 73, Valve showing the coarse
interestriae that limit the marginal chambers. Rimoportula is arrowed. Figs 74, 75, Same valve in different focuses. Note the arc of ful-
toportulae (arrowhead) and the rimoportula (arrow). Fig. 76, Large specimen showing arc with many fultoportulae (arrowhead).
THALASSIOSIRALES FROM ARGENTINIAN COASTAL WATERS 147
Vie Milieu, 2010, 60 (2)
every first or third inter-
striae (Figs 77, 78, 80-84).
The rimoportula aperture is
circular or elliptical placed
between two or more ful-
toportulae level with or
slightly above the marginal
ring of fultoportulae (Figs
80, 82, 83 arrows), in front
of the raised central field
(Figs 77, 78 arrows). There
are five to fifteen fultopor-
tulae on the raised sector
of the central field forming
an arc, they open externally
by a pore (Figs 71, 72, 74,
76 arrowheads, 79) and
internally by a short tube
surrounded by three satel-
lite pores (Figs 85, 87). The
cingulum is composed of
a valvocopula and three or
four copulae open, unorna-
mented with the openings
arranged in a dextral spiral
(Figs 80, 81, 83, 84). The
copulae are ligulate.
This species is plankton-
ic, marine.
Holotype: Slide LPC
4260 (1) designated here,
labelled holotype Cyclo-
tella cubiculata, deposited
at Colección de Diatomeas
Argentinas, Departamento
Científico Ficología, Fac-
ultad de Ciencias Naturales
y Museo.
Isotype: Slide LPC
4260 (2) designated here,
labelled isotype Cyclotella
cubiculata, deposited at
Colección de Diatomeas
Argentinas, Departamento
Científico Ficología, Fac-
ultad de Ciencias Naturales
y Museo.
Type locality: Nueva
Atlantis, 36º 45’ 81’’S-56º
40’ 04’’W, Prov. de Buenos
Aires, Argentina.
Etymology: The Latin
word “cubiculata” means
furnished with chambers,
and “cubiculum” means
Table I. – Legend
Taxon Diameter
in µm
Striae in
10 µm
Ratio
central eld/
diameter
Marginal
chambers
in 10 µm
Alveolus
opening in
each chamber
Position of marginal
fultoportulae
Number of
satellite pores
Valve face fultopotulae
number and position
Number of
satellite pores Rimoportula
Cyclotella baltica111-45 9-12 nd absent --- On 2nd, 3rd (4th) interstria 2, in radial
position
1 to several in a
semicircular (half-
moon) position uplift of
the undulation
(2) 3 Sessile, radially
oriented, above the
marginal ring of
fultoportulae
Cyclotella litoralis210-60 9-14 0.5 small
specimens,
0.66 large
specimens
absent --- On every 2nd interstria,
[1ft or 3rd ]*
2, in radial
position
2-20 in an arc on the
uplift of the undulation
3 Radially oriented,
below the marginal
ring of fultoportulae
Cyclotella litoralis310-62.8 9-14 0.45-0,66 absent --- On every 2nd interstria,
(1ft or 3rd)
2, in radial
position
1-many in an arc on the
uplift of the undulation
3 Radially oriented,
below the marginal
ring of fultoportulae
Cyclotella cubiculata323-63 11-13 0.52-0.56 present,
4-6
2, (3) On every 2nd interstria,
(1ft or 3rd)
2, in radial
position
5-15 in an arc on the
uplift of the undulation
3 Obliquely oriented,
within a chamber,
above or level with
the marginal ring of
fultoportulae
Cyclotella striata120-67 nd nd with recessed
costae
nd On every 3rd or 4th
interstria
3 absent --- [Tangentially
oriented]*,very
broad “mouth”
Cyclotella striata225-48 7-13 0.69-0.73 Present
3-4
2 On every 2nd to 4th
interstria
3 1-2 nd Tangentially
oriented, big
Cyclotella striata420-67 8-10 nd present nd On every 3rd or 4th
interstria
3 absent --- [Tangentially
oriented]*, very
broad “mouth”
Cyclotella stylorum235-67 9-12 0.47-0.54 Present
2-3
3-4 Grouped in pairs or triplets
on interstriae
2, in radial
position
6-12 in an arc on the
uplift of the undulation
[3]* Radially oriented,
small
Cyclotella stylorum525-33 8-10 nd present, 3 nd Grouped in pairs or triplets
on interstriae
2, in radial
position
6-12 in an arc on the
uplift of the undulation
3 Obliquely oriented,
within a chamber.
Håkansson (2002)1, Lange &Syvertsen (1989)2, This study3, Håkansson (1996)4, Prasad & Nienow (2006)5
[ ]* observed by authors from the quoted paper .
148 E. A. SAR, I. SUNESEN, A. S. LAVIGNE
Vie Milieu, 2010, 60 (2)
chamber. See definition of chamber in Lange & Syvertsen
(1989).
Distribution in Argentina: Cyclotella cubiculata was
found during the present study in plankton net samples
from San Clemente del Tuyú, Santa Teresita, La Lucila
del Mar, Mar de Ajó, Nueva Atlantis, Pinamar and Villa
Gesell, rare all year around. This variety was abundant in
Nueva Atlantis, on January 11, 1995 and March 27, 1995.
Photographed material: LPC 4256, 01/11/1995, Nueva
Atlantis; LPC 4260, 03/27/1995, Nueva Atlantis; LPC
4261, 03/27/1995, Nueva Atlantis. Considering that anal-
ysed with SEM the external view of Cyclotella cubiculata
Figs 77-84. – Cyclotella cubiculata sp. nov. SEM. Figs 77, 78, Tilted frustules of different sizes. Arrows show the position of rimopor-
tulae and the asterisks (Fig. 78) the striae extending from the vertical part of the central area to the edge of the valve mantle. Fig. 79,
Valve surface. Arrow shows the position of the rimoportula. Figs 80, 81, Details of Fig. 77 from opposite sides. Fig. 80, Rimoportula’s
side (arrow). Note the cingulum composed of valvocopula (v) and three copulae (c). Fig. 81, Note the cingulum composed of five
bands, the last one only visible as a ligula. Fig. 82, Detail of Fig. 79, note elliptical opening of the rimoportula (arrow) and inserted
interstriae on the valve mantle. Figs 83, 84, Details of Fig. 78 from rimoportula (arrow) and opposite sides.
THALASSIOSIRALES FROM ARGENTINIAN COASTAL WATERS 149
Vie Milieu, 2010, 60 (2)
Figs 85-91. – Cyclotella cubiculata sp. nov. SEM. Internal view. Figs 85-87, Valves showing chambers. Note coarse and costate inter-
striae, arc of fultoportulae on the valve surface and position of the rimoportula (arrows). Figs 88, 89, Details of Fig. 85. Fig. 88, Cham-
ber containing rimoportula (arrow), with six alveolus openings and five recessed costate interstriae. Fultoportulae placed on costate
interstriae. Fig. 89, Marginal chambers containing one costate interstriae. Figs 90, 91, Details of Fig. 86. Fig. 90, Chamber containing
rimoportula (arrow) with four alveolus openings and three costate interstriae. Fig. 91, Each marginal chamber containing one costate
interstria with fultoportula. Note fultoportulae with two satellite pores.
150 E. A. SAR, I. SUNESEN, A. S. LAVIGNE
Vie Milieu, 2010, 60 (2)
resembles Cyclotella litoralis and that both species fre-
quently coexist in the samples, we chose the photographs
of the samples 4256, 4260 and 4261 from Nueva Atlantis
where the new species was abundant and Cyclotella lito-
ralis rare.
Remarks: Cyclotella cubiculata resembles C. litoralis
and C. baltica (Grunow) Håkansson in external view, and
shows some similarities with C. striata (Kützing) Grunow
and C. stylorum Brightwell in internal view (see Table I).
We had to use published images for LM and SEM com-
parisons between the new taxon and the morphologically
related taxa in order to establish the striking features for
distinguishing them, and to justify the creation of the new
species.
DISCUSSION
Cymatotheca weissflogii, particularly specimens with
circular valve outline found in Buenos Aires coastal
waters, resembles two marine species of Thalassiosira
Cleve, T. hyperborea (Grunow) Hasle (Hasle & Lange
1989) and T. cedarkeyensis Prasad (Prasad et al. 1993)
in having tangentially undulate valves, internal separate
cribra, subcentral fultoportula placed at the convex part
of the valve surface, marginal ring of operculate fultopor-
tulae and marginal sessile rimoportula. Despite the above
similarities, it is distinguished from both Thalassiosira
species by the pattern of striation with wider interstriae in
the raised sector and narrower interstriae in the depressed
sector, the rimoportula placed in the position of a fulto-
portula but in a slightly different horizon, the processes
with no tubes outwards and the conspicuous hyaline area
placed at the depressed sector between valve surface and
mantle. Additionally, Thalassiosira hyperborea presents
one to eight subcentral fultoportulae and T. cedarkeyensis
several occluded processes, and both taxa have the mar-
ginal fultoportulae with four satellite pores.
Studied material of Tryblioptychus cocconeiformis
(Grunow ex Cleve) Hendey resembles those analysed
by Prasad et al. (2002) in their detailed morphological
study. We agree with authors that pointed out that this
taxon resembles Cymatotheca weissflogii. Both taxa pres-
ent tangentially undulate valves, valvar outline circular
to broadly elliptical, a subcentral fultoportula placed at
the convex part of the valve surface and a marginal ring
of fultoportulae including a rimoportula placed in the
depressed side of the valve. However, T. cocconeiformis
is quite different in having radial depressed sectors with
areolae in fascicles and raised sectors (inter-fascicles), a
hyaline area free of areolation around the valve surface,
valve mantle with a ring of larger areolae, fultoportulae
with four satellite pores placed in the inter-fascicles and
rimoportula with external tube.
Julius & Tanimura (2001) made a cladistic analysis of
several species of Thalassiosira with tangentially undu-
late valves in which they included Cymatotheca weiss-
flogii and Tryblioptychus cocconeiformis. The authors
concluded that the plicate studied taxa form a mono-
phyletic group and proposed to transfer them to a genus
whose name should be Cymatotheca or Tryblioptychus
for priority reason. Prasad et al. (2002) pointed out that
Tryblioptychus should remain separate as a distinct genus,
we share the supported opinion of Prasad et al. (2002)
and we think that the genus Cymatotheca should also
remain separate as a distinct genus. We believe that the
analysis of Julius & Tanimura (2001) failed in consider-
ing some morphological characters such as the striation
pattern, radial undulations delimiting fascicles and inter-
fascicles, width of the interstriae in depressed and raised
sectors, and presence of marginal hyaline areas. Besides,
these authors erroneously included some character states
e.g., the external opening of the marginal fultoportulae for
both taxa as tubes (they present pores, according to their
illustration 16), subcentral fultoportula with two satellites
pores for Cymatotheca weissflogii (it presents three satel-
lite pores).
Skeletonema tropicum was frequently misidentified in
the literature as S. costatum (Greville) Cleve (eg Hasle
1973b, Aké Castillo et al. 1995, Sar et al. 2001). Koo-
istra et al. (2008) pointed out that “Skeletonema costatum
s. l. was considered morphologically plastic, genotypi-
cally diverse, physiologically versatile, and was found
worldwide except in the Antarctic Ocean”. Zingone et al.
(2005) based on the analysis of the lectotype material des-
ignated by Ross et al. (1996), clarified the specific limit
of S. costatum (Greville) Cleve emend. Zingone & Sarno
and designated an illustration as epitype selected to serve
as interpretative of the lectotype (Art. 19.7 of the ICBN,
McNeill et al. 2006). Additionally, authors created a new
species Skeletonema grevillei Sarno & Zingone based on
material much rarer and smaller in size present in the lec-
totype slide of S. costatum. Besides, Sarno et al. (2005)
clarified the specific limits of Skeletonema tropicum
among others previously created species of Skeletonema
and described Skeletonema grethae Zingone & Sarno and
other three new species. In our material, Skeletonema
tropicum and S. grethae can be easily differentiated with
LM considering the number of chloroplasts, several in the
former and one or two in the latter. The SEM analysis of
both species allow us to find the striking features estab-
lished by Sarno et al. (2005): the position of the terminal
rimoportulae, half-way between the central annulus and
the marginal ring of rimoportulae in the former and adja-
cent to the central annulus in the latter; the morphology
of the external tube of the intercalary rimoportula, larger
and flattened in the former and shorter and cylindrical in
the latter; and the junction of the tubes of the intercalary
fultoportulae, 1:1 or 1:2 in the former and 1:1 in the lat-
ter. Skeletonema costatum differs from both analysed spe-
cies in the position and morphology of the terminal tube
of the rimoportula, near the marginal ring of fultoportulae
THALASSIOSIRALES FROM ARGENTINIAN COASTAL WATERS 151
Vie Milieu, 2010, 60 (2)
and with the distal end never flared; in the position and
the morphology of the tube of the intercalary rimoportula,
placed in the marginal ring of fultoportulae and similar
in length with the fultoportulae; in the morphology of
the tubes of intercalary fultoportulae, completely closed
or sometimes only closed in the basal part. Skeletonema
costatum, profusely recorded from Argentinian coastal
waters in the literature (see Vouilloud 2003), was never
found during the present study.
Analysed material of Cyclotella choctawhatcheeana
resembles those illustrated by Prasad et al. (1990), Pras-
ad & Nienow (2006), Wendkler (1991) and Håkansson
(1993) from marine coastal waters, by Maidana & Rome-
ro (1995), and Carvalho et al. (1995) from hypersaline
lakes, and by Oliva et al. (2008) from a hyposaline aquat-
ic system. Minor differences in the presence/absence, and
position of the granules were observed between our mate-
rial and other’s shown in the quoted literature. According
to Prasad et al. (1990), Maidana & Romero (1995) and
Melo et al. (2006), the cingulum of C. choctawhatcheea-
na consists of one valvocopula and one copula. However,
the cingulum of analysed specimens is formed by four
bands with aligned openings, the valvocopula and the
second copula have approximately the same width, the
first copula is reduced to a long and prominent ligula at
the pars exterior (Figs 47, 49), and third copula is narrow
and broadly ligulate (Fig. 47). The cingular morphology
is similar in the specimens photographed by Melo et al.
(2006, Fig. 7) and Maidana & Romero (1995, Fig. 15).
Based on the facts that the ligula lacking valvocopula and
that both valvocopulae of the same frustule are similar,
thus the last narrow ligulate band is a copula and the girdle
is composed by four bands. This morphological pattern
of the girdle is consistent with the pattern described for
Cyclotella litoralis by Lange & Syvertsen (1989) and for
Cyclotella cubiculata in this study with the difference that
in the two latter species the band openings are arranged
in a dextral spiral. The morphology of the second copula
and the band openings aligned should be considered as
striking features of Cyclotella choctawhatcheeana. More
variability of band openings pattern was found for the
genus Thalassiosira by Fryxell et al. (1981), since a sinis-
tral spiral pattern was also observed. Additionally, while
all the bands of the species of Cyclotella analysed in this
study are non porous, the valvocopula, the first copula
and in some cases all the copulae are porous in Thalas-
siosira (Fryxell et al. 1981).
Studied specimens of Cyclotella litoralis perfectly
coincide in morphology with those described by Lange &
Syvertsen (1989) (see Table I), however, some informa-
tion about the colony formation in this species is added.
In the sampling area together with C. litoralis there was
found a new taxon that we created under the name Cyclo-
tella cubiculata sp. nov. Both species resemble in general
external aspect of the valve, elevation of the tangential
undulation, structure of the central field, ratio diameter of
the central field/total diameter, density of alveolate striae,
arrangement of the fultoportulae in the central field and in
the valve mantle, and morphology of the cingulum (Table
I). Only a minor difference was found in external view,
the opening of the rimoportula placed level with or above
the marginal ring of fultoportulae in Cyclotella cubicu-
lata, similar in position to that of C. baltica, and below
the level of the marginal ring of fultoportula in C. lito-
ralis. However, Cyclotella cubiculata clearly differs from
C. litoralis and C. baltica by presenting marginal cham-
bers easily visible with LM and with SEM only in internal
view. Additionally, C. cubiculata differs from C. baltica
in external arrangement of the fultoportulae in the valve
mantle, more densely arranged in the former than in the
latter.
Cyclotella cubiculata was also compared to two
marine species with marginal chambers, C. striata and
C. stylorum (see Table I). In LM analysis the new vari-
ety differs from type material of C. striata illustrated by
Håkansson (1996, Figs 9, 10) and by Lange & Syvertsen
(1989, Figs 34, 35) in the ratio diameter of the central
field/total diameter, 0.52-0.56 in the former and 0.69-0.73
in the latter; in stria density, 11-13 in 10 µm in the former
and 8-10 in 10 µm in the latter, and in the distribution of
fultoportulae on the valve surface, five to 15 on undula-
tion of the valve surface in the former and completely
absent in the latter. Håkansson (1996, Figs 20-24) and
Lange & Syvertsen (1989, Figs 36, 37) also presented a
SEM analysis of C. striata from the type locality. These
specimens internally present chambers, 3-4 in 10 µm,
separated by two, three or more coarse interstriae, with
two alveolus openings, marginal fultoportulae with three
satellite pores, and rimoportula tangentially oriented. The
new species is clearly different, it presents 4-6 chambers
in 10 µm, generally separated by only one (sometimes
two) coarse interstria, with two (three) alveolus open-
ings, marginal fultoportulae with two satellite pores, and
rimoportula obliquely oriented. Additionally, both taxa
differ in the arrangement of marginal fultoportula open-
ings, placed on every third or fourth interstria in C. striata
and on every second (less frequently first or third) inter-
stria in C. cubiculata. The specimens of C. stylorum from
Sierra Leona and from Brazil photographed with LM by
Lange & Syvertsen (1989) and Prasad & Nienow (2006)
and specimens of C. cubiculata analysed with LM in this
study, show notable differences in chamber morphology,
the coarse interstriae are very robust in the former and
they are more subtle in the latter, and in chamber density,
2-3 in 10 µm in the former and 4-6 in 10 µm in the lat-
ter. A comparative SEM analysis of chamber morphology
shows that in C. stylorum (see Lange & Syvertsen 1989,
Fig. 33) chambers contain two or three costate interstriae,
while in C. cubiculata they generally contain only one,
less frequently two, costate interstria. Additionally, the
costate interstriae are very different in thickness and posi-
tion, lying more recessed in the chamber in C. stylorum.
152 E. A. SAR, I. SUNESEN, A. S. LAVIGNE
Vie Milieu, 2010, 60 (2)
C. cubiculata superficially resembles another species
with marginal chambers, C. desikacharyi Prasad (see
Prasad & Nienow 2006, Figs 16-34), but differs from it
by the external morphology of the valve, density of the
striae, morphology of the chambers and position of the
rimoportulae in internal view. The new species was the
only taxon with marginal chambers found in the area dur-
ing the present study; we never found either C. striata or
C. stylorum.
Our material of Cyclotella cubiculata sp. nov. perfectly
fits with material illustrated by Tanaka (2007: pl. 23-25)
under the name C. litoralis Lange & Syvertsen from Isaha-
ya Bay, Nagasaki Prefecture. This author interpreted that
the figure 26 given by Lange & Syvertsen (1989) shows
the fultoportulae on slightly recessed interstriae however,
in this figure as in our figures 60, 69, 70 the intestriae are
all at the same level and the fultoportulae protrude from
this level. Based on this point of view he stretched the
determination of his material as C. litoralis. In material
of C. cubiculata from Buenos Aires coastal waters and
from Isahaya Bay (see our Figs 85-91 and Tanaka’s plate
25 Figs 1-3) the recessed interstriae bear the fultoportulae
and these never reach the level of the coarser interstriae.
Besides, we also consider that Tanaka’s specimens illus-
trated with light micrographs (plate 11 figures 2a, 2b, 3 a,)
as Cyclotella baltica do not fit with this species but with
Cyclotella cubiculata because they clearly show marginal
chambers which are completely absent in internal view of
the valve of C. baltica (see Tanaka’s plate 13, figs 1, 2, 4,
5). Based on this evidence we can speculate that the new
species is widely distributed, probably cosmopolitan.
ACKNOWLEDGEMENTS. – We would like to thank Dr A
K S K Prasad for providing some important bibliography and
his valuable opinion about some material presented in this paper,
Dr D Giuliano for improving our Latin description, Lic Cecilia
Castaños, Vet Y Bacci and Mr J Pablo Almeida for helping us
with the sampling and Mr Pablo Lalín for his technical assis-
tance. We also thank the anonymous reviewers and the editor for
very useful comments which improved our paper and J Sayell
for the English revision. The electron microscopy was done in
the Servicio de Microscopía Electrónica of the Facultad de
Ciencias Naturales y Museo. The research was supported by
grants from the CONICET, PIP 5312/06 and from the UNLP
11/N 516.
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Received July 7, 2009
Accepted November 2009
Associate Editor: C Gobin