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New records of planktonic dinoflagellates (Dinophyceae) from the Mexican Pacific Ocean

  • Instituto de Ciencias del Mar y Limnología, UNAM, México


Phytoplankton samples were taken during several oceanographic cruises in the Mexican Pacific Ocean (1998–2000), following three different protocols of collection and analysis, and from the material we report six new records of planktonic dinoflagellates in the region. Two species, Asterodinium spinosum and Brachydinium capitatum, are unarmored, another species, Actiniscus pentasterias, has internal siliceous skeletons, whereas Thoracosphaera heimii usually develops a calcareous coccoid vegetative stage. Calciodinellum operosum produces calcareous cysts that were also found in this study, and Achradina pulchra has an internal skeleton of organic material. Three species, A. spinosum, B. capitatum and C. operosum, were represented by very few specimens, whereas all others were more frequent. Brief descriptions and illustrations of these species by light and scanning electron microscopy are provided. The methods and techniques to study this group have been diverse and useful in finding a greater diversity. The world distribution of the species recorded here is revised.
Botanica Marina 47 (2004): 417–423 2004 by Walter de Gruyter Berlin New York. DOI 10.1515/BOT.2004.051
New records of planktonic dinoflagellates (Dinophyceae)
from the Mexican Pacific Ocean
David U. Herna´ ndez-Becerril* and Ernesto
Laboratorio de Diversidad y Ecologı´a del Fitoplancton
Marino, Instituto de Ciencias del Mar y Limnologı´a,
Universidad Nacional Auto´ noma de Me´ xico (UNAM),
Apdo. postal 70-305, Me´ xico, D.F. 04510 Mexico,
*Corresponding author
Phytoplankton samples were taken during several ocean-
ographic cruises in the Mexican Pacific Ocean
(1998–2000), following three different protocols of collec-
tion and analysis, and from the material we report six new
records of planktonic dinoflagellates in the region. Two
species, Asterodinium spinosum and Brachydinium capi-
tatum, are unarmored, another species, Actiniscus pen-
tasterias, has internal siliceous skeletons, whereas
Thoracosphaera heimii usually develops a calcareous
coccoid vegetative stage. Calciodinellum operosum pro-
duces calcareous cysts that were also found in this
study, and Achradina pulchra has an internal skeleton of
organic material. Three species, A. spinosum,B. capita-
tum and C. operosum, were represented by very few
specimens, whereas all others were more frequent. Brief
descriptions and illustrations of these species by light
and scanning electron microscopy are provided. The
methods and techniques to study this group have been
diverse and useful in finding a greater diversity. The world
distribution of the species recorded here is revised.
Keywords: dinoflagellates; Mexican Pacific Ocean; new
records; phytoplankton.
Dinoflagellates (Class Dinophyceae) belong to a very
diverse and heterogeneous microalgal group, which is
very important in the marine phytoplankton. These algae
(together with diatoms), contribute significantly to both
the biomass and productivity of coastal pelagic systems.
The number of extant species of marine phytoplankton
is around 1880 (Sournia 1986, Sournia et al. 1991) or
approximately 2000 (Taylor 1987, Steidinger and Tangen
In the Mexican Pacific Ocean, dinoflagellates have
been studied from floristic and taxonomic points of view,
beginning with early work of Kofoid (1907); subsequently,
in adjacent waters Kofoid studied and described many
dinoflagellates. Later, Allen (1941) recorded the plank-
tonic dinoflagellates from southern California. There are
further reports from Osorio-Tafall (1942), Herna´ ndez-
Becerril (1988a,b,c, 1989, 1991, 1992) and Licea et al.
(1995), who carried out studies in more tropical waters
(i.e., Gulf of California, Acapulco, Gulf of Tehuantepec).
These studies have concentrated mostly on the
armored (or thecate) fraction of dinoflagellates, whose
external structures preserve well using even collection
methods such as nets or bottles and routine preserva-
tives (Lugol’s solution or formalin). The unarmored (or
naked) dinoflagellates have been less studied, and their
contribution to phytoplankton productivity may have
been underestimated. Other dinoflagellates with internal
skeletons or producing calcareous stages have not been
reported in Mexican waters so far, although a recent
paper contributed to our knowledge of dinoflagellate
cysts in the Gulf of California (Mexican Pacific Ocean)
(Morquecho and Lechuga-Deve´ ze 2003).
Despite continuing investigations of phytoplankton col-
lected off the Mexican Pacific coast, important areas still
remain unstudied, among them the so-called Tropical
Mexican Pacific Ocean, which may prove to be species-
rich. Our analysis of phytoplankton, obtained and studied
following different protocols, from various oceanographic
cruises carried out recently off the Pacific coast of Mex-
ico, has revealed several interesting dinoflagellate spe-
cies that are new records for the country.
Materials and methods
Between 1998 and 2000 samples were taken following
three different protocols:
1. Samples collected off the coast of Michoacan (9–10
April, 1999) by net (54 mm mesh), in vertical hauls
from 100 m to surface, fixed with 4% formalin (Table
1, Figure 1). Some forms smaller than the net mesh
size were found, probably because of clogging of the
2. Bottle samples (generally 5 l) were taken off the coast
of Baja California (5–14 December, 1998), at surface
(1–1.5 m), and filtered (filters 1.2 mm) by gravity (Table
1, Figure 1). Before the complete filtration, 10–20 ml
of the concentrated material were divided into: (a) a
reference sample fixed with Lugol’s solution and glu-
taraldehyde (Østergaard 1998), (b) material for obser-
vation in vivo by light microscopy, and (c) an inoculum
for establishing culture-isolations of single cells by the
dilution method (Throndsen 1997).
3. Bottle samples (4 l) were taken from several fixed
stations off the coast of Baja California (20 March–1
April, 1998) and the Gulf of Tehuantepec (8–15 April,
2000), at three different depths (5, 25, 50 m), and were
filtered (filters 0.45 mm) with a vacuum pump
418 D.U. Herna´ ndez-Becerril and E. Bravo-Sierra: New records of Dinophyceae from Mexico
Table 1 New records of dinoflagellates from the Mexican Pacific Ocean, with locations (Figure 1) and study protocols used.
Species Localities Protocol
Achradina pulchra Lohmann 4 Tehuantepec 3
Actiniscus pentasterias (Ehrenberg) Ehrenberg 1, 2, 4 BC and Tehuantepec 1, 3
Asterodinium spinosum Sournia 3 Michoacan 1
Brachydinium capitatum Taylor 2 BC 2
Calciodinellum operosum Deflandre emend. Montresor 4 Tehuantepec 3
Thoracosphaera heimii (Lohmann) Kamptner 1, 2, 4 BC and Tehuantepec 3
BCsBaja California.
(Bollmann et al. 2002), and then were rinsed with dis-
tilled water (Table 1, Figure 1).
Material was studied directly from the net samples, the
filtered and fixed samples, and the filters by light micro-
scopy (LM) in fresh mounts. Observations by scanning
electron microscopy (SEM) were also made, using mate-
rial treated conventionally (mounted, air-dried and coated
with gold). A Zeiss (Mexico City, Mexico) Axiolab light
microscope (bright field and phase contrast, with
attached camera -Contax 167 MT wTokyo, Japanx) and a
JEOL 1200 EX scanning electron microscope (Tokyo,
Japan) were used for our observations.
Terminology and systematics follow recent proposals
by Fensome et al. (1993) and Steidinger and Tangen
We identified 6 species of dinoflagellates, which are brief-
ly described and illustrated by LM and/or SEM. Some
relevant references are annotated for each species and
conspicuous synonyms are also provided. Table 1 pro-
vides the complete species list.
Systematic account of Actiniscus pentasterias
(Ehrenberg) Ehrenberg (Figures 2–4)
Division Dinoflagellata (Bu¨ tschli) Fensome et al.; Subdi-
vision Dinokaryota Fensome et al.; Class Dinophyceae
Pascher; Subclass Gymnodiniphycidae Fensome et al.;
Order Gymnodiniales Apstein; Suborder Actiniscineae
(Sournia) Fensome et al.
Family Actiniscaceae Ku¨ tzing; Genus Actiniscus
Ehrenberg; Actiniscus pentasterias (Ehrenberg) Ehren-
berg. – Schiller 1937, p. 2, figs 1 a–d (as Gymnaster pen-
tasterias Schu¨ tt); Bursa 1969, p. 412, figs 1– 14;
Steidinger and Williams 1970, p. 42, pl. 1, figs 1a–b; Orr
and Conley 1976, p. 92, pl. 1, figs 1–11, pl. 2, figs 1–6;
Balech 1988, p. 199, pl. 82, figs 22, 23; Larsen and Sour-
nia 1991, p. 320, fig. 21.30; Hansen and Larsen 1992, p.
90, figs. 4.46 a–c; Hansen 1993, p. 486, figs 1–5; Stei-
dinger and Tangen 1997, p. 428, pl. 24; Konovalova
1998, p. 81, figs 19.6 a–v; Be´ rard-Therriault et al. 1999,
p. 163, pl. 81 e–g, i.
The specimens encountered here agree well with all
previous descriptions. Whole cells were undetected and
only specimens showing the internal, siliceous skeleton
were found. Many authors have confirmed absence of
chloroplasts in this species (Larsen and Sournia 1991,
Hansen 1993). Dimensions: maximum diameter of skel-
etons ranged between 23–28 mm.
Distribution: specimens were found at various loca-
tions, including the coasts of Baja California and the Gulf
of Tehuantepec (localities 1, 2, 4; Figure 1). The species
was relatively frequent, hence we suggest that its distri-
bution is wide in the Mexican Pacific Ocean.
Systematic account of Achradina pulchra Lohmann
(Figures 5–8)
Order Ptychodiscales Fensome et al.; Family Amphitho-
laceae Poche; Genus Achradina Lohmann; Achradina
pulchra Lohmann. – Schiller 1937, p. 5, figs 2 a– c; Nival
1969, p. 126, figs 1–11, pl. 1, figs 1–10, pl. 2, figs 1–12;
Larsen and Sournia 1991, p. 314, fig. 21.28; Konovalova
1998, p. 82, figs 19.5 a–b.
Specimens found had no cytoplasm. The internal skel-
etons have a general oblong shape, with a constriction
in the middle. Most of the skeleton is run by longitudinal
ridges formed by large granule-like structures, and also
has a complex pattern of smaller granules in a zig-zag
pattern. The apical hemisphere has a pointed crest which
is smooth, with four slit-like openings radiating to the
margin. Below this crest, there are two larger, ovoid
openings. The antapical end presents a hexagonal or
heptagonal pattern of granules, which are larger at the
angles and center of this pattern. The dorsal view shows
an archeopyle, a large opening. This species is consid-
ered to be non-photosynthetic. Dimensions: total length
29–36.5 mm, width 18–21 mm.
Distribution: many specimens of this species were
detected in the Gulf of Tehuantepec (locality 4; Figure 1).
Systematic account of Asterodinium spinosum
Sournia (Figure 9)
Family Brachidiniaceae Sournia; Genus Asterodinium
Sournia; Asterodinium spinosum Sournia. – Sournia
1972, p. 152, fig. 5; Abboud-Abi-Saab 1989, p. 12, fig.
5a; Go´ mez and Claustre 2003, fig. 2 a (as Asterodinium
gracile Sournia).
The cells are solitary and delicate, of small size. The
shape is star-like, with the body very reduced and with
five straight or slightly curved arms or processes. The
apical arm is longer, straight and truncate, the lateral
arms are thin and delicate, with pointed ends, whereas
the posterior arms are slightly shorter and more robust:
the left posterior arm bears the prominent nucleus. The
cingulum is inconspicuous. There are several oblong and
discoid chloroplasts throughout the cell. Dimensions:
total length 22–24 mm, width (maximum separation of
lateral arms) 26–28 mm, length of apical arm 11.5 mm.
D.U. Herna´ ndez-Becerril and E. Bravo-Sierra: New records of Dinophyceae from Mexico 419
Figure 1 Map of the Mexican Pacific Ocean showing sampling locations.
1sBaja California (Ensenada), 2sBaja California (Bahia Magdalena), 3sMichoacan (La´ zaro Cardenas), 4sGulf of Tehuantepec.
Figures 2–4 Actiniscus pentasterias: LM, SEM.
(2) Apical view of a typical internal skeleton with 5 arms and ornamentation in ridges, SEM. (3) Another internal skeleton of a specimen,
LM. (4) Two skeletons in apical and lateral view showing surface morphology, SEM. Scale barss5mm (Figures 2, 4); 15 mm (Figure
Distribution: species occurring on the coasts of
Michoacan (locality 3; Figure 1), with only two specimens
Systematic account of Brachydinium capitatum
Taylor (Figures 10, 11)
Genus Brachydinium Taylor; Brachydinium capitatum
Taylor. – Taylor 1963, p. 75, pl. VIII, figs 1–3; Le´ ger 1972,
p. 29, fig.14; Sournia 1972, p. 152, figs 2, 6; Sournia et
al. 1979, p. 193, fig. 39; Abboud-Abi-Saab 1989, p. 12,
fig. 4b; Steidinger and Tangen 1997, p. 428, pl. 24.
The cells appeared solitary, delicate, of medium size.
The cells are asymmetric, with no general shape, four
relatively long, curved or more straight arms (or process-
es), which arise from the body. There is an apical pro-
tuberance, eccentric, slightly displaced to the right, and
an indentation is present between the two lateral arms
and this protuberance; this indentation represents the
cingulum. The lateral arms are longer than the posterior
arms, tapering toward the tip, which is pointed. The pos-
terior arms are almost symmetric, with the right slightly
shorter than the left. The nucleus is parietal, displaced to
the right of the body. Numerous chloroplasts throughout
the cell. Dimensions: total length 48–50 mm, width (max-
imum separation of lateral arms) 107–110 mm, maximum
length of posterior arms 37 mm.
Distribution: species found in Baja California (locality
2; Figure 1), very rare.
Systematic account of Calciodinellum operosum
Deflandre emend. Montresor (Figure 12)
Subclass Peridiniphycidae Fensome et al.; Order
Peridiniales Haeckel; Suborder Peridiniineae; Family
Peridiniaceae Ehrenberg; Subfamily Calciodinelloideae
Fensome et al.; Genus Calciodinellum Deflandre; Calcio-
dinellum operosum Deflandre emend. Montresor. – Mon-
tresor et al. 1997, p. 123, figs 10–13, 19; Williams et al.
1998, p. 86; D’Onofrio et al. 1999, p. 1066, figs 14–16;
Sgrosso et al. 2001, p. 81.
In our samples only calcareous cysts were encoun-
tered. The cysts show an arrangement of paraplates and
a conspicuous apical pore. There are four paraplates sur-
420 D.U. Herna´ ndez-Becerril and E. Bravo-Sierra: New records of Dinophyceae from Mexico
Figures 5–8 Achradina pulchra: SEM.
(5) Ventral view of an internal skeleton showing surface ornamentation and the apical crest with four openings. (6) Dorsal view of
another specimen, with the archeopyle. (7) Antapical view of a specimen. (8) Apical view of the skeleton, showing the apical crest.
Scale bars5mm.
rounding the apical pore. Other specimens showed well-
developed paratabulation ridges. The surface of the
cysts appears granular and has scattered pores. Vege-
tative cells are photosynthetic. Dimensions: diameter
29–34 mm.
Distribution: very few cysts found in the Gulf of
Tehuantepec (locality 4; Figure 1).
Systematic account of Thoracosphaera heimii
(Lohmann) Kamptner (Figure 13)
Subclass Prorocentrophycidae Fensome et al.; Order
Thoracosphaerales Tangen; Family Thoracosphaeraceae
Schiller; Genus Thoracosphaera Kamptner; Thoraco-
sphaera heimii (Lohmann) Kamptner. Synonym: Syraco-
sphaera heimii Lohmann. – Inouye and Pienaar 1982, p.
64, figs 1, 2, 24; Tangen et al. 1982, p. 195, pl. I, figs
1–6; Fensome et al. 1993, p. 168, fig. 171; Steidinger and
Tangen, 1997, p. 549; Williams et al. 1998, p. 160.
This species has a particular vegetative form, which is
predominantly a coccoid, calcareous stage, for some
time considered to be a coccolithophorid (Tangen et al.
1982). The cells are spherical and relatively small, with a
large and conspicuous aperture. The surface of the wall
is irregular, covered with granules and perforated by
small pores. The planospore is non-thecate and a Gym-
nodinium-like cell. All live stages possess chloroplasts
(Inouye and Pienaar 1982, Tangen et al. 1982). Dimen-
sions: diameter 10–12 mm, aperture 3–4 mm.
Distribution: occurred in a relatively common manner
in Baja California and the Gulf of Tehuantepec (localities
1, 2, 4; Figure 1).
Diversity of planktonic dinoflagellates from the Mexican
Pacific Ocean may be considered relatively high: recent
reviews indicate an approximate number of 350 taxa
(Herna´ ndez-Becerril 2003), and for only the Order Dino-
physiales, the number of taxa is 90 (Herna´ ndez-Becerril
et al. 2003). However, unarmored or naked planktonic
dinoflagellates have generally been underestimated,
ignored or little studied in Mexican waters. This could be
mainly due to the methods traditionally used for collect-
ing and studying dinoflagellates, which deteriorate the
unarmored fraction. Bottle samples, fixed with Lugol’s
solution preserve relatively well most naked dinoflagel-
lates, and concentrated samples from passive filtration
(this study, protocol 2) are ideal for studying naked forms
D.U. Herna´ ndez-Becerril and E. Bravo-Sierra: New records of Dinophyceae from Mexico 421
Figures 9–11 Asterodinium spinosum and Brachydinium capitatum:LM.
(9) A. spinosum, a complete cell in dorsal view, showing the typical star-like shape of the cell, phase contrast. (10, 11) B. capitatum,
a cell in dorsal view, showing four processes and numerous chloroplasts, bright field. (11) Same cell, phase contrast. Scale bars10 mm
(Figure 9); 20 mm (Figures 10, 11).
Figures 12–13 Calciodinellum operosum and Thoracosphaera heimii: SEM.
(12) C. operosum, apical view of a cyst with the apical pore and apical plates. (13) T. heimii, a complete coccoid cell, showing large
aperture and surface granulation. Scale bars5mm.
in vivo, to cultivate them, or to preserve them with a mix-
ture of Lugol’s solution and glutaraldehyde. We found
one unarmored new record, Brachydinium capitatum
(Table 1) following this method, and we are still working
with naked forms that have been cultivated.
There are four possible explanations for finding new
records of planktonic dinoflagellates in the Mexican
Pacific Ocean: (1) some areas still remain unstudied, par-
ticularly in the Tropics, (2) the methods traditionally used
to collect and study phytoplankton have underestimated
the diversity of certain forms, especially the naked frac-
tion, (3) the routine analyses have been made by poorly
trained personnel, who have misidentified or ignored
some species difficult to recognize (due to their size or
shape) or who lack literature to identify species, and (4)
there have been introductions of exotic species into the
Introduction of planktonic species into the Mexican
Pacific waters may only be speculated upon, for medium
to long-term studies or monitoring do not exist for most
regions. However, this fact has been discussed in the
context of increasing events of harmful microalgal
blooms (Hallegraeff 1998).
World distribution of the species recorded here indi-
cates that Achradina pulchra,Actiniscus pentasterias and
Thoracosphaera heimii are forms very widely distributed
in temperate to tropical regions. They may be referred
to as ‘‘cosmopolitan’’, with no certainty of their habitat:
oceanic or neritic, although they appear more in coastal
waters. All locations where we found them are coastal.
The distribution of Calciodinellum operosum is not well
known and it was only detected at the calcareous cyst
stage. It is likely that further collections and studies in
Mexican waters will find the vegetative cell, too.
Actiniscus pentasterias has a considerable fossil rec-
ord (Williams et al. 1998) and all other species found here
with a calcareous external/internal structure have also
been recorded from fossil material (Fensome et al. 1993).
This species is well represented in world waters, and it
may also be considered to be ‘‘cosmopolitan’’.
Two genera of the Family Brachydiniaceae, Asterodi-
nium and Brachydinium, were recently recorded for the
first time from the subtropical (Philippine Sea, Sulu and
East China Seas) and equatorial western Pacific Ocean
(Go´ mez et al. 2003). The species we report herein for the
Mexican Pacific Ocean belong to those genera: Astero-
dinium spinosum and Brachydinium capitatum. There-
fore, we confirm that the two genera are more widely
distributed than previously thought, as they were origi-
nally described for Indian Ocean waters (Taylor 1963,
422 D.U. Herna´ ndez-Becerril and E. Bravo-Sierra: New records of Dinophyceae from Mexico
Sournia 1972), and then the species Brachydinium capi-
tatum,Asterodinium gracile Sournia and Asterodinium
libanum Abboud-Abi Saab were reported for the Medi-
terranean Sea (Le´ ger 1972, Go´ mez and Claustre 2003,
respectively). The presence of Asterodinium species may
well be favored by the progressive warming of the Med-
iterranean Sea (Go´ mez and Claustre 2003). The two spe-
cies are unquestionably tropical forms, probably also
neritic, although Sournia et al. (1979) found the species
in a supposedly colder area, still in the Indian Ocean.
We are grateful to Drs V. Arenas, C. Robinson, A. Carranza, Ma.
L. Machaı´n for inviting us to participate in the oceanographic
cruises where material was obtained for this study (cruises SIM-
SUP XIV, XVI, SEDIMENTO III and PACMEX III), and to the crew
of R/V ‘‘El Puma’’. F.I. Barbosa collected samples on one cruise,
Y. Hornelas and J. Sepu´ lveda provided assistance with SEM.
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Received 2 December, 2003; accepted 5 August, 2004
... It was originally described with the type species Asterodinium gracile Sournia from the Mozambique Channel in the southwest Indian Ocean (Sournia 1972a). Subsequently, Asterodinium was reported from the Mediterranean Sea, Atlantic and Pacific Oceans, and the Mexican coast (Abboud-Abi Saab 1985Saab , 1989Estrada 1979;Gómez 2003Gómez , 2011Gómez et al. 2005a;Hernandez-Becerril & Bravo-Sierra 2004;Reñé et al. 2015;Sournia 1972b). Based on the morphological similarity with Brachidinium, especially with the characteristic cellular extensions, Asterodinium was assigned to the family Brachidiniaceae in the Brachidiniales (Sournia 1984) or Ptychodiscales (Fensome et al. 1993). ...
... These morphological differences were based on preserved specimens usually collected during research cruises (e.g. Gómez 2003Gómez , 2006Gómez , 2011Hernandez-Becerril & Bravo-Sierra 2004). ...
Morphological variation, ultrastructure, pigment composition and phylogeny of an oceanic, star-shaped, unarmored dinoflagellate Asterodinium gracile were examined using a culture established from Nagasaki, Japan, in 2017. Our examinations were based on LM, SEM, TEM, high-performance liquid chromatography (HPLC) and molecular phylogeny inferred from nuclear-encoded internal transcribed spacer (ITS) and 28S rDNA and chloroplast-encoded 16S rDNA sequences. Typical cells were stellate, possessing an apical, two lateral, and two antapical extensions. Cells ranged in size from 62.5 to 105.6 µm long and 21.2 to 39.5 µm in cingular width. The length and orientation of cellular extensions were variable; that is, two lateral extensions were usually symmetrically bent or retracted. Ellipsoidal cells without extensions were also observed. The apical structure complex was straight or slightly sigmoid. A spherical nucleus was located at the left side in the hyposome. The numerous discoid, yellowish-brown chloroplasts were variable in size and distributed also in the cell extensions. Among Kareniaceae, the lack of a pyrenoid in Asterodinium is unique. Nuclear-encoded ITS and 28S phylogenies suggested that A. gracile is closely related to Karenia papilionacea in the Kareniaceae, but its affinity to Brachidinium capitatum, another species with extensions, was unclear. A phylogeny of 16S rDNA showed that chloroplasts of A. gracile are related to other kareniaceans derived from a haptophyte. These chloroplasts were of the fucoxanthin type, composed of pigments similar to those in other Kareniaceae; however, the detection of 19′-hexanoyloxyfucoxanthin as a major carotenoid, the low amount of fucoxanthin, and lack of 19′-butanoyloxyfucoxanthin in A. gracile were unusual for the family. ARTICLE HISTORY
... These recent reports were possible because of examination of morphology of living cells. Although most naked dinoflagellates are normally deformed or destroyed by sampling nets and fixative agents, some species are not completely damaged and can be identified during the routine analysis of phytoplankton (Hernández-Becerril and Bravo-Sierra, 2004;Okolodkov and Gárate-Lizárraga, 2006;Maciel-Baltazar and Hernández-Becerril, 2013;Gárate-Lizárraga, 2014a, 2014b. ...
Monthly phytoplankton samples were collected from January 2013 to December 2015 at a fixed sampling site in Bahía de La Paz, Gulf of California. During this study 26 samplings were Amphidinium cf. carterae positive. The highest densities of A. cf. carterae (754.2×103 to 1022.4×103 cells L−1) were recorded during a bloom detected in January 2015 when water temperatures were 20–22 °C. This dinoflagellate showed a well-marked seasonal variation, being found mainly from November to April. Blooms of the species were linked to the upwelled water due to the northwesterly wind. Cysts surrounded by a mucilaginous membrane of A. cf. carterae were found. We also observed these hyaline cysts inside zooplankton fecal pellets. Other benthic/tychoplanktonic dinoflagellates and diatoms, including some potentially toxic species were also found. The occurrence of blooms of A. cf. carterae in Bahía de La Paz could represent a risk for aquaculture activities and human health.
... Only a handful of dinoflagellates species with skeletal element are known. Heterotrophic dinoflagellates with a basket-like skeleton of variable morphology have been described under the genera Monaster F. Schütt, Amphilothus Kofoid ex Poche and Achradina Lohmann (Schütt, 1895;Lohmann, 1903Lohmann, , 1919Nival, 1969;Sournia, 1986;Hernández-Becerril and Bravo-Sierra, 2004). Schütt (1895) described Monaster rete and Amphilothus elegans as having an identical skeletal meshwork in the hypotheca and a pointed antapex or antapical spine. ...
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The basket-like skeleton-bearing dinoflagellates have been divided into three genera: the littleknown Monaster as having a skeleton with longitudinal ribs in the epitheca, Amphilothus with a dense and geometric skeletal tessellation in the epitheca, and Achradina with characteristics intermediate between the other two genera. Cells of different sizes and morphologies corresponding to these genera co-occurred within the same samples from the Mediterranean Sea and South Atlantic Ocean. During cell division, a bigger daughter cell kept the endoskeleton, while the smaller daughter cell formed a new skeleton, beginning with the formation of the hypotheca. The different degree of maturation of the skeleton explained the great intraspecific variability in skeletal morphology. These forms share a distinctive crest-like apical structure with several internal radiating slits. These evidences indicate that the genus Monaster corresponds to immature cells with incomplete developed endoskeleton in the epitheca; Amphilothus corresponds to the mature cells with more developed epithecal endoskeleton, while Achradina shows intermediate morphologies and it is the most common form in the plankton samples. The genera Achradina, Amphilothus and Monaster correspond to a single species, with the name Monaster rete having priority.
... Achradina pulchra, known from warm seas, possesses a basket-like skeleton which composition has been matter of speculation for a century. Some authors have considered it as an exoskeleton of organic composition, and an opening or window in the skeleton has even been compared to an archeopyle, or excystment opening (Hernández-Becerril and Bravo-Sierra 2004). Other authors have considered the skeleton to be siliceous (Taylor 1987). ...
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We examined the planktonic dinoflagellate Achradina pulchra by light and scanning electron microscopies from the South and North Atlantic oceans. The basket-like skeleton has been interpreted as a thick cell covering or pellicle of organic composition, or as a siliceous endoskeleton. The skeleton of Achradina is known only from fresh material, being absent in preserved samples, sediments or the fossil record. X-ray microanalysis revealed that the endoskeleton of Achradina is composed of celestite (strontium sulfate) with traces of barite (barium sulfate), two minerals that readily dissolve after cell death. To date, Acantharia and polycystine radiolarians (Retaria) were the only known organisms with a skeleton of this composition. We can now add a dinoflagellate to the list of such mineralized skeletons, which influence on the biogeochemical fluxes of strontium and barium in the oceans. Moreover, we provided the first molecular data for a skeleton-bearing dinoflagellate. Molecular phylogeny based on the SSU rRNA gene sequences revealed that Achradina and several environmental clones branched as an independent lineage within the short-branching dinokaryotic dinoflagellates. To date, seven clades of dino-karyotic dinoflagellates are known living as symbionts in the endoplasm of Acantharia and polycystine radiolarians. Because celestite built skeletons were unknown outside radiolarians, we suggested that the ancestors of Achradina acquired the genes implicated in the deposition of strontium and barium from radiolarian hosts though a horizontal gene transfer event between microbial eukaryotes.
... Diatoms are the main group, with species described in different regions of the Mexican Pacific (COBC, GC, PTM y GT), Gulf of Mexico and the Mexican Caribbean (Hernández-Becerril, 2003). Dinoflagellates were mainly studied by Hernández-Becerril and Bravo-Sierra (2004) and Okolodkov (2005), as did other groups: Coccolitphoridae , Silicoflagellates , Cyanobacteria, Raphidophyceae (Band-Schmidt et al. 2004), Parmophyceae (Bravo-Sierra and Hernández-Becerril 2003), Cryptophyceae and Choanoflagellates. ...
The International Census of Marine Microbes (ICoMM), together with the South American and Caribbean Steering Committees of the Census of Marine Life program (CoML), supported the initiative of launching a regional ICoMM node (LACar ICoMM). This network aims at promoting discussions among scientists currently involved in marine microbial studies carried out at both the South American and the Caribbean regions, in order to evaluate the research capabilities and to identify complementary strengths and/or possibilities for enhanced collaboration, that would improve the knowledge on marine microbes and their biodiversity in both regions. We present an overview and discussion on some of the directions of current research on marine microbes in these regions. Concerning the marine phytoplankton studies, the best known taxonomic groups are diatoms and dinoflagellates. In Mexican marine waters, the number of taxa recorded to date is of about 1400. Studies dealing with bacterial, phytoplankton and/or cyanobacterial dynamics are carried out in the Caribbean coastal and oceanic marine systems, underscoring the importance of various environmental states, modulated by geographic and seasonal patterns as well as by the expression of large South American rivers. One of the main issues of this type of survey is the determination of wet and dry seasonal patterns of bacterial dynamics, in seascapes off Puerto Rico, with moderate to absent river inputs. Phytoplankton and bacterioplankton dynamics are also studied in F. Guiana coastal and shelf systems under direct Amazon influence, well known for their important fisheries resources, as well as in other South American marine systems influenced by important fresh water inputs or under upwelling conditions. Bacterial and/or picoeukaryotes diversity are assessed in particular marine systems such as coastal lagoons in Uruguay, the Rio de la Plata estuary and adjacent areas, as well as in sediments of the Oxygen Minimum Zone (OMZ) off South American Pacific coast, and in anoxic waters of the Cariaco Basin. Findings of a diverse range of pico-autotrophs (Patagonian shelf) and particular communities of big filamentous bacteria (OMZ zone off the South American Pacific) represent recent discoveries in those areas. In polluted coastal systems, bacteria with ability to degrade pesticides and hydrocarbons are currently monitored. In coastal areas of the Colombian Caribbean, 64 native marine bacterial strains were isolated from sediment samples. The oil-degrading bacteria are also studied in the Orinoco Delta, submitted to intensive oil exploitation. Furthermore, the Microbial Observatory of Rio de Janeiro (MoRio) established in Guanabara Bay (Brazil), constitutes a model for the study of threatened tropical coastal systems by exploring microbial biodiversity in different coastal systems (including unpolluted sites). The estimation of the activity and diversity of hydrocarbon and oil-degrading bacteria is assessed also in temperate waters and sediments of coastal systems of Argentina. Sharing knowledge and capabilities in common strategies would allow a better understanding of marine microbial diversity patterns in both regions.
... In Mexico, historical studies on marine phytoplankton from the Pacific Ocean have yielded recognized diverse floras, with important tropical and subtropical components, and continuous findings of new records, especially of diatoms and dinoflagellates, and even new species (e.g. HERNÁNDEZ-BECERRIL and TAPIA PEÑA 1995, AKÉ-CASTILLO et al. 1999, HERNÁNDEZ-BECERRIL and BRAVO-SIERRA 2004, HERNÁNDEZ-BECERRIL et al. 2008. However, it has also been recommended that future investigations should consider new and modern study methods and concepts (HERNÁNDEZ-BECERRIL 2003), including culturing of species and molecular studies. ...
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Cultures of marine microalgae have greatly contributed to the better understanding of the morphology, phylogeny, life cycles, physiology and ecology of these species. In this paper, the planktonic diatom Thalassiosira delicatula Ostenfeld emend. Hasle, originally isolated and cultured (in f/2 medium, a light-darkness cycle of 12:12, and at temperature of 20 °C ± 2 °C) from material obtained from the tropical, southern Mexican Pacific, was studied by LM, SEM and TEM. General morphology of the species agrees well with previous descriptions, including the formation of chains and colonies embedded in mucilage, the chitin threads connecting cells in the chain, the shape of the cells (in girdle view rectangular with a concavity in the valve centre), and processes (with a large rimoportula between valve face and mantle, a marginal ring of occluded ones, and two or three marginal rings of fultoportulae) and areolae arrangement. However the shape and distribution of chloroplasts and threads produced by marginal fultoportulae in living cells, and the presence of more than one central fultoportula, close to a larger areola (two and three fultoportulae were detected in this study) had never been described. Urn-shaped marginal fultoportulae were also very common in most specimens studied, whereas in the literature this character was found only once for the species. Additionally, two rimoportulae were detected in at least one valve. This morphological variability is discussed. This species is a new record for the Mexican Pacific and also the first record of the northern Pacific Ocean.
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Resumen: Antecedentes y Objetivos: El orden Gymnodiniales está compuesto por 11 familias, 63 géneros y 641 especies taxonómicamente válidas. Estos dinoflagelados se caracterizan por presentar una pared celular muy frágil. Además, algunas especies pueden llegar a producir potentes toxinas e incluso tienen la capacidad para formar grandes florecimientos. Los estudios enfocados en conocer la diversidad de este grupo, en el caso de las costas del Pacífico Mexicano, siguen siendo limitados, a pesar de la importancia económica, social y ecológica de estos microorganismos. Por lo tanto, el objetivo de este estudio fue realizar un listado florístico a partir de una revi-sión bibliográfica, que integre únicamente a los registros respaldados por micrografías, para conocer la diversidad de dinoflagelados atecados del orden Gymnodiniales presentes en el Pacífico Mexicano, con énfasis en aquellos formadores de florecimientos algales nocivos. Métodos: La búsqueda de información se realizó en publicaciones (artículos y capítulos de libros), desde el primer registro (1943) hasta la actualidad (noviembre 2022). Cada registro fue confirmado únicamente mediante la existencia de micrografías ópticas y de electrónicas de barrido. Resultados clave: El Pacífico Mexicano está conformado por 11 estados costeros, donde actualmente se tiene reportada la presencia de 10 familias, 31 géneros y 103 especies (16% del total de las registradas a nivel mundial) para el orden Gymnodiniales. De las 11 familias que conforman a este orden, la familia Gymnodiniaceae agru-pó 29% del total de especies registradas para el Pacífico Mexicano, donde los géneros Gymnodinium y Gyrodinium presentaron el mayor número de especies. Conclusiones: La evidencia presentada en este estudio demostró que existe una baja diversidad para este orden en el Pacífico Mexicano, por lo que es necesario imple-mentar un mayor esfuerzo de muestreo, además de incursionar en diferentes herramientas moleculares que permitan obtener una mejor aproximación a la diversidad alfa en las costas mexicanas. Palabras clave: FAN, Gymnodiniaceae, Gymnodinium, Gyrodinium, herramientas moleculares. Abstract: Background and Aims: The order Gymnodiniales is composed of 11 families, 63 genera and 641 taxonomically valid species. These dinoflagellates are characterized by having a very fragile cell wall. In addition, some species can produce phycotoxins and form dense blooms. In the case of the Mexican Pacific coast, studies focused on knowing the diversity of this group are still limited, despite the economic, social, and ecological importance of these microorganisms. Therefore, the objective of this study was to make a floristic list from a bibliographical review, integrating only the records supported by micrographs, to know the diversity of athecate dinoflagellates of the order Gymnodiniales present in the Mexican Pacific Ocean, with emphasis on those that form harmful algal blooms. Methods: The search for information was carried out in publications (articles and book chapters), from the first record (1943) to the present (November 2022). Each record was confirmed only by the existence of optical and scanning electron micrographs. Key results: The Mexican Pacific is made up of 11 coastal states, where the presence of 10 families, 31 genera and 103 species (which represents 16% of the total number of species recorded worldwide) is currently reported for the order Gymnodiniales. Of the 11 families that make up this order, the Gymnodiniaceae family grouped 29% of the total number of species recorded for the Mexican Pacific, where the genera Gymnodinium and Gyrodinium presented the largest number of species. Conclusions: The evidence presented in this study showed that there is a low diversity for this order in the Mexican Pacific, so it is necessary to implement a greater sampling effort, in addition to venturing into different molecular tools that allow obtaining a better approximation of the diversity in the Mexican coasts.
There exist previous studies on phytoplankton, its taxonomic groups and species, its biomass and primary productivity, mainly in winter and spring, but the structure of the phytoplankton from the Gulf of Tehuantepec in summer is poorly known. The composition and distribution of the phytoplankton photosynthetic pigments in summer conditions are provided in this paper. Hydrographic data from nine stations, during an oceanographic cruise in June, 20013, and analysis of five major phytoplanktonic pigments, Fucoxanthin, Prasinoxanthin, Violaxanthin, Zeaxanthin (marker of Synechococcus, picoplanktonic prokaryote) and Divinyl-chlorophyll a (diagnostic of Prochlorococcus, another picoplanktonic prokaryote) are given. Column water was well-stratified: surface layers had a thickness between 20 and 35 m, with well-defined thermoclines at those depths. Values of all pigments were low, but they showed similar vertical distribution patterns, with subsurface maxima peaks (between 30 and 40 m), especially Divinyl-chlorophyll a in most stations, except 3 and 4, where Fucoxanthin was the most important pigment. These peaks did not always coincide with the depths of the main thermocline at each station, buy usually they were found below the thermocline. This scenery shows the picoplankton as a very important size-fraction group in summer (at least in June), strongly contrasting with the winter-spring conditions, of intense turbulent mix and upwellings, where microplankton and diatoms appear to predominate.
We present the inventory of the planktonic algal flora of the Bahia de Acapulco and surrounding marine area, studied through a decade, including an intensive bimonthly sampling study using plankton net, bottle method and the observation of live samples, from February 2010 to February 2011. It recognized 641 taxa, corresponding to eight algal divisions. The most diverse groups were Dinophyta and Bacillariophyta with 347 and 274 taxa, respectively. Photographs of 131 taxa are presented, corresponding to 38 new records for the Mexican Pacific, 34 taxa were not identified at species level, and 59 taxa represent some taxonomic or ecological interest. Species accumulation curves allow to recognize that the species richness observed in the present study represents a good approximation of the planktonic algal flora from the Bahia de Acapulco. However, more detailed studies over phytoflagellates and picoplankton are necessary. A biological characterization of the phytoplankton community was made according to organization level, type of nutrition, life form, potential harmfulness or toxicity, origin (freshwater, brackish or marine), affinity (neritic or oceanic) and distribution (cosmopolitan, cold-temperate or subtropical-tropical). It recognized the common species of the bay and those that have produced blooms. The high species richness of planktonic algal flora observed in Acapulco may reflect a variable trophic status throughout the year, with nutrient limitation at certain times, condition which agrees with the symbiotic relationships found among phaeosomes (cyanophytes), dinoflagellates and diatoms. However, some species indicative of pollution such as Euglena pascheri, Phaeocystis sp. and the presence of the consortium Leptocilindrus mediterraneus (diatom)-Solenicola setigera (protozoan), show that some times the concentrations of nutrients and organic matter can be high. The typical form of "amphitheater" that characterizes the bay causes that, during the rainy season, the system receives an input of large amounts of waste and sewage from the surrounding densely populated hills. However, Acapulco Bay seems to have a high resilience, probably as a result of a conjugated role between ocean currents (which produce a washing effect of the anthropogen pollution) and the purification produced by the functional diversity of the phytoplankton community.
Athecate dinoflagellates have been poorly studied in the plankton of Mexican marine waters, mainly because of their fragility, as they may become deformed using nets and strong fixatives. However, their biodiversity and ecological role might be important in the planktonic realm. As part of routine phytoplankton monitoring in the Chiapas coasts, Mexico, in the southern Mexican Pacific, samples were obtained during 2009 by net (20 mu m mesh) in vertical hauls (up to 15 m), fixed with Lugol's solution and studied by light microscope (bright field and phase contrast). Athecate dinoflagellates species were identified using morphological characters such as shape and size, nucleus position, chloroplasts number and position, and particular characters ('arms', 'carina', etc.). Twenty-seven species were documented to be present in the study area, with 3 species considered to be new records for the Mexican Pacific Ocean: Cochlodinium pulchellum, Karenia bicuneiformis (= K. bidigitata) and K. papilionacea. Few species studied here have historically been reported as 'bloom-forming' species in other parts of the Mexican Pacific. It is clear that more studies should be systematically done to assess the present biodiversity of these dinoflagellates groups in Mexican waters.