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Morphological and molecular study of the cyanobiont-bearing dinoflagellate Sinophysis canaliculata from the Canary Islands (eastern central Atlantic)


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The presence of the benthic dinophysoid dinoflagellate Sinophysis canaliculata has been reported in the Canary Islands (eastern central Atlantic) in live field observations and on fixed macroalgae samples from intertidal ponds (26 sampling sites from El Hierro, Tenerife, Gran Canaria, Fuerteventura and Lanzarote islands). In vivo Sinophysis cells were typically pale pink colored. Light microscopy (LM) and scanning electron microscopy (SEM) micrographs showed a small characteristic narrow hypothecal cut that matched the original description of S. canaliculata. SSU rRNA gene (rDNA) nuclear phylogeny showed that S. canaliculata is closely related to S. microcephalus. Sinophysis specimens displayed cyanobacterial endosymbionts with orange autofluorescence from phycoerythrins. SSU rDNA analyses of the cyanobionts nearly matched a former sequence obtained from S. canaliculata in the Pacific Ocean (Japan). Sinophysis canaliculata survived up to five months in the original seawater samples. During that period cyanobionts were always present and maintained their orange autofluorescence, although the pink colour gradually vanished (<1 month) in most individuals. Molecular similarity of Sinophysis cyanobionts from the Canary Islands and Japanese waters suggest a deterministic relationship, likely a temporary maintenance inside their host via some specific grazing system. This article is protected by copyright. All rights reserved.
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Marıa Garcıa-Portela
Instituto Espa~
nol de Oceanografia (IEO), Centro Oceanogr
afico de Vigo, Subida a Radio Faro 50, Cabo Estay, Canido, 36390
Vigo, Spain
Pilar Riobo
Instituto de Investigaciones Marinas, CSIC, Eduardo Cabello, 6, 36208 Vigo, Spain
and Francisco Rodrıguez
Instituto Espa~
nol de Oceanografia (IEO), Centro Oceanogr
afico de Vigo, Subida a Radio Faro 50, Cabo Estay, Canido, 36390
Vigo, Spain
The presence of the benthic dinophysoid
dinoflagellate Sinophysis canaliculata has been
reported in the Canary Islands (eastern central
Atlantic) in live field observations and on fixed
macroalgal samples from intertidal ponds (26
sampling sites from El Hierro, Tenerife, Gran
Canaria, Fuerteventura and Lanzarote islands). In
vivo Sinophysis cells were typically pale pink
colored. Light microscopy and scanning electron
microscopy micrographs showed a small
characteristic narrow hypothecal cut that matched
the original description of S. canaliculata. SSU
rRNA gene (rDNA) nuclear phylogeny showed that
S. canaliculata is closely related to S. microcephalus.
Sinophysis specimens displayed cyanobacterial
endosymbionts with orange autofluorescence from
phycoerythrins. SSU rDNA analyses of the
cyanobionts nearly matched a former sequence
obtained from S. canaliculata in the Pacific Ocean
(Japan). S. canaliculata survived up to 5 months in
the original seawater samples. During that period
cyanobionts were always present and maintained
their orange autofluorescence, although the pink
color gradually vanished (<1 month) in most
individuals. Molecular similarity of Sinophysis
cyanobionts from the Canary Islands and Japanese
waters suggest a deterministic relationship, likely a
temporary maintenance inside their host via some
specific grazing system.
Key index words: Canary Islands; cyanobiont; di-
noflagellates; phylogenetics; Sinophysis
Abbreviations: BI, Bayesian inference; LM, light
microscopy; ML, maximum likelihood; SEM, scan-
ning electron microscopy
The dinoflagellate genus Sinophysis has nine
accepted species (S. canaliculata,S. ebriola,S. grandis,
S. microcephalus,S. minima,S. stenosoma,S. verrucu-
losa,S. hoppenrathiana, and S. vespertilio; Hoppenrath
2000, Selina and Hoppenrath 2004, G
omez et al.
2012, Chom
erat et al. 2009, Chom
erat 2016). The
holotype, S. microcephalus (China; Nie and Wang
1944), is typically found in tropical waters linked to
detritus and its closely related species, S. canalicu-
lata, is a cosmopolitan temperate-warm organism
described in La Reunion Island (Indian Ocean)
stuck to macroalgae or associated with sediments
(Quod et al. 1999, Hoppenrath 2000). During a
benthic survey in the Canary Islands (2015), it was
reported the widespread occurrence of Sinophysis cf.
canaliculata. These exhibited internal globules
resembling the cyanobacterial-like endosymbionts
reported by Escalera et al. (2011) in Japan. Morpho-
logical and molecular analyses were performed on
Sinophysis to confirm its identity. The cyanobionts
were also studied using microscopy (light micro-
scopy (LM), epifluorescence microscopy and scan-
ning electron microscopy (SEM) techniques), and
sequencing of SSU rRNA gene (rDNA).
Samples were collected between September and
October 2015 (Fig. S1 in the Supporting Informa-
tion). Sinophysis cells were obtained from macroal-
gae in intertidal ponds (02 m depth) at Charco
Manso (El Hierro), Costa Blanca (Lanzarote) and
Tajao (Tenerife). Temperatures varied from 23°Cto
26°C in the sampling stations, with an increasing
trend from the eastern to the western islands. In El
Received 30 May 2016. Accepted 17 November 2016.
Author for correspondence: e-mail
Editorial Responsibility: S. Lin (Associate Editor)
J. Phycol. *, ***–*** (2017)
©2016 Phycological Society of America
DOI: 10.1111/jpy.12508
Hierro Island, Sinophysis cells were qualitatively
abundant in comparison with other locations. In
particular, in the northern station “Charco Manso”
the largest abundances were observed and quantita-
tive data were recorded, with densities of 125471
cells g
(wet weight macroalgae). Live samples
were poured into 50 mL plastic flasks (Corning, NY,
USA) and kept at room temperature until their
examination in the laboratory (<1 week). A small
aliquot (15 mL) was fixed with Lugol’s Acid Solu-
Measurements of 17 vegetative cells and eight
endosymbionts were made with an Axiocam HRc
digital camera (Zeiss, Germany) in bright field with
a LM Leica DM LA (Leica Microsystems GmbH,
Wetzlar, Germany) at 63x. The autofluorescence of
Sinophysis cyanobionts was observed with blue excita-
tion (Ex: 488 nm, Em: 450490 nm, barrier
515 nm; same equipment as above). Sample pro-
cessing for SEM followed Escalera et al. (2011) and
was carried out on samples from Tajao (Tenerife)
and Charco Manso (El Hierro). Filters were stuck
on the stubs and coated with gold with a K550 X
sputter coater (Emitech Ltd., Ashford, Kent, UK)
and observed with a FEI QUANTA 200 scanning
electron microscope (FEI Company, Hillsboro, OR,
USA). Areolae and pores (n=40) were measured
in three cells. The number of pores and areolae per
surface units (lm
) was calculated from six cells
(three in the right side view and three in the left),
counting the pores and areolae enclosed in 10 lm
Average of pores and areolae per lm
per cell were
calculated according to left and right sides. Narrow
thecal cut length was given as the average of mea-
surements in five cells. All Sinophysis cells used in
this study were similar and resembled S. cf. canalicu-
lata: a left sided u-shape cut located in the center of
the cell was visible in all of them. Only occasionally,
a few specimens with Sinophysis ebriola-like morphol-
ogy were observed.
The host nuclear SSU rDNA (18S) and cyanobac-
terial endosymbiont 16S rRNA genes were amplified
from single cells of Sinophysis using primers Euk-A/
Euk-B (Medlin et al. 1988) and CYA106F/CYA781
(Nubel et al. 1997), respectively. The DNA amplifi-
cation conditions followed Medlin et al. (1988) and
Nubel et al. (1997). Amplicons were purified with
ExoSAPIT (USB Corp., Cleveland, OH, USA) and
sent to LIGHT run sequencing services (GATC Bio-
tech AG, Germany). The 18S rRNA sequence was
compared with 15 other sequences from Sinophysis
spp. The original and final alignment for the SSU
rDNA phylogeny consisted of 570 nt. A Kimura 2-
parameter model (Kimura 1980) with a gamma-
shaped parameter (G =0.21) was selected using
MEGA 6 software. The phylogenetic relationships
were determined using maximum likelihood (ML)
(MEGA 6) and Bayesian inference (BI) method with
a general time reversible model (Mr.Bayes v3.1;
Huelsenbeck and Ronquist 2001). Identity between
sequences was calculated using BioEdit v.7.2.5 with
a BLOSUM62 similarity matrix. Net average distance
between different groups of taxa was calculated on
MEGA 6. 16S rRNA gene of Sinophysis endosym-
bionts were compared with 43 records of 16S rRNA
cyanobacterial sequences. The original sequences of
Sinophysis endosymbionts (labeled as I and II,
respectively) consisted of 544 and 654 nt. The final
alignment for the 16S phylogeny consisted of 415
positions. A Kimura 2-parameter model (Kimura
1980) with gamma-shape parameter (G =0.90) and
proportion of invariable sites (I =0.55) was selected
on MEGA 6 and phylogenetic relationships were
carried out as above.
According to LM and SEM analysis Sinophysis cells
from the Canary Islands were almost circular to
slightly ovoid with an average length (antero-poster-
ior axis) of 43.44 2.77 lm and depth of
43.23 2.50 lm, being the length/depth ratio
1.52. A U-shaped slit was located within the center
on the left side of the cells. This character matched
FIG. 1. Micrographs of live Sinophysis canaliculata cells. (A and
D) LM micrographs. (B and E) UV excitation showing green aut-
ofluorescence from two (white arrows in micrograph B) or one
(white arrows in micrograph E) semicentral bodies and (C and
F) epifluorescence microscopy with blue light excitation showing
internal orange autofluorescence globules, SB: 10 lm.
the original description of S. canaliculata (Quod
et al. 1999), and we will designate onwards as the
Sinophysis collected in this study. Freshly collected
Sinophysis cells exhibited a pale pink color (Fig. S2
and Video S1 in the Supporting Information) not
reported before in this species that turned brown/
greenish or colorless after a few weeks in the labora-
tory. S. canaliculata cells survived in the original sea-
water samples at 25°C for 5 months in 12:12 L:D
photoperiod but neither those or their endosym-
bionts released from the host could be maintained.
Pink color in S. canaliculata was likely due to phy-
coerythrins from their orange autofluorescent cya-
nobionts (Escalera et al. 2011), also revealed in our
study under blue light excitation. A similar brown/
greenish color has been also observed in S. micro-
cephalus specimens from the Arabian Sea (M. Sabur-
ova pers. comm.). The shift from reddish to
greenish color has also been described in other
Dinophysiales like in Dinophysis caudata (Park et al.
2008). The kleptoplastids could only regain reddish
color by engulfing new cryptophyte plastids via the
ciliate Mesodinium rubrum. Our observations also
suggest that cyanobionts in S. canaliculata are of
temporary nature and need to be periodically
acquired, directly or by a vector organism. Kidney-
shape internal globules fluoresced in orange under
blue light excitation (length 5.82 0.62 lm and
width 3.83 0.24 lm) and were more concentrated
near the cingulum (Fig. 1, C and F). Sinophysis also
had one or two semicentral dark brown bodies
(Fig. S3, A and D in the Supporting Information)
with green autofluorescence under UV excitation
(Fig. 1, B and E) but not under blue light, indicat-
ing that phycoerythrins were absent (Escalera et al.
Cells were bound by an ornamented theca with a
strong areolated surface (Fig. S4, A and B in the
Supporting Information). Pores were randomly
located inside and among the areolae (Fig. S4D).
The number of pores and areolae on the right
side were 5.53 0.94 and 0.95 0.18 per lm
respectively, and on the left side, were 7.14 2.25
and 1.25 0.52 per lm
, respectively. The areolae
and pores diameter were 1.02 0.22 lm and
0.22 0.05 lm, respectively. Higher areolae sizes
Sinophysis canaliculata Endosymbiont I
Sinophysis canaliculata Endosymbiont II
AB546860 Uncultured cyanobacterium clone SC1
AB294942 Unc. cyanobacterium clone pltb-vmat-28
HM799026 Unc. cyanobacterium clone PRTBB8617
EF160009 Unc. Chroococcales cyanobacterium clone 5ad/556a
JQ726906 Unc. bacterium clone EDWFEBC04
FR666955 Unc. bacterium clone S Aug7
JF261761 Unc. bacterium clone Del0209G03
KM020010 Synechocystis sp. SAG 37.92
EU259177 Unidentified cyanobacterium CLg1
JF261756 Unc. bacterium clone Del0209F09
KJ719259 Cyanobiont of Cymbastela stipitata clone B1
EF160008 Unc. Chroococcales cyanobacterium clone p3b5b/566g
FJ358912 Unc. cyanobacterium clone AO26
EF160007 Unc. Chroococcales cyanobacterium clone 3b5a/p2e4
DQ289923 Unc. cyanobacterium clone SC1-42
JQ580183 Unc. cyanobacterium clone RII-OX096
DQ072915 Unc. cyanobacterium clone ThN-P17
KC298754 Unc. bacterium clone 988
KC298319 Unc. bacterium clone 553
AJ292193 Cyanobacterial symbiont MY3 strain MY3
AY711919 Unc. cyanobacterium clone SIMO-382
KJ546671 Synechocystis aquatilis ISB32
JF966679 Cyanobacterium IHB-410
KJ546667 Chroococcus minimus ISB36
AM238427 Cyanobacterium aponinum ETS-03 strain ETS-03
AB058249 Cyanobacterium sp. MBIC10216
KC875240 Pseudanabaena sp. NTDP02
KC859033 Synechococcus sp. NTDP03
DQ786164 Cyanobacterium sp. LLi5
KF246492 Geminocystis sp. CENA526
KC621874 Cyanobacterium sp. THH
AM258981 C. stanieri PCC 7202 strain SAG 88.79
KJ654307 Geminocystis sp. 1.1
LN997855 Cyanobacterium sp. KSU-AQIQ-3
HM573462 Nosctoc muscorum Ind33
AB045958 Planktothrix agardhii NIES-596
AF013030 Trichodesmium erythraeum
AF001466 Prochlorococcus sp. CCMP1378
AY224195 Synechocystis sp. PCC6803
AB003164 Oscillatoria rosea IAM M-220
AF32939 Spirulina subsalsa
FIG. 2. Maximum likelihood (ML) phylogenetic tree of cyanobacterial 16S rRNA gene sequences. Numbers on the major nodes repre-
sent, from left to right, posterior probabilities based on Bayesian inference and ML (1,000 pseudoreplicates) bootstrap values. Only boot-
strap values >60% are shown. The tree was rooted using Prochlorococcus sp. (AF001466).
were located near the cingulum and were not
included to calculate the average of the diameters
length. The narrow thecal cut (Fig. S3, C and E)
located on the left side of the cell was smaller than
in the original description of S. canaliculata
(7.2 0.98 lm vs. 11 1lm).
The 18S rRNA phylogeny placed S. canaliculata
(isolated in Tajao, Tenerife; Acc. No. KX139004;
Fig. S5 in the Supporting Information), in a sub-
clade with S. microcephalus. These species shared
high similarity (95.6%), with only 24 differences
along a 570 nt alignment. Those consisted in 13
transitions (being A/G the most usual), 10 transver-
sions (being C/G, G/T, A/C and T/A the most
usual ones) and one deletion (-/A). In addition,
S. canaliculata sequence contained an ambiguous
nucleotide. Slightly higher genetic distances were
found between the S. canaliculata/S. macrocephalus
subclade and S. grandis (0.130) than to the S. steno-
soma group (0.110). Two incongruities between ML
and BI were observed in the branch location of
sequences belonging to S. grandis (JN587291) and
S. ebriola (JN587292). Two endosymbiont sequences
from two S. canaliculata cells (endosymbionts I, acc.
no. KX139005 and II, acc. no. KX139006) from
Tajao (Tenerife) were used to build the 16S rRNA
phylogeny (Fig. 2). Pair-wise analyses revealed that
endosymbionts I and II from the Canary Islands
were identical (100% of similarity) and shared
99.76% and 99.24% of similarity ,respectively, with
those reported by Escalera et al. (2011). Both
sequences formed a subclade associated to a cluster,
where Synechocystis sp. (acc. no. KM020010, T. Friedl,
D. Hepperle, A. Marrero-Callico, R. Jahn, W. H. Kus-
ber, C. Hallmann unpublished data) and a Chroococ-
cales cyanobacterium (acc. no. EF160009, EF160007)
were the only records with any taxonomic informa-
tion. That cluster also contained a cyanobiont of
the sponge Cymbastela stipitata (Luter et al. 2014).
Sequences from cyanobacteria found in other Dino-
physiales (Foster et al. 2006a,b, Qiu et al. 2011)
were not included in the phylogeny given their
shorter length. Although, we examined the genetic
distances (P-values on a 280 nt long fragment),
between cyanobionts in Sinophysis and 60 sequences
retrieved from Dinophysiales). Our results indicated
that closest cyanobionts (P=0.1290.155) belonged
to a few sequences retrieved from Histioneis
(AY444938, AY444947, AY444948), Ornithocercus
(AY444959, AY444958), and Amphisolenia (AY444916;
Foster et al. 2006a,b). Nevertheless, these P-values
were similar to those between the cyanobionts in
Sinophysis and other organisms included in our
phylogeny such as Spirulina subsalsa (AF32939,
P=0.142) or Oscillatoria rosea (AB003164, P=
0.147). Our phylogenetic results confirmed that the
Sinophysis cyanobionts from Canary Islands matched
those from Japanese waters (Escalera et al. 2011).
We suggest that they might belong to the order
Chroococcales and their kidney-shape would be
consistent with those collected from epilithic
Chroococcales cyanobacteria in marine tropical areas
ıez et al. 2007). One of the diatom-diazotroph
association, involves a Chroococcales cyanobacteria liv-
ing in association with the diatom Climacodium
frauenfeldianum. (Carpenter and Janson 2000, Foster
et al. 2011). The order Dinophysiales represents the
unique case where cyanobacteria become associated
either as epibionts or endocytobionts. Histioneis
spp., Ornithocercus quadratus, and Citharistes regius are
associated with cyanobacterial ectosymbionts (Gor-
don et al. 1994). TEM and nitrogenase labeling
indicated the presence of nitrogen fixative sym-
bionts in Histioneis depressa (Foster et al. 2006a,b)
and the loss of these symbionts would be lethal for
the host (Stoecker et al. 2009). Future studies
should determine if N fixing takes place in Sinoph-
ysis, associated either with bacteria or cyanobionts,
using, for example, nifH sequencing or in vivo fluo-
rescence techniques (nanoSIMS; Foster et al. 2011).
The potential toxicity of Sinophysis spp. is
unknown and has not been considered in previous
studies. LC-HRMS analyses on Lugol’s fixed
S. canaliculata cells (n=400) from the Canary
Islands were negative for lipophylic toxins (P.
o, pers. comm.). These results were not conclu-
sive given the potential loss of toxins due to sample
fixation and the limited amount of biomass. Their
potential toxicity could be evaluated alternatively by
biological assays and it should not be discarded that
cyanobacterial endosymbionts could themselves pro-
duce toxins, as it is known to occur in several mar-
ine cyanobacteria (e.g., Trichodesmium erythraeum,
Narayana et al. 2014). Complementary analyses
searching for cyanobacterial toxins would be advis-
able in the future to determine the hypothetical
presence of these compounds in S. canaliculata.
We thank to Isabel Ramilo for helping with Sinophysis cells
identification in different sampling sites, to Pablo Salgado for
microscopy images assistance and to the Centre for Scientific
and Technological Support to Research (University of Vigo)
for SEM analysis. This study was funded by CICAN and
DINOMA projects (CGL2013-40671-R; CGL2013-48861-R,
MINECO, Spain). This is a contribution of Unidad Asociada
IEO-CSIC Microalgas Nocivas. The experimental part of this
study was carried out at the Instituto Espa~
nol de
ıa (IEO) in Vigo. This research note is going to
be part of M. Garc
ıa-Portela PhD appended to “Marine
Science, Technology and Management” (DO*MAR) doctoral
program at the University of Vigo.
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Supporting Information
Additional Supporting Information may be
found in the online version of this article at the
publisher’s web site:
Figure S1. Phytoplankton sampling sites loca-
tion in the Canary Islands where Sinophysis canalic-
ulata were collected.
Figure S2. LM micrograph of in vivo Sinophysis
canaliculata cell showing its characteristic pale
pink color, SB =10 lm.
Figure S3. Light microscopy micrographs of dif-
ferent positions and numbers semicentral bodies
in Sinophysis canaliculata cells.
Figure S4. SEM micrographs of different
S. canaliculata cells showing (a and b) strong areo-
lated surface, (c) the narrow thecal slit, (d) a ran-
domly distribution of pores (white arrows
indicating different positions, inside and among
the areolae) and (e) the narrow thecal cut
located on the left side of the cell. SB: A
C=20 lm and D, E =5lm.
Figure S5. Maximum likelihood (ML) phyloge-
netic tree of genus Sinophysis based on the 18S
rRNA gene sequences.
Video S1. Sinophysis canaliculata cell swimming
in a seawater natural sample.
... Several species of Gambierdiscus are among the most toxic benthic dinoflagellates due to the production of ciguatoxin (Lehane & Lewis, 2000). Thecadinium and Sinophysis (Fig. 2, Pl. 4) are nontoxic genera, whilst the potential toxicity of Sinophysis is still unknown (García-Portela et al., 2017). ...
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Ciguatera Fish Poisoning (CFP) is a syndrome caused by ciguatoxin-producing benthic dinoflagellate, which are typically attached to macroalgae. The toxin is responsible for the human poisoning symptom observed after the consumption of contaminated reef fish. Research on the composition and abundance of benthic dinoflagellate on macroalgae had already conducted within the 2010 - 2015 at several coral reef areas in Indonesian waters, such as Weh Island - Aceh, Belitung Island, Lampung Bay, Seribu Islands, and Lombok Island. This study reviewed all the references concern on benthic dinoflagellate researches in Indonesia, with aims to raise awareness on the presence of potentially toxic benthic dinoflagellates in Indonesian waters, also to create an inventory of the species discovered. The study revealed four of the six genera which are potentially toxic, namely Amphidinium, Gambierdiscus, Ostreopsis, and Prorocentrum. The Prorocentrum cells were identified in a larger number than any other genera in all the sampling locations. The relatively high number of benthic dinoflagellates were observed in Lampung Bay and Seribu Islands, which might be due to the high level of human activities. These findings are essential to compile a database on the CFP-causing species and to monitor the affected areas, specifically in highly populated locations or tourist sites.
... Regarding the genus Sinophysis (often observed in Cotillo station), to our knowledge it has not been associated with toxin production. The only species reported so far in the Canary Islands, S. canaliculata, harbors cyanobionts of uncertain taxonomic position [62,63]. ...
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The relationship between the ciguatoxin-producer benthic dinoflagellate Gambierdiscus and other epibenthic dinoflagellates in the Canary Islands was examined in macrophyte samples obtained from two locations of Fuerteventura Island in September 2016. The genera examined included Coolia, Gambierdiscus, Ostreopsis, Prorocentrum, Scrippsiella, Sinophysis, and Vulcanodinium. Distinct assemblages among these benthic dinoflagellates and preferential macroalgal communities were observed. Vulcanodinium showed the highest cell concentrations (81.6 × 103 cells gr−1 wet weight macrophyte), followed by Ostreopsis (25.2 × 103 cells gr−1 wet weight macrophyte). These two species were most represented at a station (Playitas) characterized by turfy Rhodophytes. In turn, Gambierdiscus (3.8 × 103 cells gr−1 wet weight macrophyte) and Sinophysis (2.6 × 103 cells gr−1 wet weight macrophyte) were mostly found in a second station (Cotillo) dominated by Rhodophytes and Phaeophytes. The influence of macrophyte’s thallus architecture on the abundance of dinoflagellates was observed. Filamentous morphotypes followed by macroalgae arranged in entangled clumps presented more richness of epiphytic dinoflagellates. Morphometric analysis was applied to Gambierdiscus specimens. By large, G. excentricus was the most abundant species and G. australes occupied the second place. The toxigenic potential of some of the genera/species distributed in the benthic habitats of the Canary coasts, together with the already known presence of ciguatera in the region, merits future studies on possible transmission of their toxins in the marine food chain.
... To make slide specimens for one species, the dinoflagellate samples were washed with distilled water and then the method described in Kim et al. (2013) was followed. Di- niz et al. 2017); Asia: Japan ( García-Portela et al. 2017). and Prorocentrum described from Korean coastal area. ...
This chapter reviews the current knowledge on “mixotrophy” among freshwater and marine dinoflagellates. The term “mixotrophy” is here used for the combination of phototrophy and phagotrophy in the same organism. Among the dinoflagellates it includes species with their own permanent chloroplasts (called constitutive mixotrophs, CMs) and species which lack their own chloroplasts and instead sequester chloroplasts from their prey (called non-constitutive mixotrophs, NCMs). We document here that mixotrophy is widespread among dinoflagellates with species representatives of both groups. Feeding may not always be expressed among the CM dinoflagellates, especially as light and nutrients impact feeding for the majority of dinoflagellates. Mixotrophic dinoflagellates primarily eat other protists, but some species can exploit large prey and metazoans as part of their diet. Some mixotrophic dinoflagellates are highly selective in which prey types they ingest, while others are quite omnivorous. Especially the NCM dinoflagellates seem to be quite restricted in which types of prey they can utilize as donors of chloroplasts and other cell organelles. Few data are available on in situ grazing rates of mixotrophic dinoflagellates, and there is a strong need to develop new techniques to measure in situ grazing rates. Development of reliable in situ techniques to measure feeding is not only important to assess the significance of phagotrophy as a way for dinoflagellates to harvest nutrients in inorganic nutrient limited waters, but also to assess the impact dinoflagellate mixotrophy on the food web.
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Levels of nitrogen in coastal areas have been rapidly increasing due to accumulative inputs of sewage and terrigenous sediments carrying fertilizers. Sponges have an immense filtering capacity and may be directly impacted (positively or negatively) by elevated concentrations of nitrogen. Sponges also host a wide diversity of microbes involved in nitrogen metabolism, yet little is known about the effects of nitrogen loading on these symbiotic partnerships. Manipulative experiments were undertaken to examine the potential effects of excess nitrogen (up to 240 μM) on microbial symbiosis in the abundant sponge species Cymbastela stipitata. Microbial composition and activity were examined using 454-pyrotag sequencing of DNA-and RNA-derived samples. Despite the high levels of nitrogen exposure (up to 124-fold above ambient), sponges appeared visibly unaffected at all treatment concentrations. At the phylum level, the microbial community was consistent between all sponge samples regardless of nitrogen treatment, with Cyanobacteria and Thaumarchaeota being the dominant taxa. Higher microbial diversity was observed at the operational taxonomic units (OTU) level (97% sequence similarity), with only 40% of OTUs shared between samples from all treatments. However, a single cyanobacterial OTU dominated the community of all individuals (average 73.5%) and this OTU did not vary with nitrogen treatment. The conserved microbial community in all sponges irrespective of nitrogen treatment highlights the stability of the sponge-microbe relationship and indicates that the holobiont is resistant to short pulses of nitrogen at levels mimicking sewage effluent.
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A new benthic marine dinoflagellate, Sinophysis canaliculata Quod, Ten-Hage, Turquet, Mascarell et Couté sp. nov., was isolated from coral and sediment samples from sites in the western Indian Ocean. This new species is described and illustrated by drawings and light and scanning electron micrographs. Members of Sinophysis Nie et Wang are generally laterally flattened with circular outlines. The new species differ from others of the genus in the following characters: cell shape and size and features of thecal plates (plate shapes, size and number of valve pores, presence of a narrow thecal cut in the left hypothecal plate). Sinophysis canaliculata is heterotrophic, lacking any chloroplasts.
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Many symbiotic associations characteristic of tropical and subtropical oceanic waters were observed near shore during a long-term study of the microbiota in the northern part of the Gulf of Aqaba, Red Sea. Among such associations were the heterotrophic dinophysoid genera Ornithocercus, Histioneis and Citharistes with cyanobacterial symbionts. The detection of these heterotroph-autotroph consortia repeatedly coincided with extended nitrogen limitation in the fall season. Populations of free-living cyanobacteria, with known N fixation capability, such as the unicellular Synechococcus/Synechocystis spp. and colonial forms, e.g. Trichodesmium spp., also peaked at the same time. We propose that heterotrophic dinoflagellate hosts may provide the cyanobacterial symbionts with the anaerobic microenvironment necessary for efficient N fixation. Thus, these self-supporting consortia increase in numbers during the long period of stratification and nitrogen limitation in the oligotrophic subtropical waters of the Gulf of Aqaba.
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Acquisition of phototrophy is widely distributed in the eukaryotic tree of life and can involve algal endosymbiosis or plastid retention from green or red origins. Species with acquired phototrophy are important components of diversity in aquatic ecosystems, but there are major differ- ences in host and algal taxa involved and in niches of protists with acquired phototrophy in marine and freshwater ecosystems. Organisms that carry out acquired phototrophy are usually mixotrophs, but the degree to which they depend on phototrophy is variable. Evidence suggests that 'excess car- bon' provided by acquired phototrophy has been important in supporting major evolutionary innova- tions that are crucial to the current ecological roles of these protists in aquatic ecosystems. Acquired phototrophy occurs primarily among radiolaria, foraminifera, ciliates and dinoflagellates, but is most ecologically important among the first three. Acquired phototrophy in foraminifera and radiolaria is crucial to their contributions to carbonate, silicate, strontium, and carbon flux in subtropical and trop- ical oceans. Planktonic ciliates with algal kleptoplastids are important in marine and fresh waters, whereas ciliates with green algal endosymbionts are mostly important in freshwaters. The photo- trophic ciliate Myrionecta rubra can be a major primary producer in coastal ecosystems. Our know- ledge of how acquired phototrophy influences trophic dynamics and biogeochemical cycles is rudi- mentary; we need to go beyond traditional concepts of 'plant' and 'animal' functions to progress in our understanding of aquatic microbial ecology. This is a rich area for exploration using a combina- tion of classical and molecular techniques, laboratory and field research, and physiological and ecosystem modeling.
The benthic dinoflagellate genus Sinophysis is known from tropical and temperate areas with seven species described. To date, none of them has been fully characterized, and the epithecal plate pattern remains unclear at the genus level. A taxonomic investigation from Martinique Island facilitated the characterization of six species: Sinophysis microcephala, Sinophysis ebriola, Sinophysis stenosoma, Sinophysis cf. verruculosa and two new species. They were studied and illustrated by light and scanning electron microscopy. The two new species, Sinophysis hoppenrathiana sp. nov. and Sinophysis vespertilio sp. nov., were characterized morphologically and shown to differ from all existing species. The cells of S. hoppenrathiana sp. nov. were medium-sized, 32-40 lm long and 23-30 lm deep. They had a peculiar ovate shape, a small crown-like epitheca and the hypotheca was ornamented by shallow alveolae. Cells of S. vespertilio sp. nov. were small, 26-31 lm long and 20-25 lm deep. They were oval in shape with a medium epitheca, and thecal plates were devoid of ornamentation. The epithecal plate pattern was elucidated using scanning electron microscopy. In all species, the epitheca was asymmetrical, pointing to the right ventral side and composed of four epithecal plates E and two apical plates A. The E1 plate was the most ventral but partially hidden by projections of other plates. The large plate E2 bordered the cingulum on the left side, while the large plates E3 and smaller plate E4 were on the right side. Two other plates, A1 and A2, were located more apically, or on the left epithecal side, and encircled a large apical pore. These plates formed prominent projections in all species. In some species, an additional accessory pore was observed more ventrally and located on the suture between E1 and E2. The relative sizes of epithecal plates were variable among the species. These results confirmed that the pattern is consistent with Dinophysales but with a very different arrangement. The generic diagnosis of Sinophysis is emended to encompass these findings.
Summary Four sand-dwelling species of the marine dinoflagellate genus Sinophysis, including one new species, have been examined from intertidal and subtidal sand, from the Sea of Japan. The morphological features of these species were observed by light and scanning electron microscopy. Sinophysis minima sp. nov. is flattened laterally and is 17.5−35.0 µm in length and 15.0−27.5 µm in depth, with a length/depth ratio of 1.1−1.4, an epitheca depth of 5.0−7.5 µm, and a sulcus length of about three-quarters the hypotheca length. Sinophysis ebriola (Herdman) Balech, Sinophysis grandis Hoppenrath and Sinophysis stenosoma Hoppenrath were recorded for the first time in the seas of Russia. Sinophysis stenosoma is the most common species in the Sea of Japan. All species usually occurred together in the region investigated. Additional information on the known species is provided.
A new species of a marine sand-dwelling dinoflagellate in the genus Sinophysis is described from South Brittany, France using both light and scanning electron microscopy. Cells of Sinophysis verruculosa sp. nov. are oval to subcircular, slightly bulging dorsally and flattened laterally, with no chloroplasts, ranging from 52.2 to 57.8 mm in length, and 43.2 to 51.0 mu m in width. The epitheca is small and tilted back to the dorsal part of the cell. At least three major plates and smaller platelets form the epitheca, but the exact number cannot be ascertained due to their reduced size and the presence of a projection hiding the sutures. Four cingular and four hypothecal plates, two large lateral and two small ventral plates are present. The sulcus is bordered by lists supported by hypothecal plates and extends less than two-thirds of the total length of the hypotheca. The most distinctive feature of S. verruculosa is the minute verrucose ornamentation covering the thecal surface, which contrasts with the smooth and areolate ornamentation of temperate and tropical species, respectively.
A reverse transcription-polymerase chain reaction (RT-PCR) method was developed for amplifying prokaryotic symbiont rRNA sequences from individual marine planktonic eukaryotic host cells belonging to the tintinnid genus Codonella, the spongiose radiolarian genus Dictyocoryne, and several Dinophysoid genera (Amphisolenia, Citharistes, Dinophysis, Histioneis, Ornithocercus). Of the 93 sequences obtained from 67 clone libraries, 26% were most similar to a variety of heterotrophic bacteria and 4% were most similar to plastids. Most (70%) of the sequences had the greatest similarity to cyanobacterial 16S rRNA sequences. Several (10%) of these had low sequence identity (<94%) to cyanobacteria in the database, suggesting that they represent novel cyanobacterial lineages. Fifty-three percent of the cyanobacterial sequences were most closely related (>96% identical) to Synechococcus sp., and three were >99% identical to Prochlorococcus sp. Subgroups of sequences most similar to Synechococcus sp. were derived from multiple host types, indicating that the same symbiont was capable of forming an association with a variety of host organisms. Sixteen libraries yielded two or three divergent (from 2% to 25% different) sequence types, indicating the presence of mixed assemblages in single host cells. This study provides the first insight into the phylogenetic diversity of the symbiotic cyanobacteria of open ocean protists.