Subido por Alberto Rosado-Espinosa


Sargassum belongs to the group brown sea
weeds of algae. The brown alga forms the division
phaeophyta and constitutes a distinct taxonomic
group due to their
includes 265 genera
and roughly about
worldwide. With few
brown sea weeds.
members grow in the
intertidal region and
upper littoral region
in cold temperate waters particularly in the northern
hemisphere. The littoral zone of cold temperate sea
is popularly known as sea forest comprising a large
number of brown algae. In the tropics, the region
where large numbers of phaeophycean are
encountered is the Sargasso Sea of Atlantic.
The phaeophyta are multicellular and range in
size from filamentous strands of sea weeds, such as
species of Ectocarpus, to the giant kelps that form
under water forests. A number of marine forms
penetrate into brackish water where they form an
important part of the salt marsh flora. These
brackish water plants have totally lost the ability to
reproduce sexually and they propagate by vegetative
means only (J. N. Butler, et al. 1983).
Scientific classification of Sargassum
Empire :Eukaryota
: Chromista
: Chromobiota
: Sargassum
Sargassum is believed to be the native of Japan
and is now believed that it has a wider distribution
than previously thought. The transplantation of
oyster seed from infected regions of Europe and the
transportation of fertile fronds by currents or by
boats or ships are believed to be the most likely
sources of inoculation to new areas.
Sargassum is a genus of generally planktonic (free
floating) macro algae (sea weeds). It is named for
the Atlantic ocea n's Sargasso Sea which hosts a
large amount of free floating mass of sea weeds,
particularly S. natans and S. fluitans in the western
Atlantic Ocean (J. H. Ryther. 1956). According to
Algae base there are 866 species names in the
database at present, of which 349 have been flagged
as currently accepted taxonomically. Most of the
species are generally attached to rocks along coasts
in temperate regions. The alga is most conspicuous
in tropical and subtropical
waters ranging from midlittoral
to sublittoral zones. Sargassum
is also known as sea holly
because of its highly branched
thallus with hollow berry-like
many leaf like saw-tooth edged
(dentate) blades. Most of the
except S. natans and S. fluitans
Habitat and distribution
Sargassum is highly tolerant to environmental
parameters such as desiccation, full sunlight and
variations in salinity and temperature. This enables it
to occupy a broad range of habitats from the upper
intertidal (mainly rock pools) to the sub tidal and
substrata from exposed rock to Zostera marina (Eelgrass) beds. A free floating meadow of sea weeds
almost as large as a continent lies between the
United States and west of Africa in the North Atlantic
Ocean. This is the famous Sargasso Sea. Christopher
Columbus discovered it while he sailed toward the
new world in 1492. Its presence suggested that land
was near and encouraged him to continue his
(Above Images Courtesy: National Oceanic and Atmospheric
Sargassum is commonly found in the beach drift
near Sargassum beds where they are also known as
Gulf weed, and colloquially as the weed of deceit, a
term also used to include all sea weed species
washed up on shore.
Numerous species of the Sargassum are
distributed throughout the temperate and tropical
oceans of the world, where they generally inhibit
shallow water rocky and coral reefs. However the
genus may be best known for its planktonic (free
floating species). Any member of the normally
benthic species may take on a planktonic, often
pelagic existence after being removed from reefs
during rough weather. However, two species (S.
natans and S. fluitans) have become holopelagicreproducing vegetatively and never attaching to the
sea floor during their life cycle.
The species of Sargassum are commonly met in
tropical seas of Southern Hemisphere. The species
are also common along the coast of Australia, Japan,
West Indies, Florida and India. The most common
centre of occurrence of the species is supposed to be
Southern hemisphere (Abbott et al. 1976).
In India the species are common along the
eastern, western and in southern coasts at Okha,
Dwarka and other places.
Vegetative Structure of Sargassum
The alga has two distinct parts: the perennial,
dark brown basal axes, and the lighter coloured
annual primary laterals. The latter are shed or torn
off in late
During the
months, the
number of
small round
vesicles (air
abundant in
just prior to the shedding of annual primary laterals.
Because of its strongly seasonal growth pattern.
Species of this genus of algae may grow to a length
of 10-200cm or more. They are generally brown,
olive or dark green in colour. The plant body
resembles the seed plants as it is diploid, perennial,
erect and bushy with a bilateral or radial symmetry.
The main body is differentiated into irregular to solid,
discoid, conical holdfast, few simple cylindrical,
terete to compressed stem like main axis called stipe
and flattened leaf like laterals or frond (leaves). The
stipe may be short (a few cm high) or long (upto
100cm or more), cylindrical and branched. The
branching is monopodial. The main axis bears
primary laterals (branches of unlimited growth)
which give rise to secondary laterals (branches of
limited growth) which may be further branched
(Bilgrami et al. 1992). Some secondary laterals
become flat, leaf like and act as photosynthetic
organs. These leaf-like laterals possess minute pores
on the surface called cryptostomata. The leaves are
sometimes replaced by golden brown colored stalked
air bladders called as pneumatocysts. These bladders
are swollen, berry like, which keep the frond afloat
by providing buoyancy. The gas in bladders of
Sargassum constitute
variable proportions of
oxygen, very little amount of carbon dioxide and a
light proportion of an inert gas supposed to be
nitrogen have been detected. It has been
demonstrated that light intensity influences the
oxygen content of bladders. Therefore it can be
concluded that the oxygen content is correlated with
the photosynthetic activity of the plant.
In the upper part of the plant body, the axis of
the laterals bears fertile and sterile receptacles.
Embedded in the fertile, hermaphrodite receptacles
are unisexual conceptacles which bear oogonia and
antheridia. The hold fast or rhizoidal branches are
discoid and it adheres to the substratum with an acid
the thallus is
in nature) and
peripheral layers of compact, columnar thin-walled
parenchymatous cortical cells, which have abundant
chromatophores (plastids) and Fucosan vesicles.
Inner to cortex is the zone of medulla, which consists
of narrow, elongated thick walled cells which serve
the function of conduction (Bilgrami et al 1992).
The internal structure of leaf resembles the main
axis. The epidermis is followed by assimilatory cells
with numerous plastids. The cryptoblasts open
outside by cryptostomata are also found in the
epidermis of leaf. These cryptoblasts are flask like
bodies with multicellular hairs arising from the base.
These hairs are believed to be respiratory and also
absorb nutrients from the water
Cellular structure
The cell wall has an inner cellulosic layer and an
outer gelatinous layer of pectic substances which
possess mucilage of algenic acid and fucinic acid.
The cell wall is distinguished into two fractions: a
fibrillar part that gives the wall its strength, and an
amorphous part in which the fibrils are embedded.
The fibrillar fraction consists of cellulose and this
structural component is probably stiffened further by
insoluble alginate. The alginate is a salt of algenic
acid, a polymer of two sugar acids, D-mannuronic
acid and L- guluronic acid which are connected by β 1,4 linkages.
Chloroplasts are discoid golden brown coloured and
contain chlorophyll a, c1 and c2 as the main
photosynthetic pigments and fucoxanthin and βcarotene as accessory pigmants.
Individual cells may contain several chloroplasts. The
Algae owe its colour to the accessory pigment
fucoxanthin. These chloroplasts bear pear-shaped
stalked pyrenoids to their inner sides. The
chloroplast DNA is organized in a ring-shaped
nucleoid. Vesicles containing reserve food material
are formed in the cytoplasm, near the pyrenoid. In
chloroplasts the thylakoids lie in stack with girdle
lamella usually enclosing all the others. The
chloroplast is surrounded not only by its own double
membrane, but also by a fold of endoplasmic
reticulum, so that in all there are four membranes
around it. Where a chloroplasts lies against the
nucleus, the nuclear envelope, the chloroplast and
endoplasmic reticulum are continuous with each
The most important reserve product of
photosynthesis is chrysolaminaran, which is a β-1,3linked glucan and lies in solution in special vacuoles.
Manitol is also found which is a low-molecular mass
sugar alcohol and has an osmoregulatory role, in
addition to its function as a reserve. Its intracellular
increasing and decreasing external salinity. The cells
also contain various small highly refractive colourless
vesicles called fucosan vesicles, abundant in
metabolically active cells. These vesicles contain an
acidic fluid (phaeophycean tannins or phlorotannin)
that stain red with vanillin and Hydrochloric acid. The
phlorotannins are polymers of phloroglucinol. They
are readily oxidized in the air leading to formation of
brown or black pigment phycopheain (Jarosch R.
1962). These vesicles actually originate from
plastids, where tannins are produced than ooze out
to cytoplasm.
Only reproductive cells are flagellate. The
flagellate cells have a typical photoreceptor
apparatus, consisting of a swelling on the posterior
pleuronematic, bearing tripartite mastigonemes
(tubular hairs) which are formed in ER cisternae. The
Golgi bodies lie with their forming faces appressed to
the nuclear envelope.
Reproduction in Sargassum
Sargassum and other Fucoid algae have an
animal-like life cycle with no alternation of
generations. Look upon this as an exception to the
general pattern found in the plant kingdom. The
plant body of Sargassum is a diploid sporophyte. It
does not multiply asexually by means of spores.
Instead it reproduces by vegetative method and the
formation of sex organs.
Vegetative reproduction:
Fragmentation is the only known method of
reproduction in the free floating species of
Sargassum. In
natans it is very
Air bladder
prolific. This is
a free floating
develops into a
Leaf on bladder
new plant.
by a diplontic
life cycle, in
which meiosis takes place just before the formation
of the gametes (gametic meiosis). Here both the tiny
motile male gamete and the large non-motile female
gamete (egg) are produced not in plurilocular but in
unilocular structures.
The sexual reproduction is oogamous and
involves the fusion of motile sperm or male gamete
with a non-motile ovum or female gamete. They are
borne inside antheridia and oogonia respectively.
They are also termed as microsporangia and
megasporangia. The spores germinate inside the
sporangia to produce gametes. The sex organs are
produced inside special cavity called conceptacles.
The conceptacles are found inside small finger-like
branchlets called receptacles. The plants are either
monoecious or dioecious. In monoecious forms the
antheridia and oogonia can be in the same or
different conceptacles. In case of dioecious forms the
male receptacles are smooth and the female ones
appear spinous.
Development of conceptacles: the conceptacles
develop from a superficial meristodermal cell which
becomes much more prominent. The surrounding
cells of this meristodermal cell divide rapidly sinking
down this prominent cell deep into a flask-like cavity.
By reaching at the base of this flask-like cavity the
prominent cell divides transversally into an upper
tongue cell and a lower basal cell. The tongue cell
degenerate while the basal cell divide anticlinaly and
periclinally into two rows of curved cells. These
layers represent fertile sheet. The antheridia and
oogonia develop on this fertile sheet from the cells of
the upper tier.
Antheridia: A large number of antheridia develop in
each male conceptacle. They are borne on the lower
Antheridial initial
Fertile sheet
Fertile cell
Stalk cell
64 uninucleate
Two unequal
paraphyses with
Sargassum: Development of Antheridium; A, V.S.Conceptacle;; B-D Development of antheridium from
antheridial initial; E-H, Development of antherozoides; I Antherozoid; J, V.S. conceptacle; K, branched
branches of paraphyses. The first antheridium is
borne at the tip of a 3-celled filament which arises
from a cell of the fertile layer. The basal cell remains
at the level of the fertile layer. The middle one is
known as stalk cell. The upper or antheridial cell
develops into an antheridium. The antheridium is
ovoid in outline. It has a thick wall which becomes
mucilaginous towards maturity. Internally the
antheridium contains initially a single diploid nucleus
and a few chromatophores. The diploid nucleus
divides meiotically and then mitotically to form 64
haploid nuclei. The chromatophores also divide and
ultimately get placed near the nuclei in one to one
ratio. The cytoplasm is cleaved and the contents of
the antheridium get divided into 64 haploid
protoplasts. Each such protoplast transforms itself
into a single sperm or antherozoid. Thus 64 sperms
develop inside an antheridium. The wall of the
mature antheridium becomes mucilaginous. It breaks
its connection from the paraphysis and comes out.
Here the wall dissolves and the sperms are released
in sea water.
A sperm is a pear shaped biflagellate structure of
pale brown colour. The flagella are unequal and
inserted laterally. The anterior shorter flagellum is of
tinsel type while the posterior longer flagellum of
whiplash type. The nucleus is larger. Chromatophore
is reduced and posses an eye spot.
Fig. Sargassum: Development of oogonium, A, V.S. of conceptacle; B, Oogonial initial; C-H,
Development of oogonium; I, seven Degenerating nuclei and one functional nuclei
Oogonia: Only a few oogonia are borne in a
conceptacle. They are formed directly from the cells
of the fertile layer, very early in the development of
the conceptacle. Some of the cells of the upper tier
of the fertile layer protrude out and function as
oogonial initial. It divides transversely into a lower
stalk cell and an upper oogonial proper cell. The stalk
cell gets pressed between the growing oogonial cell
or oogonium and the cells of the fertile layer. The
young oogonium contains a conspicuous diploid
nucleus, dense cytoplasm and a number of oil
droplets. The diploid nucleus undergoes meiosis and
mitosis to produce 8 haploid nuclei. 7 of them
usually degenerate while the functional haploid
nucleus enlarges and becomes centrally placed. The
protoplast of the oogonium then functions as a single
egg or oosphere.
The mature oogonium is globular or ellipsoidal in
outline. It has thick 3 layered wall and a single ovum
or oosphere. The three wall layers are outer exchite,
middle mesochite and inner endochite. The middle
wall layer or mesochite imbibes water and becomes
Gelatinous stalks
Sargassum Sp.: A, Oogonium with geltinous stalk; B, young oogonia;
C, fertilizing egg; D, zygote; E-H, Stage of embryo development
mucilaginous. It’s swelling breaks the exochite. The
oogonium is slowly extruded to the outside of the
ostiole. It however remains attached to its original
position by means of a mucilage threads formed by
the mucilaginous mesochite. Later on the endochite
also ruptures and the egg is liberated in the water,
still attached with mucilage threads.
Fertilization: The ova of Sargassum are not shed in
sea. They remain covered over by the gelatinized
wall of the oogonia and are held in position just
outside the ostiole by means of a mucilaginous stalk
made of mesochitin. They attract a large number of
anthrozoides approach the egg. Some times,
because of the presence of many antherozoids, the
egg appears to be a multiflagellate structure. With
the help of these antherozoids the egg may rotate in
water. The number of sperm attaches themselves to
the gelatinous sheath of the ovum by mean of their
anterior flagella. The posterior flagella continue to
lash. One of the lucky sperm penetrates the
mucilaginous covering and fuses with the ovum. The
other sperms swim away. The fertilized ovum has a
diploid (2x) nucleus and is called zygote (Panday
Germination of zygote:
After fertilization, the zygotes continue to grow
on the parent for several days before dropping to
floor. The
Main axis
Sargassum: stages in life cycle: A thallus; B, Receptacle; C, young
oogonia; D, Conceptacle with antheridia; E, Oogonia coming out through
ostiole; F Antheridia on branched paraphysis; G, fertilizing egg; H, Young
environmental stress, as does their multicellular
form. Their large size also allows them to settle
rapidly, and the well-developed rhizoids adhere
quickly to the substrate. This results in the germlings
settling near the parent (within 3 meters), where
conditions are likely to be favorable. The zygote
germinates directly without any resting period. It
begins its germination while surrounded by the
gelatinous sheath derived from the oogonial wall and
still attached to the interior of the conceptacle by
means of mucilage stalk. After some time the
gelatinous sheath dissolves and the zygote in its
early stage of germination falls down on some solid
The fertilized egg elongates and divides
transversely into two cells. The lower cell divides
transversely and develops into rhizoids which later
become eseptate. The upper cell divides and redivides periclinally and anticlinally. Vertical or
longitudinal walls appear in the terminal region
which then shows differentiation of outer and inner
cells, followed by distinction of meristoderm, cortex
and medulla. Simultaneously a three side apical cell
appears at the tip of the germling. It produces the
typical thallus.
Dispersal of gametes
Gametes are usually released during or just
after the spring tide. The timing may be determined
by hydrostatic pressure, or more probably by the
light of the moon. (Fletcher 1975.)
Gametes are released in cycles of 13 days
instead of all simultaneously, increasing the
possibility that some of them will encounter
favorable tides and conditions. (Fletcher 1975.)
Germlings are pear-shaped, enabling the rhizoids to
land first. Rhizoids stick within 48 hours. Germlings
lose their ability to adhere over time, in connection
with declining mucopolysaccaride levels. After 18
days, half can still stick, after 49 days, none can
stick. (Deysher and Norton 1982.) Germlings can
grow on kelp, but they fall off before they reach a
height of 3 cm and can no longer re-adhere.
(Deysher and Norton 1982.) Individuals that become
free-floating can survive in the water column
Alternative Dispersal Mechanism
Fertile branches break off from the holdfast and float
away. When the germlings are released a long
distance from the parent, they do not have to
compete with their own relatives and can settle in
new territory. The combination of these two dispersal
mechanisms proves to be an effective system for
global spread.
Developmental morphology or Morphogenesis
of Sargassum
The thallus structure (stem, branch and leaves)
develop by the activities of a three-sided apical cell.
The thallus consists of three compact tissues, called
for convenience the epidermal, cortical, and
conducting tissues. The latter consists of only thinwalled cells in the leaves, but in mature stems
contains both thick and thin-walled elements. Both
the conceptacles and cryptostomata originate in a
single flask-shaped initial cell which develops the
entire structure. The first division of the initial cell
results in two unlike segments: a large lower cell
which develops the walls of the conceptacle and
cryptostoma; and an upper cell, the tongue cell,
which remains inactive, divide to form a short
filament, or degenerate. The "initial cell" is
apparently the tongue cell, a product of the true
initial cell. The conceptacle and cryptostoma are
undoubtedly homologous structures. Every stage of
development in both structures is the same, from
the appearance of the similar initial cells to the
development of paraphyses in the cryptostomata and
sexual organs in the conceptacle. The paraphyses
are developed basipetally by the division of the
lowermost cell in each structure. Spermatocysts or
their degenerate representatives occur in some
cryptostomata. Such conditions indicate that the
cryptostomata have been derived from conceptacles
whose sexual organs have become sterile. The
spermatocysts develop as in other Fucales, each
finally producing sixty-four sperms which are
discharged from a partly terminal and partly lateral
vent. The sister cell of an oocyst does not become a
stalk and consequently the oocyst is an embedded
structure. The oocyst normally gives rise to but one
egg. The nucleus of the oocyst accordingly becomes
the nucleus of the egg. The oocysts were found
containing eight eggs each. These must be
considered a rare reversion to the Fucus type. The
entire oocyst of Sargassum, unlike other genera of
the Fucales which have been studied, is discharged
with its enclosed egg. The oocyst wall may break,
partially freeing the egg, or it may persist even
enveloping a many-celled sporeling. Segmentation of
the egg takes place while it is attached to the surface
of the plant by the mucilaginous wall which
surrounds it. This segmentation results first in a
many-celled undifferentiated ellipsoidal sporeling.
Rhizoids develop late at one end of the multicellular
sporeling, with no apparent relation to gravity or
other stimulus.
Economic uses of Sargassum
Human uses: Sargassum seaweeds are eaten by
people, and used fish bait in basket traps, animal
feed, fertilizer, insect repellent. Various species are
used as medicine for ailments ranging from
children's fever, cholesterol problems, cleansing the
blood and skin ailments (Chevallier 1996).
Alginates are cell-wall forming materials found in
Sargassum. Their principal organic constituents are
chain-forming hetero-polysaccharides, guluronic acid
and mannuronic acid.
Sodium alginate finds its applications as a
stabilizer and as an emulsifier. It was once used in
textile printing industry. But, things have changed
since the upheaval of textile industry as well as the
changes in textile fashions. Till today, sodium
alginate is used in ice cream and dairy products to
enhance flavour and taste.
Sodium alginate molecules are non-polar in
nature. So they are insoluble in polar solvents, like
water. This property of sodium alginate has led to
the development of high quality fibers which can be
used in the textile industry. Sodium alginate fibers
also are used to weave bandages for larger wounds
and burns. Also, they can be removed much more
easily as compared to cellulose-based bandages. The
hard part of sodium alginate fibers are used in the
manufacturing of fire-fighter’s fire-proof clothing.
In some parts of the world, it is used as a
fertilizer. Sargassum seaweeds are a preferred
additive used to create a specific favour in many
Japanese dishes like soy sauce. Sargassum seaweed
is a shelter for many marine animals as it is an ideal
hiding place from predators. It is also an abundant
food source for them.
People living alongside the seashores of Japan,
often eat fresh Sargassum seaweeds as vegetables.
The Journal of the American Medical Informatics
Association (JAMIA) claimed that Sargassum
seaweeds promote weight loss by discharging more
water thought urination.
Sargassum has been used as a topical medicine
to treat goiters (the bump in the neck due to the
enlargement of thyroid gland) in some provinces of
China. It is salty and bitter in taste. Iodine deficiency
leads to the swelling of thyroid gland because
without iodine thyroid gland cannot produce enough
thyroxin-a critical hormone secreted by thyroid
gland-in order to regulate body metabolism.
Sargassum seaweeds guarantee a continuous supply
of dietary iodine. In addition, Sargassum seaweed
promotes the excretion of urine and reduces edema.
It is also prescribed to alleviate pain from swollen
testes and hernia (AAOM).