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Introduction
• The diatoms are unicellular, sometimes colonial algae found in
almost every aquatic habitat as free-living photosynthetic
autotrophs, colorless heterotrophs, or photosynthetic symbiotes
• Phytoplakton
• Evolve early Jurassic (~185 Ma ago)
• Photo synthetic algae (Mostly)
• 20% producer of food chain
• More than 200000 sp.

• Cell wall is made up of Silicone cell wall (silic acid)-(pectin+silica)
• Silicate is any of the ionized forms of monosilicic acid [Si(OH)4]
• Huge depositor of silicone
• Cell size 2 um to 500um (majority)

Cell wall
• It is constructed of two almost equal halves, the smaller fitting into
the larger like a Petri dish
• The outer of the two half-walls is the epitheca and the inner the
hypotheca
• Each theca is composed of two parts, the valve, a more or less
flattened plate, and the connecting band
• The cells are surrounded by a rigid two-part box-like cell wall
composed of silica, called the frustule

• Two connecting bands, one attached to each valve, are called the
girdle
• Sometimes the connecting bands themselves are called girdle bands
• there are one or more additional bands between the valve and the
girdle, which are called intercalary bands
• the edge of the valve is bent inward, this portion is called the mantle
or valve jacket

• The siliceous material of the frustule is laid down in certain
regular patterns that leave the wall ornamented are four
basic types
1. Centric and radial, where the structure is arranged
according to a central point
2. Trellisoid, where the structure is arranged uniformly over
the surface without reference to a point or line
3. Gonoid, where the structure is dominated by angles
4. Pennate, where the structure is symmetrically arranged
upon either side of a central line

• Some pennate diatoms have a raphe system composed of the
raphe (a longitudinal slot in the theca), divided into two parts
by the central nodule
• Besides the raphe, there are basically two types of wall
perforations within the Bacillariophyceae: the simple pore or
hole, and the more complex loculus or areola

• Special pores (mucilage or slime pores) through which mucilage is
secreted
• In the pennate diatoms, these pores usually occur singly near one or
both poles of the valve and generally occupy thickenings in the
walls.
• The frustule is composed of quartzite or hydrated amorphous silica
and small amounts of aluminum, magnesium, iron, and titanium
mixed with it
• Diatom frustules from marine plankton contain 96.5% SiO2 and 1.5%
Al2O3 or Fe2O3

Vegetative reproduction
• Epithecas of the daughter cells with each daughter cell
producing new hypotheca
• Daughter cells is of then same size as the parent cell, and the
other is smaller
• Cellular energy for silicification and transport comes from
aerobic respiration without any direct involvement of
photosynthetic energy

• Diatoms have an absolute requirement for silicon if cell division is to
take place. In water, solid silica dissociates to produce undissociated
silicic acid Si(OH)4:
• SiO2 (solid) 2 H2O-----> Si(OH)4

• Although silicon is the second most abundant element in the
Earth’s crust, its availability is limited by its solubility in water.
• The Si(OH)4 in marine waters is about 6 ppm. In the global
ocean, about 97% of the dissolved Si is present as Si(OH)4
• Prior to cell division, the cell elongates, pushing the epitheca
away from the hypotheca, and the nucleus divides. After the
protoplasm has divided into two by the invagination of the
plasmalemma

Motility
• Some diatoms are able to glide over the surface of a substrate,
leaving a mucilaginous trail in their wake.
1. The Navicula type, with a straight movement;
2. The Amphora type, in which the path is usually curved
3. The Nitzschia type, which always exhibits curved pathways with
two different radii
• The observed rates of gliding in diatoms vary from 2 to 14 m s-1 at
room temperature

• Diatoms can glide only when the valve containing a raphe is in
contact with the surface
• the diatom secretes a mucilaginous tether from the portion of the
raphe near the central nodule
• The tether attaches to the substratum and the cell pulls itself onto a
valve containing a raphe using the tether
• Those pennate diatoms that glide have bundles of actin
microfilaments running parallel to the raphe

Plastids and storage products
• The chloroplasts contain chlorophylls a, c1, and c2
• Fucoxanthin is the principal carotenoid, giving the
cells their golden-brown color
• Fucoxanthin is an efficient carotenoid in the transfer
of energy to chlorophyll a (PS II)
• The storage product is chrysolaminarin, which is
located in vesicles in the cell
Note: (Chrysolaminarin is a linear polymer of β(1→3)
and β(1→6) linked glucose units in a ratio of 11:1)

Resting spores and resting cells
• Some diatom cells form thick, ornamented walls at different
times in their life cycle and become resting spores
• Resting spores are formed after the diatom cells have been
subjected to a stress shock like light, temperature, and salinity.
• Nutrient depletion that trigger resting spore formation
• due to the loss of vacuoles and their contents it becomes small

Auxospores
• The auxospores are formed by the fusion of two gametes
• In the centric and gonoid diatoms, the male gamete is motile
• In the pennate and trellisoid diatoms, both gametes are non-
flagellated
• Depending on the species, auxospores develop in one of three
different ways

Reproduction
• Vegetative cells of diatoms are diploid (2N) and so meiosis can take
place, producing male and female gametes which then fuse to form
the zygote.
• The zygote sheds its silica theca and grows into a large sphere
covered by an organic membrane, the auxospore

Dinoflagellates

• Living dinoflagellates are one of the most important components in
plankton.
• Marine as well as in fresh water also 1700 sp marine and 220 sp
freshwater dinoflagellates
• Spiraling motion propelled by dimorphic flagella
• Phototrophs and mixotrophs (phagotrophs and autotrophs)
• Some species are endosymbionts of marine animals and play an
important part in the biology of coral reefs

• 90% of all dinoflagellates are marine plankton
• majority are microscopic, the largest, dinoflagellates as large as
2 mm in diameter
• Some dinoflagellates produce resting stages, called
dinoflagellate cysts or dinocysts, as part of their life cycles.
• They make most of the worlds oxygen
• Chlorophylls a and c2 are present in the chloroplasts, with
peridinin and neoperidinin being the main carotenoids.

• First described by Henry Baker in 1753
“Animalcules which cause the Sparkling Light in Sea Water”
• Dinoflagellates are protists which have been classified using both the
International Code of Botanical Nomenclature (ICBN, now renamed as
ICN) and the International Code of Zoological Nomenclature (ICZN).
• In the 1830s, the German microscopist Christian Gottfried Ehrenberg
examined many water and plankton samples and proposed several
dinoflagellate genera

Dinoflagellate, Gonyaulax polyedra
Dinoflagellates exhibit two flagella which permit movement
Groove
Theca
One flagella is
located within the
groove and the other
is located at the lower
end (not visible).

Cell envelop
• Dinoflagellates have a complex cell covering called
an amphiesma or cortex, composed of a series of
membrances, flattened vesicles called alveolae and
related structures

• peculiar form of nucleus, called a dinokaryon, the chromosomes are
attached to the nuclear membrane, lack histone
• Remain condensed throughout interphase rather than just during
mitosis
• The nuclei of the more advanced dinoflagellates are striking
cytologically in that they have their chromatin condensed into 2.5
nm fibrils

• phototrophy, mixotrophy and heterotrophy.
• Some free living dinoflagellates do not have chloroplasts but host a
phototrophic endosymbiont
• Thecate and nonthecate dinoflagellates draw prey to the sulcal
• region of the cell (either via water currents set up by the flagella or
via pseudopodial extensions) and ingest the prey through the sulcus.
• Pseudopodial engulf called pallium

• both fresh and marine
waters, although a much
greater variety of forms is
found in marine members
• A typical motile
dinoflagellate consists of an
epicone and hypocone
divided by the transverse
girdle or cingulum

• Epicone and hypocone are normally divided into a number of
Thecal plates (Number can vary from genera to genera)
• longitudinal sulcus running perpendicular to the girdle
• longitudinal and transverse flagella emerge through the thecal
plates in the area where the girdle and sulcus meet

• Chloroplast covered three layered and chl a, chl c2, carotenoid,
xanthophylls
• A group of xanthophylls that appears to be unique to
dinoflagellates, typically peridinin, dinoxanthin, and
diadinoxanthin. These pigments give many dinoflagellates their
typical golden brown color
• All other organelles rough and smooth endoplasmic reticulum,
Golgi apparatus, mitochondria, lipid and starch grains, and
food vacuoles

• Chlorophylls a and c2 are present in the chloroplasts, with
peridinin and neoperidinin being the main carotenoids
• The storage product is starch, similar to the starch of higher
plants
• The nucleus has permanently condensed chromosomes and is
called a dinokaryotic or mesokaryotic nucleus
• Amphiesma is the term used to specify the outermost layers of
the dinoflagellate cell and includes all of the thecal plates

Cell structure Fig. 7.2 Light and electron
the features of the class. (C)
Chromosome; (CE) chloroplast
envelope; (CER) chloroplast
endoplasmic reticulum; (E) epicone;
(G) Golgi apparatus; (Gr) girdle; (H)
hypocone; (L) lipid globule; (LF)
longitudinal flagellum; (Nu)
nucleolus; (P) trichocyst pore; (S)
starch; (T) trichocyst; (TF)
transverse

• Dinophyceae consists of an outer plasmalemma
beneath which lies a single layer of flattened vesicles
• These vesicles, which normally contain cellulosic
plates

• Transverse and longitudinal flagella. Transverse
flagella beats to the cell left and longitudinal
flagellum, that beats posteriorly.
• The flagella lie in surface grooves: the transverse
one in the cingulum and the longitudinal one in
the sulcus

• Generally, dinoflagellates have a transverse flagellum that fits into
the transverse girdle and a longitudinal flagellum that projects out
from the longitudinal sulcus
• The longitudinal flagellum usually has a wide basal portion and a
thinner apical portion
• Mechanical stimulus of cells causes the longitudinal flagellum to be
retracted and folded so that the flagellum lies along the sulcus
• Dinoflagellates swim from 200 to 500 µm s-1

• The transverse flagellum is about two to three times as long as the
longitudinal flagellum and has a helical shape
• The transverse flagellum consists of
1. Axoneme whose form approximates a helix
2. striated strand that runs parallel to the longitudinal axis of the
axoneme
3. Flagellar sheath

Vegetative cell with a relaxed
longitudinal flagellum (LF) at full
length. (b) A cell with the
longitudinal flagellum (LF) fully
contracted and folded in the sulcus.
(TF) transverse flagellum. (c)
Schematic drawing of a retracted
flagellum showing the contracted
Rfiber
(R) and the axoneme (A). (B)
Basal body; (M) plasma membrane.

Pusule
• A pusule is a sac-like structure that opens by means of a pore into
the flagellar canal and probably has an osmoregulatory function
similar to that of a contractile vacuole

Chloroplasts and pigments
• photosynthetic dinoflagellates originated from a secondary
endosymbiosis with a red alga
• Contain chlorophyll a and c, and peridinin

Phototaxis and eyespots
• The action spectra for phototaxis is the same in all dinoflagellates
that have been studied, with maximum phototaxis obtained at a
wavelength of 450 nm
• An eyespot is not necessary for a phototactic response, indicating
that the phototactic machinery was carried in the host organisms in
the endosymbiosis leading to photosynthetic dinoflagellates

Resting spores or cysts
• The Resting spore or cyst of most dinoflagellates is morphologically
distinct from the parent cell. They are 30 to 70 µm in diameter with
smooth or spinose bodies
• Ten times more carbohydrate and 1.5% the respiratory rate of
vegetative cells
• Highly resistant to decay and contain dinosporin, a chemical similar
to sporopollenin in the pollen of higher plants

• The process of encystment or resting spore formation is regulated by
a complex interaction of day length, temperature, and nutrient
concentration

Toxins
• Some Dinophyceae have the ability to produce very potent toxins
which cause the death of fish and shellfish during red tides when
there are dinoflagellate blooms that color the water red
• Produce toxins contain chloroplasts, indicating that the ability to
produce toxins may have been derived from endosymbiotic
cyanobacteria

Kinds of poisoning
1. Diarrhetic shellfish poisoning
dinophysistoxin-4
2. Ciguatera fish poisoning
gambieric acids, ciguatoxins, and maitotoxins
3. Paralytic shellfish poisoning
saxitoxin

Bioluminescence
• There are two types of light emission in living
• organisms:
(1) bioluminescence (chemiluminescence) in which energy from an
exergonic chemical reaction is transformed into light energy
(2) photoluminescence, which is dependent on the prior absorption of
light

• marine bioluminescence, emitting a bluish-green (maximum wavelength
at 474 nm) flash of light of 0.1-second duration when the cells are
stimulated.
• The compound responsible for bioluminescence is luciferin , which is
oxidized with the aid of the enzyme luciferase

• In the basic reaction of bioluminescence a luciferin is oxidized by a
luciferase, resulting in an electronically excited product (P)* which
emits a photon (h) on decomposition:

possible partial structure of dinoflagellate
luciferin. (After Dunlap and Hastings, 1981; Hastings, 1986.)
Tetra pyrol ring

• Dinoflagellates can emit light in three modes:
(1) they can flash when stimulated mechanically,
chemically, or electrically
(2) they can flash spontaneously;
(3) late at night they can glow dimly

Heterotrophic dinoflagellates
• An estimated half of the more than 2000 living dinoflagellate
species lack chloroplasts and are exclusively heterotrophic
• many dinoflagellates that contain chloroplasts are capable of
mixotrophy where a portion of their nutrients is obtained
heterotrophically
• The different modes of heterotrophy are:
(1) Phagotrophy through the direct engulfment of prey
(2) Pallium feeding where the prey is engulfed

Direct engulfment of prey
• 300-um-long food-gathering tentacle that is covered with a slimy
exudate
• Two wing-like extensions of the cells form an oral pouch at the base
of the tentacle
• At the bottom of the oral pouch is a cytosome that opens like a slit
during ingestion of food organisms

Drawing of the ingestion of food organisms
(other algae, bacteria) by Noctiluca. (a) The tentacle (T) is
in an extended configuration. Any food organisms (FO)
that collide with the mucus-covered tentacle tip, stick to
the tentacle. (N) Nucleus; (OP) oral pouch. (b) The
tentacle bends back toward the oral pouch. (c) The
cytosome (C) at the base of the oral pouch opens, the
tentacle tip is inserted into the cytosome, and the food
organisms are swept into a food vacuole.

Pallium feeding
• feeding veil, the pallium
• Occur from flagellar pore
• A thin filament of cytoplasm (about 1 µm in
diameter) emerges from the sulcal pore and
attaches to the prey

• prey protoplasm is digested by enzymes released into the pallium,
and the digestion products are transported into the feeding cell

Peduncle feeding
• projection of cytoplasm full of microtubules, in the epicone just
above the intersection of the sulcus and cingulum
• The peduncle can extend from 8 to 12 um to attach to, and make a
hole into, the prey
• The cytoplasm of the prey moves through the peduncle to the
dinoflagellate cytoplasm

Endosymbionts
• All Zooxanthellae are dinoflagellates and most of them are members within the
genus Symbiodinium
• inhabit in invertebrates and protists
• sea anemones, jellyfish and several species of radiolarians
• dinoflagellates are parasites

Reproduction
• Asexual reproduction by binary fission
• Sexual reproduction by fussion
• This takes place by fusion of two individuals to form a zygote, which may remain
mobile in typical dinoflagellate fashion and is then called a planozygote.
• This zygote may later form a resting stage or hypnozygote, which are called
dinoflagellate cyst or dinocyst.
• After (or before) germination of the cyst, the hatchling undergoes meiosis to
produce new haploid cells called planomeiocyte

Harmful algal bloom
• Aggregate millions of cell and produced a toxin is capable to kill shellfish
and fish
• This phenomenon is called a red tide, form colour impact on water.
• They contain dinoflagellate luciferase involved in dinoflagellate
bioluminescence, and luciferin, a chlorophyll-derived tetrapyrrole ring
that acts as the substrate to the light-producing reaction.

Classification
• The diatoms into three classes on the basis of structural
morphology
1. Centric diatoms (Coscinodiscophyceae),
2. pennate diatoms without a raphe
(Fragilariophyceae),
3. Pennate diatoms with a raphe (Bacillariophyceae)

• The first recognizable fossils are centric diatoms with pennate
diatoms being recorded late
• The first pennate diatom fossils were araphid (no raphe) with raphid
diatoms appearing
• The Bacillariophyceae can be divided into two
orders as follows:

• Order 1: Biddulphiales
• Radial or gonoid ornamentation;
• Many chloroplasts;
• No raphe;
• resting spores formed;
• motile spermatozoids with a single tinsel flagellum;
• oogamous sexual reproduction.

• Order 2: Bacillariales
• pennate or trellisoid ornamentation
• One or two chloroplasts
• Raphes possibly present with gliding
• No flagellated spermatozoids
• Sexual reproduction by conjugation

CLASSIFICATION
• There is a single class in the Dinophyta, the Dinophyceae
• Four orders are considered here
Order 1 Prorocentrales:
Cell wall divided vertically into two halves;
No girdle;
Two flagella borne at cell apex.

Order 2 Dinophysiales:
Cell wall divided vertically into two halves,
Cells with elaborate extensions of the theca

Order 3 Peridiniales:
Motile cells with an epicone and hypocone separated by a girdle,
Relatively thick theca

Order 4 Gymnodiniales:
Motile cells with an epicone and hypocone separated by a girdle;
Theca thin or reduced to empty vesicles.

lichen
Prepared by: Dharmesh Sherathia, Assistant Professor,
CCSIT, Junagadh

• Firstly discovered by tulasne in 1852
• Association of fungi and algae or cyanobacteria
• Living inside the filaments of fungi
• Widely distributed – grow on soil, rocks, trees, marine or intertidal
• Variety of habitats – cold to hot, arid to moist
• Withstand environmental extremes
• Bush like or leafy structure of lichen called macrolichen and all other
lichen are microlichen

• Generally three types of structure in lichen
• 1. Fruticose 2.Foliose 3. Crustose
• Fruticose: growing up like a tuft or multiply branched
leafless mini-shrub, or hanging down in strands or tassles
• Foliose: growing in 2-dimensional, flat, leaflike
lobes that lift up from the surface
• Crustose: crust-like, adhering tightly to a surface (substrate)
like a thick coat of paint

• Fruticose – branched, strap
shaped or threadlike thallus,
upright or hanging

• Foliose – flattened branching lobes
loosely attached to the substratum,
leaflike
• Have upper and lower surfaces

• Crustose – flattened, scalelike,
• No lower surface, tightly bound to substratum

• Squamulose – intermediate between foliose and
crustose
• Scales, lobes smaller than in foliose
• Intermediates exist

Fungal symbiont
• Most lichenized fungi are Ascomycota – most
form apothecia, some form perithecia and
pseudothecia
• 12 orders include mostly lichenized members
• Some are Basidiomycota – Aphyllophorales, few
Agaricales
• Some are Deuteromycota

Classification
• On the nature of fungi, lichen classified into two main group Ascolichen
and basidiolichen
• Ascolichen may further devide in two group
1. Discolichens: cup shaped apothecia
2. Pyrenolichens: flask shaped perithecia
• There are three genera of basidiolichen
a) Cora
b) Corella
c) Dictyonema

Internal structure

Autotrophic symbionts
• Green algae – Trebouxia is a common genus, found in 75% of
lichens in temperate zone
• Cyanobacteria – Nostoc is a common genus
• 26 genera of algae and cyanobacteria found in lichens, 90% of
lichens contain Trebouxia, Nostoc or one other genus
• Autotroph may be free living
• Blue- green algae, green algae

Internal structure
Gonidial layer

Internal structure

Reproduction
• Vegetative reproduction by soredia, isidia, cephalodia, oidia,
fragmentation
• Asexually reproduction by pycnodium
• Spore germinate on thallus and send hyphae in diff. direction. If algal cell
comes in contact. Hyphe covered and formed protuberance like
structure
• In some case protuberance discharge

Reproduction
• Sexual reproduction – characteristic of fungal symbiont
• Ascospores are discharged, algal cells are not discharged with them
• Thought that after ascospores germinate, they make contact with algal
cell

Vegetative reproduction
• Specialized structures
• Soredia - algal cells enveloped by
hyphae, no cortex, form powdery masses
on surface of thallus, detach from thallus
• Isidia – column like structures with cortex

Isidia

Cephalodia
• Dark swelling on surface
• Unfortunately this one is foreign body
• discharge and formed abnormal body
Oidia
• Small segment of hyphae
Fragmentation
• Long or short fragment of thallus grow on parental thallus, branch broken up by
wind

Physiology
• Autotrophic associations – algal cells carry out photosynthesis,
lichen depends on net production of organic compounds by
photosynthesis
• Most of the photosynthate (70-80%) produced by alga is
incorporated into the fungus
• Green algae secrete polyalcohols like ribitol, cyanobacteria secrete
glucose
• Photobiont becomes leaky of carbohydrates when associated with
fungus – not so when grown alone

Growth
• Exhibit low growth rates – many grow at rates of 1-4 mm/yr, up to 9
cm/yr
• Makes studies difficult
Factors affecting growth:
• Light – variable – some prefer low light intensities, others high
• Temperature – variable
• Moisture – appears to be an important variable, do not have water
absorbing organs, depend on moisture in air
• Some aquatic lichen life is more than4500 years

Moisture
• When lichen thallus is wetted, absorbs water quickly by gelatinous
matrix in the cortex
• Starts growth process
• As thallus dries, growth process slows and stops
• Dew and humidity are important sources of moisture
• Thalli are inactive when dry – only grow when wetted – may be
responsible for slow growth rate

Separation of symbionts
• Fungal symbionts grown in culture exhibit slow growth rates (1-2 mm/yr)
• Many exhibit requirements for vitamins
• Algae also grow slowly in culture, Trebouxia prefers organic N and low
light

Symbiotic association
• Traditionally been classified as a mutualistic symbiosis where both
symbionts benefit
• Fungus appears to be chief benefactor, receives
• Organic compounds as C and energy source
• With cyanobacteria, N fixation may occur so that the fungus also
receives N source

Symbiotic association
• Benefits for autotrophic symbiont are less clear-cut
• Fungus produces substances that absorb water which is provided
to alga
• Fungus takes up inorganic nutrients from atmosphere
• Protects algal cells from mechanical injury, predation, and high
light intensities
• Association allows alga to achieve a wider distribution than if
free-living

Air pollution
• Even though lichens are very resistant to natural environmental
extremes – they are extremely sensitive to air pollution – particularly
SO2
• Obtain nutrients from atmosphere, not soil
• Both species composition and numbers of thalli decline from edge to
center of industrialized areas
• Some are useful as indicator species

Use of lichen
• Food
• Dyes (litmus paper, Harris tweed)
• Essential oils for perfumes, soaps
• Bioactive compounds (antiviral, antibacterial)
• Nesting/bedding material
• Poisons