Classification of Algae by Various Botanists

In this article we will discuss about the classification of algae by various botanists.

Classification by A. F. E. Fritsch (1935, 48):

F. E. Fritsch (1935, 48) was the first who proposed a most comprehensive and authorative classification of algae in his book.

“The Structure and Reproduction of the Algae” based on the following characteristics:

i. Pigmentation.

ii. The metabolic or assimilatory food products.

iii. Types of flagella, he classified the algae into eleven (11) classes.

These are as follows:

1. Chlorophyceae (Isokontae, green algae):

a. Cells are eukaryotic and cell wall is mainly composed of cellulose.

b. Pigments. Presence of Chlorophyll a and b, carotenoid and xanthophylls.

c. Chloroplast usually has pyrenoids.

d. Reserve food is starch.

e. Flagella if present are equal in length and are situated anteriorly. One is whiplash and other one is tinsel type.

f. Reproduction takes place by vegetative, asexual and sexual methods. Sexual reproduction may be iso-, aniso- and oogamous type.

The class has been divided into nine (9) orders:

i. Volvocales. e.g., Chlamydomonas.

ii. Chlorococcales. e.g., Chlorella, Hydrodictyon.

iii. Ulotrichales. e.g., Ulothrix.

iv. Cladophorales. e.g., Cladophora, Pithophora.

v. Chaetophorales. e.g., Ulvella, Coleo­chaete.

vi. Oedogoniales. e.g., Oedogonium.

vii. Conjugales. e.g., Spirogyra, Zygnema.

viii. Siphonales. e.g., Vaucheria.

ix. Charales. e.g., Chara, Nitella.

2. Xanthophyceae (Heterokontae, yellow green algae):

a. Cells are eukaryotic and cell wall is composed of pectic substance.

b. The main pigments are Chlorophyll a and e, β-carotene and xanthophylls.

c. Chloroplasts are without pytisnoid.

d. Reserve food is oil.

e. Flagella are two, unequal in length and are situated anteriorly. The longer one tinsel and shorter one is whiplash type.

f. Reproduction. It takes place by all the three means vegetative, asexual and sexual (isogamous type).

The class has been divided into four (4) orders:

i. Heterochioridales e.g, Heterochloris.

ii. Heterococcales e.g., Myxochloris.

iii. Heterotrichales e.g., Microspora.

iv. Heterosiphonales e.g., Botrydium.

3. Chrysophyceae:

a. Cells are eukaryotic and cell wall is silicified or calcified (cellulose absent).

b. Pigments. The dominating pigment is phycochrysin.

c. Chromatophores have naked pyrenoid- like bodies.

d. The reserve food is crysolaminarin and lucosin.

e. The motile cells have two flagella (either equal or unequal) inserted ante­riorly.

f. Reproduction. It takes place by vege­tative and sexual means. Sexual repro­duction if present is of isogamous type.

The class has been divided into three (3) orders:

i. Chrysomonadales e.g., Crysodendron.

ii. Chrysosphaerales e.g., Chrysosphaera.

iii. Chrysotrichaies e.g., Chrysoclonium.

4. Bacillariophyceae (Diatom, yellow or golden brown algae)

a. The cells are eukaryotic and consist of two halves, epitheca and hypotheca; which are bilaterally or radially sym­metrical.

b. Cell wall is pectic and silicified and ornamented variously.

c. Pigments. The dominant pigments are fucoxanthin, diatoxanthin and diadinoxanthin

d. Chromatophore has pyrenoids.

e. Reserve food is fat and volutin.

f. Motile cells have single flagellum.

g. Reproduction takes place by cell divi­sion and auxospore formation.

The class has been divided into two (2) orders:

i. Centrales e.g., Chaetoceras, Cyclotella.

ii. Pennales e.g., Pinnularia, Denticula.

5. Cryptophyceae:

a. The cells are eukaryotic in nature.

b. Pigments. The dominant pigments are xanthophylls — give red or brown colour.

c. Pyrenoid-like bodies are present but they are independent of chromato­phores.

d. Reserve food is starch and/or oil.

e. Sexual reproduction is rare and iso­gamous type only.

The class has been divided into two (2) orders:

i. Cryptomonadales e.g., Cryptomonas, Cyanomonas.

ii. Cryptococcales e.g., Tetragonidium.

6. Dinophyceae:

a. The cells are eukaryotic in nature.

b. Pigments. The dominant pigments are xanthophylls which give red or brown colouration.

c. Cells contain many discoid chro­matophores.

d. Reserve food is starch and fat.

e. Most members are unicellular and motile with two flagella.

f. Some members show holozoic mode of nutrition.

g. Sexual reproduction is rare and isogamous type only.

The class has been divided into six (6) orders:

i. Desmomonadales e.g., Desmocapsa, Desmomastrix.

ii. Thecatales e.g., Prorocentrum, Exuviaella.

iii. Dinophysiales e.g., Dinophysis, Phalacroma.

iv. Dinoflagellata e.g., Elastodinium, Heterocapsa.

v. Dinococcales e.g., Dinastridium, Dissodinium.

vi. Dinotrichales e.g., Dinothrix, Dinoclonium.

7. Chloromonadineae:

a. Cells are eukaryotic in nature.

b. Pigments. Dominant pigment is xantho­phylls, present in excess amount.

c. Chromatophore. Cells have numerous discoid chromatophores without pyrenoid.

d. Reserve food is fat and oil.

e. Flagella. Motile forms are with two equal flagella.

f. Reproduction. It takes place by cell divi­sion. Sexual reproduction is absent.

The class has only one (1) order:

i. Chloromonadales e.g., Vacuolaria, Trentonia.

8. Euglenoineae:

a. Plant body is unicellular and eukaryotic in nature.

b. The dominant pigment is chlorophyll.

c. Cells have many chromatophores.

d. Pyrenoid-like bodies are present in some members.

e. Reserve food is paramylon, a polysac­charide.

f. Flagella. Most of them have one or two flagella.

g. They possess complex vacuolar system.

h. Reproduction. It takes place by cell divi­sion. Sexual reproduction if present is of isogamous type.

The class has been divided into three (3) families:

i. Euglenaceae e.g., Euglena, Ascoglena.

ii. Astasiaceae e.g., Astasia, Menoidium.

iii. Peranemaceae e.g., Petalomonas, Anisonema.

9. Phaeophyceae (brown algae):

a. Most of the members are marine.

b. Cell wall is composed of cellulose along with alginic and fucinic acid.

c. Pigments. Fucoxanthin is the dominant pigment, in addition to chlorophyll a, c and carotene.

d. Reserve food is laminarin (polysaccha­ride), manitol (alcohol) and fats.

e. Some lower members have naked pyrenoid like bodies.

f. Zoospores are flagellated, one of which is tinsel type.

g. Sexual reproduction ranges from isogamy to oogamy.

The class has been divided into nine (9) orders:

i. Ectocarpales e.g., Ectocarpus, Punctaria.

ii. Tilopteridales e.g., Tilopteris.

iii. Cuteriales e.g., Cutleria.

iv. Sporochnales e.g., Carpomitra, Sporochnus.

v. Desmarestiales e.g., Desmarestia.

vi. Laminariales e.g., Laminaria, Macrocystis.

vii. Sphacelariales e.g., Sphacelaria.

viii. Dictyotales e.g., Dictyota, Padina.

ix. Fucales e.g., Fucus, Sargassum.

10. Rhodophyceae:

a. Plant body is multicellular (either uni­axial or multiaxial) and cells are eukary­otic in nature.

b. Cell wall is composed of outer pectic and inner cellulose.

c. Chromatophores are present. Pyrenoid- like bodies are present in lower forms.

d. The dominant pigment is r-phycoerythrin (C₃₄H₄₆O₈N₄) which gives red colour to the algae. In addition, other pigments like c-phycocyanin, chloro­phyll a, d, carotene and xanthophylls are also present.

e. Storage food is floridean starch, a polysaccharide.

f. Reproductive cells are non-motile. Sexual reproduction is of advanced oogamous type.

The class has been divided into seven (7) orders:

i. Bangiales e.g., Bangia, Porphyra.

ii. Nemalionales e.g., Nemalion, Naccaria.

iii. Gelidiales e.g., Gelidium.

iv. Cryptonemiales e.g., Gloeopeltis, Dumontia.

v. Gigartinales e.g., Gigartina, Gracilaria.

vi. Rhodymeniaies e.g., Rhodymenia, Champia.

vii. Ceramiales e.g., Polysiphonia, Ceramium.

11. Myxophyceae (Cyanophyceae, blue green algae):

a. They are mostly fresh water.

b. Plant body may be- unicellular or multi­cellular and the cells are prokaryotic in nature.

c. The cell wall is composed of mucopeptide, together with amino acidsi fatty acids and carbohydrate.

d. The dominant pigment is c-phycocyanin which gives blue green coloura­tion to the cells. In addition, other pig­ments like chlorophyll a, β-carotene and c-phycoerythrin are also present.

e. The reserve food is cyanophycean starch and cyanophycean granule (pro­tein).

f. There is no motile stage in the members of this class.

g. Reproduction takes place by both vege­tative (cell division, fragmentation etc.) and asexual means (exospore, endospore, heterocysts etc.). Sexual repro­duction is absent (genetic recombina­tion is reported in a few members).

The class has been divided into five (5) orders:

i. Chroococcales e.g., Gloeocapsa, Chroo- coccus.

ii. Chamaesiphonales e.g., Chamaesiphon.

iii. Pleurocapsales e.g., Pleurocapsa.

iv. Nostocales e.g., Nostoc, Oscillatoria.

v. Stigonematales e.g., Nostochopsis, Stigonema.

Classification by Robert Edward Lee (1989):

Robert Edward Lee (1989) classified the algae into 4 evolutionary groups, 15 divisions and classes.

The classification is given below:

Group 1. Prokaryotic algae:

1. Division. Cyanophyta (blue green algae): Chlorophyll a; phycobiliproteins.

2. Division. Prochlorophyta (prochloro- phytes): Chlorophyll a and b; no phyco­biliproteins.

Group 2. Eukaryotic algae:

Eukaryotic algae with chloroplast surrounded only by the two membranes of the chloroplast envelope.

1. Division. Glaucophyta: algae that repre­sent an intermediate position in the evolu­tion of chloroplast; photosynthesis is carried out by modified endosymbiotic blue-green algae.

2. Division. Rhodophyta (red algae): Chlorophyll a and d; phycobiliproteins; no flagellated cells; storage product is floridean starch.

3. Division. Chlorophyta (green algae): Chlorophyll a and b; storage product starch is found inside the chloroplast.

Group 3. Eukaryotic algae:

Eukaryotic algae with chloroplast surrounded only by one membrane of chloro­plast endoplasmic reticulum.

1. Division. Euglenophyta (euglenoid): chloro­phylls a and b, one flagellum with a spiralled row of fibrillar hairs; proteinaceous pellicle in strips under the plasma membrane; storage product is paramylon; characteristic type of cell division.

2. Division. Dinophyta (dinoflagellates): meso­karyotic nucleus; chlorophyll a and c₁; cell commonly divides into an epicone and a hypocone by a girdle; helical transverse flagellum; thecal plates in vesicles under the plasma membrane.

Group 4. Eukaryotic algae:

Eukaryotic algae with chloroplast surrounded by two membranes of chloroplast endoplasmic reticulum.

1. Division. Cryptophyta (cryptophytes): nucleomorph present between inner and outer membrane of chloroplast endoplasmic reticulum; starch is formed in grains between inner membrane of chloroplast endoplasmic reticulum and chloroplast envelop; chlorophyll a and c; phycobilipro­teins; periplast is found inside plasma mem­brane.

2. Division. Crysophyta (golden-brown algae): chlorophyll a and c₁ and sometimes c₂; fucoxanthin; anterior tinsel and poste­rior whiplash flagella; storage product chrysolaminarin is found in vesicles in cytoplasm.

3. Division. Prymnesiophyta (haptophytes): haptonema, chlorophyll a, c₁ and c₂, fuco- xanthin; two whiplash flagella; scales com­mon outside cell; storage product chryso­laminarin is found in vesicles in cytoplasm.

4. Division. Bacillariophyta (diatom): silica in cell walls; chlorophyll a, c₁ and c₂; fuco- xanthin; one posterior tinsel flagellum on sperm; storage product chrysolaminarin is found in vesicles in cytoplasm.

5. Division. Xanthophyta (yellow green algae): eye-spot in chloroplast; chlorophyll a and c; anterior tinsel flagellum and posterior whiplash flagellum.

6. Division. Eustigmatophyta: eye-spot large and outside chloroplast; chlorophyll a; posterior whiplash flagellum (commonly reduced) and anterior tinsel flagellum.

7. Division. Raphidophyta (chloromonads): chlorophyll a and c; anterior tinsel flagellum and posterior whiplash flagellum.

8. Division. Phaeophyta (brown algae): unilocular and plurilocular sporangia, chlorophyll a, c₁ and c₂; fucoxanthin; sto­rage product chrysolaminarin is found in vesicles in cytoplasm; anterior tinsel flagel­lum and posterior whiplash flagellum.

A brief outline of the classification up to class (with characteristics) is given below:

Group 1. Prokaryotic algae:

The prokaryotic algae have an outer plasma membrane enclosing protoplasm containing photosynthetic thyla­koids, 70S ribosomes and DNA fibrils not enclosed within a separate membrane. Chloro­phyll a is the main photosynthetic pigment.

1. Division. Cyanophyta (blue green algae).

Presence of chlorophyll a and phycobiliprotein, e.g., Anabaena, Gloeotrichia etc.

2. Division. Prochlorophyta (prochlorophytes). Presence of chlorophyll a and b, phycobiliproteins absent, e.g., Prochloron.

Group 2. Eukaryotic algae:

Eukaryotic algae with chloroplast sur­rounded only by the two membranes of the chloroplast envelope.

1. Division. Glaucophyta:

The algae have endosymbiotic blue-green algae (BGA) in the cytoplasm instead of chloro­plasts. Pasteur (1 914) coined the terms Cyanelles to endosymbiotic BGA, Cyanone for host and Syncyanosis for the association. Chlorophyll a and phycobiliproteins are present like BGA but BGA like carotenoids, myxoxanthophyll and echinenone are absent e.g., Cyanophora para- dosa, Glaucocystis etc.

2. Division. Rhodophyta (red algae):

The Division Rhodophyta has a single class Rhodophyceae.

Class. Rhodophyceae:

1. The plants are generally of marine habi­tat called sea weeds, grows in various depth. (Out of about 4000 species, about 200 species are fresh water.)

2. Pit connections between the cells in all of the orders except Porphyridales, Erythropeltidales and haploid phase of the Bangiales.

3. Chloroplast with one thylakoid per band and no chloroplast endoplasmic reticulum.

4. Presence of Chlorophyll a and d, Phycobiliproteins includes r-phyco- cyanin, allophycocyanin and three forms of phycoerythrins (b, r and c).

5. Floridean starch as a storage product.

6. Lack of flagellate cells.

The class Rhodophyceae is divided into 12 orders:

1. Porphyridales. e.g., Porphyridium, Rhodosorus etc.

2. Rhodochaetales e.g., Rhodochaete.

3. Acrochaetiales. e.g., Audouinella, Rhodochorton etc.

4. Bangiales. e.g., Bangia, Porphyra etc.

5. Erythropeltidales. e.g., Erythrocladia, Porphyropsis etc.

6. Lemaneales. e.g., Batrachospermum, Lemanea etc.

7. Nemaliales. e.g., Nemalion, Liagoraetc.

8. Gelidiales. e.g., Harveyella, Ceratocolax etc.

9. Gigertinales. e.g., Gigertina, Chondrus, etc.

10. Rhodymeniales e.g., Rhodymenia etc.

11. Palmariales. e.g., Palmariaetc.

12. Ceramiales e.g., Delesseria, Phycodrys etc.

3. Division. Chlorophyta (green algae)

It is divided into 4 classes:

A. Class. Micromonadophyceae:

1. Scaly or naked flagellates with inter­zonal spindles those are persistent during cytokinesis,

2. Primitive green algae, some of which gave rise to other classes in the Chlorophyta.

B. Class. Charophyceae (flagella are attached in a lateral position of the cell).

1. Motile cells asymmetrical, two flagella are attached in a lateral position of the cell.

2. Flagellar root consist of a broad band of microtubules and a second smaller microtubular root.

3. Multilayered structure (MLS) may be present; rhizoplast absent.

4. Scales common outside the motile cells.

5. Persistant interzonal mitotic spindle in telophase.

6. Phragmoplast produces new cross-wall after cell division.

7. Eye spots usually not present.

8. Sexual reproduction involves the forma­tion of a dominant zygote. Meiosis occurs during zygote germination.

The class Charophyceae is further divided into 4 orders:

1. Klebsormidiales. e.g., Stichococcus, Raphidonema, Klebsormidium etc.

2. Zygnematales. e.g., Spirogyra, Zygnema, Cosmerium, Cylindrocystis, Mesotaenium etc.

3. Coleochaetales e.g., Coleochaete.

4. Charales e.g., Chara, Nitella.

C. Class. Ulvophyceae (flagella are attached at the anterior end of the cell).

1. Plants are predominantly marine.

2. Flagella are attached at anterior end of cell.

3. Externally, the motile cells have near- radial symmetry.

4. Flagella roots consist of 4 cruciately arranged microtubular roots and some­times a rhizoplast.

5. Multilayered structure (MLS) is absent.

6. Scales may be present on motile cells.

7. Presence of persistent interzonal spindle in telophase.

8. Eye-spots are common.

9. Dormant zygote is absent.

10. Alternation of generation is common.

Common genus: Ulva.

D. Class. Chlorophyceae (flagella are attached at the anterior end of the cell).

1. Plants are predominantly fresh water.

2. Motile cells are with radial or near- radial external symmetry.

3. Flagella are attached at the anterior end of cell.

4. Flagella roots consists of 4 cruciately arranged microtubular roots and some­times a rhizoplast.

5. Multilayered structure (MLS) is absent.

6. Theca is common in motile cells.

7. In telophase, the interzonal spindle collapses; phycoplast produces the new cross wall in cell division.

8. Eye-spots are common.

9. Zygote undergoes a dormant period; meiosis occurs when the zygote germi­nates.

The class Chlorophyceae is further divided into 8 orders:

1. Volvocales. e.g., Chlamydomonas, Volvox.

2. Tetrasporales. e.g., Tetraspora, Palmella.

3. Schizogoniales. e.g., Parasiola.

4. Chlorococcales. e.g., Chlorococcum, Hydrodictyon, Scenedesmus, Chlorella.

5. Sphaeropleales. e.g., Microspora, Sphaeroplea.

6. Chlorosarcinales e.g., Chlorosarcina.

7. Chaetophorales. e.g., Stigeoclonium, Chaetophora.

8. Oedogoniales. e.g., Oedogonium, Oedocladium, Bulbochaete.

Group 3. Eukaryotic algae:

Eukaryotic algae with chloroplast surrounded by one membrane of chloroplast endoplasmic reticulum.

1. Division. Euglenophyta (euglenoid)

It consists of only one Class:

Euglenaceae.

Class. Euglenaceae:

1. They are unicellular.

2. They have chlorophyll a and b.

3. One membrane of chloroplast and endoplasmic reticulum.

4. The nucleus is mesokaryotic in nature.

5. Flagella with fibrillar hairs in one row.

6. Sexual reproduction is absent.

7. The storage product is paramylon, formed in the cytoplasm.

Common genus: Euglena.

2. Division. Dinophyta (dinoflagellates).

It consists of only one Class:

Dinophyceae.

Class. Dinophyceae:

1. A typical motile dinoflagellate consists of an epicone and hypocone divided by a transverse girdle or cingulum.

2. The epicone and hypocone are normally divided into a number of thecal plates.

3. The cells can be photosynthetic or colourless and heterotrophic.

4. Photosynthetic organisms have chloro­plasts surrounded by one membrane of chloroplast endoplasmic reticulum; which is not continuous with the outer membrane of the nuclear envelop.

5. Chlorophyll a and c₂ are present in the chloroplasts, with peridinin and neo- peridinin being the main carotenoids.

6. Presence of pyrenoid in chloroplast.

7. Storage product is starch.

8. Eye-spot is present.

9. Nucleus is dinokaryotic or mesokaryo­tic in nature.

Common genera: Oxyrrhis, Heterocapsa, Peridinium, Ceratium, Amphinidium etc.

Group 4. Eukaryotic algae:

Eukaryotic algae with chloroplast surrounded by two membranes of chloroplast endoplasmic reticulum.

1. Division. Cryptophyta (cryptophytes)

It consists of only one Class:

Cryptophyceae.

Class. Chryptophyceae:

1. Plants are found in both marine and fresh water habitat.

2. The plant body is dorsiventral in shape, with the cells flattened in one plane.

3. Cells contain chlorophyll a and c₂.

4. A few members lack chloroplast and are heterotrophic in nature, but most have a single-lobed chloroplast with a central pyrenoid.

5. Phycobiliproteins occur inside the thylakoids of the choloroplasts.

Common genera: Cyathomonas, Chilomonas etc.

2. Division. Crysophyta (golden-brown algae)

It consists only of two Classes:

Chryso­phyceae and Synurophyceae.

Class. Chrysophyceae:

1. Presence of chlorophyll c₁ and c₂.

2. Flagella inserted in the cell perpendi­cular to one another.

3. One photoreceptor as a swelling on the short flagellum.

4. Eye-spot commonly present.

5. Choloroplast endoplasmic reticulum present.

6. Radially or bilaterally symmetrical silica scales may occur.

7. Contractile vacuole anterior.

Common genera: Pedinella, Phaeaster etc.

Class. Synurophyceae:

1. Presence of chlorophyll c₁.

2. Flagella inserted into the cell approxi­mately parallel to each other.

3. Presence of two photoreceptors, one on each flagellum.

4. Eye-spot absent.

5. Chloroplast endoplasmic reticulum usu­ally absent.

6. Plant body bilaterally symmetrical.

7. Silica scales are common.

8. Contractile vacuole is posterior.

Common genera: Dictyocta, Synura etc.

3. Division. Prymnesiophyta (haptophytes)

It consists of only one Class:

Prymnesiophyceae.

Class. Prymnesiophyceae:

1. It is a group of unicellular flagellates characterised by the possession of a haptonema between two smooth flage­lla.

2. Chloroplasts have chlorophyll a, c₁ and c₂ with fucoxanthin as the major carotenoid.

3. Diadinoxanthin and 19′ – hexanoyl fucoxanthin also occur in the group.

4. Two membranes of the chloroplast endoplasmic reticulum are present.

5. The anterior end of the cell has a large golgi apparatus and sometimes contrac­tile vacuole.

6. The cells are commonly covered with scales.

Common genera: Prymnesium, Diacronema etc.

4. Division. Bacillariophyta (diatom)

It consists of only one Class:

Bacillario­phyceae.

Class. Bacillariophyceae:

1. Plant body is unicellular and free-living. Sometimes they are present in colony.

2. Depending on the mode of nutrition they may be photosynthetic auto­trophs, photosynthetic symbionts or colourless heterotrophs.

3. Vegetative cells are diploid (2n).

4. The cells are surrounded by a rigid two- part box-like cell wall (upper part is epitheca and lower part is hypotheca) composed of silica called the frustule.

5. The cells are bilaterally or radially sym­metrical.

6. The chloroplast contains chlorophylls a, c₁ and c₂ with the major carotenoid being the golden-brown fucoxanthin.

7. Reserve food is fat and volutin.

8. Motile cells have single flagellum.

9. Reproduction takes place by cell divi­sion and auxospore formation.

Common genera: Cyclotella, Biddulphia, Rutilaria etc.

5. Division. Xanthophyta (yellow green algae)

It consists of only one Class:

Xanthophyceae.

Class. Xanthophyceae:

1. Cells are eukaryotic and cell wall is composed of pectic substance.

2. The main pigments are chlorophyll a and e, β-carotene and xanthophylls.

3. Chloroplasts are without pyrenoids.

4. Reserve food is oil.

5. Flagella are two, equal in length and are situated anteriorly. The longer one tinsel and shorter one is whiplash type.

6. Reproduction takes place by all the three means — vegetative, asexual, and sexual (isogamous type).

Common genera: Botrydium, Ophiocytium, Tribonema, Vaucheria etc.

6. Division. Eustigmatophyta

It consists of only one Class:

Eustigmatophyceae.

Class. Eustigmatophyceae:

1. Plant body is unicellular and live in fresh water or in soil.

2. Chloroplasts contain chlorophyll a, β carotene with two major xanthophylls being violaxanthin and vaucheriaxan- thin.

3. Vegetative cells usually have a charac­teristic polygonal pyrenoids (absent in zoospores).

4. The pyrenoid projects from the inner face of the plastid on a narrow stalk and in the cytoplasm are surrounded by flat plates of the unidentified photosynthate.

Common genera: Pleurochloris, Polyedriella.

7. Division. Raphidophyta (chloromonads)

It consists of only one Class:

Raphidophyceae

Class. Raphidophyceae:

1. They are commonly marine.

2. Chloroplasts contain chlorophyll a and c.

3. Two membrane of chloroplast endo­plasmic reticulum.

4. Anterior flagella is commonly tinsel, whereas the posterior flagella is naked.

Common genera: Heterosigma, Chattonella etc.

8. Division. Phaeophyta (brown algae)

It consists of only one class:

Phaeophyceae.

Class. Phaeophyceae:

1. Most of the members are marine.

2. Cell wall composed of cellulose along with alginic and fucinic acid.

3. Pigments. Fucoxanthin is the dominant pigment, in addition to chlorophylls a, c and carotene.

4. Reserve food is laminarin (polysaccha­ride), manitol (alcohol) and fat.

5. Some lower members have naked pyrenoid-like bodies.

6. Zoospores are flagellated, one of which is tinsel type.

7. Sexual reproduction ranges from isogamy to oogamy.

Common genera: Ectocarpus, Laminaria, Dictyota etc.

Later on Robert Edward Lee (1999) revised the classification of algae (“Phycology”, R.E. Lee, 1999, 3rd Edn.) with some modification of his earlier classification proposed in 1989 in his book “Phycology”.

Robert Edward Lee (1999) classified the algae into four evolutionary groups, nine phyla and different classes.

The 1st group consists of prokaryotic algae only, the others are eukaryotic.

The eukaryotic algae are further divided into three groups:

(a) Chloroplast surrounded only by the two mem­branes of the chloroplast envelope,

(b) Chloro­plast surrounded by one membrane of chloro­plast endoplasmic reticulum (E.R.) and (c) chloro­plast surrounded by two membranes of chloro­plast endoplasmic reticulum (E.R).

The standard botanical classification system used (suffix) in the systematics of the algae:

The brief outline of classification is given below:

Group 1. Prokaryotic algae:

1. Phylum. Cyanophyta (cyanobacteria):

Chlorophyll a; phycobiliproteins.

Group 2. Eukaryotic algae:

Eukaryotic algae with chloroplast surrounded only by the two membranes of the chloroplast envelope.

1. Phylum. Glaucophyta:

Algae that represent an intermediate position in the evolution of chloroplast; photosynthesis is carried out by modified endosymbiotic blue-green algae.

2. Phylum. Rhodophyta (red algae):

Chloro­phylls a and d; phycobiliproteins; no flagel­lated cells; storage product is floridean starch.

3. Phylum. Chlorophyta (green algae):

Chloro­phyll a and b; storage products starch is found inside the chloroplast.

Group 3. Eukaryotic algae with chloroplast sur­rounded by one membrane of chloroplast endo­plasmic reticulum.

1. Phylum. Euglenophyta (euglenoid):

Chloro­phylls a and b, one flagellum with a spiral row of fibrillar hairs; proteinaceous pellicle in strips under the plasma membrane; sto­rage product paramylon; characteristic type of cell division.

2. Phylum. Dinophyta (dinoflagellates):

Meso­karyotic nucleus; chlorophylls a and c₁; cell commonly divided into an epicone and a hypocone by a girdle; helical transverse fla­gellum; thecal plates in vesicles under the plasma membrane.

Group 4. Eukaryotic algae:

Eukaryotic algae with chloroplast sur­rounded by two membranes of chloroplast endo­plasmic reticulum.

1. Phylum. Cryptophyta (cryptophytes):

Nucleomorph is present between inner and outer membranes of chloroplast endoplasmic reticulum; Starch is formed in grains between inner membrane of chloroplast endoplasmic reticulum and chloroplast envelop; chloro­phylls a and c; phycobiliproteins; periplast is found inside plasma membrane.

2. Phylum. Heterokontophyta (heterokonts):

Anterior tinsel and posterior whiplash flagella, chlorophylls a and c₁, fucoxanthin, storage product usually chrysolaminarin occurs in vesicles in cytoplasm.

The phylum is further divided into nine (9) classes.

These are as follows:

1. Class. Crysophyceae (golden-brown algae):

Chlorophyll a and c₁ and some­times c₂; fucoxanthin; anterior tinsel and posterior whiplash flagella; storage product chrysolaminarin, found in vesi­cles in cytoplasm.

2. Class. Synurophyceae:

Plant body bilate­rally symmetrical. Flagella inserted into the cell approximately parallel to each other. Chloroplast endoplasmic reticu­lum usually absent. Flagella inserted into the cell approximately parallel to each other. Presence of chlorophyll c₁.

3. Class. Dictyochophyceae (silicoflagellates):

Golden brown algae, characte­rized by tentacles or rhizopodia on basi­cally amoeboid vegetative cells. Amoeboid cells are mostly restricted to this group.

4. Class. Pelagophyceae:

Basically unicel­lular algae. Cells are very small (3-5µm) and appear as small spheres with indis­tinct protoplasm.

5. Class. Bacillariophyceae (diatoms):

Silica in cell walls; chlorophylls a, c₁ and c₂; fucoxanthin; one posterior tinsel flagellum on sperm; storage product chrysolaminarin found in vesicles in cytoplasm.

6. Class. Raphidophyceae (chloromonads):

Chlorophylls a and c; anterior tinsel flagellum and posterior whiplash flagel­lum.

7. Class. Xanthophyceae (yellow green algae):

Eyespot in chloroplast; chloro­phylls a and e; presence of anterior tinsel flagellum and posterior whiplash flagellum.

8. Class. Eustigmatophyceae:

Eye spot large, remains out side the chloroplast; chlorophyll a; presence of posterior whiplash flagellum (commonly reduced) and anterior tinsel flagellum.

9. Class. Phaeophyceae (brown algae):

Presence of unilocular and plurilocular sporangia, chlorophylls a, c₁ and c₂, fucoxanthin; storage product chryso­laminarin found in vesicles in cyto­plasm; presence of anterior tinsel flagel­lum and posterior whiplash flagellum.

3. Phylum. Prymnesiophyta (haptophytes) : Haptonema, chlorophylls a and c₁ and cy fucoxanthin; two whiplash flagella; scales common outside cell; storage product chrysolaminarin, found in vesicles in cyto­plasm.

A brief outline of the classification up to class (with characters) is given below:

Group 1. Procaryotic algae

1. Phylum. Cyanophyta

Class. Cyanophyceae

1. The individual cells are prokaryotic in nature. The nucleus is incipient type and lacks membrane bound organelles.

2. Both vegetative and reproductive cells are non-flagellated.

3. Cell wall is made up of microfibrils and is differentiated into four (4) layers. The cell wall is composed of mucopeptide, along with carbohydrates, amino acids and fatty acids.

4. Locomotion is generally absent, but where occurs, it is of gliding or jerky type.

5. The principal pigments are chlorophylls a (green), c-phycocyanin (blue) and c-phycoerythrin (red). In addition, other pigments like β-carotene and different xanthophylls like myxoxanthin and myxoxanthophyll are also present.

6. Membrane-bound chromatophores are absent. Pigments are found embedded in thylakoids.

7. The reserve foods are cyanophycean starch and cyanophycean granules (pro­tein).

8. Many filamentous members possess specialized cells of disputed function (supposed to be the centre of N₂ fixa­tion) known as heterocyst.

9. Reproduction takes place by vegetative and asexual methods. Vegetative repro­duction takes place by cell division, fragmentation etc. Asexual reproduction takes place by endospores, exospores, akinetes, nannospores etc.

10. Sexual reproduction is completely absent. Genetic recombination is repor­ted in two cases.

Common genus: Nostoc, Oscillatoria, Gloeocapsa, Gloeotrichia etc.

Group 2. Eukaryotic algae with chloroplast sur­rounded only by the two membranes of the chloroplast envelope.

1. Phylum. Glaucophyta:

1. Members of this group have endosymbi­otic cyanobacteria (cyanelles) in the cytoplasm instead of chloroplast.

2. Most of the cyanelles in this phylum lack a wall and are surrounded by two mem­branes – the old food vesicle membrane of the cyanome (host) and the plasma membrane of the cyanelle. In course of evolution these two membranes became the chloroplast envelop.

3. Various inclusions of the cyanobacteria like polyhedral bodies, cyanophycean granules, polyphosphate bodies are lost. The cyanome cytoplasm took over the formation of the storage product.

4. A pyrenoid, being differentiated from proteinaceous bodies, is present in the cyanelle.

5. Pigments like chlorophyll a and the phycobiliproteins are present.

Common genus: Cyanophora, Glaucocystis, Geosiphon etc.

2. Phylum. Rhodophyta (red algae)

The phylum Rhodophyta has a single class Rhodophyceae.

Class. Rhodophyceae:

1. Plants are generally marine habitat, called sea weeds, grow in various depth. (Out of about 4,000 species, about 200 species are of fresh water).

2. Pit connections between the cells in all of the orders except Porphyridales, Erythropeltidales and haploid phase of the Bangiales.

3. Chloroplast with one thylakoid per band and absence of chloroplast endo­plasmic reticulum.

4. Presence of chlorophylls a and d, phy­cobiliproteins include r-phycocyanin, allophycocyanin, and three forms of phycoerythrins (b, r and c).

5. Floridean starch as a storage product.

6. Lack of flagellated cells.

The class Rhodophyceae is divided into 10 orders:

1. Porphyridiales. e.g., Porphyridium, Rhodosorus etc.

2. Rhodochaetales. e.g., Rhodochaete.

3. Acrochaetiales. e.g., Audouinella, Rhodochorton etc.

4. Bangiales. e.g., Bangia, Porphyra etc.

5. Batrachospermales. e.g., Batrachosper­mum.

6. Nemaliales. e.g., Nemalionetc.

7. Corallinales. e.g., Corallina, Melobesia etc.

8. Gelidiales. e.g., Gelidium.

9. Gracilariales. e.g., Gracilaria.

10. Ceramiales. e.g., Polysiphonia etc. 3. Phylum. Chlorophyta (green algae)

It is divided into 4 clases:

A. Class. Micromonadophyceae:

Important characteristics:

Scaly or naked flagellates with interzonal spindles are persistent during cytokinesis; primi­tive green algae, some of which gave rise to the other classes in the Chlorophyta.

B. Class. Charophyceae (flagella are attached in a lateral position in the cell):

1. Motile cells asymmetrical, two flagella attached in a lateral position in cell.

2. Flagellar root consisting of a broad band of microtubules and a second smaller microtubular root.

3. Multilayered structure (MLS) may be present, rhizoplast absent.

4. Scales are common, outside the motile cells.

5. Persistant interzonal mitotic spindle in telophase.

6. Phragmoplast produces new cross-walls after cell division.

7. Eye-spots usually not present.

8. Sexual reproduction involves the forma­tion of a dominant zygote. Meiosis occurs during zygote germination.

The class Charophyceae is further divided into 4 orders:

1. Klebsormidiales. e.g., Stichococcus, Raphidonema, Klebsormidium etc.

2. Zygnematales. e.g., Spirogyra, Zygnema, Cosmerium, Cylindrocystis, Mesotaenium etc.

3. Coleochaetales e.g., Coleochaete.

4. Charales e.g., Chara, Nitella.

C. Class. Ulvophyceae (flagella are attached at the anterior end of the cell).

1. Plants are predominantly marine.

2. Flagella attached at anterior end of cell.

3. Externally, the motile cells have near- radial symmetry.

4. Flagella roots consist of 4 cruciately arranged microtubular roots and some­times a rhizoplast.

5. Multilayered structure (MLS) is absent.

6. Scales may be present on motile cells.

7. Presence of persistent interzonal spindle in telophase.

8. Eye-spots are common.

9. Dormant zygote is absent.

10. Alternation of generation is common.

The class Ulvophyceae is further divided into 6 orders:

1. Ulotrichales. e.g., Ulothrix.

2. Ulvales. e.g., Ulva, Monostroma.

3. Cladophorales. e.g., Cladophora, Chaetomorpha.

4. Dasycladales. e.g., Acetabularia, Neo- meris etc.

5. Caulerpales. e.g., Derbesia, Caulerpa, Codium etc.

6. Siphonocladales. e.g., Siphonocladus, Valonia etc.

Common genera: Ulva, Ulothrix, Clado­phora etc.

D. Class. Chlorophyceae (flagella are attached at the anterior end of the cell)

 1. Plants are predominantly fresh water.

2. Motile cells are with radial or near- radial external symmetry.

3. Flagella are attached at the anterior end of cell.

4. Flagella roots consist of 4 cruciately arranged microtubular roots and some­times a rhizoplast.

5. Multilayered structure (MLS) is absent.

6. Theca is common in motile cells.

7. In telophase, the interzonal spindle col­lapses; phycoplast produces the new cross wall in cell division.

8. Eye-spots are common.

9. Zygote undergoes a dormant period; meiosis occurs when the zygote germi­nates.

The class Chlorophyceae is further divided into 8 orders:

1. Volvocales. e.g., Chlamydomonas, Volvox.

2. Tetrasporales. e.g., Tetraspora, Palmella.

3. Schizogoniales. e.g., Parasiola.

4. Chlorococcales.e.g., Chlorococcum, Hydrodictyon, Scenedesmus, Chlorella.

5. Sphaeropleales. e.g., Microspora, Sphaeroplea.

6. Chlorosarcinales e.g., Chlorosarcina.

7. Chaetophorales. e.g., Stigeoclonium, Chaetophora.

8. Oedogoniales. e.g., Oedogonium, Oedocladium, Bulbochaete.

Group 3. Eukaryotic algae:

Eukaryotic algae with chloroplast sur­rounded by one membrane of chloroplast endo­plasmic reticulum.

1. Phylum. Euglenophyta (euglenoid)

It consists of only one Class:

Euglenaceae.

Class Euglenaceae:

1. They are unicellular.

2. They have chlorophyll a and b.

3. One membrane of chloroplast and endoplasmic reticulum.

4. The nucleus is mesokaryotic in nature.

5. Flagella with fibrillar hairs in one row.

6. Sexual reproduction is absent.

7. The storage product is paramylon, formed in the cytoplasm.

The class Euglenophyceae is further divided into 3 orders:

1. Heteronematales. e.g., Peranema, etc.

2. Eutreptiales. e.g., Eutreptia, Eutreptiella etc.

3. Euglenales. e.g., Euglena, Trachelo- monas, Phacus etc.

2. Phylum. Dinophyta (dinoflagellates)

It consists of only one Class:

Dinophyceae.

Class Dinophyceae:

1. A typical motile dinoflagellate consists of an epicone and hypocone divided by a transverse girdle or cingulum.

2. The epicone and hypocone are normal­ly divided into a number of thecal plates.

3. The cells can be photosynthetic or colourless and heterotrophic.

4. Photosynthetic organisms have chloro­plasts surrounded by one membrane of chloroplast endoplasmic reticulum, which is not continuous with the outer membrane of the nuclear envelop.

5. Chlorophyll a and c₂ are present in the chloroplasts, with peridinin and neo- peridinin being the main carotenoids.

6. Presence of pyrenoid in chloroplast.

7. Storage product is starch.

8. Eye-spot is present.

9. Nucleus is dinokaryoyic or mesokaryo­tic in nature.

The class Dinophyceae is further divided into 4 orders:

1. Prorocentrales. e.g., Prorocentrum.

2. Dinophysales. e.g., Ornithocercus.

3. Peridiniales. e.g., Ceratium.

4. Gymnodiales. e.g., Gymnodinium.

Group 4. Eukaryotic algae:

Eukaryotic algae with chloroplast sur­rounded by two membranes of chloroplast endo­plasmic reticulum.

1. Phylum. Cryptophyta (cryptophytes)

It consists of only one Class:

Cryptophyceae.

Class Cryptophyceae:

1. Plants are found in both marine and fresh water habitat.

2. The plant body is dorsiventral in shape, with the cells flattened in one plane.

3. Cells contain chlorophylls a and c₂.

4. A few members lack chloroplast and are heterotrophic in nature, but most have a single-lobed chloroplast with a central pyrenoid.

5. Phycobiliproteins occur inside the thyla­koids of the choloroplasts.

Common genera: Cyathomonas, Chilomonas etc.

1. Phylum. Heterokontophyta (heterokonts):

The phylum is further divided into nine (9) classes.

These are:

A. Class. Crysophyceae (golden-brown algae)

1. Presence of chlorophyll c₁ and c₂.

2. Flagella inserted in the cell perpendi­cular to one another.

3. One photoreceptor as a swelling on the short flagellum.

4. Eye-spot commonly present.

5. Chlooroplast endoplasmic reticulum present.

6. Radially or bilaterally symmetrical silica scales may occur.

7. Contractile vacuole anterior.

Common genera: Ochromonas, Paraphyso- monas, Dinobryon, Anthophysa etc.

B. Class. Synurophyceae:

1. Presence of chlorophyll c₁.

2. Flagella inserted into the cell approxi­mately parallel to each other.

3. Presence of two photoreceptors, one on each flagellum.

4. Eye-spot absent.

5. Chloroplast endoplasmic reticulum usu­ally absent.

6. Plant body bilaterally symmetrical.

7. Silica scales are common.

8. Contractile vacuole posterior.

Common genera: Sinura, Mallomonas, Tessellaria etc.

The class is divided into 3 orders:

1. Goniomonadales. E.g., Goniomonas.

2. Cryptomonadales. E.g., Cryptomonas.

3. Chroomonadales. E.g., Chroomonas.

C. Class. Dictyochophyceae (silicoflagellates):

1. These are golden-brown algae.

2. They have tentacles or rhizopodia on basically amoeboid vegetative cells.

3. Amoeboid vegetative cells are mostly restricted in this group (and Xantho­phyceae).

Dictyochophyceae is divided into 3 orders:

1. Rhizochromulinales. e.g., Rhizochro- mulina, Phaeaster, Chrysoamoeba etc.

2. Pedinellales. e.g., Pedinella Apedinella, Pseudopedinella, etc.

3. Dictyocales. e.g., Dictyocha etc.

D. Class. Pelagophyceae

1. Basically unicellular algae.

2. The cells are very small (3-5μm) mem­bers of the ultraplankton and appear as small spheres with indistinct protoplasm under the light microscope.

Common genus: Pelagomonas.

E. Class. Bacillariophyceae (diatoms):

Important characteristics:

1. Plant body is unicellular and free-living. Sometimes they are present in colony.

2. Depending on the mode of nutrition, they may be photosynthetic autotrophs, photosynthetic symbionts or colourless heterotrophs.

3. Vegetative cells are diploid (2n).

4. The cells are surrounded by a rigid two- part box-like cell wall (upper part is epitheca and lower part is hypotheca), composed of silica, called the frustule.

5. The cells are bilaterally or radially sym­metrical.

6. The chloroplast contains chlorophylls a, c₁ and c₂ with the major carotenoid being the golden-brown fucoxanthin.

7. Reserve food is fat and volutin.

8. Motile cells have single flagellum.

9. Reproduction takes place by cell divi­sion and auxospore formation.

Bacillariophyceae is divided into 2 orders:

1. Biddulphiales. e.g., Melosira, Chaeto- ceros etc.

2. Bacillariales. e.g., Amphora, Navicula, Pinnularia etc.

F. Class Raphidophyceae (chloromonads):

1. They are commonly marine.

2. Chloroplasts contain chlorophyll a and c.

3. Two membrane of chloroplast endo­plasmic reticulum.

4. Anterior flagellum is commonly tinsel, whereas the posterior flagellum is naked.

Common genera: Heterosigma, Chattonella.

G. Class. Xanthophyceae (yellow-green algae):

1. Cells are eukaryotic and cell wall is composed of pectic substance.

2. The main pigments are Chlorophyll a and e, β-carotene and xanthophylls.

3. Chloroplasts are without pyrenoids.

4. Reserve food is oil.

5. Flagella are two in number, unequal in length and are situated anteriorly. The longer one tinsel and shorter one whiplash type.

6. Reproduction takes place by all the three means vegetative, asexual and sexual (isogamous type).

Common genera: Botrydium, Ophiocytium, Tribonema etc.

The class is divided into 3 orders:

1. Tribonematales. e.g., Tribonema.

2. Botrydiales. e.g., Botrydium.

3. Vaucheriales. e.g., Vaucheria.

H. Class. Eustigmatophyceae:

1. Plant body is unicellular and live in fresh water or in soil.

2. Chloroplasts contain chlorophylls a, β- carotene with two major xanthophylls being violaxanthin and vaucherioxanthin.

3. Vegetative cells usually have characte­ristic polygonal pyrenoids (absent in zoospores).

4. The pyrenoid projects from the inner face of the plastid on a narrow stalk and cytoplasm is surrounded by flat plates of the unidentified photosynthate.

Common genera: Pleurochloris, Polyedriella.

I. Class. Phaeophyceae:

1. Most of the members are marine.

2. Cell wall is composed of cellulose along with alginic and fucinic acid.

3. Pigments. Fucoxanthin is the dominant pigment, in addition to chlorophylls a, c and carotene.

4. Reserve food is laminarin (polysaccha­ride), manitol (alcohol) and fat.

5. Some lower members have naked pyrenoid like bodies.

6. Zoospores are flagellated, one of which is tinsel type.

7. Sexual reproduction ranges from iso­gamy to oogamy.

Phaeophyceae is divided into 7 orders:

1. Ectocarpales. e.g., Ectocarpus, Raifsia etc.

2. Desmarestiales. e.g., Desmarestia.

3. Cutleriales. e.g., Cutleria, Aglaozonia, etc.

4. Laminariales. e.g., Laminaria, Chorda etc.

5. Sphacelariales. e.g., Sphacelaria.

6. Dictyotales. e.g., Dictyota.

7. Fucales. e.g., Fucus, Ascophyllum, Sargassum etc.

Common genera: Ectocarpus, Laminaria, Dictyota etc.

3. Phylum. Prymnesiophyta (haptophytes)

It consists of only one Class:

Prymnesiophyceae.

Class. Prymnesiophyceae:

1. It is a group of unicellular flagellates, characterized by the possession of a haptonema between two smooth flagella.

2. Chloroplasts have chlorophylls a, c₁ and c₂ with fucoxanthin as the major carotenoid.

3. Diadinoxanthin and β-hexanoyl fuco­xanthin also occur in the group.

4. Two membranes of the chloroplast endoplasmic reticulum are present.

5. The anterior end of the cell has a large golgi apparatus, and sometimes con­tractile vacuole.

6. The cells are commonly covered with scales.

The class Prymnesiophyceae is divided into two orders:

1. Prymnesiales. e.g., Prymnesium, Emiliania, Hymenomonas etc.

2. Pavlovales. e.g., Pavlova etc. Life cycle patterns.