Ectocarpus
Classification
Sub-division — AlgaeClass — Phaeophyceae
Order — Ectocarpales
Family — Ectocarpaceae
Genus — Ectocarpus
Work to be done To study
[I] Thallus. To study the external features of the thallus and a cell.
[II] Unilocular sporangium. To study the structure of unilocular sporangium.
[III] Plurilocular sporangium. To study the structure of plurilocular sporangium.
[I] Thallus. To study the external features of the thallus and a cell.
[II] Unilocular sporangium. To study the structure of unilocular sporangium.
[III] Plurilocular sporangium. To study the structure of plurilocular sporangium.
[IV] Reproduction in Ectocarpus
Practical study and work
(I) Thallus
(I) Thallus
Mount a few filaments in glycerine after staining in safranin, Study the structure of thallus and also a single cell.
1. Thallus is multicellular and filamentous and branched.
2. Filaments are heterotrichous and differentiated into (i) prostrate portion and (ii) an erect portion.
3. In some species prostrate portion is irregularly and profusely branched or altogether absent. It serves the purpose of attachment.
4. Erect portion is crowded tuft of branches. Main axis is broad from which lateral branches arise just beneath the septum and taper into a point. Ultimate branches give an appearance of a hair.
1. Thallus is multicellular and filamentous and branched.
2. Filaments are heterotrichous and differentiated into (i) prostrate portion and (ii) an erect portion.
3. In some species prostrate portion is irregularly and profusely branched or altogether absent. It serves the purpose of attachment.
4. Erect portion is crowded tuft of branches. Main axis is broad from which lateral branches arise just beneath the septum and taper into a point. Ultimate branches give an appearance of a hair.
5. The branches and the main axis are uniseriate.
6. The erect branches have intercalary meristem just below the terminal hair. It results in growth called trichothallic growth.
7. The cells are squarish to cylindrical and uninucleate.
8. The cell wall is double layered. Outer is gelatinous and inner is firm and cellulosic.
9. There may be one or many chromatophores varying from irregular to band-like to discoid. Pyrenoids are absent.
10. Reserve food products occur as shining fucosan granules.
11. The cell is filled with cytoplasm in which lies a single nucleus.
[II] Unilocular sporangium
[II] Unilocular sporangium
Search for filaments with unilocular sporangia, stain in safranin, mount in glycerine and study.
1. Unilocular sporangium is a structure of asexual reproduction, always present on diploid plants.
2. The sessile or stalked sporangium is situated terminally on lateral branches.
3. The shape varies from globose to ellipsoidal.
4. It is single celled and uninucleate when young but becomes multinucleate later.
6. Many biflagellate zoospores are produced when unilocular sporangium matures.
Search for filaments with plurilocular sporangia, stain in safranin, mount in glycerine and study.
1. These occur on both haploid and diploid plants. The structure when borne by haploid plant serves as a gamctangium whereas on diploid plant it functions as sporangium.
2. These bodies situated laterally may be sessile or stalked. Shape ranges from ovate to siliquose.
3. Plurilocular sporangium is divided into large number of cells.
4. A mature sporangium produces biflagellate swarmers, one each from every cell.
5. If plurilocular sporangium is borne on a haploid plant, the swarmers behave as gametes and if borne on diploid plant, these act as haploid zoospores.
2. These bodies situated laterally may be sessile or stalked. Shape ranges from ovate to siliquose.
3. Plurilocular sporangium is divided into large number of cells.
4. A mature sporangium produces biflagellate swarmers, one each from every cell.
5. If plurilocular sporangium is borne on a haploid plant, the swarmers behave as gametes and if borne on diploid plant, these act as haploid zoospores.
It is, therefore, suggested that use of the term plurilocular sporangium be discarded. In case the plurilocular organ produces zoospores, the organ be called as neutral sporangium and spores as neutral spores and if it produces gametes on a haploid plant, it be referred to as gametangium and swarmers as gametes.
The life cycle exhibits typical alternation of generations (isomorphic). Both haploid and diploid phases are morphologically identical.
Reproductive structure of ectocarpus
Asexual Reproduction of Ectocarpus:
Asexual reproduction is with the help of zoospores.Haploid zoospores are formed in unilocular sporangia while the diploid zoospores in plurilocular (neutral) sporangia.
Both the unilocular and plurilocular sporangia are formed on diploid asexual plants.
Sexual Reproduction of Ectocarpus:
Most of the species are isogamous but some show clear anisogamy. Gametes are formed in the pluriloculargametangia, formed on the haploid, gametophytic or sexual plant.Identification
Sub-division—Algae
(1) Simple thallus,
(2) Presence of chlorophyll,
(3) Cell wall of cellulose.
Class—Phaeophyceae.
Class—Phaeophyceae.
(1) Yellowish-brown chromatophores,
(2) Photosynthetic reserve-—laminarin and mannitol,
(3) Motile reproductive cell—pyriform and flagellated,
(4) Flagella laterally inserted and unequal.
(2) Photosynthetic reserve-—laminarin and mannitol,
(3) Motile reproductive cell—pyriform and flagellated,
(4) Flagella laterally inserted and unequal.
Order—Ectocarpales,
(1) Thallus filamentous,
(2) Growth trichothallic,
(3) Reproductive organs-unilocular and plurilocular sporangia,
(4) Isomorphic alternation of generations.
Family—Ectocarpaceae,
(1) Thallus monoaxial, branched branches uniseriate,
(2) Growth _ trichothallic,
(3) Sporophytes with uni- or plutilocular sporangia, terminal or intercalary.
Genus—Ectocarpus.
(3) Sporophytes with uni- or plutilocular sporangia, terminal or intercalary.
Genus—Ectocarpus.
(1) Chromatophores discoid or band-shaped,
(2) Pyrenoids absent,
(3) Reproductive parts terminal, stalked.
Hints for collection
It occurs in marine habitat the world over, mostly along the coasts of colder seas. It also grows along the Indian coasts and forms brown tufts attached to rocks and large kelps in littoral and sub-littoral regions.
Hints for collection
It occurs in marine habitat the world over, mostly along the coasts of colder seas. It also grows along the Indian coasts and forms brown tufts attached to rocks and large kelps in littoral and sub-littoral regions.