OEDOGONIUM

CLASSIFICATION OF OEDOGONIUM​

Sub-division :- Algae

Class :- Chlorophyceae

Order :- Oedogoniales

Family :- Oedogoniaceae

Genus :- Oedogonium

THALLUS OF OEDOGONIUM​

• Thallus is multicellular, filamentous and unbranched.
• A filament is differentiated into three types of cells according to their position :
  1. basal
  2. intercalary and
  3. apical. 
• The basal cell of a filament functions as a holdfast. The lower part of the holdfast is either disc-like or finger-shaped. The upper part is mostly broad and rounded. The basal part of the cell generally lacks green pigment and, therefore, is non-green unlike other cells of the filament. 
• A cell at the tip of the filament is known as’ apical cell. It is rounded at its free surface. 
• The cells present between basal and the apical cells are intercalary cells. These show typical cell structure.
• The typical cell is cylindrical.
• Cell wall is thick and three layered.
• Inner to cell wall is a reticulate chloroplast that runs parallel to the long axis of the cell. Many pyrenoids are present in the chloroplast.
• The cell is uninucleate. The nucleus is situated near the cell wall and is held by thin and delicate cytoplasmic strands. 
• Mature and old cells show ‘cap cells’ at their upper end. These are characteristic of the members of Oedogoniales.

OOGONIUM OF OEDOGONIUM

• Oogonia are intercalary or terminal in position. 
• Oogonium may be solitary or occur in a row of 2-3 or even more.
• Oogonium generally shows one or more cap cells at its upper end, indicating its development from a comparatively older cell. 
• It is mostly spherical or oval in shape and larger than a vegetative cell. 
• At the base of each oogonium lies a small and flat daughter cell, known as supporting or suffultory cell. 
• Oogonium encloses a single large ovum.
• The wall of the oogonium has a small pore on one side, Known as receptive pore. 
• Just opposite the receptive pore, protoplast of the oogonium has a hyaline area-receptive spot. 
• Uninucleate protoplast is rich in reserve food.

ANTHERIDIUM OF OEDOGONIUM​

• Antheridia are mostly intercalary in position. 
• Numerous antheridia form a long chain being arranged in a series.
• An antheridium is a small and flat cell.
• Each antheridium has two nuclei lying side by side, surrounded by dense cytoplasmic contents. Each of such protoplasmic groups later on metamorphoses into a multiflagellate antherozoid.

DWARF MALE OR NANNANDRIUM OF OEDOGONIUM​

• The dwarf male (or nannandrium) is characteristic of nannandrous species.
• The dwarf male is produced by the germination of androspore. 
• Androspores are formed inside the androsporangia. 
• Androsporangia form a long chain of small and flat cells in intercalary position in the filament.
• Each androsporangium develops a single multiflagellate androspore (in contrast, per antheridium two antherozoids are produced). 
• Androspore germinates to produce a dwarf male or nannandrium which remains attached either to the wall of the oogonium or to the suffultory cell. 
• A dwarf male is made of a stalk cell and a terminal row of 2-3 cells. 
• Stalk cell is at the base by which the dwarf male is attached to the filament. It has a disclike or finger-like structure at its base.
• The terminal row has 2-3 small, flat and narrow antheridia. 
• Each anteridium has two multiflagellate antherozoids.

zygote of oedogonium

• Zygote is thick-walled post-fertilization structure. The wall is generally three layered.
• The layer outside the innermost may be smooth, ornamented or verrucose. 
• Zygote develops red colour due to the accumulation of reserve food in the form of reddish oil drops.

IDENTIFICATION

1. Sub-division– Algae
   1. Presence of a simple thallus.
   2. Chlorophyll present
   3. Cell wall made of cellulose.
2. Class – Chlorophyceae
   1. Presence of a definite nucleus
   2. Chloroplast present. grass green colour
   3. Presence of starch
   4. Reproductive structure motile and flagella equal in length.
3. Order – Oedogoniales
   1. Cells uninucleate, filaments branched or unbrahched,
   2. Cell division forming ‘caps’.
   3. Chloroplast reticulate
   4. Zoospores and antherozoids bear a whorl of flagella
   5. Production of dwarf males.
4. Family – Oedogoniaceae  (A single family) 
5. Genus – Oedogonium
   1. Filaments unbranched
   2. Cells cylindrical
   3. Holdfast well developed.

REFERENCES

• https://en.wikipedia.org/wiki/Oedogonium
• https://en.wikipedia.org/wiki/Oedogonium#/media/File:Oedogonium_oogonium_and_antheridia.jpg