What is Spirogyra

Spirogyra are a free-floating filamentous form of green algae, commonly seen as bright green masses on the surfaces of freshwater ponds and ditches. It belongs to a genus of green algae, of the order Zygnematales. The name 'spirogyra' is derived from the spiral arrangement of chloroplast in its filament-like body. This feature is unique to this genus, which has almost 400 species. Spirogyra looks like green filaments moving with the water current and is very slimy to touch. This helps the spirogyra prevent other water organisms from attaching themselves to it.

Structure

Spirogyra cells are cylindrical in shape and are connected end to end, forming a long, unbranched filament-like structure. The cell wall is made up of an outer layer of cellulose and an inner layer of pectin. The inner surface of the cell wall is lined with a thin layer of cytoplasm. The spiraled ribbon-shaped chloroplasts are embedded in the cytoplasm lining. The number of chloroplasts in each cell may vary from one to sixteen. Each chloroplast has several round bodies called 'pyrenoids', which are responsible for the production of starch. Each cell has a prominent nucleus in the center, suspended by thin strands of cytoplasm from the inner part of the cell wall. The cells are long and thin, and each spirogyra filament measures between 10 to 100 micrometer in width. Sometimes, these filaments have root-like structures, which help them attach themselves to the substratum.

Reproduction

Spirogyra is capable of both sexual and asexual reproduction. Asexual reproduction happens through the fragmentation of cells. Sexual reproduction can be of two types: scalariform conjugation and lateral conjugation. In scalariform conjugation, the cells of adjacent filaments develop small tube-like structures called 'conjugation tubes', which fuse together to form a 'conjugation canal'. The cytoplasm of the male cell flows through this canal to the female cell and fuses with the latter's cytoplasm. The next step is the fusion of gametes (mature sexual reproductive cell with a single set of unpaired chromosomes) to form the zygospore. The zygospore, which is thick-walled, is brownish in color and is oval or circular in shape. The spores are released to form new filaments. This type of conjugation gives the algae a ladder-like appearance, due to the interlinking of filaments.

In lateral conjugation, adjacent cells of the same filament develop conjugation tubes to form a curved conjugation canal. The process of development of a zygospore is same as that of a scalariform conjugation. The only difference between the two forms is that in the former, conjugation happens between two adjacent filaments, but in the latter, adjacent cells of the same filament conjugates to form the zygospore.

Spirogyra is commonly found in clean water and it produces food through the process of photosynthesis. You can easily identify this algae with its green filamentous structure and freshwater habitat.