Spirogyra


Spirogyra is a filamentous charophyte green algae of the order Zygnematales, named for the helical or spiral arrangement of the chloroplasts that is characteristic of the genus. It is commonly found in freshwater habitats, and there are more than 400 species of Spirogyra in the world. Spirogyra measures approximately 10 to 100 μm in width and may grow to several centimetres in length.

General characteristics

Spirogyra is very common in relatively clear eutrophic water, developing slimy filamentous green masses. In spring Spirogyra grows under water, but when there is enough sunlight and warmth they produce large amounts of oxygen, adhering as bubbles between the tangled filaments. The filamentous masses come to the surface and become visible as slimy green mats.
Spirogyra has a cell wall, nucleus, pyrenoid and spiral chloroplasts.

Reproduction

Spirogyra can reproduce both sexually and asexually. In vegetative reproduction, fragmentation takes place, and Spirogyra simply undergoes intercalary cell division to extend the length of the new filaments.
Sexual reproduction is of two types:
  1. Scalariform conjugation requires association of two or more different filaments lined side by side either partially or throughout their length. One cell each from opposite lined filaments emits tubular protuberances known as conjugation tubes, which elongate and fuse, to make a passage called the conjugation canal. The cytoplasm of the cell acting as the male travels through this tube and fuses with the female cytoplasm, and the gametes fuse to form a zygospore.
  2. In lateral conjugation, gametes are formed in a single filament. Two adjoining cells near the common transverse wall give out protuberances known as conjugation tubes, which further form the conjugation canal upon contact. The male cytoplasm migrates through the conjugation canal, fusing with the female. The rest of the process proceeds as in scalariform conjugation.
The essential difference is that scalariform conjugation occurs between two filaments and lateral conjugation occurs between two adjacent cells on the same filament.

Species

The following species are currently accepted: