In nutrition cells of chlamydomonas are autotrophic due to the presence of chloroplasts water and inorganic salts are absorbed over whole surface of the cell.
REPRODUCTION:
It takes place either by asexual or sexual method.
(1) Asexual reproduction
(i) by Zoospore formation: This type of reproduction occurs in favourable conditions. Active cells of organism comes to rest, the flagella re withdrawn, and the ell contents divide into four, eight or sixteen parts, which become zoospore. These daughter individuals develop their individual cell wall and flagella. The parent cell wall is lost and the new individuals attain independent existence. They grow and develop into new chlamydomonas.
(ii) Palmella stage: Under favourable conditions the pond becomes dry. Zoospores remain enclosed within the parent cell wall, it grows in size and divides and large number of zoospores without flagella may be found in clusters inside an envelope of mucilage. This aggregation of cells is called palmella stage. On approach of favourable condition cell change to motile condition.
(2) Sexual Reproduction:
It takes place by fusion of gametes and is isogamous. Inchlamydomonas sexual reproduction is variable from isogamy to anisogamy and oogamy. Some species are monoecious and others are diocious.
In clamydomonas media and C debaryana the sexual reproduction is isogamous. In this case contents of cell divide to form 2 to 64 biflagellate gametes (like zoospores). Gametes may be naked or may have a cell wall. These are identical in shape and size and are called isogametes. They unite in pairs from their anterior end and form quadric-flagellate zygospore. It then loses cilia and becomes rounded.
In chlamydomonas braumi sexual reproduction is of amisogamous type. One cell divides twice to form four big biflagellate gametes (female gametes) and other cells divide 3 to 4 times to form 8 or 16 small biflagellate gametes (male gametes). In this way gametes of different sizes are formed one big and one small gamete unit together which result in the formation of zygospore.
In chlamydomonas coccifera and Coogamum the sexual reproduction is of oogamous type. In male cell produces 16 or 32 small biflagellate male gamete and the female are produced singly non motile female gamete. Male and female gamete fuse together to form zygote.
Germination of Zygote: Zoospore of zygote is formed by fusion of gametes. When favourable conditions come, the zygote nucleus which is diploid (2n) divides by meiotic (reduction) division and then divides mitotically to form four zoospores which are biflagellate and contain haploid nucleus. They come out by the burting of zygote wall and develop into new individuals.
