The Volvocine Line: 

Chlamydomonas is a single celled, motile algae found in damp soil, lakes, and ditches. It is isogamous, meaning that during sexual reproduction all its gametes are structurally identical. Its identifying feature is a large chloroplast containing the pyrenoid which aids in starch formation. There is flagella located at the anterior end of the cell. ( note low power lab photo; web high)

Chlamydomonas can reproduce asexually or sexually. During asexual reproduction, mitosis results in the formation of daughter protoplasts. A cell wall is formed around each of these, building temporary colonies that rupture and release individual daughter cells called zoospores. In sexual reproduction, vegetative cells may function as gametes, one functioning as male, the other as female. A diploid zygote is formed that secretes a thick, spiny wall and enters a period of dormancy. When conditions become favorable, the zygote nucleus undergoes meiotic division to form four haploid nuclei.

Gonium, unlike Chlamydomonas, is a colonial organism, made up of cells loosely arranged into a flat platelike disc. The cells are held together by a gelantinous matrix. The Gonium cells exhibit a degree of coordination as the cells in the colony swim in unison . The entire plate moves as a unit. All cells involved in the colony are identical. Gonium is also isogamous.

Pandorina

Like Chlamydomonas and Gonium, Pandorina is also isogamous. Pandorina is more highly developed than Chlamydomonas and Gonium in that the colony coordinates its movements to swim in one direction and its anterior cells are different from its posterior cells.

Reproduction in Pandorina is similar to Gonium.. Upon maturity, each cell within the colony produces a new colony through asexual means. This new colony is held within the gelatinous envelope that contains the parent colony. Pandorina can also reproduce sexually. Zygotes are formed from the fusion of isogametes. The zygote then undergoes meiosis to form zoospores, which are capable of developing into a new colony.

Volvox

You can see from the photos taken from the web and from our lab the

individual cells embedded intthe gelatinous matrix

Volvox is the most complex organism in the Volvocine Line of Green Algae. The Volvox is similar to Chlamydomonas in that they both have stigma (an eyespot used to detect light), flagella, and large chloroplasts. In Volvox, however, only specialized cells participate in reproduction. Specific cells within the colony undergo asexual reproduction to form a daughter colony. The daughter colony first forms a flat plate structure and then grows to become a sphere. When the daughter colony reaches a suitable size, it turns itself inside out and releases the daughter colonies. At this time, the parent colony disintegrates.

Volvox is also capable of sexual reproduction. Volvox produce gametes that differentiate into sperm and egg. When fused, they develop into a heavy, spiny walled zygote. Germination takes place in the spring and leads to the formation of a new colony.

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