Volvox (Protozoan) Videos
Volvox is a colonial organism, a semi-transparent hollow sphere about the size of a pinhead, made up of 500 to 60,000 bi-flagellated cells embedded in a gelatinous wall. The largest colonies exceed one millimeter in diameter and are easily visible to the naked eye.
This organism has something of a dual identity amongst biologists, placed by zoologists into the order Volvocida and classified by botanists as a green algae, Chlorophyta. Globally, twenty species of Volvox are known to occur with most species occurring in tropical and subtropical areas.
Volvox colonies are either sexual or asexual. In addition to the biflagellated somatic cells, asexual colonies have specialized reproductive cells (gonidia) that produce small daughter colonies within the parent colony. In sexual colonies, the gonidia are replaced by eggs or spermatozoa. After the eggs are fertilized, the zygotes encyst and are released from the parent colony after it dies. Thick-walled zygotes formed late in the summer serve as winter resting stages.