Volvox is a freshwater phytoplankton (microalgae that contains chlorophyll) that takes advantage of the seasonal lower salinity in Henderson Creek – they perish in higher salinities. These colonial organisms are amazing in so many ways. They are remarkably light sensitive and will move in the direction of a light source (i.e. the sun).
When the light source is diffuse the volvox move in many directions and at varying speeds.
The volvox in the video with the black background seem beautifully synchronized as they all move towards a single light source. “Positive phototaxis” is the name for an organisms movement towards the light. Moving towards light is vitally important for algae so they can photosynthesize and produce that wonderful byproduct that we all depend on – oxygen! Volvox have cilia all over their bodies that help propel them through the water. They can be made up of tens of thousands of cells. They have cells with cilia all around the outside of their “globe.” They can reproduce sexually or asexually and appear to do more of the latter when conditions are ideal.
“Daughter cells,” or asexually produced offspring, are clearly visible as miniature versions of mature cells in these photos. The daughter cells will then emerge, grow, and disperse their own daughter cells and therefore the population can explode fairly quickly when conditions are optimal.