At a glance
Essentials
- Size
- Colonies 400–575 µm long and 380–540 µm wide. The range may vary with age, sex and population.
- Distribution
- Cosmopolitan.
- Habitat
- Freshwater.
- Activity
- Swims toward light.
- Diet
- Holophytic nutrition.
Observation guide
What to look for
- 01
Hollow spherical colonies of biflagellate cells embedded in a gelatinous matrix.
- 02
Mature colony size of 400–575 µm in length.
- 03
Cells with parietal chloroplast, red stigma and contractile vacuoles.
Lighting, age and viewing angle can hide features. If identification affects consumption, handling or conservation, consult specialist sources.
Ecology
Description and characteristics
Volvox globator is a species of green algae belonging to the family Volvocaceae. It was originally described by Carl Linnaeus in 1758 in his work Systema Naturae and constitutes the type species of the genus Volvox. It is an organism of freshwater with a cosmopolitan distribution.
The morphology of this species is characterized by forming hollow spherical colonies composed of thousands of biflagellate cells. These cells are arranged in a single peripheral layer embedded in a gelatinous matrix. Mature colonies measure between 400 and 575 µm in length and between 380 and 540 µm in width. Each cell possesses a parietal chloroplast with several tiny pyrenoids, a small red stigma and two to six contractile vacuoles. Nutrition is holophytic.
Regarding reproduction, Volvox globator presents a cycle that includes both asexual and sexual phases. Asexual colonies contain between three and 17 gonidia (usually four to seven) distributed irregularly on the posterior side. These gonidia, 10–13 µm in diameter, divide by binary fission to form embryos. Once cellular division is complete, the embryo undergoes a type‑B inversion, where the posterior pole is introduced inward and the anterior pole opens an opening called fialopore, allowing the embryo to flip over to orient its flagella correctly toward the exterior. Mature embryos reach up to 250 µm in diameter.
Sexual reproduction is homothallic, with colonies of similar size to the asexual ones. These sexual colonies contain three to seven packages of antheridia and between 11 and 72 eggs (typically 20–30). The resulting zygotes are round, covered with straight and rough spines, and measure between 36 and 44 µm (or 45–54 µm including the spines). Taxonomically, it is placed in the section Volvox (or Euvolvox), characterized by thick cytoplasmic connections between cells and spiny zygotes.
For more than a century, this species has served as a model organism for studying cellular movement. Volvox globator colonies tend to swim toward the direction of light.