Volvox barberi (Chlorophyceae) actively forms two-dimensional flocks in culture

Area of Science:

• Algal biology
• Biophysics
• Developmental biology

Background:

• Volvox barberi is a multicellular green alga.
• Colonies consist of 10,000-50,000 differentiated somatic and germ cells.
• These algae exhibit complex behaviors in culture.

Purpose of the Study:

• To investigate the self-organization of Volvox barberi colonies.
• To characterize the structure and dynamics of colony groupings.
• To explore potential mechanisms driving aggregation.

Main Methods:

• Observation of Volvox barberi colonies in laboratory cultures.
• Analysis of colony movement and rotation patterns.
• Use of tracer dye to visualize fluid dynamics.

Main Results:

• Colonies rapidly self-organized into 'flocks' of up to 100 individuals.
• Flocks exhibited collective movement and rotation, forming 2D active crystals.
• Colony and flock rotations generated fluid vortices, potentially facilitating aggregation.
• Flock formation and disassembly occurred on timescales of minutes to hours.

Conclusions:

• Volvox barberi colonies demonstrate remarkable self-organization capabilities.
• Active crystal formation and collective behavior are key features of these groupings.
• Fluid dynamics, specifically vortex generation, likely plays a crucial role in flock formation and stability.