a: without UVR: the symbionts are arranged in 1-2 layers directly under the cell surface

b: under UVR+PAR (photosynthetically active radiation) exposure: the symbionts are accumulated in one cell end in many layers that provide an effective physical shelter from UVR+PAR and the nuclei are protected

c: under UVR+PAR exposure: many individuals form a ‚dense green spot‘, the so-called ‚collective shield‘ (hypothetical assumption)

Collective shield�