Mesophyllum expansumMesophyllum expansum is a species of red alga belonging to the family Hapalidiaceae.DescriptionMesophyllum expansum can reach a diameter of about. Illuminated by artificial light they show a beautiful pink color, with hanging branches. These calcareous encrusting organisms can be observed occasionally near the surface and can reach a depth of.DistributionThis species is widespread in the Mediterranean Sea.