SKETCHY SUNDAY: Symbiodinium spp.
Corals have developed an important symbiotic relationship with photoautotrophic dinoflagellates, i.e. zooxanthellae, which live inside coral tissue for protection and inorganic nutrients. In return, the algae produce a photosynthate that provides the coral with energy to complete growth, reproduction, and calcification processes.
This is a drawing of an individual Symbiodinium, which populate a coral along the lines of hundreds of thousands per square centimeter.
Drawing by Stacy Peltier, 2013