Figure 2. A single tentacle from a symbiotic polyp is visualized by Garrett et al (2013). This polyp contains thousands of individual Symbiodinium cells, these symbionts are visible as small golden brown spheres within the gastrodermal tissue of the tentacle. Note that the epidermal tissue does not contain symbionts and is visible as the thin transparent layer at the periphery of the tentacle. This image additionally demonstrates the relatively thin walls of this genus.