Fig. 26.17 The coral Porites porites. The figure shows the coral Porites porites and the location of
its mutualistic endosymbionts, which are dinoflagellates of the genus Symbiodinium. The
Symbiodinium are housed intracellularly inside symbiosomes within the endodermal tissues of
corals. The Symbiodinium undergo mitotic division within those endodermal cells. These symbionts
provide products of photoshythesis in exchange for being sheltered by their host. The symbionts
also provide the typical coloration of their host. The upper image is titled “Porites porites French
Bay.jpg” by author Jstuby at the Wikipedia project and is in the public domain. It shows a small
colony of Porites porites in French Bay, San Salvador Island, Bahamas and the image has been
cropped. The lower image is a scanning electron micrograph of freeze-fractured internal mesentery
from a reef coral polyp of Porites porites. The lower image is titled “HostTissue section.png” by
author Allisonmlewis and is being used under a Creative Commons Attribution-Share Alike 4.0
International license
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C. J. Hurst