What is "zooxanthella"

plural zooxanthellae, yellow pigmentary particles found in nature, 1889, from German (Brandt, 1881), from comb. form of Greek zoion "animal" (see zoo-) + xantho- "yellow" (see xantho-) + Latin suffix -ella.

n. 1 An animal of the genus (taxlink Symbiodinium genus noshow=1), a yellow dinoflagellate, notably found in coral reefs. 2 (context dated English) Any golden-brown planktonic endosymbiont.