Zooxanthellae are a very special type of marine plant with an important
place on the reef. The zooxanthellae are single celled algae which
live inside the translucent fleshy tissue of many marine animals including
types of giant clams, nudibranchs and even jellyfish, however they play
their most important role when living within coral polyps. Like all other
plants zooxanthellae need sunlight in order to photosynthesise and grow.
Photosynthesis produces sugars essential for the plants to grow, however
with the zooxanthellae enough sugar is produced to allow some to be shared
with their hosts. In return the host will assist the growth of the zooxanthellae
by passing on some of its dissolved organic waste. The host animal cannot
usually survive if the zooxanthellae are not present.
The host animals do not have any zooxanthellae in their larval forms
and therefore must acquire them from the water column. The juvenile host
filters the zooxanthellae from the seawater along with its food and once
in the stomach of the host the zooxanthellae is passed into the surface
flesh. Zooxanthellae multiply within the host due simple cell division.
pete@reefpix.com.au