Wednesday, March 7, 2012

Algal Symbioses

One noteworthy feature of several sorts of green algae is the ease with which they form symbiotic relationships of various kinds with other organisms. Many fungi have green algae growing closely with them. The symbiotic organism composed of the alga and the fungus is called a lichen. In Addition, many green algea actually live inside de cells of other organisms, usually within a vacuole. More than a hundred different genera of invertebrates in eight different phyla have green algal symbionts growing within their cells. A familiar example is the green hydra, Chlorohydra viridissima, which has a species of the green alga Chlorella growing within its cells. The algea secrete a sugar, which the hydra uses for nourishment. In some animals the animal establish host cells; inside certain cells of mollusks called sea slugs are found the chloroplasta of certain algae which the slug has eaten, still alive and photosynthesizing.