zoochlorella

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of various one-celled green algae that live symbiotically within the cells of aquatic invertebrate organisms such as sponges and sea anemones or within certain protists.

from The Century Dictionary.

• noun One of the green pigmentary particles, or minute corpuscles of green coloring matter, which are found in various low invertebrates, as the hydras among polyps and the stentors among infusorians. Compare zoöxanthella.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Zoöl.) One of the small green granulelike bodies found in the interior of certain stentors, hydras, and other invertebrates.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Alternative form of zoöchlorella.