Prochloron is a unicellular oxygenic photosynthetic prokaryote commonly found as symbionts in coral reefs, particularly in didemnid ascidians

Ascidiacea

Ascidiacea is a class in the Tunicata subphylum of sac-like marine invertebrate filter feeders. Ascidians are characterized by a tough outer "tunic" made of the polysaccharide tunicin, as compared to other tunicates which are less rigid.Ascidians are found all over the world, usually in shallow...

 (sea squirts). Part of the phylum cyanobacteria, it was theorized (endosymbiotic theory

Endosymbiotic theory

The endosymbiotic theory concerns the mitochondria, plastids , and possibly other organelles of eukaryotic cells. According to this theory, certain organelles originated as free-living bacteria that were taken inside another cell as endosymbionts...

) that prochloron is a predecessor of the photosynthetic components found in eukaryotic cells. However this theory is largely refuted by phylogenetic

Phylogenetics

In biology, phylogenetics is the study of evolutionary relatedness among groups of organisms , which is discovered through molecular sequencing data and morphological data matrices...

 studies which indicate Prochloron is not on the same line of descent that lead to chlorplast containing plants.

Prochloron was discovered in 1975 by Ralph A. Lewin

Ralph A. Lewin

Ralph Arnold Lewin was an Anglo-American biologist, known as "the father of green algae genetics". He was born in London and later moved to America. He also was known as a poetry author.-Education:...

 of the Scripps Institution of Oceanography

Scripps Institution of Oceanography

Scripps Institution of Oceanography in La Jolla, California, is one of the oldest and largest centers for ocean and earth science research, graduate training, and public service in the world...

. Prochloron is one of three known prochlorophytes, cyanobacteria that contain both chlorophyll a and b as light-harvesting pigments.