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Science News

February 1, 2011
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The Rappemonads, a new branch of the tree of life has been traced: Dr  Tom Richards (Zoology), in collaboration with scientists from Monterey  Bay Aquarium Research Institute USA, and Dalhousie University Canada,  has identified a previously unknown group of single-celled organisms related to red algae. These newly discovered marine and freshwater cells contain plastids (of which chloroplasts are an example) that photosynthesise, producing energy from sunlight.

It is  estimated that almost 2 million species of plants, animals, fungi and other life forms have been described and  identified in the past two hundred and fifty years.  Much of this science of diversity has been based on physical form - morphology - but in recent years DNA sequencing has made it possible to explore biodiversity in new ways and different environments.  It is thought that much of the biodiversity remaining to be discovered - possibly around 10 million species - lies in single-celled organisms and bacteria, which are too small to see with the naked eye and live in vast numbers in soils, water or sediments. Our understanding of what biodiversity is, and why it is important in ecosystems, continues to change as the technology develops.

Tom and his collaborators used DNA techniques to to investigate unidentified microbes from shorelines in the UK and US, from open sea water and from UK fresh waters.  Their DNA results were compared with information in large scientific databases and proved to be from a new group of organisms, the rappemonads, related to algae, phytoplankton and seaweeds, a unique form of photosynthetic life. It appears that rappemonads occur from time to time in large numbers in transient oceanic blooms, suggesting that it may play a significant role in the global carbon cycle and marine food webs.

Kim, E., Harrison, J., Sudek, S., Jones, M. D. M., Wilcox, H. M., Richards, T. A., Worden, A. Z., & Archibald, J. M. 2011. Newly identified and diverse plastid-bearing branch on the eukaryotic tree of life. Proc. Natl. Acad. Sci. U.S.A. Online Early.