Evolution

Pico- Pico- Pico-zoa Picozoa

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Science  03 May 2013:
Vol. 340, Issue 6132, pp. 527
DOI: 10.1126/science.340.6132.527-c
CREDIT: SEENIVASAN ET AL., PLoS ONE 8, 3 (26 MARCH 2013)

It's not often that a new phylum is described, but the vanishingly small eukaryotes that constitute the equivalent of dark matter of the plankton have now been named the Picozoa. These highly diverse organisms, previously known as (pico)biliphytes, are about 2 to 3 µm in size and dominate aquatic ecosystems. Characterized by the pigment phycobilin and once thought to be photosynthetic, they appear instead to lack plastids and seem to be heterotrophic. Seenivasan et al. used a mitochondrial marker to isolate single (pico)billiphyte cells by fluorescence-activated cell sorting and established a first culture. The result was Picomonas judraskeda, a colloid feeder that moves through the North Sea by means of flagellae. This organism is a bipartite cell, joined at the mitochondrion, packaging all the feeding apparatus into one sac and the major organelles with the motility apparatus in the other.

PLoS One 8, 10.1371/journal.pone.0059565 (2013).

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