Coral cilia cause a stir

Though acting as a single organism, a reef-building coral is actually a colony of individual polyps. Dense canopies of hair-like cilia cover the entire surface of the colony. The effects of ciliary flows on mass transport near the surface are currently being studied by Roman Stocker and colleagues at MIT. The complexities of those flows are captured in this video microscopy image by Vicente Fernandez, Melissa Garren, Theresa Santiano-McHatton, and Stocker at MIT in collaboration with Orr Shapiro and Assaf Vardi at the Weizmann Institute of Science. (This image was one of several on exhibit in the Gallery of Fluid Motion at the 2012 meeting of the American Physical Society’s division of fluid dynamics.)

Naturally occurring green fluorescent protein gives the coral Pocillopora damicornis, also known as cauliflower coral, its green appearance here; the brightly colored polyps are about 1 mm in diameter. The arcs, generated from 120 video frames taken over 12 seconds, track the motion of 2-µm fluorescent beads and reveal the flows over the coral surface. Understanding those complex flows and their influence on mass transport may provide key insights into coral disease and threats to the fragile ecosystems of coral reefs. (Image by the Stocker Group, civil and environmental engineering, MIT.)

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