Friday Fellow: Sailor’s Eyeball

by Piter Kehoma Boll

Once more our Friday Fellow is hidden among the coral reefs. Its name: Valonia ventricosa, commonly known as sailor’s eyeball.

This green shiny alga is one of the largest single-celled organisms, reaching more than 5 cm in diameter. It is found in tropical seas all around the world, usually associated to coral reefs. It has a spheric to oval shape and a shiny dark to light green surface, making it look like a cut gemstone.

A living jewel of the sea,

A living jewel of the sea. Credits to Philippe Bourjon.

Due to its unusually large size for a unicellular organism, the sailor’s eyeball has been extensively studied regarding its cell wall structure, and it seems to be quite peculiar. The cellulose fibers in its cell wall, which is almost as thick as the cytoplasm, are arranged in a complex structure, including parallel and crossing fibers, as well as some strange fiber swirls with no known function. Its membranes do not seem to have any aquaporines, i.e., pores for letting water go through.

On your next visit to a coral reef, try to find some!

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Eslick, E. M.; Beilby, M.J.; Moon, A. R. 2014. A study of the native cell wall structures of the marine alga Ventricaria ventricosa (Siphonocladales, Chlorophyceae) using atomic force microscopy. Microscopy. DOI: 10.1093/jmicro/dft083

Preston, R. D.; Astbury, W. T. 1937. The structure of the wall of the green alga Valonia ventricosaProceedings of the Royal Society of London, Series B, Biological Sciences122(826): 76-97.

Wikipedia. Valonia ventricosa. Availabe at: < >. Access on April 6, 2016.



Filed under Algae, Botany, Friday Fellow

3 responses to “Friday Fellow: Sailor’s Eyeball

  1. A single-celled organism the size of a golf ball! Amazing! And all this time, I was repeatedly told in elementary school, high school, and college that all single-celled organisms were microscopic.

  2. Pingback: Friday Fellow: Giant Gromia | Earthling Nature

  3. Pingback: species of alga – News94

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