The Forbidden Grape (Valonia ventricosa)

When it comes to single-celled organisms, we tend to only think of them as being microscopic. If they are larger, we tend to associate them with something going wrong, like cancer cells. However, these single-celled organisms (often called Sailor's Eyeballs or even Bubble Algae) are naturally massive! So let's found out why and how they can exist being so big.

Physical Description and Behavior


This algae looks like a grape and can be of various sizes. They are generally around 1 to 4 centimeters (0.4 to 1.6 in) in diameter, but can potentially be as large as 5.1 centimeters (2 in) in diameter. They are spherical, with their harder outer shell being green. That said, they can have a more teardrop shape as a result of being stretched by other objects during development.


Fun Fact: The outer shell of this a cell wall, similar to that seen in most plant cells. Due to how tight this cell wall is, it can be highly reflective, making them look like pearls underwater. In fact, their more silvery-blue color underwater and spherical tightness is the reason they are called Sailor's Eyeballs.

This cell can survive despite being so large because it has multiple nuclei and multiple chloroplasts. The nuclei are not separated by a cell wall; interestingly, if they were they would be considered separate cells.


Like other cells, they reproduce through cellular division but through budding. Small parts of this algae will break off, staying in contact with the mother cell or traveling further away before settling down and starting to grow as its own independent cell.


Habitat and Location

These spheres can mainly be found in mangrove forests near the roots of the trees, as well as at many coral reefs. They live exclusively underwater in order to not dry out.


They are found in various places all over the world, such as in the US, Brazil, Madagascar, Egypt, India, China, Phillippines, Australia, New Zealand, Central Polynesia, The Caribbean, and more. That said, they are seen as a pest to people who own aquariums, many of whom claim that bursting one of these cells just causes many more of them to grow in its place.


Learn more about this and other large single-cell organisms by watching the video below:


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