Sailor’s Eyeball Blob: How Big Is the Largest Single-Celled Organism on Earth?

Strange blobs called sailor's eyeballs lurk in coral rubble in tidal zones of tropical and subtropical areas. Also known as 'bubble algae' or 'sea grape,' this creature can be found in oceans worldwide, mostly in the Pacific Ocean and Western Central Atlantic. The greatest depth of viability has been discovered as approximately 80 meters.

(Photo: Wikimedia/ Philippe Bourjon)

Sailor's Eyeball Blob

Sailor's eyeballs are a species of algae formally known as Valonia ventricosa. They typically grow individually but can also develop in groups in rare cases. These creatures exist in various forms ranging from spherical to ovoid, with color varying from grass green to dark green.

Valonia ventricosa reproduces by segregative cell division, a process in which the multinucleate mother cell produces daughter cells, and single rhizoids create new bubbles that become separate from the mother cell.

Because this cell is extremely smooth, its surface shines like glass that catches light, resembling an eyeball from where it got its name. Some aquarium owners consider Valonia ventricosa to be a pest. Since this species reproduces very quickly, it can potentially endanger the health of fish or other marine organisms.

How Big is Valonia Ventricosa?

This whole ball with strange characteristics is a single cell. It is one of the largest known unicellular organisms.

The size of bubble algae can vary from a speck as small as a pinhead to as big as a golf ball, approximately 9 centimeters in diameter. Its thallus consists of a multinucleate cell with a diameter of 0.4 to 1.6 inches (1-4 centimeters). In rare cases, it may achieve a diameter of up to 2 inches (5.1 centimeters).

How big it can get depends on the contents of its vacuole or space inside its cell wall. An average human has about 1 billion cells for every gram of their body.

Although sea grape is a unicellular creature, it can contain the nuclei of many cells. This is because it comprises a mass of cytoplasm containing many cell nuclei that are not separated by a cell wall. It has a coenocytic structure with multiple nuclei and chloroplasts. This creature also possesses a large central vacuole that is multilobular in nature.

This unusual arrangement comes with a strange reproduction behavior. If a blob is popped, it can result in more blobs since they only need a single-cell nucleus to grow into new organisms.

Valonia ventricosa is poppable because its cytoplasm vacuole contains nuclei arranged in lobes that radiate from its center. This creates an internal anatomy described as something like a Tesla plasma ball.

Due to its huge size, Valonia ventricosa is a convenient subject for exploring the transfer of water and water-soluble compounds across biological membranes. They have been studied extensively for more than a century, with more than 2,000 scientific papers.

Sea grapes have undergone extensive X-ray analysis as experts explore their biological structures. This algae species has also been investigated for its electrical properties because of its unusually high electrical potential relative to the seawater surrounding it.