A dark green sphere the size of a marble, so smooth and reflective that it throws back a torch beam like polished glass. It sits wedged in cracks and on dead coral and is one of the few reef organisms that looks manufactured.
Each bubble is a single cell. This is one of the largest single-celled organisms on Earth, and a specimen 5 cm (2 in) across is one continuous membrane holding one enormous cytoplasm - a structure that ought not to work, since a cell that size cannot move materials around by diffusion. It gets away with it by having thousands of nuclei distributed through the cytoplasm rather than one, so no part of the cell is far from its own control center.
That unusual construction made it a laboratory animal. Because the cell is big enough to insert an electrode into by hand, Valonia was used in the foundational work on how cells move ions across membranes, and a good deal of what is understood about the electrical behavior of cell walls started here.
Pop one and you have not killed it. Fragments regenerate into new bubbles, which is why it is a persistent nuisance in aquariums and why scrubbing a rock spreads it.
- shiny dark green to almost black sphere, like a wet marble on the reef
- smooth mirror surface that reflects a torch beam
- grows singly or in loose clusters wedged in cracks
- up to 5 cm across
