On the sunlit surface of the ocean, the blue button (Porpita porpita) drifts like a jewel. At first glance, it looks like a delicate jellyfish, but in reality, it’s a colony of tiny zooids clinging to a chitinous float, a living raft that survives wherever the currents carry it.
For decades, scientists struggled to understand these elusive creatures. They are hardy at sea, enduring waves, wind, and sun, yet notoriously difficult to keep alive in captivity. That challenge has left their life cycle largely a mystery.
Now, researchers at the University of Tokyo’s Misaki Marine Biological Station, working with specialists at two Japanese aquariums, have managed to keep colonies alive long enough to glimpse their secrets.
The blue button (Porpita porpita) is a colony of tiny animals attached to a disc‑shaped float made of chitin, which helps it stay afloat. Scientists haven’t yet measured how this float grows or how long the colony can live.
“We were able to keep 10 blue button colonies alive for up to 21 days,” reported Associate Professor Kohei Oguchi. “From our observations of these colonies, we can now estimate that blue buttons may actually live for several years, drifting on the ocean surface. This is much longer than previously thought, which was less than a year.”
The team experimented with containers of different sizes, temperatures, water flow, and diets. Surprisingly, the simplest setup worked best: a 30‑cm plastic tub of filtered seawater, changed daily, placed in sunlight, and fed small shrimp.
Photographs taken at collection and after rearing revealed growth patterns. The float itself told another story.
“The chitinous float that supports the colony looks just like the cross-section of a tree, with concentric rings. We found that new layers grow from the periphery of the outer ring,” said Oguchi. “This means that it doesn’t grow from the expansion of preexisting layers, which we didn’t know for sure before.”
Credit
2026 D. Wakita et al.
Smaller blue button colonies showed clear growth of their floats, while larger ones didn’t seem to grow at all. Histology analysis reveals the outermost accretion of new cuticular laminae at the float’s edge. It indicates margin‑specific growth in the budding of new zooids.
Because growth slowed as colonies got bigger, the researchers used a Bayesian von Bertalanffy growth model to fit the observed colony sizes. Postdoctoral researcher Daiki Wakita estimated colony ages: a 4‑mm specimen was about 3 months old, a 12‑mm specimen was about 1 year old, and a 23‑mm colony was unexpectedly 5 years old.
Oguchi’s ambition now is to rear blue buttons through their entire life cycle.
“My research focuses on how the different specialized individuals that make up a blue button colony develop, and how they are integrated so that the colony behaves almost like a single organism,” he explained. “Being able to keep colonies alive for as long as we have for this study is an encouraging step forward.”
For marine biology, the discovery reframes the blue button not as a fragile curiosity but as a resilient drifter with a surprisingly long life. And for young scientists, it’s a reminder that even the smallest creatures can hold vast mysteries, waiting to be uncovered with patience, persistence, and a simple plastic tub.
Journal Reference:
- Wakita, D., Murai, K., Yamamoto, G. et al. A neustonic hydrozoan Porpita porpita drifts for over a year. Sci Rep 16, 13766 (2026). DOI: 10.1038/s41598-026-49897-y
