The secret lives of bluebottles: Another weird organism
There's more beneath the surface than just a painful sting.
Jessica Guerchon is a UNSW PhD candidate studying the ecology, behaviour, and morphology of bluebottles.
They drift onto our beaches every summer, dazzling blue and hard to miss—particularly if one wraps its long, trailing stinger around your leg when you’re swimming.
It might look like they just bob into shore on the tides, but bluebottles are not as helpless as they seem.
Bluebottles, or Physalia, are known as “colonial organisms”, meaning they’re not one creature, but several—connected individuals called zooids, each with a specific role.
Some feed, others reproduce, and one forms the gas-filled float that keeps the colony at the ocean’s surface.
None could survive individually but together they live as one, an intricate collaboration that has sailed the world’s oceans for tens of millions of years, and fascinated scientists for centuries.
And while those stings are a pain for beachgoers, bluebottles play a set of important roles, acting as both predator and prey, as well as habitat for some specialised species of small fish, which use the tentacles for protection like a floating reef.
For decades, bluebottles have been described as passive drifters, carried entirely by the wind and currents.
But what if that’s not the whole story? Could they respond to changes in light, temperature, or wind, influencing where they end up?
That’s exactly what I’m trying to find out.
As part of my PhD at UNSW, I’m setting up controlled experiments at the Sydney Institute of Marine Science to study how bluebottles react to different environmental conditions.
By testing how they respond to changes in light, temperature, and wind, we will better understand whether these colonies have some control over their movement at the surface, and what that means for when and where they appear.
And that question isn’t just scientific curiosity.
Each summer, bluebottles cause hundreds of beach closures and thousands of stings along Australia’s coast, costing lifeguard services and local councils time and resources.
Understanding bluebottle behaviour could help us predict when they’ll strike, improving beach safety, and reducing bluebottle impact on both people and ecosystems.
And there’s still a lot to learn.
For example, it was only recently discovered that there’s more than one species of bluebottle.
Along Australia’s east coast, including Sydney, the most common are Physalia utriculus and Physalia megalista.
In another aspect of my research, I compare their structure and function to offer clues about how each species is adapted to life at the surface.
I do this by preparing thin tissue sections of key colony parts and using image analysis to measure how tissues are organised and how their cells differ.
So next time you see a bluebottle washed up on the sand, don’t just step away, look closer.
You might be looking at one of the ocean’s most misunderstood survivors, a reminder that even the simplest forms of life can be remarkably complex.
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Good luck with your research and keep us posted! We sure want to know when they drift onto the beach.