This species is commonly known as the blue bottle jellyfish or the Portuguese man o’ war. Its floating sac sits on the surface of the water while its tentacles dangle below the surface. Photo: Steven Kuiter
The size of blue bottles can vary drastically with the ‘float’ being between 2-15 centimetres long. Photo: Steven Kuiter
Blue bottles eat a variety of different fish including fry which are young fish and small adult fish. They also eat a variety of crustaceans and plankton. They will use their long tentacles that have in stinging cells all over them to grab the prey in which the prey will then become immobilised. Photo: Steven Kuiter
Welcome to the Marine Mili series, a regular column about all things marine! During this series I aim to inspire people to want to protect our oceans and all the marine life that call our oceans home. Hopefully after reading each column, you would have learnt something new, including what we can do to help protect and preserve our oceans. You can follow me and my journey on my Instagram page: _marine_mili.
The blue bottle jellyfish got their name from the bottle-like sac (which is known as the float) that looks like a bottle that is blue when it floats on the surface. This species is also commonly known as the Portuguese man o’ war.
Blue bottles are not a true species of jellyfish but instead they belong to a group called siphonophore. Siphonophore are a colonial marine invertebrate, marine creatures that lack a backbone. They clone themselves, which is their way of reproducing.
The size range of blue bottles can vary drastically with the ‘float’ being between two and 15 centimetres and the tentacles reaching up to ten metres which is as long as two adult great white sharks!
Blue bottles eat a variety of different fish including fry which are young fish and small adult fish. They also eat a variety of crustaceans and plankton.
How do they chat prey you may wonder?
Well, they will use their long tentacles that have in stinging cells all over them to grab the prey. The prey will then become immobilised.
As these creatures have no bones, fins, brain, heart or even eyes, they not only have no sense of direction, but they cannot move themselves around or swim at all.
Instead, they rely on the current and wind for any sort of movement. That means that blue bottle jellyfish can only hope that there is food nearby. They also cannot keep themselves out of danger including washing up on the shore from strong winds, as they will dry out and die if they wash up on the beach.
However, it is still best to not touch them as they can still have a very painful sting, even if they look dried up.
Around five years ago, thousands of blue bottle jellyfish washed up along beaches around Phillip Island from a strong change in the wind direction, that brought a current hosting thousands of blue bottles to the island.
