Species: Physalia utriculus

Also known as: Indo-Pacific Man O’ War

Bundjalung name: Unknown
Status (IUCN): Not evaluated

Characteristics

• Length/size: The bluebottle is made up of a colony of four specifically modified individuals called “zooids” that all rely on each other for survival – the zooids make up a float, tentacles, digestion and reproduction. They possess a pneumatophore, more commonly known as a float, that consists of a pear shaped sac that can reach up to 15 centimeters in length. Their tentacles can reach several meters long and have the ability to retract to just a few centimeters.

• Colour: The bluebottle mainly consists of a distinctive blue coloured float and tentacle, although the upper margins of the float can sometimes show shades of green or pink.

• Breeding/reproduction: They live for around 12 months and reproduce mostly in autumn. Bluebottles are hermaphrodites so each gonozooid, the zooids responsible for reproduction, has both male and female parts. Once eggs are fertilised, planktonic larvae undergo asexual budding to become a colonial Physalia. Once the pneumatophore reaches a size that is sufficient, the juveniles are then able to float on the surface of the ocean.

• Diet: Bluebottles feed primarily on molluscs, small crustaceans and larval fish. They have developed long, thick tentacles that contain stinging cells called nematocysts that are used to immobilise their prey. When fired, the nematocysts work by immobilizing the victim with the toxins contained within the cells. The muscles in the tentacles then contract in order to drag the prey toward their digestive polyps.

Habitat: Bluebottles are found throughout the Indian and Pacific oceans and are encountered primarily in the summer months on the eastern coast of Australia and during autumn and winter in south western Australia. They are most commonly found on exposed beaches after strong onshore north east winds have washed them onto the beach.

Threats: With up to 30,000 stings reported a year, these creatures seem to be more of a threat to humans than the other way around! 

 

Bluebottles can be “left-handed” or “right-handed” – an attribute that stops all of them being blown into shore at once. The ridge on top of the float projects either left or right, forming a sail that either sends them in to shore or out to sea, depending on the wind direction.