#CreatureFeature – Physalia physalis(Bluebottle)

The Bluebottle, also known as the Indo-Pacific or Portuguese Man o’War, is habitual through the Indian and Pacific Oceans and are commonly encountered in the summer months throughout Australia. They are more common on exposed ocean beaches after being washed up by strong onshore north easterly winds. 

Bluebottles are not but one single animal, they are made up of a colony of four kinds of individuals (zooids). This includes the float which is a bottle shaped sac that can grow to as long as 15cm. It is blue and can show slight reflections of green or pink. The float secretes its own gas, similar to air and has aerodynamic properties and can sail through the water depending on which way its crest is facing. They have tentacles, which capture food and convey their prey to their digestive polyps and lastly, reproduction that is carried out by another type of polyp. 

Diet and Feeding 

Bluebottles feed on larval fish, molluscs, and mini crustations such as copepods and amphipods. The tentacles drift downwind continuously fishing through the water waiting to hook onto food to drag in range if their digestive polyps. The digestive pulps are the “stomach” of the bluebottle colony, and respond to the presence of food quickly, their food wiggles until they can fasten their flexible mouths around it. Once attached, the jellyfish becomes all mouth, spreading over the surface of the food. The resting polyp itself measures 1-2mm in diameter but may expand up to 20mm. They digest food by secreting enzymes that break down proteins, carbohydrates, and fats. 

Bluebottle Stings 

Among the tentacles are nematocysts. Nematocysts are extremely complex, they are 0.05mm in diameter. Each is a hollow sphere with its external wall turned in at one point, the opening left in the surface of the capsule is covered by a lid held down by a hairlike trigger. When the trigger is stimulated, the tube shoots outward turning itself right side out. The tube is armed with barbs that aid with the penetration of the sting. The sting capsules contain a toxic mixture of phenols and proteins that is injected through the victim’s skin through a terminal pore in the thread. 

Bluebottles are irritating to the skin but are not poisonous to humans. They may be harmful to young children, the elderly, or people who are allergic to jellyfish. If stung by one: 

  • Don’t rub the sting area 
  • Wash off remaining tentacles with salt water 
  • Immerse the sting in hot water at a temperature which you can tolerate. Studies have shown that immersing your sting in 40 degrees Celsius for 10 minutes can mildly reduce the pain, it kills the proteins in the venom. 
  • If the symptoms persist or if they start to form rash or puffiness through the face or neck or cover other large areas, call triple zero. 

Life Cycle 

Bluebottles are hermaphrodites, which means they consist of female and male parts. The fertalised egg develops into planktonic larval form which produces the colony by asexual budding. 

Reference: https://australian.museum/learn/animals/jellyfish/bluebottle/ 

Paige Kirby – Biodiversity Program Trainee

Title photo: Ianere Sevi

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