Bluebottle factsheet

Article | Updated 6 years ago

Physalia utriculus

Bluebottles have a conspicuous elongate blue float and a long blue tentacle. In Physalia utriculus the float rarely exceeds 10 cm with the tentacle less than 3 metres. The bluebottle is very similar to the large Pacific Man-of-War which has floats to 15 cm in length and multiple fishing tentacles which can extend to 10 metres in large animals.
These complex floating colonies consist of four different types of polyps. The float that lies horizontally on the sea surface is a single individual that supports the polyps that reproduce, the polyps that digest the food, and the polyps that capture the prey. The single main fishing tentacle that hangs beneath the colony has a frilled and beaded appearance. Each bead consists of hundreds of nematocysts (stinging capsules).
Fleets of bluebottles are often carried by warm currents to more temperate waters. In southern Western Australia they are blown onshore and can be seen on beaches in autumn and winter, less often in summer. They are frequently seen on Perth beaches. 
Bluebottles feed mostly on larval fish and small crustaceans such as copepods and amphipods.
Physalia utriculus stings are mild, producing localised pain and swelling.
Immediate intense local pain which can last for an hour or more. The skin may be marked with a raised red line or small bead-like weals. 
Avoid swimming when bluebottles have been washed onto the beach as they are likely to still be in the ocean. The tentacles frequently break off in rough water and can sting. 
Do not touch dead animals as the venom remains active, and nematocysts can still fire long after the animals are dead and dried.
Wear protective clothing such as a lycra top, skivvy or stinger suit. 
First Aid
  1. Do not treat with vinegar.
  2. Remove any tentacles from the skin using tweezers or a gloved hand.
  3. If possible soak for 20 minutes in hot water (42˚C).
  4. Apply cold packs, and possibly a pain relieving cream, to the affected area for pain relief. This may need to be repeated for some weeks if the itchiness persists.
Loisette M. Marsh & Shirley M. Slack-Smith (2010). Field Guide to Sea Stingers and other venomous and poisonous marine invertebrates of Western Australia. Western Australian Museum. Perth, Western Australia.
A bluebottle stinger floating in water

A small colony of Physalia utriculus showing the horizontal float with the polyps beneath. Note the main tentacle is long, frilled and beaded in appearance.
Photo by Clay Bryce, copyright WA Museum