- Colour: it has a blue float made of a flat, circular disc with many gas-filled tubes which keep it afloat. The disc is surrounded by tiny blue tentacles.
- The Blue Button is, in fact, a colony made up of different types of polyps, including some that are specialised for catching food, defense, or reproduction.
- Size: its disc is up to 2.5 cm across.
- Diet: small marine animals such as copepods, crab larvae and tiny fish fry. Its tentacles kill prey with their sting and then move the food to its mouth, which is on the underside of its disc.
- Movement: it floats freely in the water, and is moved along by ocean currents and wind.
- Breeding: Blue buttons are hermaphrodites (i.e. both male and female). The specialised reproductive polyps release both eggs and sperm into the water. When the eggs have been fertilised by the sperm, they develop into larvae that subsequently metamorphose into individual polyps. A Blue Button colony forms when one polyp divides to form new types of polyps which become specialised for different functions.
What to Observe
- Presence (to establish the first and last sighting of the season)
ClimateWatch Science Advisor
We don't yet know whether water temperature affects where jellyfish are found. Data on their distribution will help determine whether their range is changing and how climate change may impact their distribution.
When To Look
All year round, but particularly in the warmer months, around summer time.
Where To Look
- On the surface of coastal waters around Australia. It is more common on exposed ocean beaches after strong onshore winds have blown it in from the tropical north.
- On exposed ocean beaches. They are often washed up in large numbers, particularly after strong onshore winds.
Bennett I 1987. W. J. Dakin's classic study: Australian Seashores: a guide to the temperate shores for the beach-lover, the naturalist, the shore-fisherman and the student. Angus & Robertson.
Davey K 1998. A Photographic Guide to Seashore Life of Australia. New Holland Press, Sydney.
- Blue Bottle Jellyfish (Physalia utriculus): has an air sac for a float and long blue tentacles which can be up to 10 metres long (the Blue Button's tentacles are short).
- By-the-Wind Sailor (Velella velella): doesn't have any tentacles fringing its disc and does have a sail sitting upright on its disc.
Did You Know?
It is often found floating with the Blue Sea Slug which floats upside down!
The sting from its tentacles is not known to be dangerous to humans.