Stalked jellyfish are closely related to anemones, free-floating jellyfish, and corals, all of which have stinging tentacles to paralyse or kill their prey and to protect themselves from predators.
This stalked jellyfish is the smallest member of its family. Even at its largest, it does not quite reach 1cm in height. It lives on rocky shores that are exposed to moderately strong waves and currents, and is found close to the low tide mark or in shallow water. Unlike other stalked jellyfish, it is rarely attached to seagrass but is often found on small, red seaweeds, such as Irish moss.
In appearance, it resembles an upside-down jellyfish, with its translucent bell underneath and tentacles on the top. There are eight webbed arms within the maroon bell, with up to 35 rounded tentacles at the end of each.
The UK distribution of this stalked jellyfish appears to be limited to the south-west of England, from Swanage in Dorset to north Devon, and the Atlantic coasts of Ireland. It may occur in the wider north-east Atlantic.
UKBAP Priority Species
In England, it is a species of principal importance for the purpose of conservation of biodiversity under the Natural Environment and Rural Communities Act 2006
St John’s jellyfish - Lucernariopsis cruxmelitensis - Marine life information network
Lucernariopsis cruxmelitensis - World register of marine species (WoRMS)
The stinging organs of this stalked jellyfish are very distinctive as white spots on surface of bell forming the shape of a Maltese cross.