Barrel Jellyfish

Cnidarian

Identification & Biology

• IdentificationThe largest jellyfish in the Mediterranean, with a massive dome-shaped bell that is pale blue to white, sometimes with a purple or blue tinge at the edges. Eight thick, frilly oral arms hang below the bell instead of true trailing tentacles. No long stinging tentacles.
• SizeBell diameter up to 90 cm. Weight up to 35 kg.
• Social HabitCan be solitary or in large groups (blooms), especially in spring and early summer. Drifts passively with currents. Young fish often shelter among the oral arms.
• HabitatOpen water (pelagic). Drifts in coastal waters, bays, and harbours. Often washed ashore during onshore winds.
• Depth0 to 40 m. Found at the surface and in the upper water column.
• Feeds OnPlankton, particularly small crustaceans and fish larvae, trapped in mucus on the oral arms.
• DistributionEastern Atlantic from the North Sea to West Africa, and throughout the Mediterranean Sea. Seasonally common in Maltese waters.
• DescriptionRhizostoma pulmo is a gentle giant that poses virtually no sting risk to humans. Its sting is too weak to penetrate human skin. Large blooms can appear in Maltese bays during spring and summer, sometimes numbering hundreds of individuals. Small fish, particularly juvenile jacks, often shelter in the protection of its bell. One of the most impressive sights when encountered in clear blue water.