Calcareous Medusa

Little more than a floating rock with trailing tentacles.

The Calcareous Medusa, better known as the Rock Jelly, is a large jellyfish native to the shallow tidal Turquoise Pools, which they serenely float and swim around aimlessly. The bells of mature medusae can reach just over 30 centimetres in diameter, and their trailing tentacles can reach up to a metre in length. Lacking any natural predator, and relying on a mix of microscopic zooplankton and symbiotic Zooxanthellae for sustenance, these medusae have lost their venomous stings. The mineral rich waters of the Turquoise Sea filters into the pools at high tides, and deposits themselves on the upper dermis of the locomotive bell, forming a hard mineral crust that contributes to the species' lack of predators. Numerous small gas bladders form in the locomotive bell in order to provide positive buoyancy and offset the mass of the mineral crust.
They are edible, if one can pry off the mineral crust and can stomach the gelatinous flesh. When raised in mineral poor saltwater, they do not form a mineral crust. Some people have been known to keep crustless rock jellies as pets, and the medusae seem to enjoy being petted on the tops of their locomotive bells.

Scientific Name

Mastigias Calcaforma

Geographic Distribution

• Turquoise Pools