Fried Egg Jellyfish – Cotylorhiza tuberculata

A species of jellyfish called Cotylorhiza tuberculata.

Commonly know as the Fried Egg jellyfish or Mediterranean jelly, they are back in full force right now. The Cotylorhiza tuberculate species of jellyfish belongs to the phylum Cnidaria They always appear around Gozo and Malta at the beginning of the Lampuki fishing season- usually in September. They are commonly found in the Aegean Sea, Mediterranean Sea and the Adriatic Sea.


The Cotylorhiza tuberculata can reach a diameter of 40cm, having a width of less than 17cm wide. Their sting has little to no impact on human beings. The Fried Egg Jelly has a smooth, elevated central dome which is surrounded by a gutter-like ring. 


These jellyfish are the most common species of all found in the Mediterranean Sea. They have a life cycle of one year. Sexual reproduction between adults take place between August and October. The female Cotylorhiza tuberculata are internally fertilized with sperm from her partners mouth-arm appendages. After the gestation period, she will release large amounts of planulae into the water.

Damage and Distruction

With increasing age, the adult jellyfish suffers increasing damage. Most of this damage takes place on the main central dome of their top umbrella. Wave and wind driven abrasion causes injury, but motor boots and fishing nets cause severe damage. For young jellyfish this is a minor setback, they regenerate the injured anatomy, although it might grow back asymmetrically. Older fried egg jellyfish loose their colour and often show signs of physical deterioration. 

A large problem for the Cotylorhiza tuberculata is the threat from human beings. Due to the annual blooms of this species, usually in September, they are often regarded as interference with human recreational and financial activities. During the summer holiday period, it is often the time when the Fried Egg Jellyfish numbers are at their highest. This results in the removal of thousands of Mediterranean jellies from the waters by coastal official, either by using large nets or fishing boats.


The Fried Egg jellyfish consumes tiny aquatic organisms, a mixture of phytoplankton and zooplankton. It has been recorded that anywhere between 69% and 82% of their diet consists of organisms associated with the genus Spiroplasma. The jellyfish takes in the tiny organisms through its mouth-arms, from there it travels to the stomach. The interconnectedness of the Mediterranean Jelly and its surrounding waters allows for an easy flow of plankton into its gastric cavity. One of Cotylorhiza tuberculata’s natural predators is the sea turtle Caretta caretta. Unlike the Caretta caretta, the Fried Egg jellyfish is not in immediate danger of extinction.

Studies for Human Use

Humans also benefit from the jellyfish. The Cotylorhiza tuberculata have been studied due to their specified cyctotoxicity in regards to targeting breast cancer. There is still not much investigation on this topic, but this type of jellyfish may become a model organism for the treatment of those human ailments.

Photo was taken by Janet Bulmer at Dive Smart Gozo

Dive site: Blue Hole at 5 m depth