FunNature & AnimalPelagia noctiluca, the Mediterranean summer jellyfish

Pelagia noctiluca, the Mediterranean summer jellyfish

There are almost 2,000 known species of jellyfish in the world, with more or less wide distributions. There are tiny jellyfish, barely a millimeter long, and there are colossal species, such as the lion’s mane jellyfish, which can exceed 36 meters in length. There are those with a practically innocuous poison, and there are those that have a deadly sting.

The carnation jellyfish or purple jellyfish , Pelagia noctiluca , is distributed throughout the North Atlantic, from the equator to the North Sea, reaching the shores of both the Gulf of Mexico and the Bay of Biscay. It also enters the Mediterranean Sea, and from time to time, swarms arrive at the coast, large outcrops that force the red flag to be raised on the beaches. And although it is not the only species that causes these episodes, it is the predominant species.

An unusual life cycle

The life cycle of Pelagia noctiluca barely lasts a year, but it is a very peculiar cycle. Unlike most jellyfish, which have a polyp stage, the carnation jellyfish lacks such a stage. This species of jellyfish reproduces sexually , with adult males and females simultaneously releasing sperm and eggs into the water, throughout the year, but peaking in autumn and spring.

When the egg is fertilized, it hatches into a free-living larva called a planula , which swims thanks to the cilia that cover its body. After a week, the planula develops into a second larval stage called efira , which a month later will finally transform into an adult jellyfish, which will die after laying eggs, no more than nine months later.

Causes of Carnation Jellyfish Pests

The peculiar reproductive biology of the carnation jellyfish, different from other jellyfish, is one of the main drivers of its massive appearance on our coasts. But it is not the only cause.

Until the 1980s, the massive bloom of carnation jellyfish occurred approximately every 12 years , with a more or less cyclical behavior. Climatic variables were found to be good predictors of this phenomenon, favored especially by mild winters, low rainfall, high atmospheric pressure and, especially, high temperatures.

The warm waters greatly help the proliferation of carnation jellyfish, and the Mediterranean Sea meets the geomorphological and climatic conditions to be the perfect breeding ground. Every summer, due to anthropogenic climate change, the temperature of the Mediterranean rises and stays higher and higher for longer. Therefore, we can say that climate change is modifying these 12-year upwelling cycles , making them more frequent and larger.

But there is another effect. The jellyfish Pelagia noctiluca likes water that is somewhat polluted –particularly by heavy metals–, decomposing organic matter and excess nutrients, especially nitrates. This is because these pollutants stimulate colony growth, and also because they are factors that negatively affect other life forms that compete with or prey on jellyfish.

The most visual example of this event is found on the shores of the Mar Menor . Historically, this hypersaline coastal lagoon had insignificant populations of jellyfish Aurelia aurita . However, from time to time the alarms of enormous outcrops of carnation jellyfish go off, coinciding with the increasing impacts that human beings are causing in this environment. The Mar Menor receives an enormous amount of pollution each year, mainly from agriculture and intensive livestock farming, fishing, mining and tourism .

The sting of the carnation jellyfish

Like most jellyfish, Pelagia noctiluca has special cells that have a kind of inverted whip, which when activated, suddenly uncoils as if shot by a spring, causing small injuries to the victim, and discharging a relevant dose of poison. These cells are called nematocysts .

But what makes them different from the rest of the jellyfish, which only have nematocysts in their tentacles, is that the carnation jellyfish is completely covered with them , not only in the tentacles and oral arms, but also in the umbel, the body of the jellyfish. So the simple contact with her can be dangerous.

Carnation jellyfish stings occur mainly on the skin, as whiplash-like lesions , with local pain that can persist for up to two weeks, and urticaria-like effects. It is easy to leave mauve-tinted scars, due to a tattoo effect : the stinger, in addition to carrying a load of toxin, also has a pigment that can enter the wound and remain on the skin. Although rare, the bite can trigger an allergic reaction with a fatal outcome.

Ten days after the bite, rashes may appear, more or less recurrent, and even several years later, a relapse may occur. The mechanism by which this happens is still under investigation, but the most widely accepted hypothesis is that the venom probably reacts with dermal collagen and produces an active antigen, which accumulates under the skin, and at a certain point stimulates a response. immune.


Brotz, L. et al. 2012. Jellyfish populations in the Mediterranean Sea. ACTA ADRIATICA, 19.

Canepa, A. et al. 2014. Pelagia noctiluca in the Mediterranean Sea. En KA Pitt et al. (Eds.), Jellyfish Blooms (pp. 237-266). Springer Netherlands. DOI: 10.1007/978-94-007-7015-7_11

Goy, J. et al. 1989. Long-term fluctuations of Pelagia noctiluca (Cnidaria, Scyphomedusa) in the western Mediterranean Sea. Prediction by climatic variables. Deep Sea Research Part A. Oceanographic Research Papers, 36(2), 269-279. DOI: 10.1016/0198-0149(89)90138-6

Mariottini, G. et al. 2008. The Mauve Stinger Pelagia noctiluca (Forsskål, 1775). Distribution, Ecology, Toxicity and Epidemiology of Stings. Marine Drugs, 6(3), 496-513. DOI: 10.3390/md6030496

Milisenda, G. et al. 2018. Reproductive and bloom patterns of Pelagia noctiluca in the Strait of Messina, Italy. Estuarine, Coastal and Shelf Science, 201, 29-39. DOI: 10.1016/j.ecss.2016.01.002

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