Humans and jellyfish can be friends

This last summer was full of numerous encounters between man and the increasing number of jellyfish who live in our seas. In the last decades in fact, we have seen an exponential growth in the number of these animals due to the environmental imbalances induced by the anthropic activities, leading the experts to coin the definition of “jellyfish ocean”, considering that we have progressively impoverished the “fish ocean” through our fishing activities.

Gliding over environmental issues, the growing presence of jellyfish in the seas naturally also represents a concern for us humans. In fact, these marine animals with their characteristic gelatinous consistency presents a pitfall that makes them unpleasant to unsuspecting swimmers: they can deliver more or less painful stings, which in some cases, especially for a few tropical species, can even be fatal. This peculiarity of the jellyfish has a consequence of no small importance, since it very often leads people to adopt incorrect and cruel behaviours, which can also be prosecuted by the law. It is therefore important to know which species are commonly encountered in our seas and what are the precautions to be taken and the mistakes not to be committed when being stung by a jellyfish.

In Italy for example, the in-depth knowledge of jellyfish species and their distribution in our seas is the result of a lot of work; collecting reports made by swimmers over the years, as well as studies by experts, which we can all be easily accessed on a free mobile App called “MeteoMeduse” (“Jellyfish Forecast”): a scientific monitoring platform of phenomenon, as well as a service for tourists and swimmers who can easily understand how to spot jellyfish, how to share sightings, and what to do in case of a sting.
Thanks to the valuable contribution of the reader-scientists, the team of scientific associations and researchers from the University of Salento, in collaboration with the scientific magazine Focus, has the resources to monitor 8,500 kilometers of Italian coastline, something that no research funding could have allowed.

Without going into the details of the classification, we can mention some of the most reported species:
Rhizostoma pulmo, commonly known as “Barrel jellyfish”, is recognisable by the blue-purple border of the umbrella and does not have a particularly strong sting;
Pelagia noctiluca, commonly known as “luminous jellyfish” recognisable by its violet-brown colour and the small spots covering its body, is sting is strong but not lethal;
Cotylorhiza tubercolata, also called, inaccurately from a taxonomic point of view, “Mediterranean cassiopeia”, or “Fried-egg jellyfish” because it resembles a fried egg due to its white-yellow rounded umbrella with a yellow-orange hump in the centre; it is does not have a particularly strong sting;
Aurelia aurita, also called “moon jellyfish” or “four-leaf jellyfish” so called by virtue of the morphology of the gonads that form a four-leaf clover in a central position and which can be observed thanks to the transparency of the umbrella, and it does not sting;
Carybdea marsupialis, easily recognizable by the cubic shape of its body and completely transparent, it can sting a lot but is not deadly, unlike the tropical cubomedusas;
Velella velella, also known as “St. Peter’s boat” or as “By-the-wind sailor”, is not a real jellyfish, but like them it is equipped with tentacles that do not sting particularly and it has the shape of an oval blue disk surmounted by a small crest that resembles a sail;
Porpita porpita or “blue button” so called by virtue of its round and flattened shape, surrounded by tentacles that do not sting, and its intense blue color.

This is just a sample list of some of the most popular jellyfish in the Italian Mediterranean area, so you can imagine how many species we are aware of and how many others can still be discovered.

Seen during the 700-meter water column exploration tract of Dive 20 of the 2021 North Atlantic Stepping Stones expedition, this beautiful red jellyfish in the genus Poralia may be an undescribed species.
Video courtesy of NOAA Ocean Exploration, 2021 North Atlantic Stepping Stones

Regardless of the degree of danger of the species, it is always advisable to pay attention when in you are in the water, especially in case of previous reports. Some jellyfish, moreover, are equipped with extremely long tentacles, so that, even if distant, they may equally constitute a danger. It is really important to emphasize that these animals do not voluntarily choose to attack another organism: the jellyfish sting is in fact one of the fastest reactions to exist in nature, as it is not mediated by the nervous system of these animals. The cells that are responsible for this are equipped with an autonomous sensory receptor that perceives a stimulus, constituted precisely by contact with another organism, and immediately determines a response. This therefore implies that a dead jellyfish does not stop posing a risk, because the sting could still happen.

At this point, let’s briefly analyse what behaviours should be adopted in the case of a jellyfish sting. Assuming that it is obviously necessary to remain calm, although the pain can also be particularly intense, the first thing to do is to get out of the water: the venom of some jellyfish can also cause serious reactions in some cases. A person would instinctively be inclined to rinse the affected area with running water, but there is nothing more wrong: in fact, fresh water favours the release of the poison. For this reason it is instead important to rinse the affected part with sea water, in order to remove the parts of jellyfish still attached to the skin, and for that purpose ID cards, credit cards or shopping loyalty cards can also be useful: these can in fact be used to scrape away residual tentacles. Of course, all these operations must be carried out paying attention to avoid contact with other parts of the body, especially the more sensitive ones such as the eyes.
And finally, we can confirm that no, urine has no effect on jellyfish stings as it is commonly thought (and largely spread due to that funny episode of ‘Friends’).

To conclude, it is important to reiterate that jellyfish are not found in the sea in order to harm us, but because that is their habitat of which we are simple guests.
This means that nothing gives us the right to torture and kill these animals, a concept that seems not yet clear enough to many bathers who prefer to beach them and let them cook in the sun.
In a society that is still highly insensitive to environmental issues and not adequately educated to respect all biodiversity, it is important to convey the message that humans no longer have the right of other animals to occupy a certain environment.

The author, Ilaria Stefanile, is a 20-year-old student in the Department of Biology at the Federico II University of Naples, and she has always been passionate about marine biology and the protection of marine environments.

Cover photo by Eric Kilby released under Creative Commons BY-SA 2.0 license.

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