Jellyfishes

Jellyfish are animals that belong to the Cnidarian group and, when they are adults, they live floating in the sea -they are pelagic organisms-. All Cnidarians are characterized by the possession of stinging cells, the cnidocysts, which they use to capture prey and defend themselves. When these cells come into contact with a potential prey, a mechanism is triggered that creates a small wound in which a stinging substance is inoculated. This mechanism is the same one that starts when a person touches a jellyfish. A jellyfish has thousands of cnidocysts, located in the tentacles and these continue to be active even when the jellyfish is dead or in the sand. They can also shoot and inoculate the stinging substance by osmotic or thermal shock, without the need for contact.

Jellyfish live far from the coast as isolated individuals or in schools, but periodically they approach the coast in variable quantities, depending on the year, transported by currents. The arrival of jellyfish on the coast is a natural phenomenon that mainly takes place during spring and much of summer. It is not known exactly what the oceanographic and biological factors that control their arrivals and/or proliferation on the beaches and coastal areas are, and it is not possible to make predictions about the quantities of jellyfish that will arrive each year.

 

WHAT TO DO WHEN LARGE AMOUNTS OF JELLYFISH ARRIVE AT THE BEACH

Due to the inconvenience and injuries that the stinging cells of jellyfish can cause to swimmers, the following recommendations are made in the event that they are found in large quantities on the beaches:

Inform bathers of the risk of coming into contact with these organisms (including broken tentacles) even when they are on the sand.
Prohibit bathing if the concentration of jellyfish in the water is very high (wave the red flag).
Pick up carefully those that have reached the sand.
Do not break them, neither in the water nor in the sand. The cnidocysts retain their stinging capacity in the still broken tentacles and thus increase the possibility of stings.
In the event of a bite, follow the recommendations below.

 

JELLYFISH STING. WHAT TO DO. 

The stinging substances are specific to each species and, therefore, not all jellyfish have the same stinging capacity. The most common species on the coast of Catalonia can cause local reactions in the form of hives and skin eruptions, which can manifest for hours. Exceptionally, more serious symptoms such as nausea, vomiting, etc. may occur. In general, children, people with a history of allergies and those who have already been stung by jellyfish are the most sensitive.

Fresh water should never be applied to the affected area; any cleaning attempt should always be done with seawater.
You have to apply cold on the bite area: a plastic bag with cubes for 15 minutes. Ice cubes should never be placed directly on the affected area. If the pain persists, a second application of 15 minutes can be made.
The remains of tentacles adhered to the skin must be removed during or after the application of the ice, protecting your fingers.
Do not rub the bite area with anything, not with sand, or with a towel, etc.
Do not scratch the bite area.
Ammonia should not be used.
Remember that a person who has been stung by a jellyfish is sensitized and is likely to have a more severe reaction if stung a second time.
If after the application of cold, the person worsens and complications appear, such as respiratory distress, seizures or heart rhythm disorders, you should go to the nearest hospital or health center.

Additional information