Several Malaga province beaches detect box jellyfish

"We have a great deal of biodiversity in our waters. I live in San Pedro and I've just been out for a swim. I stopped when I saw one. They're harmless(...) We open-water swimming enthusiasts sometimes come across surprises and we need to be cautious," biologist Jesús Mackintosh said.

Fortunately, the box jellyfish of the Mediterranean are nothing like their Australian relatives, which can paralyse limbs and even cause life-threatening reactions.

Director of the Costa del Sol chair of coastal sciences Francisco Franco reassured the public: "This one is certainly less dangerous than the Australian species. It does not cause any serious effects and has a stinging capacity similar to that of the Pelagia noctiluca."

"When westerly winds prevail, colder waters rise from the depths and dying specimens are often found on the coast. This usually occurs in September, although by then the jellyfish are often already in a very decayed state and have lost some of their cube-like shape. The tentacles can remain active even after they have died," he explained.

Franco said that the "attack" mechanism of these jellyfish is similar to that of other species. Their tentacles contain nestocytes, which are stinging cells. These cells have an internal capsule containing a coiled filament and a toxic fluid.

Using a small external "hair" that comes into contact with the skin, they fire out a filament like a harpoon, embedding the venom in the skin. The venom is also water-soluble.

Franco does not rule out the possibility that box jellyfish tentacles could be the as yet unexplained cause of the skin reactions more than 20 bathers suffered on the beaches of Benalmádena. Tests ruled out the presence of faecal bacteria and the town hall subsequently put forward the theory that the cause was chemical or biological in nature.

Biologist Jorge Baro highlighted how unusual this species is and said that he had already heard reports about it this summer.

The photo in this article shows one of the specimens caught this weekend in Benajarafe. It proves how difficult it is to make out these jellyfish clearly. You really have to strain your eyes to make out their characteristic cube-like shape. What you can see, however, are the four tentacles, which look like brownish "worms".

The Mediterranean box jellyfish is a small cnidarian with a transparent cube-shaped body and four long tentacles. Its sting is very painful. The transparent, box- or cube-shaped body is three to five centimetres high. Its four slender tentacles can measure over a metre in length. Its natural habitat is the shallow coastal waters of the Mediterranean Sea and it is most active in summer.

Its sting causes intense and immediate pain similar to a burn, red marks, swelling and skin reactions. These lesions are usually self-limiting. It is rare for them to cause general symptoms.

The procedure for dealing with a sting is the same as in other cases. It is important to rinse the area thoroughly with sea water. Do not to use fresh water, as this could make it worse by causing the remaining cells to rupture. Check for any remaining tentacles and remove them using tweezers or a stiff card. Applying a cold compress to the area can provide relief and it is essential to try not to scratch it.

If symptoms are severe, visit a medical centre, where you may be prescribed corticosteroids (either as injections, a cream or oral tablets) and antihistamines. In such cases, doctors usually advice against sun exposure.

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