The box jellyfishalso known as “box jellyfish“, are highly marine invertebrates poisonous belonging to the Cubozoa class. Characterized by a shape cubic and long tentacles, have balance organs and well-developed eyes. They are excellent swimmers and predators, capable of causing serious burns with their nematocysts. However, there is no need to worry excessively: although some species are lethal, such as the Chironex fleckeri (“sea wasp”), others like the Carybdea marsupial I am less dangerous. In Italythe present species is the Carybdea marsupialso not so dangerous. It should be noted, however, that this jellyfish, with tentacles that can reach 30 cm, is quite stinging and can cause significant burns. It is frequently sighted off the coast of Syracuse, in the Gulf of Trieste, near Lignano Sabbiadoro and in the Grado lagoon, but it is also expanding in other areas. Let’s look at the biology of these jellyfish in detail.
Characteristics of box jellyfish: what they look like and where they live
Known in English as “box jellyfish” or “sea wasps,” the box jellyfish are small marine invertebrates belonging to the class Cubozoa, phylum Cnidaria. They are known for being among the most poisonous animals that live in our seas. Their name derives from the Typically cubic shape of the umbrellafrom which 4 groups of long, thin tentacles branch off, which they use for swimming and hunting.
They own some organs of balance and are excellent swimmers, they can reach considerable speeds compared to common jellyfish (Scyphozoa) and effectively capture their prey thanks to a visual system composed of well-formed eyes (up to 6 in total) capable of perceiving light and the surrounding space.
Some species have simple eyes called rhopalis (singular rhopalium), others can use lenses similar to our crystalline lens for a very well developed visionThey do not have a central brain but appear to have cognitive abilities and association skills. Their diet consists mainly of crustaceans and small fish which they capture with the help of their own stinging tentacles.
There are approximately 50 species of box jellyfish throughout the world, distributed mostly in the tropical regionswhere they colonize surface waters (medusoid phase) and sandy and/or rocky substrates (polypoid phase). Particularly well-known here in Italy is the species Carybdea marsupial: it is a rather stinging species with tentacles up to 30 cm long capable of causing serious burns. It is often sighted off the coast of Syracuse, in the Gulf of Trieste, near Lignano Sabbiadoro and the Grado lagoon but is colonizing increasingly larger areas.
Dangerousness to humans
Box jellyfish have stinging structures called nematocysts which they use to prey, defend themselves and compete spatially. They are a sort of harpoon guns injected with poison which are everted to paralyze and capture prey. Nematocysts contain highly complex and toxic mixtures of proteins, peptides and small organic molecules of variable composition. These “harpoons”, in contact with the skin, can cause a ache extremely intense, capable of leading in the most serious cases to faintingto thecardiac arrest and to the death.
Being attracted by light, coastal activities and being small in size, these animals can get closer to the beach and reach swimmers without being noticed. Furthermore, having tentacles that extend for tens of centimetres they can easily wrap around arms and legs generating major burns.
The The degree of danger varies from species to specieswith a good degree of lethality in the Australian species. However, there is no need to worry excessively: of the approximately 50 species of cubozoans, only some are truly lethal and colonize the Indo-Pacific regions and northern Australia as the box jellyfish Chironex fleckeri considered the most dangerous marine animal in the world.
In the case of Carybdea marsupialone of the most common and sighted species in the Mediterranean, these are stinging organisms but not so dangerous as the mass media would have us believe. The effects can be painful but often do not last long and do not require any particular post-sting treatments. To avoid unpleasant encounters, experts recommend avoid bathing at nightespecially near the coast and not to panic in case of sighting.
Environmental problems due to the proliferation of box jellyfish
Beyond the danger to humans, there is another big problem we need to talk about and that is ecological role of box jellyfish in the environment. Box jellyfish are invertebrates very old and adaptablehave been colonising our seas for time immemorial but their proliferation was favored by human actionin particular from the modification of the coastal profile and the creation of new anchorage points for the polyps (benthic stage of their life cycle). Many species require rocky substrates to attach themselves to and in recent years they are finding safe spots where reproduce.
Their massive and unusual presence must be kept under control: more jellyfish feeding on larvae means encouraging the impoverishment of fish populationsalready under pressure from intensive fishing. A potentially effective way to limit their number is to favor the natural predators of box jellyfish (turtles in this case), rebalancing the ecological system and the food web. This precaution, in addition to improve coexistence with us humans, it should be accompanied by a good and correct information to ensure safety and tranquility for the population during the summer period.
Just a little reminder: in case of direct contact with these animals, remember to report its presence and to do reference always at competent units!
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