Did you know that 95% of the body of a jellyfish is water? You would be surprised to know that these animals have no heart or brain. The list of curiosities seems never to end when it comes to these peculiar organisms. Its presence on earth dates back millions of years, even long before the dinosaurs did, and it has been proven that they are capable of feeding on specimens of the same species. Amazing, right?
Other surprising data refer to its morphology, because jellyfish have a single mouth, through which they feed and expel waste. Regarding its toxicity, it is known that they have a network of nematocysts (cellular structure that secretes the poison), distributed along its mouth and its tentacles. In this sense, the Cubozoos (Box jellyfish) are considered as the most dangerous class of all, although there are about 2000 species of jellyfish to discover and admire. Let’s see the three large groups in which these wonders of nature are classified.
Cubozoos (Box jellyfish)
They abound in the tropical and subtropical regions of the planet, being the surroundings of the Australian continent and the sea of the Philippines where we find a greater presence of this class. The cubozoos are named as such because of the characteristic form of their anatomy (in the form of a cube), and to date some 40 subspecies are known, among which is the sea wasp, highly lethal due to its strong venom content.
In effect, a cubomedusa specimen can have up to 500,000 cnidocytes (stinging cells) with which to cause the death of a person in a matter of minutes. Despite the above, they do not have aggressive behavior, and most encounters with humans are totally accidental. In such cases, the injected toxin can unleash a cardiovascular collapse that in most cases is fatal.
In this order, polyps (such as the Portuguese caravel) and hydromedusaes share the spotlight. In the case of the former, the Hydropolyps constitute colonies of polymorphic organisms interconnected with each other (with the exception of the hydra), specialized in various functions such as reproduction and digestion. These invertebrates lack a skeleton and a relatively moderate level of toxicity for humans.
As for hydromedusae, they are carnivorous, and their diet includes small crustaceans and fish that devour through a hanging opening towards the central part of the interior of their body. It also has four tentacles full of cnidocytes and a gelatinous layer called mesoglea. In general, hydromedusae are individuals that do not exceed 6 cm in diameter.
Finally we find the group of scyphozoans (often recognized as the true jellyfish). This order includes such popular specimens as the moon jellyfish, the blue dune and the blue water, abundant in the Mediterranean and part of the Atlantic. The size of the scyphozoa ranges between four centimeters and up to two meters in diameter, and can weigh more than forty kilograms.
In this order have been studied about 200 species, which have a biological cycle that starts from the metamorphosis of a larva planula to originate an adult jellyfish. Some specimens have luminescent qualities, which offer an unparalleled visual spectacle. In adulthood, a scytheus jellyfish will have about ten meters of tentacles, with stinging features common to the rest of the species.