There are many types of jellyfish in the Mediterranean, and depending on the species, their sting can be more or less dangerous. In recent years, the population of this gelatinous animal has increased substantially, causing serious problems for marine ecosystems and the environment.
According to experts, the main reason for the increase in jellyfish is believed to be the decrease in the number of their predators (primarily turtles) due to overfishing, pollution, and warming oceans. This article explains the most common types of jellyfish in Spain and the consequences of their stings.
What are jellyfish?
They are invertebrate animals that belong to the group of cnidarians (knidé = nettle, from the Greek). The Cnidarian group is classified into the following four classes:
- Hydrozoa: Hydra, small jellyfish and other colonies of polyps.
- Cubozoa: Box jellyfish.
- Scyphozoa: Big jellyfish. It is the class that we mainly recognize as jellyfish.
- Anthozoans: Anemones and corals.
They have stinging cells called cnidocytes , which they use to defend themselves and hunt prey. Cnidocytes are very sensitive. They are contained within a capsule that has a coiled filament, like a fishing line, and the venom inside. When prey touches the jellyfish's surface, the capsule opens, and the filaments emerge and attach to the prey, where the venom is injected. Unfortunately, sometimes they are triggered by our touch, even though we are by no means the jellyfish's intended target.
Jellyfish are also called sea nettles or sea sea creatures . They are pelagic animals, meaning they live in the open ocean. One of their characteristics is that they are carried by ocean currents, although they can propel themselves to slightly change direction using their bell.
They are radially symmetrical animals, with 95% of their body composition being water , and their main parts are:
- Umbrella
- Manubrium (or tentacles or oral arms). They are the tentacles that surround the mouth and help it to feed.
- Stinging tentacles. They are the most external and the ones they use to defend themselves and hunt.
- Gastrovascular cavity. Internal cavity with a single opening that acts as both anus and mouth, where digestion takes place.
But how do jellyfish eat and reproduce?
They are carnivorous and can grow rapidly and congregate in large numbers when food is plentiful. But if food is scarce, they can shrink back down. These little creatures, which remind us a bit of that slimy mass from the movie Flubber, have a remarkably simple anatomy. You can even see their last prey through their transparent bodies before it's digested. They feed mainly on zooplankton, small crustaceans, and some small fish.
Jellyfish reproduction is fascinating. Jellyfish have male and female individuals and reproduce sexually by releasing sperm and eggs into the water. This union gives rise to planulae , which are the jellyfish larvae. The planulae attach to the seabed and develop into polyps. Through asexual reproduction , the polyps produce numerous tiny jellyfish called ephyrae , which grow over time as they feed. Their name comes from their ephemeral nature, as this stage lasts only a very short time.
What are the natural predators of jellyfish?
Today the jellyfish predators that are known are:
- Sunfish (Mola mola)
- Sea turtles, especially the leatherback sea turtle (Dermochelys coriacea)
- Sea birdssuch as fulmars (Fulmarus)
- Whale shark (Rhincodon typus)
- some ccrabs, like the arrow (Stenorhynchus seticornis) and the hermits (Paguroidea)
- Some Whales, such as the humpback or hunchback (Megaptera novaeangliae)
- Other cnidarians like anemones (actinaria)
- nudibranchs (nudibranch) or sea slugs, which use the jellyfish's stinging cells to defend themselves against other predators!
Most common jellyfish on the Spanish coast
You've probably seen brown jellyfish at the beach a few times, but what are they called? Is their sting dangerous? Since we know you have all these questions, especially during the summer months, we're going to give you a list and information about the most common jellyfish in Spain . First, let's list the jellyfish themselves, that is, those belonging to the class Scyphozoa:
Cotylorhiza tuberculata
- belongs to the order Rhizostomeaespecifically to the family Cepheidae. They are also commonly called aguacuajada, fried egg jellyfish or curly acalefo.
- They are characterized because they are yellowish brown jellyfish, with a greenish touch due to some symbiotic algae that they have inside and a protuberance in the middle of a brownish orange color, and its umbrella is flattened. Due to its morphology, that is why it is known as a fried egg.
- They are one size 20 to 25 cm in diameter, 8 oral arms covered with a kind of mini tentacles with white or bluish buttons. And its umbrella is divided into 16 lobes, subdivided at once into more than a hundred. On the edges of their umbrella they do not have tentacles.
- They are pelagic, inhabiting both the open sea and the coast. Although there are usually more on the coast where their polyps can take root. It is quite common to see them in the Mar Menor, and in the Mediterranean during summer and autumn.. In winter they are rather in the form of polyps
- The danger of its sting is low, in part because their tentacles are very short and because they barely have cnidocytes (urticate cells). So do not worry if it stings you, its effects are very mild and it does not usually cause anything more than skin irritation and hives. However, in some exceptional cases an allergic reaction could occur.
Aurelia aurita
- belongs to the order Semaeostomeae, Family ulmaridae. It is commonly called as jellyfish moon. It is the form that we best identify as a jellyfish.
- They can measure up to 25 cm in diameter.
- They have the umbrella in dish shape, and the arms from his mouth are scalloped (wavy) and much longer than the short tentacles at the edge of its umbrella. From their appearance, it is characteristic that if you look at them from above they have a kind of purple-violet "flower with four petals", which are their reproductive organs and their general color is transparent stained with a whitish blue.
- They usually live in shallow waters, in lagoons and coastal areas, their development being better in brackish waters.
- They are not usually seen much on the Spanish coasts, they are particularly seen in coastal areas and lagoons such as the Mar Menor, fjords and closed bays where inland water enters.
- As for its danger, it is very low..
Pelagia noctiluca
- belonging to the order semacostomeae, Family Pelagiidand, they are known as luminescent jellyfish.
- They can measure more than 20 cm in diameter. Its umbrella has a hemispherical shape, rather flattened, with four long, scalloped, well-stout oral tentacles. At the edge of their umbrella they have 16 tentacles that when they are deployed they can reach up to more than 20 meters in length!. Something characteristic of these beautiful but highly stinging creatures is that they have the entire surface (oral arms, tentacles and including the umbrella) of Warts where cnidocytes accumulate. They have a reddish pink color, which makes them quite striking.
- They are pelagic and do not have a polyp phase like other jellyfish. As they live in the open sea, it is where large schools of these individuals are usually seen. Being their periods of reproduction in spring and autumn, so these will be the times in which more individuals are seen.
- They usually live in the open sea, and if they reach the coast it is because the storms drag them to the coast, are usually quite common in summer. And they can be seen in both the Atlantic Ocean and the Mediterranean Sea.
- As for the its danger is very high. produce a lot of irritation and itching, they can even cause wounds that can become infected. As they have such long tentacles they can affect a considerable surface of the skin, this implies that the effect of the poison it can even cause respiratory, cardiovascular and dermatological problems that can last for weeks or even months. So be very careful with these jellyfish!
Rhizostoma pulmo
- They belong to the order Rhizostomeae, Family Rhizostomatidae. They are also called aguamala, aguaviva or blue acalefo.
- Regarding its size, They are the largest we can find, with a diameter that can reach 90 and 100 cm. The umbrella has bell-shaped, bluish-white in color and with many lobes on the edge of the umbrella, violet in color, in addition to tentacles on its edge. Have 8 oral tentacles fused into a bluish-white manubrium. And this in turn forms a scalloped crown with 16 points, from which 8 bluish little arms come out that end in the shape of a club.
- They can be found both in open and shallow waters, although they are rather coastal because they need a substrate for their polyps, and because it is thought that among the jellyfish they are the ones that have the greatest ability to move when going to regions where there is more amount of food.
- It is a native species of the Atlantic Ocean and the Mediterranean Sea. So they can be seen from late spring to fall. You may see them both alone and in banks. And in winter, they are in the form of a polyp in the shallow waters.
- They are not as dangerous as Pelagia noctiluca, we would still classify its dangerousness as medium. It is curious because they do not produce serious dermatological conditions. However they can produce irritations only with its presence in coastal waters closed to the open sea, it is not even necessary to have direct contact with the jellyfish or any fragment of its body.
Other jellyfish, which are not officially jellyfish
Yes, to clarify, these creatures do not belong to the class Scyphozoa , therefore, they are not officially jellyfish. However, to the naked eye, they can easily be mistaken for jellyfish. Here are the most common ones found on Spanish coasts:
Velella Velella
Belonging to the class Hydrozoa , this bluish-colored , disc-shaped creature has a "weather vane" on top . They are small, measuring 1 to 8 cm . And although it looks like a jellyfish , it's actually a floating colony of polyps! They usually travel in swarms and are most common in spring and early summer. They are completely harmless.
Aequorea forskalea
Belonging to the class Hydrozoa , they resemble jellyfish, with a flattened, transparent bell that can reach up to 30 cm in diameter . The edge of the bell has numerous very fine filaments that allow them to feed. Their habitat is usually the Atlantic Ocean, although they rarely appear in the Mediterranean . However, as climatic conditions are changing, they are beginning to be observed on the coasts of Catalonia and the Balearic Islands. Regarding their danger, they are completely harmless.
Carybdea marsupialis
Belonging to the class Cubozoa , they are cube-shaped with four tentacles, one at each corner . They are small, measuring between 5-6 cm in diameter . Their transparent color shifts between blue and white. They usually live in deep waters, although sometimes they can be seen at the surface due to currents, making them difficult to spot near the coast—and thankfully so, because they are very dangerous.
Physalia physalis
Also called the Portuguese man o' war . It belongs to the class Hydrozoa and forms a colony of polyps , one of which is shaped like a "float ," which is the most visible and measures between 30 cm long and 10 cm wide . For its size, it has very long tentacles, heavily laden with nematocysts, making it highly dangerous.
In fact, even a simple brush against one of its tentacles can have serious consequences, such as neurogenic shock due to intense pain, as well as burning, severe pain, and skin wounds. It typically lives in the warm waters of the Atlantic Ocean, although it has occasionally been observed in the Mediterranean.
Here's a link to an app that alerts you about jellyfish sightings in your area , so you can enjoy a more peaceful trip to the beach this summer. I hope you find this information helpful.
