Learn more about jellyfish

Aurelia is a cosmopolitan genus of scyphozoan jellyfish, with around 30 species described to date and many more thought to exist. It is one of the so-called cryptic species, which are morphologically almost identical and can only be distinguished by molecular analysis. The moon jellyfish has a transparent body with characteristic rings, or gonads, in the centre of its bell. In our exhibition you can see Aurelia coerulea, the most common jellyfish in the Adriatic Sea, as well as moon jellies from different parts of the world.

Barrel jellyfish are one of the larger jellyfish in the Adriatic Sea, with a bell diameter of around 40 cm, although they can grow to over 100 cm. Unlike other jellyfish, such as the moon jellyfish (Aurelia sp.) or the compass jellyfish (Chrysaora sp.), barrel jellyfish have a very unusual feeding mechanism. Instead of using a central mouth, they ingest food using eight specialised oral arms covered with millimetre-sized "mouths".

In recent years, barrel jellyfish have become one of the most abundant jellyfish species in coastal waters. Global warming, human impact, overfishing and ocean acidification are all contributing factors to the increasing abundance of jellyfish. Although not entirely harmless to humans, contact with their skin under stress can release mucus containing a higher concentration of nematocysts (stinging cells), which can cause mild rashes or skin irritation.

It is an endemic species of the Mediterranean and easily recognisable. It has a characteristic bell shape, resembling a fried egg, and its tentacles end in white or purple balls. The appearance of juveniles is common in July, and by the end of August they have matured and reached a bell diameter of around 40 cm. Interestingly, it plays an important ecological role by providing shelter for the juveniles of certain fish species. Young amberjacks, horse mackerels and bogues, together with their close relatives, often find safety from predators in the tentacles of the Mediterranean jellyfish.

This species is photosynthetic, meaning that symbiotic microalgae live in its tissues, reducing its need to catch prey. It can be assumed that, for this reason, it has fewer stinging cells on its body and is considered harmless to humans. Only very sensitive individuals may feel a mild stinging sensation upon contact with the skin.

The Compass Jellyfish can be recognised by its yellow to brown bell, which is marked with darker "V" shaped patterns that resemble a compass, hence its name. It is a fierce predator, armed with stinging cells on its 24 tentacles. Although most of the stinging cells are concentrated on the tentacles, they are also found in smaller numbers all over the surface of the jellyfish. It is considered one of the most dangerous species in the Adriatic (second only to the sea nettle according to literature) and can cause severe burns on the skin, especially in sensitive individuals.

Compass jellyfish are most commonly found in the upper layers of the water column, rarely descending below 30 metres. They are protandric hermaphrodites, meaning that all individuals start out as males and later change sex to become females. This sequential hermaphroditism, with staggered maturation of the sex cells, helps to avoid self-fertilisation. As in most hermaphrodites, the male sex cells mature first (protandry).

Since 2016, a mass occurrence of this gelatinous species, whose natural habitat is the Atlantic Ocean, has been observed in the Adriatic, especially in its northern part. It is thought to have arrived in the Adriatic through ballast water and its presence has had a negative impact on fish stocks. It is primarily a carnivore that feeds on zooplankton, fish eggs and larvae, significantly reducing the food available to fish. This species is highly invasive and extremely adaptable; it thrives in areas with salinity above 4‰, tolerates temperatures up to 28°C and reproduces rapidly.

Due to the structure of their body, especially the gelatinous substance, they are similar to cnidarians, in particular to some jellyfish, but they differ from them in that they do not have stinging cells. Another characteristic of comb jellies is their bilateral symmetry, which is not found in any cnidarian. Their bodies are usually transparent, with longitudinal bands or 'combs' that sparkle in a rainbow of colours during the day due to light interference and glow at night due to bioluminescence. Instead of stinging cells, comb jellies have sticky cells (cilia or tentacles) used to catch plankton. They are mostly carnivorous and feed on zooplankton, fish eggs and larvae, significantly reducing the food available for fish.

The cannonball jellyfish is common in the western Atlantic and eastern Pacific. Its bell resembles a cannonball, hence its name. There are currently two described and accepted species within the genus Stomolophus, but there are several known undescribed species with different pigmentation. These jellyfish have a symbiotic relationship with certain species of fish and juvenile crabs, which use the jellyfish for protection and feed on the zooplankton that the jellyfish capture. The relationship between jellyfish and their symbionts is not fully understood, but is thought to be either commensal (where one party benefits without harming the other) or parasitic.

Amakusa is naturally distributed throughout the Indo-Pacific. Its sting cells are very strong and can kill a fish within seconds. However, captive jellyfish have weaker and less painful stings. Like other jellyfish, it reproduces both sexually and asexually. Interestingly, Amakusa reproduces asexually in nine different ways, including budding, cyst formation, fission and strobilation. Strobilation is the only form that produces free-swimming larvae, called ephyrae, which become sexually mature after a few months. In addition, unlike other jellyfish in the family Pelagiidae, Amakusa undergoes monodisc strobilation, meaning it produces only one ephyra during strobilation. However, it invests more energy in its development, resulting in a significantly larger ephyra, which therefore has a better chance of survival than ephyra produced by polydisc scyphopolyps.

It is naturally found in the waters around Australia and is one of the most common jellyfish along the east coast. It can grow up to 35cm in diameter and can range in colour from white, blue, purple to brown. It has 8 oral arms which often host symbiotic copepods. Up to 600 copepods can live on a single jellyfish. This species is photosynthetic, meaning that symbiotic microalgae live in its tissues, reducing its need to capture prey. Its stinging cells can cause mild skin irritation, but it is not considered dangerous to humans.

It inhabits the northeastern Pacific Ocean, from the Gulf of Alaska to Baja California. It lives in shallow harbours and bays during the autumn and winter, and migrates to deeper ocean waters in the spring and summer. Its bell is golden-brown in colour, up to 30 centimetres in diameter, with tentacles that can extend up to 4.5 metres. It feeds on zooplankton, including other species of jellyfish, and is preyed upon by sea turtles, the ocean sunfish (Mola mola) and the northern fulmar (Fulmarus glacialis). Interestingly, the sting of this species is similar in intensity to a bee sting.

The marbled jellyfish can grow to 30cm in length and is typically transparent or pale white to ochre in colour. It is widespread along the east coast of South America and is one of the most common scyphozoans in the region. Its seasonal mass outbreaks are a major problem for fishermen as they not only reduce fish stocks but can also damage fishing equipment. Interestingly, the Lucerne jellyfish provides protection to pelagic crustaceans during their most vulnerable life stages. However, more research is needed to better understand these relationships within marine ecosystems.

Due to its large population, low toxicity, and rapid growth (30-50 kg), the flame jellyfish became the second jellyfish species in the world to be cultivated in the 1980s in China, while it has been traditionally consumed in Asia for over a thousand years. Jellyfish of the order Rhizostomeae are rich in collagen proteins and minerals, and low in fat and calories. Although over 95% of their total mass is water, after drying, over 40% of the remaining dry matter is collagen. Research has shown that collagen from flame jellyfish plays an important role in medicine by speeding up the wound-healing process.

It is naturally distributed in the waters around Australia and the Philippines. The bell is brownish with white spots and can reach 50cm in diameter. It is an invasive species, with sightings recorded in the mid-20th century in Hawaii and the Mediterranean, as well as in some parts of the Atlantic. Its spread is thought to have been via ballast water or polyps attached to ships. It has been observed to threaten shrimp populations in areas where it is present.

Hydrozoans are not classified as true jellyfish (Scyphozoa), but are a separate class within the phylum Cnidaria. Their bell diameter ranges from 0.5 to 6 cm, depending on the species. Interestingly, in the life cycle of hydrozoans, unlike true jellyfish (scyphozoans), hydrozoans do not have an ephyra stage but develop directly into adult-like forms.