Identification of live jellyfish is usually easy but once they've washed up on the beach it can become more difficult. Once you have identified your jellyfish, report it to the MCS National Jellyfish Survey.
Health and Safety
Some jellyfish can sting, so:
- Never touch jellyfish with bare hands
- Always use a stick or wear arm length rubber gloves if you need to turn them over for identification
- Beware of the stinging tentacles and keep your face and any exposed skin well clear
- Seek medical attention in the case of a severe sting
Jellyfish and leatherbacks
Little is known about jellyfish in UK waters, but we do know that they are the staple diet of the critically endangered leatherback turtle. These spectacular reptiles are seasonal visitors to UK seas, migrating from their tropical nesting beaches, and analyses of stomach contents of dead leatherbacks stranded on UK shores have revealed that they feed on several species of British jellyfish.
Scientific name: -
Other scientific names: - Rhizostoma pulmo
Maximum diametre: - approx 90 cm
Depth: - .
Environment: - Pelagic, confined to the southern and western shores of the British Isles. Recorded from Essex throughout the English Channel and Irish Sea and the coast of Ireland, the Outer Hebrides and the north west coast of Scotland.
You are most likely to see barrel jellyfish from a boat while out at sea; they are less common close to the coast. Barrel jellyfish are unmistakeable, their large bodies highly visible, and the smooth bell and cauliflower-shaped mass beneath very distinctive. Jellyfish are classified as Scyphozoa, from the Greek scyphos, a cup, and zoon, an animal. The specific name 'octopus' means 'with eight legs' (or arms), and has nothing to do with octopus - except, of course, that they are named 'octopus' for the same reason.
The scientific name Rhizostoma means 'root pores', and gives a clue as to how the barrel jellyfish lives. The big 'arms' of this impressive jellyfish trail behind the huge, solid bell, and are quite complex structures. They are fused together for much of their length, and on the highly convoluted 'cauliflower' part, beneath the bell, are hundreds of tiny mouths (the 'pores'), leading to a highly branched digestive system. Each mouth is surrounded by tiny stinging tentacles, able to catch plankton small enough to enter the minute mouths. Rhizostoma is the 'basking shark' of jellyfish - despite its huge size, it lives on tiny plankton, and its sting is not powerful enough to harm humans.
The barrel jellyfish often has tiny passengers in the form of stout amphipods (Hyperia galba), crustaceans up to a centimetre long, that hang onto the jelly with spine-like feet, often inside the stomach or reproductive cavities. These crustaceans can change colour to match their background, blanching while among the jellyfish tissues to avoid detection - small fish, which might eat them, often accompany this jellyfish. Heavy infestation of jellyfish by these amphipods can lead to progressive breakdown of their jellyfish hosts. Research has shown that Hyperia amphipods produce many more eggs than other amphipods, enabling a rapid population explosion in summer when their host jellyfish are most abundant. The amphipod embryos develop inside the safe environment of the jellyfish, only swimming off to look for a new host as young adults. In winter, this amphipod apparently has another generation of slower-growing individuals which hibernate on the sea bed. This ensures that the populations of Hyperia are synchronised with the life cycle of their host jellyfish. In most jellyfish, sperm released by males fertilises eggs formed in small pouches in the tissue of female jellyfish. A small swimming larva develops from fertilised eggs. This larva settles on the sea bed and grows into a small polyp, which buds off tiny new jellyfish each season.
It is sporadic in occurrence from year to year but occurs in 'swarms' in summer and autumn. It is believed that some specimens probably live in deep water during winter.
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Blue jellyfish: - Cyanea lamarckii
Other scientific names: - Cyanea nozakii or Cyanea capillata nozakii
Maximum diametre: - approx 30 cm
Environment: - Pelagic, but can occur in coastal waters all around the British Isles. It has been recorded from the Shetland Islands, the Orkneys, along the east coast of England, Dartmouth in the south and up through the west coasts of England and Wales.
Up to 15cms in diameter, the Blue Jellyfish or Cyanea lamarkii is a common visitor to our coasts from May to October. It feeds on plankton primarily but will eat anything that sticks to its long train of stinging tentacles, including other jellyfish.
To a human, the sting is less severe than a nettle sting and does not last long but this may depend on an individual's sensitivity. Belying its name, the Blue Jellyfish is sometimes pure white!
Like other jellyfish, this is an annual animal that starts out life in late Winter as a tiny animal about the size of a finger nail but as it drifts feeding in the plankton, it develops rapidly. At its peak its tentacles are probably 1m long. Once the plankton supply diminishes in late Autumn and the seas become very rough, the Blue Jellyfish dies.
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By the Wind Salior: - Velella Velella
Scientific name: from velum, a sail
Other scientific names: - Velella spirans
Maximum diametre: - approx 10 cm
Depth: - Surface
Environment: - pelagic species but is occasionally seen washed up around Britain and Ireland.
These small cnidarians are part of a specialised ocean surface community that includes the cnidarian siphonophore Portuguese man o' war and some specialised molluscan nudibranchs (sea slugs), including Glaucus and the purple snails Janthina, that prey on them. Each Velella is a hydroid colony, and most are less than about 7 cm long. They are usually deep blue in colour, but their most obvious feature is a small stiff sail that catches the wind and propels them over the surface of the sea. Under certain wind conditions, they can become stranded on beaches in the thousands.
Although not dangerous to people, it's best not to handle them or touch your face or eyes if you've been touching beached individuals since some irritation may result.
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Compass jellyfish: - Chrysaora hysoscella
Scientific name: Chrysaora is derived from chrysaor in Greek mythology, the son of Poseidon and the god of lightening. Hysoscella is derived form the two Greek words, isos, meaning alike, and scelis, meaning ribbone.
Other scientific names: - Chrysaora isosceles
Maximum diametre: - approx. 20 cm.
Depth: - From sea-level to unkown depth.
Environment: - Pelagic, but occurs in coastal waters all round the British Isles. It is prevalent off the south and west coasts of England and Wales. It has been recorded off the Cumbrian coast, the Isle of Man and off the north coast of Ireland.
The compass jellyfish has a saucer-shaped bell, with 32 semi-circular lobes around the fringe, each one with a brown spot. On the upper surface of the bell, 16 brown V-shaped marks radiate outwards from a dark central spot. The mouth, the only opening to the exterior, is located on the centre of the underside of the bell, and is surrounded by 4 arms. There are also 24 tentacles around the edge of the bell, grouped in threes. The colour of this jellyfish varies, with a variable level of brown pigment.
Compass jellyfish change sex: first they are male, followed after by female. The medusae live mainly off other medusae, comb jellyfish and arrow worms.
May be confused with the common jellyfish Aurelia aurita when stranded. Aurelia aurita however, has shorter tentacles with no brown v-shaped markings on the bell. Instead it has 4 purplish-blue horseshoe shaped gonads that are easily distinguished through the upper surface of the bell. The stinging cells and venom of Chrysaora hysoscella are strong and can produce painful, long lasting weals in humans.
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Lions Mane jellyfish: - Cyanea capillata
Scientific name: -
Other scientific names: -
Maximum diametre: - 40 metres
Depth: - .
Environment: - Pelagic, but found around the coasts of the British Isles, most commonly along the east coast of England and Scotland. Also common in the Irish Sea.
The lion's mane jellyfish can attain enormous size. In fact, the largest Lion's Mane jellyfish is not merely the largest species of jellyfish in the world; it is the largest animal in the world. The one specimen of Lion's Mane which was found in Massachusetts Bay in 1870 was over 7 feet in diameter and its tentacles were longer than 120 feet in length. However, the bell of the Artic Lion's Mane is known to be able to grow up to 8 feet in diameter, and their tentacles can acquire the length of 150 feet. That is much longer than blue whale, which is generally thought to be the largest animal in the world.
Lion's mane jellyfish are highly variable in size. While the largest lion's mane jellyfish are found in the northernmost peaks of the Arctic ocean, the size of the jellyfish diminishes as you travel further south. The jellyfish found between 40 degrees latitude and 42 degrees latitude are amongst the smallest varieties of lion's mane jellyfish. On an average, the body of the lion's mane jellyfish usually only grows up to 8 feet in diameter. Similarly the length of the tentacles also decreases as the size itself begins to diminish. The color of the lion's mane jellyfish is also dependent on its size. The largest specimens of the lion's mane jellyfish are a dark crimson in color. As their size reduces, the color becomes lighter until it is light orange or tan.
The bell of the Lion's Mane jellyfish is divided into eight lobes. Each lobe has a cluster of 60 to 130 tentacles at the margin of its gelatinous body. Lion's mane jellyfish also have a number of oral arms near the mouth to facilitate transporting the food to the jellyfish's mouth. Lion's Mane, like most other species of jellyfish, is carnivorous and feeds on zooplankton, small fish, and ctenophores. Lion's Mane jellyfish is also cannibalistic and feeds on other jellyfish like moon jellies. The predators of the lion's mane jellyfish include seabirds, larger fish, other jellyfish species and sea turtles.
Lion's mane jellyfish have a very severe sting that can produce blisters, irritation, and muscular cramp and may even affect respiratory and heart function. Cyanea capillata can still sting long after being stranded on the shore.
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Mauve Jellyfish: - Pelagia noctiluca
Scientific name: - In Greek Pelagia means “of the sea”, nocti stands for night and luca means light thus Pelagia noctiluca can be described as a marine organism with the ability to glow in the dark.
Other scientific names: -
Maximum diametre: -
Depth: - .
Environment: - Pelagic, but is an uncommon jellyfish around the British Isles, may be found anywhere over deep water off the west and north coasts
This species of jellyfish commonly known as the mauve stinger in Europe, amongst many other common names, is widely distributed in all warm and temperate waters of the world's oceans, including the Mediterranean Sea, Red Sea and Atlantic Ocean. It is also found in the Pacific Ocean, with sightings in warm waters off Hawaii, southern California and Mexico, as well as other Pacific locations.
This is typically an offshore species, although sometimes it is washed near the coastlines and may be stranded in great numbers on beaches. The colour varies worldwide, and in addition to pink or mauve, it is sometimes shades of golden yellow to tan.
Although the sting of Pelagia noctiluca is potent and painful, it is limited in time and extent.
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Moon jellyfish: - Aurelia aurita
Other Scientific name: -
Maximum diametre: - approx 40 cm
Environment: - pelagic species but may be found washed up on the shore. It is known to occur up estuaries and into harbours and is especially common in Scottish sea lochs.
The Moon Jellyfish is also known as the moon jelly, common jellyfish or saucer jellyfish. The name Moonjelly fish can refer to a specific species of jellyfish Aurelia aurita, but can also refer to all jellyfish species in the genus Aurelia. Because they are extremely similar to each other and can only be distinguished genetically, the entire species in the genus Aureilia is commonly referred to as Moon Jellyfish. We do not yet know exactly how many species of jellyfish belong to this common genus; new species are discovered regularly.
The medusa, or the bell of the moon jellyfish can range between 5 to 40 cm in size. Their medusa, or bell, is translucent and often has a pattern of stripes or spots. The four horseshoe shaped gonads of the moon jellyfish are easily visible through its translucent bell and offer the simplest way to identify a moon jellyfish. The moon jellyfish, unlike some other species of jellyfish, has both oral arms and tentacles to facilitate its feeding process.
The moon jellyfish are commonly found in coastal regions in warm and temperate waters. They are found in almost all the waters of the world between 70 degrees N and 40 degrees S, but are most abundant in Atlantic, Pacific and Indian Oceans. They are also known to inhabit inland seas and sometimes, even brackish waters. In brackish waters, however, the bell of the moon jellyfish is a lot flatter due to decreased salinity. Although moon jellyfish can withstand salinity as low as 0.6%, they thrive best in waters with relatively high salinity. Moon jellyfish can also withstand temperatures between -6 degrees C and 31 degrees C, their optimum temperature range is between 9 degrees C and 19 degrees C.
Like most other jellyfish are only capable of an upward thrust on their own and essentially depend upon the tides and currents of the waters to keep them suspended and for horizontal movement. Moon jellyfish usually stay near the surface of the water and travel with the tides.
The Moon jellyfish is carnivorous and mainly feeds on plankton like mollusks, crustaceans and copepods. They are also known to feed on zooplankton like hydromedusae and ctenophores. Moon jellyfish of all ages are equipped with venom filled nematocysts on their tentacles to help them procure food by stinging their victim and trapping in within mucus. On the other hand, moon jellyfish are fed upon by a number of large fish and the sea turtle. Even some marine birds are known to feed on moon jellyfish, especially because moon jellyfish tend to stay close to the surface of the water.
Moon jellyfish reproduce sexually and have both males and females in the species. They are most likely to be sexually mature around spring and summer of each year.
Moon Jellyfish are the most commonly kept species of jellyfish, in both public aquariums and by serious hobbyists. If you have visited an aquarium that keeps jellyfish, you are very likely to have seen specimens of these species.
The sting of the moon jellyfish is not fatal or dangerous to humans. In severe cases, the victim may experience some stinging sensation on the surface of the skin where they have been stung.
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Portuguese Man of War: - Physalia physalis
Scientific name: -
Other scientific names: - Physalia utriculus
Maximum diametre: - approx 25 cm
Depth: - .surface
Environment: - Pelagic.
While the Portuguese Man o' War resembles a jellyfish, it is in fact a floating, compound marine animal found in warm regions of all oceans. It is made up of a colony of four kinds of polyps (individual, tubular water animals). One kind of polyp forms the gas-filled float, 8 to 10 inches (20 to 25 cm) long, which is usually iridescent blue with a pink crest. Below the float hang the food-catching, feeding, and reproductive polyps. The food-catching polyps form tentacles that may be more than 40 feet (12 m) long, with stinging parts that paralyze or kill most fish and other prey on contact. (For a notable exception, The feeding then polyps close around the prey and digest it.
The Portuguese man-of-war is a cnidarian belonging to the genus Physalia of the order Siphonophora, although structurally similar to other solitary animals, are all attached to each other and physiologically integrated rather than living independently. Such zooids are specialized to such an extent that they lack the structures associated with other functions and are therefore dependent for survival on the others to do what the particular zooid cannot do by itself.
If a tentacle attaches itself to a human, it releases a poison (through the use of nematocysts), and if you continue to rub the skin after the tentacle has been removed more poison or venom will be released.
The sting is painful to humans and can cause nausea and convulsions. If you are stung, it is best to wash the area without touching it. A cold pack should be used to relieve the pain.
If stung, you should consult a doctor immediately.
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