Lion's mane jellyfish
|Lion's mane jellyfish|
The lion's mane jellyfish, also known as the giant jellyfish or the hair jelly, is the largest known species of jellyfish. Its range is confined to cold, boreal waters of the Arctic, northern Atlantic, and northern Pacific Oceans. It is common in the English Channel, Irish Sea, North Sea, and in western Scandinavian waters south to Kattegat and Øresund. It may also drift into the southwestern part of the Baltic Sea (where it cannot breed due to the low salinity). Similar jellyfish – which may be the same species – are known to inhabit seas near Australia and New Zealand. The largest recorded specimen, found washed up on the shore of Massachusetts Bay in 1870, had a bell with a diameter of 2.3 metres (7 ft 6 in) and tentacles 37 m (120 ft) long. Lion's mane jellyfish have been observed below 42°N latitude for some time in the larger bays of the east coast of the United States.
The lion's mane jellyfish uses its stinging tentacles to capture, pull in, and eat prey such as fish, sea creatures, and smaller jellyfish.
The taxonomy of the Cyanea species is not fully agreed upon; some zoologists have suggested that all species within the genus should be treated as one. Two distinct taxa, however, occur together in at least the eastern North Atlantic, with the blue jellyfish (Cyanea lamarckii Péron & Lesueur, 1810) differing in color (blue, not red) and smaller size (10–20 cm diameter, rarely 35 cm). Populations in the western Pacific around Japan are sometimes distinguished as Cyanea nozakii, or as a subspecies, C. c. nozakii. In 2015, Russian researchers announced a possible sister species, Cyanea tzetlinii found in the White Sea, but this has not yet been recognized by other authoritative databases such as WoRMS or ITIS.
Lion's mane jellyfish (Cyanea capillata) are named for their showy, trailing tentacles reminiscent of a lion's mane. They can vary greatly in size: although capable of attaining a bell diameter of over 2 metres (6 ft 7 in), those found in lower latitudes are much smaller than their far northern counterparts, with a bell about 50 centimetres (20 in) in diameter.
Size seems to dictate coloration: larger specimens are a vivid crimson to dark purple while smaller specimens grade to a lighter orange or tan, occasionally colorless.
The bell of the lion's mane jellyfish is scalloped into eight lobes (lappets), each lobe containing from 70 to 150 tentacles, arranged in four fairly distinct rows. Along the bell margin is a balance organ at each of the eight indentations between the lobes – the rhopalium – which helps the jellyfish orient itself. From the central mouth extend broad frilly oral arms with many stinging cells. Closer to its mouth, its total number of tentacles is around 1200.
The long, thin tentacles which emanate from the bell's subumbrella have been characterised as “extremely sticky”; they also have stinging cells. The tentacles of larger specimens may trail as long as 30 m (100 ft) or more, with the tentacles of the longest known specimen measured at 37 m (120 ft) in length. This unusual length – longer than a blue whale – has earned it the status of one of the longest known animals in the world.
As coldwater species, these jellyfish cannot cope with warmer waters. The jellyfish are pelagic for most of their lives but tend to settle in shallow, sheltered bays towards the end of their one-year lifespan. In the open ocean, lion's mane jellyfish act as floating oases for certain species, such as shrimp, medusafish, butterfish, harvestfish, and juvenile prowfish, providing both a reliable source of food and protection from predators.
Predators of the lion's mane jellyfish include seabirds, larger fish such as ocean sunfish, other jellyfish species, and sea turtles. The leatherback sea turtle feeds almost exclusively on them in large quantities during the summer season around Eastern Canada. The jellyfish themselves feed mostly on zooplankton, small fish, ctenophores, and moon jellies.
Behavior and reproduction
Lion's mane jellyfish remain mostly very near the surface, at no more than 20 m depth. Their slow pulsations drive them forwards weakly, so they depend on ocean currents to travel great distances. The jellyfish are most often spotted during the late summer and autumn, when they have grown to a large size and the currents begin to sweep them to shore.
Like other jellyfish, lion's manes are capable of both sexual reproduction in the medusa stage and asexual reproduction in the polyp stage. Lion's mane jellyfish have four different stages in their year-long lifespan: a larval stage, a polyp stage, an ephyrae stage, and the medusa stage. The female jellyfish carries its fertilized eggs in its tentacle, where the eggs grow into larva. When the larva are old enough, the female deposits them on a hard surface, where the larva soon grow into polyps. The polyps begin to reproduce asexually, creating stacks of small creatures called ephyrae. The individual ephyrae break off the stacks, where they eventually grow into the medusa stage and become full-grown jellyfish.
Sting and human contact
Most encounters cause temporary pain and localized redness. In normal circumstances, and in healthy individuals, their stings are not known to be fatal. Vinegar can be used to deactivate the nematocysts, but due to the large number of tentacles, medical attention is recommended after exposure.
There may be a significant difference between touching a few tentacles with finger tips at a beach, compared to accidental swimming into one. The initial sensation is more strange than painful and feels like swimming into warmer and somewhat effervescent water. Some minor pains will though soon follow. Normally there is no real danger to humans (with exception of people suffering from special allergies). But in cases when someone has been stung over large parts of their body by not just the longest tentacles but the entire jellyfish (including the inner tentacles, of which there are around 1200), a visit to a health care centre or similar is recommendable. Although rare, at deep water severe stings can also cause panic followed by drowning.
On a July day in 2010, around 150 beachgoers were stung by the remains of a lion's mane jellyfish that had broken up into countless pieces in Wallis Sands State Beach, Rye, New Hampshire, in the United States. Considering the size of the species, it is possible that this mass incident was caused by a single specimen.
In popular culture
The lion's mane jellyfish appears in the Sherlock Holmes short story "The Adventure of the Lion's Mane" published in The Case-Book of Sherlock Holmes. Holmes discovers at the end of the story that the true killer of a professor who died shortly after going swimming (shouting "the lion's mane" before he succumbed) was actually this jellyfish. Suspicion was originally laid upon the professor's rival in love, until the latter was similarly attacked (he survived, although badly stung). In the context of the story, it is only because the school professor has a weak heart that he succumbs, as is confirmed by the survival of the second victim.
On the popular television program QI the show claimed that the longest animal in the world was the lion's mane jellyfish. This was later corrected – in 1864, a bootlace worm (Lineus longissimus) was found washed up on a Scottish shore that was 55 m (180 ft) long. (That claim has its critics: because bootlace worms can easily stretch to several times their natural length, it is possible the worm did not actually grow to be that length.)
A lion's mane jelly capturing a sea gooseberry
Life-sized model in the Smithsonian Museum of Natural History, Washington DC, US
Blue lion's mane jellyfish in Askeröfjorden outside Stenungsund, Sweden.
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