Lions mane jellyfish

Appearance

Although capable of attaining a bell diameter of over 2 metres, these jellyfish can vary greatly in size; those found in lower latitudes are much smaller than their far northern counterparts with bell about 50 centimetres in diameter. The tentacles of larger specimens may trail as long as 30 m or more. These extremely sticky tentacles are grouped into eight clusters, each cluster containing over 100 tentacles, arranged in a series of rows.

At 37 m in length, the largest known specimen was longer than a blue whale and is considered one of the longest known animals in the world. This title, however, may be contested: in 1864, a bootlace worm was found washed up on a Scottish shore that was 55 m long. But 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.

The bell is divided into eight lobes. A tangled arrangement of colorful arms emanates from the centre of the bell, much shorter than the silvery, thin tentacles which emanate from the bell's subumbrella.

Size also dictates coloration – larger specimens are a vivid crimson to dark purple while smaller specimens grade to a lighter orange or tan. These jellyfish are named for their showy, trailing tentacles reminiscent of a lion's mane.

Behavior

Lion's mane jellyfish remain mostly very near the surface at no more than 20 m depth, their slow pulsations weakly driving them forwards; they depend on ocean currents whereby they 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 closer to shore.

Habitat

As coldwater species, this 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.

Reproduction

Like other jellyfish, Lions 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 life span: 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 ephyraes. The individual ephyraes break off the stacks, where they eventually grow into the medusa stage and become full grown jellyfish.

Defense

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.

On July 21, 2010, around 150 people are thought to have been stung by the remains of a lion's mane jellyfish that had broken up into countless pieces in 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.

Cultural

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 school professor who died shortly after going swimming was actually this jellyfish. Suspicion was originally laid upon the professor's rival in love, until the latter was similarly attacked . 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, but this was later corrected - as the longest in the world is actually the bootlace worm.