Lion's mane jellyfish
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 A lion's mane jelly capturing a ctenophore
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| Cyanea capillata (Linnaeus, 1758) |
The lion's mane jellyfish (Cyanea capillata) is the largest known species of jellyfish. Its range is confined to cold, boreal waters of the Arctic, northern Atlantic and northern Pacific Oceans, seldom found farther south than 42°N latitude. Similar jellyfish (which may be the same species) are known from the seas off Australia and New Zealand. The arctic Lion's mane jellyfish is one of the longest known animals; the largest recorded specimen had a bell (body) with a diameter of 2.3 m (7 feet 6 inches) and the tentacles reached 36.5 m (120 feet). It was found washed up on the shore of Massachusetts Bay in 1870.[1]
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[edit] Taxonomy
The taxonomy of Cyanea species is not fully agreed; 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 blue (not red) colour and smaller size (10-20 cm diameter, rarely 35 cm). Populations in the western Pacific around Japan are sometimes distinguished as Cyanea nozakii Kisinouye, 1891, or as a race, Cyanea capillata nozakii.
[edit] Description
A common species, the lion's mane jellyfish is well known to divers for its painful, but seldom fatal stings; they are toxic and can cause severe burns. Most encounters cause only temporary pain and localized redness.
Although capable of attaining a bell diameter of 2.5 m (8 feet), these jellyfish are highly variable in size; those found in lower latitudes are much smaller than their far northern counterparts with bells about 50 cm (20 inches) in diameter. The tentacles of larger specimens may trail as long as 30 m (100 feet) or more. These extremely sticky tentacles are grouped into eight clusters, each cluster containing 65-150 tentacles, arranged in a series of rows.
The bell is divided into eight lobes, giving it the appearance of an eight-pointed star. An ostentatiously tangled arrangement of colourful 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 understandably named for their showy, trailing tentacles reminiscent of a lion's mane.
[edit] Ecology
A 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, other jellyfish species and sea turtles. The jellies themselves feed mostly on zooplankton, small fish, ctenophores, and moon jellies.
[edit] Behavior and reproduction
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 the jellies travel great distances. The jellyfish are most often spotted during the late summer and fall, when they have grown to a large size and the currents begin to sweep them closer to shore.
These jellyfish are capable of both sexual reproduction in the medusa stage and asexual reproduction in the polyp stage.
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Much speculation and even superstition revolves around predicting Lion's Mane population blooms and concentrations in locations popular for recreation. Among the Outer Islands (Long Island, Block Island, Martha's Vineyard, Nantucket, Monomoy, lesser islands, and Cape Cod) Lion's Mane populations show a very regular yearly population, and a very predictable seasonal flux. Starting with the first warm day of spring, often when sea thermoclines occur just inches below the surface, countless young Lion's Manes can be seen. These are as small as sand grains, and appear in the billions. As the water continues to warm, the majority of these will die. The remaining few (likely three or more orders of magnitude fewer) will slowly grow. By summers end, the average bell size may exceed 6 inches (Typical of Long Island). Barring drastic climate variations, jelly populations are unlikely to change even from one decade to the next. Tides, currents, and wind patterns may temporarily change conditions at a swimming location, however this does not reflect overall jelly population dynamics. The reliability of jelly populations from one year to the next is such that one can predict bell size and concentrations with great accuracy given only water temperature information. Concerned swimmers must either wear protection, tolerate stings, or swim during seasons known to feature a reduced risk of stings. In spring, when water remains cold, the young Lion's Manes are too small to hurt. By the end of the summer, the remaining animals are quite large, but rather uncommon. The worst time for encounters, then, is during the core of the summer. On Long Island, the peak jelly period is between the beginning of June and the beginning of August. May and August are the best times to swim if Lion's Manes are a concern.
[edit] In popular culture
- The Lion's mane jellyfish was mentioned in the Sherlock Holmes short story The Adventure of the Lion's Mane, in which Holmes, in one of his rare independent cases (Dr. Watson did not participate in the matter at all, and the story was written as if by Holmes himself), discovers that the true murderer of a school professor was actually this jellyfish. Suspicion was originally laid upon the professor's rival in love, until the latter was also attacked by the same jellyfish.
[edit] References
- British Marine Life Study Society - C. capillata and C. lamarcki
- Marine Life Information (UK)
- Marine Biological Laboratory (Massachusetts)
- Pacific Coast jellies
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