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Rare sighting of a lion’s mane jellyfish in Tramore Bay PDF Print E-mail

There was a rare sighting of a lion’s mane jellyfish in Tramore Bay recently reported to the Eye On Nature section of the Irish Times Weekend Review.

The sighting, reported by a Mr Ray Cullinane of Tramore described how he "swam over a large and scary jellyfish in Tramore Bay. It was about two feet across, had a white crown and was brown farther down." He added that "The flat tentacles were thin, and three or four feet long".

Officially known as Cyanea capillata, the lion’s mane jellyfish emits a poisonous sting and is the largest known species of jellyfish.

Its range is confined to cold, boreal waters of the Arctic, northern Atlantic and northern Pacific Oceans, and is 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. The ribbon worm Lineus longissimus may be even longer, growing to 55 m.

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 localised 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.

A cold-water 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 life-span.

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.

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.

Swimmers in Tramore Bay need not fear however, it seems that sightings of the incredible lion’s mane jellyfish are a seldom occurrence in the area.


 
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