Lion's Mane the deadliest jellyfish on our shores
Depending on your definition of what a jellyfish is, between five and nine different kinds of these marine life forms and their look-alikes are regularly found in our inshore waters and on our beaches, and the biggest, most venomous and deadliest is the Lion's Mane.
The animal gets its name for the obvious reason that it has a mass of tan or fawn coloured appendages that are somewhat reminiscent of the mane of an adult male Lion. Young jellyfish tend to be pale brown; as they age they darken though shades of orange, red and deep purple.
The Lion's Mane Jellyfish has been in the news of late because several large individuals have been reported in Irish waters.
As shown in the image above, the margin of the jellyfish's bell is divided into eight distinct lobes. The animal's mouth is in the centre of the underside of the bell and it is surrounded by a tangle of short, brown oral arms; the lion's mane.
Long, trailing tentacles hang in clusters from under each marginal lobe of the bell. Each cluster can contain over 100 tentacles so there can be up to 1,000 in all.
The tentacles are armed with stinging cells. The animal's mode of feeding is for it to drift in the sea waiting for prey, like fish, to make contact with the mass of trailing tentacles. Once contact is made, the tentacles fire their stings in the expectation of stunning the prey so that it can be hauled up to the waiting mouth.
Small Lion's Mane Jellyfishes can deliver a painful sting if they brush against a swimmer. The sting from a very large, mature individual can require hospital treatment but is not usually life-threatening for people without specific allergies. How best to treat a jellyfish sting is controversial but the basic first aid dos and don'ts are pretty straightforward.
Do get away from the jellyfish as soon as possible. Do remove any tentacles attached to the skin by scraping with a stick. Do flush the affected area with lots of seawater. Do seek lifeguard advice or medical attention, if required. If available, do use a cold pack to relieve pain. Don't rub the affected area. Don't rinse the affected area with fresh water, pee, alcohol or vinegar. Don't put on a tight bandage.
Jellyfish stranded on the beach should be avoided as they can remain venomous for a few days after death.