There's 30 different species of jellyfish in Irish coastal waters, but there's one lad in particular you should be wary about

It's the season for jellyfish spotting on Irish beaches. Dr Tom Doyle from the School of Biological, Earth and Environmental Science in UCC, who also runs The Big Jellyfish Hunt, joined Drivetime on RTÉ Radio 1 to tell us more about these creatures. (This piece includes excerpts from the conversation which have been edited for length and clarity - you can hear the discussion in full above)

Doyle believes many of us find jellyfish so fascinating because they're alien-like. "They don't have any structures such as arms or legs or even eyes or heart or lungs, so I suppose it might make us wonder. Then, many of them are round, they don't have a left or a right side like we have a left and right hand, and then they can be completely transparent. I guess it's that kind of almost alien-like experience that you see on the shore, but it's probably the fear of being stung, if I'm completely honest. That's what most people are fascinated by.

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From RTÉ 1's Six One News, beachgoers urged to be vigilant as man o' war jellyfish spotted in Irish waters

So let's meet the Irish jellyfish. "Believe it or not, there's actually over 30 different species of what we call jellyfish-like animals in Irish coastal waters", says Doyle. "Some of these are completely different things that most people wouldn't see and some of them are really small that you wouldn't see. Of the true jellyfish, the ones that we're talking about in terms of the round and they have tentacles and they sting you, there's about six common ones that most people will encounter, but then there's another four or five large jellyfish-like animals that we encounter as well on our shore."

The number one lad? The moon jellyfish, which Doyle says everybody would be very familiar. "They're almost completely transparent, they're about the size of the size of your hand. They've got these four pink and gonads or rings in the center of it. Most people will recognize those. They're the type of jellyfish most people would pick up and fling at each other. They have a very mild thing, if any. That's the common jellyfish. You can see thousands of them washed up on our beaches because they form these spectacular aggregations or swarms or blooms of jellyfish."

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From RTÉ Lyric FM's Nature File, how jellyfish were once ahead of the crowd when it came to evolution, being the first group of animals to develop a nervous system

Then, there's the compass jellyfish. "This is probably your most striking jellyfish. It has these 16 brown, triangular shaped markings on the bell that make it look like a compass rose, so when you look straight down on this, it does look like a compass. It has these long trailing tentacles and these other structures called oral arms hanging underneath. They can be really long, they can be a metre, a metre and half in length, so these are large jellyfish and there's been some fantastic footage posted on YouTube where you can have tens or hundreds of these swimming around. They're a south, west and northwest coastal species."

The barrel jellyfish tends to hang around in the sunny southeast. "The one that most people probably wouldn't be familiar with, unless you live in Wexford, would be the barrel jellyfish. This is the largest jellyfish in Irish waters. It's extremely robust, it can have a large dome shell or shape, and it's white in colour. When these wash up on a beach down in Wexford, it can be quite scary because it almost looks like an octopus or something and that's where it gets its Latin name."

When it comes to stings, these jellyfish are fairly harmless, says Doyle. "You don't need to be worried at all because their sting will be something like a nettle sting. The barrel jellyfish doesn't sting at all because it doesn't have any tentacle spot. It does produce a mucus so unless you're repeatedly handling barrel jelly fish, you should be all right."

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From NUI Galway, how to deal with a sting from a lion's mane jellyfish

On the other hand, there's the lion's mane jellyfish. "The lion's mane is our most venomous jellyfish", says Doyle. "Unfortunately, Dublin Bay is a hotspot for the lion's mane jellyfish because of the temperature of water there and it's linked with the Irish Sea. The good news is that they don't form these spectacular aggregations or blooms that you see for the common jellyfish. You might see a thousand common jellyfish, but there might only be one lion's mane jellyfish."

They're also big fellows. "The lion's mane can get up to a metre in diameter, but I've rarely seen them bigger than 60, 70 centimeters in diameter. They have nearly a thousand tentacles that can be three or four metres long. These are the jellyfish to watch out for because they're here every year. They are a native species and they do pack an extremely painful sting. As I said, you typically just found them in Dublin and maybe up the east coast, but we've certainly been getting reports of them off Mayo and Galway and Co Clare as well over the last couple of years."

What's Doyle's advice if you do get stung by one of them? "The traditional recommendations are that you apply saltwater, and then you apply a cold pack. But we've carried out several scientific experiments on this over the last couple of years, and what we've shown is that you should subject it to a two-part treatment. One, you rinse with vinegar, which stops any further venom being injected into your body because you might brush off a tentacle or there still might be some tentacles still on your arm or leg.

"But then the next thing is to apply heat, so a hot pack of 45 degrees. We're not talking boiling water here. It's just hot bath water that you apply then, and that will relieve the pain.