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NATURE Sandhoppers’ nighttime display

Outdoor Living
Fairies ag damhsa on the shore

Marine Life
John Paul Tieran

Séamus Mac an Iomaire, in his benchmark book on shore life, called them an tonachán, but a man in Connemara advised me yesterday of a different name: an míol críonna. Requiring a slight pause to achieve the correct pronunciation, ‘míol críonna’ sounded nicer we thought, but it is less than accurate, as it really refers to a wood-louse.
His friend offered a different version again, but none of us liked that name; and I’ve already forgotten it, although I suspect it was dreancaid mhara (sea flea). One of the younger members of the party knew them as ‘the sandhopper’, which everyone agreed upon.
I told her to throw the piece of fheamainn (which I had given to her to hold while I explained to the rest how the tonachán lives underneath it) into the fire when she goes home – to listen to them explode. Her mother looked startled; I clarified that I was referring to the air bladders exploding, not the tonacháns.
Noting the air bladders, the man corrected my description of the piece of seaweed she was holding as fheamainn bhoilgíneach. Fheamainn, of course meaning seaweed and bhoilig meaning stomach. Which is what someone a long time ago thought the little air bladders which occur on Fucus vesiculosis, or bladder wrack, looked like; little swollen stomachs.
But back to the tonachán, or míol críonna, or sandhopper. Most people’s first encounter with these cryptic crustaceans is a less scientific and more enchanting experience; an unforeseen after-party maybe, late on a summer’s night. Like this time last year, when we chanced on thousands of them, pulsing and bounding – ag damhsa – to an unheard beat, on a shore which was turning lighter shades of grey as the rising sun threatened to reveal us before we reached home.
The sandhopper resembles a tiny prawn or shrimp, which remains burrowed in the sand or under wrack all day. At night, this leaping activity is simply an excited feeding state, although scientists aren’t sure why exactly it behaves like this. It leaps or hops up to a foot or two off the ground by sudden outward flicks of the lower half of its abdomen, with no control over the direction it lands in.
All this of course we knew, so we didn’t rise the next morning wondering whether we should risk being scorned for our state of sobriety by sharing tales of fairies dancing on the beach the night before … but how many have?

John Paul Tiernan
Louisburgh, runs, a website dedicated to the creation of knowledge of our marine ecosystems. He is currently studying for an MSc in Marine Science.

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