Karen Boswarva turns her attention to a tiny marine insect with a superpower when it comes to breathing underwater
OCEANSCIENCE
Envy the springtail
Karen Boswarva turns her attention to a tiny marine insect with a superpower when it comes to breathing underwater
It was during a recent visit to Orkney’ s most northerly island for the annual North Ronaldsay Science Festival that I joined a wellness walk led by the RSPB Species on the Edge team.
We gathered in a small group and headed to the white sandy shores of South Bay. It was a stunning spring day, skylarks were singing and the sun illuminated turquoise waters as the waves broke gently on the ebbing tide. After a moment of calm the group scattered. Some went beach combing, others dipped toes into cool wet sand. I was drawn to some rocks fringing the lower shore, specifically the life contained in the small pools, now enduring the long wait for the tide to return.
As I peered under the surface at the lush green seaweeds, I spotted one of my favourite sights of spring. The comical whizzing and whirling of springtails! Skittling over the surface in a haphazard manner as soon as the slightest breeze hit the pool’ s surface. Forming and breaking bonds with their neighbours as they go.
Springtails or Anurida maritima are a marine insect related to crustaceans. They are slate grey blue in colour and grow to a whopping 3mm … yes, they are
“ I spotted one of my favourite sights of spring”
tiny! Springtails are found throughout the northern hemisphere in the upper intertidal zone. You’ ve got a good chance of seeing them all over the UK from March to September. But its best to look when the sun’ s out.
Despite the name, this species has lost the use of its springing organ. Instead, they‘ walk’ across the surface film of water( when it’ s calm). Any motion sends clusters of springtails hurtling round pools like dodgems till they collide and form even bigger groups.
They survive in the extremes of the intertidal zone due to some fascinating adaptations.
A springtail’ s body is made up of chitinous cuticles covered in lots of tiny white hairs, and wax coated macro tubercles. When exposed to air, a layer of water is trapped beneath, preventing dehydration. This enables springtails to forage on the upper shore for dead animals such as molluscs and barnacles during the low tide.
One hour before the tide begins to rise, springtails will aggregate into‘ nests’ either tucked in rock crevices or burrowed in the weed and sediment. Their hydrophobic( water repellent) hairs then act as a waterproof layer. As springtails submerge, a stable and compressible layer of air forms around them( a bubble) which is resistant to pressure and surfactants, the chemicals that decrease surface tension.
Now this is where it gets super interesting! And I promise you don’ t need to remember your gas laws. The air bubble contains enough stored oxygen to last only one hour, yet springtails will remain submerged for three to four hours hours. So how do they not suffocate?
Somehow, the air bubble lasts three times longer than stored oxygen allows. But how?
Scientists identified a decline in ambient oxygen in water close to submerged sprigtails. A micro needle electrode was used to measure oxygen partial pressure profiles. The decline is caused by an inward diffusion of oxygen from seawater into the air bubble. Water is a poor source of oxygen; the content of oxygen in seawater is 30 times lower than in air. However, the air bubble acting like a compressed gas gill, exploits the oxygen within seawater. The springtail breathes through its cuticles, regulating its oxygen uptake from both the air bubble store and the surrounding seawater throughout the time it’ s submerged. This ensures its survival until the tide finally ebbs and it can breathe air again. I’ d imagine the divers are thinking“ If only we could do that!” �
Spring break: a massing of springtails in a rock pool
Springtails have two strategies for breathing underwater
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