How spiders breathe underwater for more than a day

The iconic diving-bell spider Argyroneta aquatica can live most of its life underwater. But how does it make sure it always has enough oxygen?

Now, scientists have discovered that the spiders use the diving bell like a gill to extract oxygen from water to remain hidden beneath the surface.

However, despite satisfying the spider's oxygen demands, the bubble continually shrinks because nitrogen diffuses back into the water, eventually forcing the occupant to venture to the surface to resupply the diving bell.

So how long could the bubble survive before the spider had to dash up for air?

Calculating the diffusion rate of nitrogen out of the bubble, Roger Seymour from the University of Adelaide and Stefan Hetz from Humboldt University, Germany were surprised to find that the spiders could sit tight for more than a day.

"The previous literature suggested they had to come to the surface as often as every 20min throughout the day," Seymour said.

"It is advantageous for the spiders to stay still for so long without having to go to the surface to renew the bubble, not only to protect themselves from predation but also so they don't alert potential prey that come near," he added.

The study has been published in the Journal of Experimental Biology.