(Diving bell spider underwater inside its bubble gill where it retreats in oxygen-rich comfort to nosh. Via.)
The diving bell spider (Argyroneta aquatica) spends its life underwater—collecting air from the surface, carrying it below in the grasp of belly hairs, feeding it into a tiny sac woven of its own silk.
That much we've know for a while.
Now a new paper in the Journal of Experimental Biology describes how these air sacs are so much more than diving bells. They're also gills, drawing oxygen from the water:
After watching the spiders build their shimmering diving bells, the duo [Roger Seymour, Stefan Hetz] gingerly poked an oxygen sensing optode into the bubble to see how the animal reacted. Miraculously, the spider was unperturbed, so they continued recording the oxygen level. ‘Then it occurred to me that we could use the bubble as a respirometer,’ says Seymour, to find out how much oxygen the spiders consume. Taking a series of oxygen measurements in the bubble and surrounding water, the team calculated the amount of oxygen flowing into the bubble before calculating the spider’s oxygen consumption rate and found that the diving bell could extract oxygen from the most stagnant water—even on a hot day. Also, the metabolic rate of the aquatic spider was low and similar to the low metabolic rates of other spiders that sit waiting for prey to pass... Calculating the diffusion rate of nitrogen out of the bubble, Seymour and Hetz were surprised to find that the spiders could sit tight for more than a day.
You can see how it all works in the video below, complete with techno spider ambient track.
Knight, K. (2011). HOW THE WATER SPIDER USES ITS DIVING BELL Journal of Experimental Biology, 214 (13) DOI: 10.1242/jeb.060731