This is the question asked by Roger Seymour, a researcher at the University of Adelaide (Australia), and Stefan Hetz, a researcher at the University of Humboldt (Germany). After collecting and studying some specimens of this water spider in the Eider River, they have concluded that these animals are capable ofuse the air chamber as a gill to extract oxygenfrom the water, and thus remain hidden under the surface.
For the study, which is published inJournal of Experimental Biology, the team of researchers reproduced the conditions of a pond with warm water stagnant weeds on a hot summer day to discover how spiders react in the most challenging conditions. After watching the spiders build their air chambers, the scientists carefully zoomed in on an oxygen-sensitive optode (optical sensor) on the bubbles to see how the animals reacted. “Then it occurred to me that we could use the bubble as a respirometer to see how much oxygen the spiders are consuming,” Seymour explains.
Seymour y Hetz they first calculated the amount of oxygen flowing from the bubble and then the spider’s oxygen consumption rate. They found that the air chamber is capable of extracting oxygen from stagnant water even on a hot day. However, despite meeting the spider’s oxygen needs, the bubble continually shrinks as nitrogen diffuses back into the water, forcing the occupant to venture to the surface to replenish the air chamber.
How long, then, could the bubble survive before the spider has to go for air? By calculating the rate of nitrogen diffusion out of the bubble, the team found thatspiders could be quiet for more than a day“It is an advantage for spiders to be able to sit still for so long because they protect themselves from predation and do not alert potential prey to approach,” Seymour concludes.
