Diving Bell Spider never need to come to surface for air, they use water dissolved Oxygen for living
The spiders are named for their sub-aqua webs which they fill with air in order to breathe underwater.
Scientists studying the European arachnids measured oxygen levels inside and around an air bubble web.
They found that the bubble acted like a gill, extracting dissolved oxygen from the water and dispersing carbon dioxide.
To fill the “diving-bell” webs with air so they can breathe, the spiders use fine hairs on their abdomen to transport bubbles from above the water surface.
“As the spider consumes oxygen from the air in the bell, it lowers the oxygen concentration inside. The oxygen can decrease below the level of dissolved oxygen in the water, and when this happens, oxygen can be driven into the bubble from the water,” said Prof Seymour.
“The carbon dioxide that the spider produces is not a problem at all, because it is readily dissolved in the water and it never builds up.”
Unlike animals that exchange oxygen and carbon dioxide across gills however, the spiders have to contend with the other gases in the air they transport.
“If you absorb one gas from a gas mixture in a collapsible bubble, the remaining gases must increase in concentration,” explained Prof Seymour.
“Because oxygen is taken from the bubble air, and CO2 does not build up, it causes the nitrogen in the bubble to rise in concentration,” he said.
As the nitrogen disperses from the bubble, the bubble collapses but it does so slowly, roughly over the course of a day according to the scientists’ results.
“The spider is able to remain in the diving bell on very hot days, when its metabolic rate is higher than normal, if the water is well oxygenated,” said Prof Seymour.
This means the spiders can return to the surface infrequently, avoiding the risk of being caught by predators such as birds.
Source: BBC,Wikipedia, Google images