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Discover Magazine -
In the days before scuba tanks, people used to explore the underwater world with the aid of diving bells. These large open-bottomed chambers were dunked into the water, and divers used the air trapped inside them to breathe. The bells have been around since at least the time of Aristotle, but in the rivers and lakes of Europe, one animal has been using similar structures for far longer – the diving bell spider.
The diving bell spider is the only member of its group to spend its entire life underwater. But it still needs to breathe air, and it does so by building its own diving bell.First, it spins a dome-shaped web between underwater plants. Next, it rises to the surface and traps bubbles using the fine hairs on its legs and belly. It carries them down to its web and releases them, gradually filling the dome with air. After a few trips, the spider has amassed a bubble so large that it can fit inside.
The bubble acts as a home, a staging ground for hunting trips, and a nursery for its eggs. It’s also a gill. Human engineers eventually worked out ways of sending fresh air into their diving bells, either via hoses or sunken barrels. But the spider’s bubble does this automatically.There’s typically more oxygen in the surrounding water than in the air within the bell, so the gas naturally diffuses into the bubble. For similar reasons, carbon dioxide diffuses out and the air inside stays fresh and habitable. The bubble acts as a detachable gill that the spider can breathe with and leave behind. It’s like one of the spider’s own organs.
The spider’s diving bell is extraordinarily efficient at exchanging gases. Roger Seymour from the University of Adelaide and Stefan Hetz from Berlin’s Humboldt University have found that it can extract oxygen from even the most stagnant of water. As such, the spiders can stay inside their sanctuaries for more than a day without having to replenish them.Full story...Posted via http://batavia08.posterous.com batavia08's posterous
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