Posted by jlwile on October 11, 2011
The Eurasian diving bell spider (Argyroneta aquatica) is a truly fascinating animal. It lives almost its entire life underwater, but it breathes air. Of course, that’s not very unusual. There are aquatic species of reptiles (like sea turtles and sea snakes) and mammals (like dolphins and manatees) that must breathe air as well. There are even some species of fish (like the Betta – a favorite among aquarium owners) that must breathe air in order to live.1 These reptiles, mammals, and fish regularly rise to the surface to breathe the air that exists above the water. If they are unable to do so, they will drown. The Eurasian diving bell spider does something different, however. As you can see in the video, it brings the air underwater and stores it in a large bubble, which is usually called its “diving bell.”
How does it accomplish this feat? It spins a silken web underwater that holds the air. That way, the spider doesn’t have to return to the surface to breathe. It just has to return to its diving bell. As you can see in the video, once the spider has caught prey, it expands the bell and crawls inside so it can eat its prey in the comfort of an oxygen-rich environment.
While this is all quite amazing, it is not new. The habits of Eurasian diving bell spiders and other, similar species have been known for quite some time. However, up until now, many scientists have thought of a spider’s diving bell as the equivalent of a scuba tank: a one-time supply of air that must be continually replaced. Not surprisingly, new research has shown that it’s significantly more complex than that!
Researchers from Australia and Germany recently reported that the spider’s diving bell is more like a “physical gill” than a scuba tank.2 This is because the silk that holds the air inside is woven so that the oxygen dissolved in the water can seep into the diving bell. That way, as the spider uses up the oxygen inside the diving bell, it is replaced with new oxygen from the water that surrounds the bell.
How good is this “physical gill?” The authors say that their research shows
…the spiders produce physical gills capable of satisfying at least their resting requirements for O2 under the most extreme conditions of warm stagnant water.
Warm, stagnant water holds less oxygen than cool, flowing water. Thus, the spider’s physical gill works well, even in low-oxygen conditions!
As a result, they say, a spider can rest inside its diving bell for more than a day without needing to renew the air inside! In fact, their report indicates that as long as the spider is resting, the main reason it must renew the air is not because it needs more oxygen. Instead, since the bell allows oxygen to seep in, it also allows nitrogen to seep out. The air inside the bell starts out as more than 70% nitrogen, so the loss of nitrogen causes the bell to get smaller over time. Eventually, the spider needs to replenish the air just to keep the diving bell from getting too small.
I am an avid scuba diver, and I would love to have a scuba tank that could replenish my oxygen supply while I am breathing underwater. That way, I could spend even more time exploring God’s incredible underwater creation. Unfortunately, human technology is a bit primitive compared to what this spider can do.
1. John Dawes, Complete Encyclopedia of the Freshwater Aquarium, Firefly books, 2001, p 232.
Return to Text
2. Roger S. Seymour and Stefan K. Hetz, “The diving bell and the spider: the physical gill of Argyroneta aquatica,” The Journal of Experimental Biology 214:2175-2181, 2011.
Return to Text