Self-Spun Submersible

Diving bell spiders are the only spiders in the world that spend most of their lives underwater. Since they don’t have gills, they live inside a self-spun submersible, a kind of underwater bubble that holds the oxygen the spiders need to breathe.

The spiders do surface to collect oxygen to replenish these air bubbles, called “diving bells”. Science News reports that

They trap the air between their back legs and abdomens, later adding it to the bell. This keeps the diving bell from collapsing.

Scientist Roger Seymour of the University of Adelaide has been interested in these rare spiders since he was a kid. He traveled to Germany to study them with Stefan Hetz of Humboldt University.

After watching the spiders build their shimmering diving bells in the lab, the duo poked an tiny 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.

Essentially, the researchers found that the bell is acting as a gill for the spiders, grabbing oxygen from the water. The bell is able to sustain the spiders for up to 24 hours! The spiders then resurface not for air, but because the bubble continually shrinks due to nitrogen diffusing back into the water.

The research was published last week in the Journal of Experimental Biology.