The Scuba-Diving Spider That Could Teach Us A Thing Or Two About the Sport!
The countless ways in which animals and insects adapt and thrive in environments that would normally be hostile to them is amazing. There are the tiny insects and bacteria that have adapted to living without oxygen, the lizards that shrunk in size when food sources dried up and now, a 'Scuba diving' spider that lives underwater.
Found largely in stagnant fresh water ponds in Europe and Asia, the Diving Bell or Water Spider is the only arachnid species that spends its entire life underwater. However, since it does not have gills, the only way it could breath would be by constantly coming to the surface for air - Not really practical given that it would leave the spider no time to seek out the underwater insects and crustaceans, it feeds on.
Therefore, the tiny spider that measures only between 9-15mm came up with the brilliant idea of spinning a silken scuba suit or in this case a bell, that is much less cumbersome that the one invented by humans and also, much more efficient. The size of the bell differs depending on if it is a male spider in which case it is smaller and encases only its abdomen or a female that tend to weave bigger bells or ones that can be stretched, to accommodate eggs or prey. In fact, most females spend their entire lives inside this bubble emerging only, to catch prey or refill air.
Once the air sack is ready, the spider scrambles to the surface and lying on its back with belly upside down, it crosses the last pair of its eight legs and traps air bubbles between them and the fine hair that lie atop its belly. It continues this routine a few times, until the sack is full and then heads back underwater.
Because the spider leads a relatively sedentary life, it does not need that much oxygen - However, it does need more than the amount that is trapped inside the air sack. But, and this is very it gets really interesting, the spider does not constantly have to head to the surface for a refill, like humans scuba divers do - They have figured out a refill mechanism underwater, by using the sack as what scientists refer to as a physical gill, as opposed to an anatomical gill, which is what most marine life have.
Here is how it works - As the spider breathes in the oxygen from the air trapped in its sack, the concentration of the gas inside the bubble gets to a lower level than that present in the surrounding water - This in turn helps draw in oxygen from the water into the bubble until the concentration levels are equal a phenomenon that scientists call diffusion. As for the carbon dioxide it breathes out? That just dissolves in the water and dissipates.
This could continue forever, except for one pesky gas - the high concentration of nitrogen that is present in our atmosphere. Because the level of the gas is not as high in the water, it slowly starts to seep out for the same reason the oxygen is seeping in. This causes the bubble to eventually shrink and collapse, forcing the spider to scramble to the surface for a refill - Something that the scientists estimate happens only once a day!
Of course a creature this amazing cannot escape humans for too long. Scientists say that these Eurasian spiders are becoming rarer to find - Part of it is due to loss of habitat and the other, aquatic enthusiasts, especially in Germany seeking them out to study their amazing underwater survival abilities!