Diving Bell Spider Frustrates Evolution

Humans and critters are designed to live in their own ecological niches, and it usually does not go well to venture beyond them. We know that if we are going to venture into outer space, protection and bringing part of our environment are necessary.

The same for being underwater for more than a few minutes. Comparatively few people have experienced it, but many have seen television and movies involving submarines. The environment is brought along. On a smaller scale, people are submerged in a diving bell. When air begins to run out, they must surface.

European water spider, iNaturalist / hakkahamushi (CC BY-NC 4.0)

Some creatures as well as humans can take a breath of air and hold it, submerge, then come to the surface again and replenish. Consider the diving bell spider. It is unique in many ways, living most of the time underwater but needing to breathe air. It shoves its specially-designed abdomen into the air, which traps a small layer of air called a plastron. Then Diver Don takes it into the water and makes a cave in which he can live for days until it needs refreshing.

Evolution is supposed to include efficiency, but there is no believable way that a spider evolved to live underwater in the first place. Also, to build the cave of air requires repeated trips to the surface and back. Papa Darwin would cringe at all this inefficiency. Regular readers may recall that I believe our Creator has a sense of humor. This is occasionally displayed by creatures he made to defy evolutionary pronouncements, and the specified complexity in their designs. Mayhaps this spider is a kind of prank.

The hairs on the diving bell spider (and some other insects and spiders) create an air bubble through a mixture of both mechanics and chemistry. Mechanically, the surface the air bubble sticks to must be extremely rough. For the spider, the millions of hairs on its abdomen do this. This makes it easy for the air and hard for the water, with its high surface tension, to latch onto. But the surface also needs to have a low surface energy. In other words, it needs to be slippery to water. In the diving bell spider, this is achieved by the waxy coating on the hairs. This combination of factors allows the air molecules to form a stable, intact structure next to the spider’s surface without the water breaking up this air bubble.

To read the article in its entirety, see "Underwater spiders — Engineering marvel and evolutionary enigma."