Trapdoors in different genera

[Gogyeng]

Most of the ancient spiders of the family Liphistiidae (Mesothelidae - segmented abdomen spiders) construct rudimentary trapdoors, so trapdoor strategy is not novel evolutively. Specimens of the african baboons, Pterinochilus Lugarddi and the distant contender of the genus Typhochlaena (the popular Seladonia) are able to make trapdoors alike. So a natural question arises, what type of natural pressure could have pushed repeatedly this type of elaborate behaviour in different genera? Could it be a strategy against predation, from hymenoptera e.g pompilidae? Or is it simply related to a very particular habitat requirements (extreme droughts). What is there in common between all these contenders?

 

[EtienneN]

I'd think it has to do with similar climate and environmental selection pressures. Like trapdoors are much cooler underground than in an open mouthed burrow as well as being safe from predators. But also the soil has to be dry otherwise heavy rains would wash out the trapdoors from the ground. The segmented spiders of Mesothelidae have been around for millions of years and evolved "out of" trapdoor burrows. I'm pretty sure the oldest arachnids found in the fossil record are these type of spiders. They are technically called "primitive spiders", since trapdoor spiders came onto the scene of life way, way, way before any true spiders ever existed. It's a niche thing, too. These mygales (tarantulas and tarantula-like spiders) have adapted to their environments to be specialised hunters. Their lightning quick reflexes are what allow them to be so efficient at what they do. While of course other theraphosidae have this, the trapdoors utilise this strategy in a unique way that allows them to succeed in a place that is very inhospitable.

 

[Gogyeng]

Excellent reply. Thank you so much for sharing !