Adaptation

Sicarius hahni has acquired some unbelievable adaptations to improve its ability to live in deserts and sandy places in southern Africa. As I have mentioned before, it is able to bury itself under sand, and hairs protruding from its exoskeleton, called setae, make it possible for sand particles to stick to its cuticle. Interestingly, this is not the only desert-dwelling spider that has acquired these “hairlettes” that allow for sand particle retention. This characteristic has been documented in six unrelated spider genera, such as Homalonychus, but is still a rare enhancement for spiders. Convergent evolution is hypothesized to be the reason this adaptation has occurred in these unrelated genera. This term refers to the acquisition of the same trait in unrelated organisms that share similar environmental characteristics. In this case, the environments of all these species are regions with lots of small sand particles.
In the picture above, microscopic images of the cuticles of two different spider species were taken. These images were taken after the spiders had been in association with sand particles for a certain period of time. The image on the right is taken from a spider with setae (or hairlettes) that occur much more densely than the spider on the left. As a result of this, more sand particles adhere to the exoskeleton of that species, and it can camouflage in sandy areas much easier. Pictures below show how amazing it looks when the spider is completely covered in sand.

Many other organisms, such as earthworms, also have these hair-like structures on their body, but are used differently when interacting with their environment. Although this spider has three pairs of legs that are used for walking around, this species is mostly sedentary. It likes to remain partially or fully covered in sand, waiting for prey to wander too close. Another adaptation this spider acquired is a flattened out body pattern, which makes it easier to dig and cover its entire body surface with sand. Even when it is not buried, the spider is built to be so close to the surface it is walking on that it would be hard to pick out in a sandy environment.

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