The AMAZING Horseshoe Crab!!

Behold the Horseshoe Crab! This extraordinary creature is both ancient and irreplaceable - for humankind and others. A small bird's very survival depends on the horseshoe crab. From ArgoFIlms, CRASH: A TALE OF TWO SPECIES premiered on PBS in 2008. This Emmy-nominated film was Produced, Directed, Edited and Narrated by Allison Argo. Magnificent photography by Michael Male, Keith Brust and Chris Szwedo.

[@marcuspurdy7611]

okay, now i know... these stuff need some good CBD from plantandhemp IMO, need to chilly the craby

[@stephenfennell]

0:47 "Their simple design" - come on, you mustn't say silly things like that, there is nothing simple about them. You'll be saying next that cells are simple. By the way, how can horsehoe crabs have remained the same for 400 million years (they date from the Cambrian, practically the lowest fossil-bearing rocks; www.livescience.com/51467-photos-moroccan-marine-fossils.html) despite the fact that the earth's environment has not been stable through that time? If the environment were _stable_, one could imagine that some species would settle into a stable genetic pattern that would go on for millions of years. If the environment doesn't change, there is nothing to push the horseshoe crab to change. If any offspring are genetically different, the environment that does the selecting would delete those offspring, since their unmodified brothers and sisters have a body that works perfectly well in that unchanging environment, so the modified offspring has no advantage, and indeed has a disadvantage. But the earth's environment has not been stable, certainly not over 400 million years. I would have thought that this crab would have had the usual random changes in its DNA, which would then have been picked over by natural selection (changes in the environment), so that some variants thrived in different environments better than others, and surely there would be bound to be changes to their structure over 400 million years? And yet their Cambrian fossils look the same as the living versions.
Furthermore, if these horsehoe crabs appeared suddenly in the Cambrian rocks, and nobody can find any organism that is similar-but-different in the layers below them, then presumably the DNA of their recent ancestor (whatever it was; a soft-bodied, unfossilizable species, hence unfound) had undergone a sudden fundamental change and became the horsehoe crab. And if their DNA _had_ recently undergone extensive sudden changes one would have thought it would not be stable DNA. How could DNA that was unstable enough to suddenly flip from some substantially different ancestor (different enough that it never even fossilized) into a horsehoe crab immediately chance upon a form so stable and successful that changing environments could not change it for 400 million years?