Not crabs, in fact not even close. Chelicerates like the arachnids.
Have photoreceptors in their “tail” (telson).
Edit: For some taxonomic context, king crabs are closer than shrimp are closer than woodlouse are closer than barnacles are closer than bees are closer than myriapods (centipedes and millipedes) are closer than horseshoe crabs to being crabs.
![Advanced Evolution [BeetleMoses]](https://media.piefed.world/posts/TB/43/TB43mfsYiKQ85GL.webp){kind=link}
Fun facts about horseshoe crabs:
Edit: For some taxonomic context, king crabs are closer than shrimp are closer than woodlouse are closer than barnacles are closer than bees are closer than myriapods (centipedes and millipedes) are closer than horseshoe crabs to being crabs.
Thanks for the very specifically detailed order🫡
The question is though, are they in fact a horse, shoe, or horseshoe?
Fun fact: horse shoe crabs are more closely related to horses than shoes