Sea urchins have several adaptations to help them survive. To protect themselves from predators, sea urchins will react immediately if something sharp touches their shell and they will point all of their spines towards the area being poked. They are also light-sensitive. This is why they are nocturnal.
How do urchins live?
Sea urchins live only in the ocean and cannot survive in fresh water. They are found from the intertidal to the deep ocean. The species that we are likely to use in the lab are either from the intertidal or the shallow subtidal. This may explain why these species are most gravid in the winter months.
Do sea urchins die when you touch them?
In extreme cases, such as numerous puncture wounds, the relatively small amount of venom from spines and pedicellarines can accumulate to cause severe muscle spasms, faintness, difficulty breathing, and death. The best way for divers to avoid touching sea urchins is to maintain good awareness of their surroundings.
Is it OK to touch sea urchins?
Urchins do have tiny pincers called pedicellariae that cover their body, and although they can deliver a paralyzing toxin to small predators they are too small to pierce human skin.