Sea urchins, albeit having a limited and ancestral sensory system, can show a complex behavior when escaping a predator. These marine invertebrates tend to move slowly and with unpredictable movements, but when they smell a predator, they escape following a ballistic motion —straightforward, quick and directional— to escape the threat.
Click here for original story, Study reveals the complex behaviour of sea urchins regarding the predators’ threat
Source: Phys.org