A Urchin curiosity I noticed

PeterEde · Mar 22, 2022

I have a long spine urchin and I noticed recently if I move my glass cleaning magnet near the urchin that the spines steer towards the magnet.
Are they drawn to magnetism or is the urchin that aware of a possible danger and actually steers the spines towards a possible enemy?

blaxsun · Mar 22, 2022

Hard to say. You could try some non-magnetic objects to see how it responds.

Tired · Jul 20, 2022

Since this never got answered: that's typical longspine urchin behavior. They direct their spines towards potential threats. I have a video somewhere of me moving my hand towards a large wild longspine urchin, and you can see all the spines on that side moving to point at my hand.

PeterEde · Jul 20, 2022

Tired said:
Since this never got answered: that's typical longspine urchin behavior. They direct their spines towards potential threats. I have a video somewhere of me moving my hand towards a large wild longspine urchin, and you can see all the spines on that side moving to point at my hand.

For a critter with no eyes its sense is amazing

Hairyteeth · Jul 20, 2022

I believe that they have photo receptors in their feet so they can kinda see your hands coming lol

Tired · Jul 20, 2022

They definitely have some ability to see light and dark, and probably simple shapes. They react if you wave a shadow over them. Likely they don't see much past that, though.