Brittle Stars can Detach their Arms!

Look who is hiding in this redbeard sponge that washed up on the beach: a spiny brittle star. There are actually several in this sponge. These echinoderms have 5 long bristly arms with spines and tube feet that can capture phytoplankton and microscopic debris. And here’s a crazy defense strategy: if they think they are in danger, they can drop one of their own arms as a way to confuse the predator. Lets see that in slow motion: the brittle star simply disengages an arm. The arm will grow back, and if the detached arm has part of the original disc, an entire new starfish can be regenerated! In another cool adaptation, there are light sensors in these arms that help the brittle star seek the relative safety of deeper parts of the sponge. We’ll put it in the water with the sponge so it feels safer.