Cannibal Urchins

Six sea urchins of different types and sizes were living harmoniously in my 5 gallon tank while I was getting the 20 gallon tank ready for their return.  My car was not working for a few days so a trip to the beach for sea grasses had to wait.  I guess I waited too late because one morning I found the pink sea urchin on top of the black sea urchin.  After a second look I realized it wasn’t just passing over the purple guy on a trip around the tank…it was eating him from top down. I couldn’t imagine the black one being dead; it looked so lively the night before.  Was the pink urchin that hungry?

I quickly got my wooden spoon (no one getting a spanking!), and pryed the pink one off of the black one.  The black one was missing spines and it was still alive!  How could you do such a thing little pink thing?  I quickly moved the black one to the big tank.   He was still moving around.  He didn’t seem dead, just exhibiting male-patterned baldness.

I’ve heard/read that sea urchins replace their spines.  They’re from the same family as sea stars, echinoderms, which we all know replace their arms when they’re broken off. 

Well, the black urchin has been in the big tank for a few days by himself.  He seems fine; actually thriving.  He’s eating well, climbing on the side walls of the tank, playing with sea shells (you know how they cover themselves).  I added the apple murex eggs and the two apple murex snails.  I noticed a new snail walking around and a new anemone looking thing.  I’ll keep checking on that creature.

We did go out that afternoon to the beach to get a bag of sea grass.

Stay tuned…I can’t wait to see what happens to the sea urchin.  Will it grow new spines?