According to my marine invertebrates book, collector urchins (Tripneustes gratilla) gather algae, shells, and other material on their spines. Why they do this is not entirely clear. It might be for disguise, protection from the light, or even to store food. These urchins are quite common in the shallows and their adornments are many and varied.
Posted in response to Becky’s October Squares challenge theme of ‘Past Squares – Spiky.’ See more responses here.
Graham's Island 
How extraordinary. I enjoyed this collection of collectors – I should think you could add further to this collection over time as it is such an interesting theme with great visual appeal.
LikeLiked by 1 person
I’ll probably keep taking photos of them and do another post somewhere down the line.
LikeLiked by 1 person
I was thinking, poor guy with the hairband stuck on his back until I read the text.
LikeLiked by 1 person
They do end up with a wide variety of items on their backs.
LikeLiked by 1 person
Intriguing – and just how do they do it too?!
LikeLiked by 1 person
I never knew that! Great photos Graham 🙂 🙂
LikeLiked by 2 people
I hadn’t really appreciated what was going on with them, but once I read up a bit, I started looking out for them whenever I swim.
LikeLiked by 1 person
Very nice series of images! Enjoyed seeing them!
LikeLiked by 1 person