Sometimes you stumble upon a ghost (and after realizing it is a ghost) and wonder what the real thing would look like. That’s what happens to me when I see a “sand dollar” on a beach. If you have never handled a sand dollar in your hand – you should. Walk on a beach looking for this odd flat shaped object embedded in sand. When you find it; you will be face to face with the most remarkably constructed organism.

Sand dollars are even more remarkable  when they are alive. Recently, I was able to get my hands onto some live sand dollars. Here is one ploughing through sand – it’s such a remarkable site.

(I will be posting another series on the walking mechanics soon).

We spawned some of the sand dollars and were able to get fresh eggs to fertilize and watch larval development. I will post the embryos developing under Foldscope soon; but here is a larvae swimming around. To take videos like this; I usually put my Foldscope down on the table with the attached iPhone; and setup focus using stacks of paper.

As you notice, the larvae looks nothing like a sand dollar. A remarkable series of transformations will convert the larva into an adult; which will eventually look like a sand dollar. Metamorphosis at its finest.

One trick to remember for things like larvae – is to use a little bit of a spacer between the top cover slip and bottom glass slide – so as not to squash the larvae. I used a little bit of silly putty on the four edges of the cover slip to create enough of a space for the larvae to swim.

Cheers
Manu

Ps: thanks to the Lowe lab (and specially Nat) for all the help and the samples. The series of upcoming posts will be developmental biology  of marine organisms – see through a Foldscope. Lots of fun ahead – so keep an eye out for it.