Layers of complexity

This photo was taken near Kasitsna bay, where we occasionally run programs.  At first glance the subject of the photo appears to be a striped hermit crab.  The picture itself isn't bad, the colors turned out well and the lighting is nice, but if you look again at the hermit crab you might start to notice some things.

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  First of all, the shell that the hermit crab is using is red.  This is because the hermit crab is living inside a wandering sponge.  There are some species of sea sponge that will attach themselves to snail shells and slowly consume the shell until nothing is left but the sponge. Once the snail is dead it is not uncommon for a hermit crab to move in and allow the sponge to continue its wanderings.  

Not many things eat sponges; they are full of sharp spicules that can wreak havoc on a creature's digestive tract.  In an earlier post I covered mollusks and talked a little bit about Nudibranchs, which often eat organisms that nothing else will.  The yellow blob you see sitting on top of the hermit crab is actually a False Lemon Peel Nudibranch that specializes in eating sponges.  

To recap, a wandering sponge began growing on a snail shell which was then inhabited by a hermit crab.  The sponge attracted a nudibranch which is now eating the hermit crab's home.  If you've been following this blog you should be able to name two of the three phylums represented in this photo.  Athropods are represented by the crab, Mollusca by the Nudibranch and Porifera by the sponge.

Even after three seasons of doing this, I'm still consistently amazed by the things that show up on our beaches.