Help us idenitfy who lives on ancient Horseshoe crabs!

You are walking along the beach on a sunny spring day. But what is that? Something is moving slowly out of the water. It looks like a sea monster, covered in barnacles and algae. Creepy? Ugly? No, its home! At least for all those critters that live on Horseshoe crabs. Horseshoe crabs have been around for more than 250 million years, unimpressed by dinosaurs and ice ages. Since then, Horseshoe crabs have played a key role in coastal ecosystems: the eggs are eaten by shore birds, juveniles are food for sea turtles, and adults aerate the ocean floor through their digging activity.

Horseshoe crabs may serve another important function: as substrate for many invertebrate species such as mussels, barnacles and snails. Many marine species require hard substrates to live on, and such substrates are historically rare on the predominantly sandy beaches of the Eastern US. 
In more recent times, docks and boats may offer new opportunities for intertidal species - but what about animals that do not like the tidal influence? Are there even species living on Horseshoe crabs that we have not discovered yet?

Help us decipher which epibionts live on Horseshoe crabs! Take clear pictures of Horseshoe crabs and their "tenants" when you see them on the beach, and post them via twitter or Facebook. Just let us know when and where you saw the crab. That's it.
In return, we will post the best pictures on our website and Facebook and explain every epibiont that you discovered on the Horseshoe crab. New species will be featured on the website, and we would like to name our most successful discoverers on Facebook.

With your help, we will be able to address the following questions:
Which region has the highest diversity of Horseshoe crab epibionts? When are the crabs fouled the most? When the least?
Moreover, we will build a valuable resource for school classes, beach walkers and everybody else who ever wanted to know: What is that thing sitting on this Horseshoe crab?

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