Muddy buddy

On a rocky, muddy beach north of the city, with the tide going out, I was flipping rocks, watching muddy crabs and snails, all in shades of brown mud, when I saw a flash of bright blue. I had to move several rocks to track it down; a hurrying hermit with a blue right hand.

Blue knees, orange and green banded antennae. Too big for his shell. And lots of hair.

He looked like a Hairy hermit, Pagurus hirsutiusculus, except for that brilliant blue pincer, and a distinct black square on his carapace. Hairies are usually olive green or brown, chelipeds (pincers) and all, with small blue or white spots on the knees. The carapace is often striped.

I wrapped him in wet sea lettuce and rockweed and brought him home to examine him more closely.

From the back, on my hand. That pincer is so big, it drags along underneath him when he walks.

At home, in a tray of seawater, he was unhappy until I gave him back the seaweed. He hid underneath it and refused to budge, not giving me a chance to look at him cleaned up.

I let him rest a while, then dropped him in the tank. He looked around for a few minutes, then charged and fought with the largest male Hairy. Because he was a different species? I had to separate them to give him a chance to settle down.

Along came a large Grainy Hand hermit; they touched antennae, ("Hi, stranger!"), sat together for a while, peacefully. But he's definitely not a Grainy Hand, not with those striped antennae, although the Grainy Hands sometimes do have a bluish tinge to their pincers.

I came back to check on him after a couple of hours. He was still in the same place, but now he has a girlfriend, a smaller Hairy hermit. He's holding her by the edge of the shell, waiting for her to molt. She seems contented enough, resting, occasionally waving her antennae at him.

So he's a Hairy hermit. With a blue pincer. And the fight with the other Hairy was adult male rivalry.

But why is that pincer so blue?