Blue blood and dinner forks

My hermit crabs have come down with spring fever. Most of the larger males are courting; some trying to convince a female to allow herself to be carried, others, each clutching his chosen mate, sitting on high places, waiting for her to molt.

Hopeful parents, on top of the big abalone shell. Waiting.

And as always, there has been some competition for mates, a few tug-of-wars with the unfortunate female as rope, a couple of frantic chases, and, sadly, a few duels; pincers at a quarter inch. A smaller male was the loser in one of these battles, and limped away with two legs on one side, none on the other. And no pincers. I thought he would die, but he's tough.

He still gets around; slowly, dragging his over-sized shell behind him. He rests in the shadow of a kelp holdfast or in a tangle of eelgrass roots, out of the way of his more active neighbours. But his blue and orange flags still wave happily, he manages to find food and eat it, even without his hands.

What's more; twice I've seen him "flirting"; face to face with a female, trying to hold the lip of her shell in the customary fashion, without success, not having the required pincers. The girls were not impressed and soon wandered away.

There's hope for him; if he can hold out until the next time he molts, he will have grown back some of the missing limbs.

I've been keeping an eye on him, making sure food lands in his vicinity morning and evening, admiring his persistence.

I noticed a blackish spot on his maimed side. A lump, glossy blue-black, the blue-black of a mussel shell. A parasite? Or what? I kept watching, trying to get a photo or get a clear view with my hand lens, worrying.

With the extra light from the flash, the addition is deep blue.

I finally got close enough to see; it's a forming pincer arm, still coiled, still without movement, but with all the parts; joints and pincer tips, well formed. Hermit crab blood is blue, which may explain the colour.

The white ovals behind it are the stubs of the missing two legs.

The stub of one leg is clearer here.

How does a hermit crab, bereft of hands, manage to eat? This guy holds onto something solid with one back leg, drags over a chunk of food with the pointed tip of the second leg, and then uses his first set of mouthparts, or maxillipeds, to grab it and bring it to his mouth.

The first two maxillipeds serve as forks.

He's lucky to have three separate sets of maxillipeds; the inner two sets do the work of jaws. So he won't starve.