A friend for Boy Blue

A month ago, I was surprised by a new development in my aquarium; Hermit Rex seemed to have a girlfriend! At least, he was carrying a smaller hairy hermit around, none too gently.

... Or were they fighting? I shouldn't be jumping to conclusions. And wasn't the small hermit too young for breeding? So I waited and watched, and Googled.  "Hermit crab mating." "Hermit crab breeding." "... reproduction." I kept finding the same answer, over and over; "Hermits don't breed in captivity." And no information on how they behaved in the wild.

I kept watching. Over the next few days, Rex carried around the little one. He didn't eat much, and he was snappy with anything that came close; crabs, hermits, even snails. Everywhere he went, he held the edge of his  captive's shell with the smaller cheliped. She (I still thought of her as the female) didn't seem to mind; she didn't struggle. At the most, she occasionally stretched, as she is above. Mostly, she just rested.

Then, on the White Rock beach, Laurie found me another couple, more equal in size.

I brought them home and watched. The next day, the big one had released the little one, who had then left her shell. So was this a battle for shells? But he didn't seem interested in the vacated shell; it was far too small, anyhow. When he continued ignoring her, I dumped him in the aquarium, and left her in a sheltered spot to recover and get back into her shell. Unfortunately, she died that day.

I kept on looking for info, but still found nothing useful. (Except all that background on crab/hermit species.)

Rex abandoned his friend and soon found another, and another; he carried each one around for a few days. None of them protested.

The other day, on Centennial beach, I picked up an empty whelk shell that I thought would be just the right size for Rex's next suit. When I brought it home and dropped it in the aquarium, two pincers poked out; it was occupied!

Hermits are social beings; they love a crowd. And my lot are multiplying, whether by stowaway immigration or by reproducing, I can't tell. But all but Rex, the hairy hermit, and Boy Blue, the grainy hand hermit, are tiny. And all the tiny ones are hairy. Boy Blue is the odd man out.

When the whelk shell hermit poked its eyestalks out, Boy Blue raced over to it, waved tentacles, (hers were red, just like his), "shook hands", touched noses. And grabbed onto that shell.

Boy Blue, gf, with bonus polychaete worm, slipper snail (on whelk shell), limpet on glass, and various amphipods.

The two of them retired under a piece of kelp, and sat there for two full days. Boy Blue, unlike Rex, kept on eating, sometimes holding his friend with a pincer, sometimes with a walking leg. Then he left her alone and went about his life again. She retreated into the shell and lay still for another day or so. Now she's out and wandering around.

I tried Googling again; I had to know; was this normal mating behaviour? I saw no sign of the females (if they were females; how could I be sure?) molting, as female crabs do before they are able to mate. Wouldn't she at least have to come out of the shell?

What I found out, finally, I'll post tomorrow.