Après-orgy

The orgy is over.

Among the couple of dozen hermit crabs that came home with me (under false pretenses) a week ago, were three couples preparing to mate. It's a bit early, but we have had a warm winter; maybe they're anticipating an early summer.

When breeding season comes around, the males capture a female, usually smaller. They get a good grip on the edge of her shell with their large pincers, and hold on, never letting go, even for a moment. The female usually just retreats into her shell, and apparently waits.

Male trying to climb a wall, female along for the ride.

But inside the shell, she is very busy. She lays her eggs, gluing them to one side of her abdomen, ready to be fertilized. As she does this, she releases pheromones, which influence her male to hold on tighter. Sometimes, they also attract other males; one of my couples turned for a while into a threesome, with two males playing tug-of-war over her. The larger one won.

Couple resting in a bowl. The male is the one upright. Females often are held upside-down.

Whether it was the effect of the pheromones, or just because it was time, the rest of the hermits in the tank got the idea, and every time I looked, I saw another couple linked together. There are three species of hermits in the tank; all three were pairing up.

When the female is ready, maybe after several days of being dragged around, she partially leaves her protective shell, the male follows suit, and they mate. I have never seen this happen; it's over quickly and I'm never there at just the right moment. And then the courtship is over and done with; the male goes his own way and leaves the female to deal with the family.

It's not an easy job. Ma Hermit has a humongous "baby bump" attached to her abdomen, and it can't be comfortable. She wriggles around in her shell, trying to fit, sometimes jerking back and forth, sometimes pulling half out of the shell and fanning the eggs, then making repeated attempts to squish herself back in.

Ma Hairy Hermit, with a mass of pink eggs.

She gives up, and goes searching for a new shell, something a bit more roomy. As I watched the shell battles, various females competing for the largest shell in stock, I caught on and donated a handful of the largest mud snail shells I had; they were all occupied in a couple of hours.

Sometimes they forced bigger males out of their shells. They, in turn, went shell shopping, having to settle, as often as not, for a shell too small for their taste. They got in fights; I watched one male drag another out of his shell and move in. The evictee was too big for the abandoned shell, and panicked, running around and over his old shell, snapping at the thief, refusing to go looking elsewhere. Eventually, he got his way; the usurper gave him his shell back, and went off to find a more co-operative donor.

Besides finding a good maternity shell, the mother has to keep her eggs healthy. Like a "true" crab, she brings them out into the water and fans them, to remove waste products and aerate them. And she has to keep them safe at the same time; hermits are vulnerable out of the shell, pregnant hermits even more so. She spends a good part of her time up on the seaweed, out of reach of the crab.

Blue berries

Some of the hermits have pink eggs, or "berries", while others' berries are a deep blue-black. I'm not sure if these are greenmark hermits, or if they're just in a different stage.

I'm hoping some of these survive. It's difficult in a tank environment.