In berry, or not?

Hermit crab. Not carrying eggs, I don't think. But maybe.

Hairy hermit, Pagurus hirsutiusculus. With anemone.

The only usual way to tell a female hermit crab from a male is to catch her out of the shell, not moving (which almost never happens) and look for two tiny dots on the underside of her belly. I've managed it once.

The other two signs are:

1. A mature male captures a female. (They seem to have no problem distinguishing which is which.) He grabs her by the edge of her shell and carts her around, sometimes for days, until she is ready to mate. This was happening a few weeks ago.

2. The female is carrying eggs. These will be attached to the side of her thorax, (the red area on the side of the one above.) As they grow, they fill in the gap and get in her way; she pushes them outwards and fans them, jiggles herself around in the shell, trying to get comfortable. At this stage, there's no doubt about her gender.

So: is that red area the beginning of the growth of eggs? Or not? Wait and see.

Happy hermits

The stars in my aquarium (or maybe the clowns) are always the hermit crabs. They're social animals, and never happier than when they're climbing over each other, or playing a rousing game of "King of the Castle". They love a crowd.

Before the mishap with the pump, there were thirty hermits in the tank, Hairies, Grainy hands, and a bunch of tiny ones, possibly Greenmarks. I took them all out and counted them tonight; twenty-five survived. They look healthy; bright-eyed, curious and lively.

And a fair number are in berry, carrying developing eggs.

In berry. She's carrying reddish eggs on the side of her cephalothorax. The eggs are new; the mass is still small.

After the new pump was installed several of the hermits molted the same day. This would be the moment when they were able to mate; once their new exoskeleton has hardened, it is again impossible.

Very tiny pale blue and green hermit. Probably recently molted, as the colour darkens later on.

Another female, a Hairy hermit, in berry.

A small hermit. I love the graceful "flags" they are always waving. The one on the left (our left) is probably folded back at the moment.

When the eggs mature and are released, the hatchlings will be planktonic swimmers called zoeas. Once again, they will probably be too small to survive in a tank with a pump and filter.

Some critters do breed well in the tank; I'll talk about them tomorrow.

Mothering is a full-time job

One of the hermit crabs that came home with me the other day was in berry, carrying her brood of eggs just inside her shell. Today, I noticed another one fanning her babies. And I think there's a third; I just caught a glimpse of pink inside the shell mouth.

One of them spent most of the day yesterday perched on the highest blade of eelgrass, periodically fanning and picking at the eggs. She has to keep them clean and oxygenated until they are ready to be released into the water. And it seemed to me that sometimes she was just getting comfortable: pulling the mass out of the shell and stretching her back legs, scratching her back against the shell interior, taking a few deep breaths, as it were, before she gave the eggs a quick brushing and pulled them back under cover. (Human females may wish they had that capability!)

Pink and greenish berries. And are those black dots eyes?

It's safer up on the eelgrass, even if she needs to hold on constantly as the grass sways in the current; the ravenous crab below would love fresh eggs for breakfast. And the oxygen levels are higher just under the surface. Growing babies need their air!

She's in a broken shell, so the white interior of the first round provides good contrast for the eggs. This may be a disadvantage in a crab-infested environment; another reason to stay out of reach.

The eggs at this stage are pink. I've seen a few mothers with blue or even purple eggs; these are mature and ready to be released. That may be a few weeks from now.

UPDATE on the baby nudibranchs: they're thriving in the other tank, congregating near the bubble stone, and growing like weeds.

Tomorrow (well, today, really) I'll be going to Chilliwack for a triple party: three kid birthdays, Easter egg hunt, and welcome home party. I'll probably be too tired to blog tomorrow night. See you Sunday!

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.