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.

Hermit shenanigans

It was time to put the aquarium to bed for the night: feed the anemones, add ice, turn off the light. But in the middle of the tank, behind the anemones, a lump of waving legs and antennae turned out to be two hermit crabs, embracing face to face, half out of their shells. I ran for the camera.

I had a few seconds only; hermits don't stay in vulnerable positions for long.

Two hairy hermits (Pagurus hirsutiusculus), mating. The smaller, green legs belong to the female; the male is bigger, and has red algae growing on his hairs.

It's springtime, and love is in the air. And the water. But it's difficult for hermit crabs; to mate, they have to crawl at least partway out of their shells, exposing their soft, juicy abdomens. And crabs are always on the lookout for fresh meat. A researcher timed his hermits; copulation lasted from 10 to 36 seconds, repeated up to 4 times.

I managed to get half a dozen blurry, bubbly photos. No time to wipe down the glass first, nor to turn off the pump.

View from the top. Bubbles and swimming copepods deleted, contrast increased. The female is the one on the right; her abdomen is visible, almost entirely out of the shell.

Either she had just molted (crabs have to wait until the female molts, because of the hard carapace she's wearing normally), or she molted soon afterwards; I found her molted bits and pieces up against the glass in the morning.

I paused to wipe off the glass quickly. When I looked again, a few seconds later, both hermits were back in their shells and walking away, in different directions.

If the mating was successful, the female will be visibly in berry soon; the baby hermits will hatch in about 3 weeks. They'll be too small to see, except as moving specks in a filter, against a bright light.

I have watched the preliminary courting behaviour many times. (I reported on it here: "A friend for Boy Blue", and "Little Bo-Peep is fast asleep.") I had never managed to catch them actually in the act.

Made my day. Theirs, too, I think.

All those little eyes!

I had brought in a fresh batch of eelgrass for the aquarium, and a hermit crab in berry found herself a safe place there, far above the marauding crabs and nosy fellow hermits, where she could do a bit of housekeeping, and give her babies a bath.

I happened by just at the right moment to see what she was doing and took photos and a video.

Ma hermit and family.

This was three weeks ago, just before my family arrived and we took off on vacation. When I was back home and settled in again, she seemed to be baby-free.

I cleaned the tank, added fresh water, and, as usual, screened the old water before I discarded it. First, I strain out the big stuff, bits of seaweed and so on, look it over carefully, collect any stray critters, and dump the rest. Then I run the water through a fine sieve, check the sieve for moving critters, and replace them in the tank.

Finally, I strain the water through a coffee filter, and look over that under a bright light, watching for movement, even if the animals are too small to really see. And here, I found two tiny dots, about the size of copepods (under 1 mm.), that moved too slowly for copepods, and too fast for snails. I captured them with an eye-dropper, and looked at them under a microscope.

I could see, there, the tiny coiled snail shells. (I'm glad some of my baby snails don't make it, and leave their shells for other babies.) And in front of each miniature shell, I could also see the two tiny dots that were their hermit crab eyes, looking up at the world.

They went back in the tank. Maybe they'll have a chance to grow up.

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.

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!

Out of character

He's polite, peace-loving, gentle, co-operative. A good neighbour, tolerant of youngsters, patient. A typical Canadian (YMMV).

He's a hermit crab, of course. They're like that; pleasant company.

And then he goes and transmogrifies into a stereotypical cartoon caveman*, when he discovers girls.

Oog, the hairy hermit, with his captive mate.

A mature male hairy, big and strong and about 3/4 of an inch long, chooses a female. She's smaller than he is, usually quite a bit smaller. He grabs her by the corner of her shell, near her face, and drags her wherever he goes. Oog, here, chose the top of the tall abalone shell as a perch; from here, he has the drop on any challengers. And there he waited, only coming down for lunch, still dragging the female with him. (She didn't get much; she was trapped and could only catch a few spare crumbs.)

From the time I first saw him with her, until she finally was allowed to go her own way, was three days. Night and day he held her; she lay quietly in her shell, not bothering to struggle.

He was waiting for her to molt. Only then could he fertilize her eggs. Until then, he wouldn't let any other male near her. On the third day, I was watching when she started to signal to him that she was ready; she stretched part way out of the shell, and tapped at his big pincer with hers. After a bit, he let go, so that she could get out of the shell to molt.

And then another male, slightly smaller, (Glok, I'll call him) decided to horn in. He came up and grabbed the female's shell. Not allowed! Oog attacked!

I have never seen such an angry hermit before. He tangled with the intruder, tugging and hitting and pinching until Glok had to drop his prize and run away, with Oog pursuing him furiously for half a tank length before he turned back to his mate.

Now he stood guard, at arm's length from her, watching, watching. Glok tried to sneak up from behind a blade of seaweed; Oog caught him and pounded him some more. Glok came around from the back; Oog chased him away again. And again. And again. Each time, the pursuit was longer, angrier.

I don't know if they ever managed to mate; I missed it, if they did. The next day, Oog was wandering around, sadly poking at random females without picking them up.

I haven't named the female. I don't know if I could recognize her again; her shell is much like anyone else's, and I never saw her features. I'll be watching to see if one turns up in berry.

*Re the "stereotypical cartoon caveman": I wouldn't be at all surprised to learn that they've been maligned; maybe they were quite the gentlemen. And maybe they had nicer, more musical names, too.

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.

Appetizer

I'm working late, so the promised beastie is having to wait. And I've been wasting time staring into the aquarium because the hermits have caught spring fever, and are indulging in a mass orgy. I have photos, but most of them are still in the camera.

Here's an early one, though.

Hermit courtship

Story and photos of hermits in berry coming soon.

Worth the work

A marine invertebrates aquarium needs babying; the ocean the residents come from is a complex environment, always changing, always refreshing itself, always in motion. They won't tolerate stale or quiet water or boring food.

I have a routine; I check and adjust the water pump daily, check the temperature and lighting, and add an appropriate amount of foodstuffs, taking care to vary the diet as much as possible. Every second day, I clean the filter, replace about an eighth of the water with fresh sea water, and remove large chunks of leftovers. As needed, I re-arrange or replace the plantings and playground equipment (large curvy shells, clumps of barnacles and/or mussels, stones); the crabs are constantly uprooting, tunneling, rock-flipping, sometimes to their own disadvantage.

Tiny hermit up a eel-grass and sea lettuce "tree".  All the ambulatory critters love these.

At least once a month, I call it low-tide day*; drain out most of the water, remove the animals and seaweeds, scrub the algae off the inner walls, and rinse the sand beneath. The first rinse water comes out thick with decaying plant matter. I always have to check it carefully and run it through a filter (coffee) to see if any of my critters got washed out with it. There are usually a few amphipods and plenty of copepods. Barnacle and anemone food, on the hoof. I put them in clean water and return them to the tank when I'm done.

Some of the animals, yesterday, refused to leave the filter. They ran around the bottom, holding on, not swimming like amphipods do. They were almost transparent, and too small to see clearly; what I was seeing was the way the light glinted off their wet bodies. I had to swish them around in the water to dislodge them, then shake the filter to get them out. Interesting.

But I was busy, so I set them aside until the aquarium was full again, and then poured them all in.

Later, my work finished, I was checking the leftover rinse water before I dumped it, and another of these beasties turned up in the filter. This time, I went for the magnifying glass. And it was a hermit crab! I've never seen one so tiny.

Newborn greenmark hermit, not wearing a shell  yet. About 2 mm. long.

I had noticed some mating behaviour in the tank, earlier. Male hermit crabs choose a female, and hold onto her, sometimes for days, until she consents to mate.** I'd seen a couple of adult greenmarks dragging occupied shells around; it's springtime, after all. But I never expected anything to come out of it, not in my small tank. But here they were; a whole family of baby hermits!

Green shore crab with rider.

Here's a tiny one, walking on the pincer of a green shore crab. I saw this guy for the first time last week, and wondered how he got here. Now I think I know. He's much bigger than yesterday's babies already.

"Got my eye on you." Greenmark hermit with the crab's eye in the background. The crab is about 1/2 inch across the shell.

*I know; the ocean does it twice daily. I'm not an ocean.
**See two previous posts on mating hermits: "A friend for Boy Blue" and "Little Bo-Peep is fast asleep".