Chance encounter

 Sometimes you're just in the right place at the right time ... Passing my aquarium on the way to start supper, I caught a glimpse of a naked hermit sheltered in the rosy seaweed. Supper forgotten.

A hairy hermit, Pagurus hirsutiusculus, without the protective shell.

Think about crabs. "True" crabs, they call them; the crabs you see scuttling sideways on the shore. They have a soft body encased in a hinged hard exoskeleton, the carapace on top, the abdomen beneath, sort of like a clamshell. When they grow and need to molt, they open this shell and back out, leaving the perfectly formed crab shape behind.

Hermit crabs don't have the hard covering for the abdomen, which is much larger than that of the "trues". The upper body is encased in a hard casing, but the abdomen hangs out, looking like a sausage, soft and juicy, a tempting taste treat for fish and crabs and shorebirds. So they wear a borrowed shell for protection.

Freshly-molted hermit, showing the upper carapace, two tiny grasping legs, and the front end of the soft abdomen.

As a hermit (or crab) grows, the exoskeleton becomes a tight fit. It doesn't grow with the critter inside, so there comes a moment when he pulls himrself free and backs out, pulling the eyes down out of the eyestalks, the legs and pincers out of their chitinous coating; even the antennas are retracted, leaving the antenna shape behind, attached to the old body shell.

Dried abandoned hairy hermit molt. (2010)

And now the hermit is in danger. He's soft all over; not only that dangling abdomen looks good to eat.  So he heads up, away from the always hungry crabs beneath. He climbs a blade of eelgrass, or, as here, drifts on the seaweed.

Like a butterfly just out of the chrysalis, who rests in the sunlight, slowly unfolding and stretching out her wings until they are stiff enough to fly, the hermit waits in his safe place. He takes in water and swells out before the new carapace hardens, he waits until he feels strong enough to brave the dangers below in his search for a new shell to enclose that vulnerable abdomen.

His colours are pale at this stage, and free of algae and grunge.

My bad: trying to get a clear photo, I moved the seaweed and he fell off, down to the sand. Down where a crab lurked. I quickly rescued him, and set him to rest safely in a small bowl of water, then searched the tank for shells that looked about the right size for him. (Normally, he would do this when he was ready and able to run from the crab.)

And he rested only a few minutes, then chose a shell and moved in.

This one looks about right. Body hardened, abdomen protected. Ready to roll!

I gave him some time to settle in, then returned him and the other shells to the tank. And he ran off, happily, to look for food. Needed a pick-me-up after all that work!

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A veces el azar te sitúa en el preciso momento y lugar ... Iba a la cocina para preparar la cena, pero pasé el acuario y vi un ermitaño desnudo. Se me olvidó lo de la cena.

Foto #1: El ermitaño, un ermitaño "peludo", Pagurus hirsutiusculus, escondido entre las algas marinas.

Considera los cangrejos. Un cangrejo "verdadero", como les llaman: los cangrejos que ves corriendo lateralmente en la playa. Tienen un cuerpo blando, encerrado dentro de un exoesqueleto quitinoso articulado, el caparazón arriba, el abdomen abajo, algo así como la concha de una almeja. Cuando crecen y les llega la necesidad de mudar, abren este exoesqueleto y se retiran, despegándose hacia atrás, dejando en la playa la forma perfecta del cangrejo ausente.

Los cangrejos ermitaños no tienen la corteza dura para el abdomen, y éste es mucho más grande que el de los cangrejos "verdaderos". El cuerpo anterior está cubierto de un caparazón, pero el abdomen se cuelga sin protección. Parece algo así como un chorizo, y así lo ven los cangrejos, los peces, hasta los pájaros costeros, un chorizo delicioso. Por lo tanto, los ermitaños esconden ese abdomen dentro de una concha de caracol prestada.

Foto: un ermitaño recién mudado, mostrando el caparazón, dos patitas que sirven para fijarse a la concha prestada, y la parte anterior del abdomen.

Cuando crece un ermitaño, o por cierto, un cangrejo, este exoesqueleto llega a quedarle chico, incómodo. No crece con el animalito por dentro, y viene el momento cuando se separa buscando la libertad, retirando los ojos de los pedúnculos oculares, las patas y las pinzas de sus formas, hasta las antenas de su corteza, dejando la forma de la antena todavía haciendo parte del viejo exoesqueleto.

Foto: una muda de un ermitaño P. hirsutiusculus, resecada.

Y ahora está en una situación peligrosa. Todo el cuerpo recién mudado es blando; ahora parece buen alimento para los cangrejos y otros depredadores. El ermitaño se escapa, subiendo por las hierbas o escondiéndose entre las algas donde no le alcancen los cangrejos.

Como una mariposa recién eclosionada de su crisálida descansa en el sol, estirando y desdoblando las alas, esperando a que estén suficientemente rígidas para poder volar, el ermitaño espera en su lugar protegido. Toma agua, y se hincha antes de que su piel se vuelva dura, un nuevo exoesqueleto, espera hasta que se siente capaz de arriesgarse allá abajo, donde tiene que buscarse una nueva concha.

Foto: un ermitaño recién mudado tiene los colores claros, las patas limpias, sin algas.

Y fue culpa mia; tratando de sacar una foto, arrimé el alga, y el ermitaño se cayó al suelo, donde peligraba su vida por la presencia de un cangrejo. Lo rescaté de prisa, y le puse en un platito con agua donde nada de amenazaba. Luego le busqué una variedad de conchas más o menos de un tamaño que le quedaría. (Normalmente, el mismo haría esto cuando se sentía con fuerzas.) 

Esperó unos cuantos minutos, y luego escogió una concha y se insertó en ello.

Foto: el ermitaño en el plato, con su nueva concha.

Le dejé un tiempecito para descansar, y luego lo regresé al tanque. Y se fue muy contento a buscar algo que comer. Después de todo ese trámite, tenía hambre.

Workout moves

In my aquarium, something, probably a crab, dug an eelgrass' roots out of the sand, leaving it floating upside-down, roots near the surface. Looks like fun, a little hermit crab said, and climbed up to practice his trapeze artist skills.

Head down

Feet up

Balancing on the bar

He's got a few holes in his shell. One is big enough to expose his backside.

The stripy section is the back of his cephalothorax, his head/thorax section. The abdomen is curled up in the bottom of the shell, as it lies here. There are a couple of holes there, too. Good fresh water circulation!

And then he climbed down again and went to pester the anemones.

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En mi acuario, alguien, probablemente un cangrejo, excavó las raices de una planta Zostera marina, dejándola flotando con las raices para arriba, cerca de la superficie del agua. Un cangrejito ermitaño, Pagurus hirsutiusculus, la vió y decidió ir a practicar sus habilidades de trapecista.

Tiene varios agujeros en la concha que lleva, uno bastante grande. Se le ve el cefalotórax en este. El abdomen queda en la parte inferior de la concha, como está dispuesta en la última foto, pero ahí también hay un par de agujeros. ¡Ventilación!

Y terminado el ejercicio, se regresó a la arena y fue a molestar a las anémonas.

Shopping is such hard work

I discovered one of my hermit crabs in the process of choosing a new outfit. I'll let her tell the story.

Let me see; this one looks new, and it's my size. It's empty and clean inside.

So I'll try it on.

Yes! It fits perfectly!

Let me check the back, and the pockets. Yes, it's all snug and there are no holes. Good!

The outside feels good, too. I can reach almost to the tip.

But wait. Before I go, let me look at the old one again. It served me well.

And I think, now it comes to it, that it did feel more comfortable. Well broken in, and that little hole at the back made for good ventilation.

I'll try it on again.

Yes. You know, travel-stained and chipped and all, it does feel better. I'll keep it, after all.

And off she went, leaving the new outfit behind for the next shopper.

The hermit is a hairy hermit, Pagurus hirsutiusculus, an old-timer in my aquarium. Her shell is just under an inch long. The shells are imports, found in a dollar store, washed and boiled. They seem popular with the hairies, not so much with the grainy-hand hermits, who like big, sturdy shells.

A worried look

Young hairy hermit, checking out the camera.

"What does that big eye belong to? Will it eat me?"

Even in a protected tank, with no predators, life can be difficult. This hermit is missing most of one antenna. The other is fine, just bent back behind his shell.

Mostly, the hermits and crabs get along peacefully, but when it's feeding time, tempers can flare. They snatch at the food that another has captured; sometimes a hermit retires into his shell, carrying the shrimp pellet with him. Another of the hermits, or maybe a crab, will spend several minutes poking inside the shell, trying to steal the food. Never mind that the thief is probably straddling two or three pellets, just as fresh. No, he wants that one! Forbidden fruit always tastes better.

Or a hermit will chase another across the tank, grabbing at legs, antennae, shells, trying to slow down the other to take away that delicious piece of shrimp. So one of the crabs is missing her back leg. Another of the hermits has lost two legs on one side.

Never mind; they manage fine with only three or four legs and one antenna. The food comes down regularly; they're in no danger of starving. Or of being eaten by a gull because they didn't hide fast enough. Here there are no gulls.

(This hermit's shell has grown a crop of green algae and it looks as if a tribe of copepods is feeding on it.)

I call him Joseph

Our local hermit crabs, the Hairies, Pagurus hirsutiusculus, are usually a drab greenish-brownish-greyish mud colour. It's a mask; they're wearing a coating of algae, mud, leftover grunge, and sometimes a few barnacles. Underneath all that, they're a pale green, with blue knees and white patches on the legs. The body, of course, is hidden by the borrowed shell.

When they're freshly molted, and haven't had a chance to muddy themselves up yet, the true colours shine through. I caught one a few minutes after a molt, hanging out on the seaweed right in front of the wall, without a shell, showing off his coat of many colours.

Red, orange, yellow, green, blue, indigo, violet; all the colours of the rainbow.

The photo is fuzzy; the seaweed is swaying, the glass wall algae-coated. But the colours shine through.

Hairy hermit, as found on the shore, in his normal coating of mud and algae.

(Title from the Biblical story of Joseph.)

Spare parts

Hermit crab enjoying his lunch.

Shrimp pellets; Yum!

Hermit crabs, besides the chelipeds (pincers) that they use to grab and carry things, have three pairs of mouthparts, which they use to hold and manipulate their food. Here, two are plainly visible as the hermit holds onto his fresh shrimp pellet.

He seems to have lost at least one of his chelipeds, probably after an argument with a crab, or even another hermit. He'll do fine, though; hermits can use the legs to grab their food, too. They're not as efficient, but they'll do. And with the next molt, he'll have a new cheliped. The blue appendage on the left is the growing replacement; hermit blood is blue, and the skin on the new pincer is still thin.

Meanwhile, back in the tank ...

The new hermit with the blue pincer is settling in nicely.

Big Blue, in hiding deep in the tank, in the semi-dark. He likes it there.

So far, he's selected three girlfriends, holding onto each one for several days, then abandoning her, probably after he's mated with her. I'll be watching them for growing eggs.

Deep in the tank, the blue pincer fades to green. When he comes up front, to the light, it glows as brightly blue as the day I saw him first, on the shore.

Blocky eyes

The hermit crabs in my aquarium carry their eyes on stalks. The eye itself is round, with a pale stripe across the centre, and the circular lens in the stripe.

Hairy hermit, Pagurus hirsutiusculus.

Tonight, while I tried to photograph a snail eating algae, trying to get a glimpse of its radula, a small hermit photobombed the scene. Maybe it's the angle: the hermit is above me, staring straight down at the flashing light that had attracted her attention: the whole eye is dark, and looks rectangular. I'd never seen one like that before.

"My turn! Forget that boring, slowpoke snail!"

She stepped on the snail's head, and he (the snail) promptly retreated into the shell. End of photo op.

Hermit crab fashion statement

Hermit crabs are picky about the shells they wear. The size matters. So does the shape of the opening, and the thickness of the shell. They usually will not take a shell from the wrong species, no matter how pretty it is, even if it's almost the same shape and size as the one they eventually choose. Almost isn't close enough.

They examine their next shells carefully, inside and out, rolling them over, lifting them, poking legs and pincers deep inside, then trying them on, sometimes several times before they finally decide. You could think of them as girls trying on a new pair of jeans in front of a mirror, turning this way and that; "Does this make me look fat?"

But they don't mind broken shells. Again, like girls in frayed and torn blue jeans.

Hairy hermit, with her backside showing through the hole in her jeans.

Hermit crabs fit themselves into a spiral-shaped shell. And the spiral has to turn to the right, which also reduces the number of suitable shells; some snails turn to the right, some to the left. A left-turning spiral just doesn't fit.

In this photo, the curve of the back end of the abdomen is visible, as well as a bit of one of the back legs.

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.

Barnacles on his knees

Beauty yesterday; the beast today.

The largest hermit crab in my aquarium is a hairy, shaggy, scruffy, awkward old geezer. He's far too big for the shells he wears, so his back feet, there to hold the shell in place, hang out, uselessly. And his main pincer is too big, again, to be used. He drags it along the ground, a dead weight doubled underneath him.

And he has barnacles on his back.

"Barney", with his right pincer curled back, and the tiny holding leg dangling.

Three good-sized barnacles, and a couple of tiny ones, along his waist. It looks like he's growing seaweed on his back, too.

More barnacles on his knees and ankles.

The shell he was wearing for the photo shoot also has barnacles and a two-tentacled worm, to boot. Today's shell is a bit larger, and black. He changes his shell every day; he likes variety. And when you're twice as big as your competition, you get to choose any shell you want, occupied or not.

Swept off her feet

The big male hairy hermit crabs pick up a new girlfriend almost every day. Then they carry her to a high spot, away from rival males, where they wait until she's ready to mate. Or he sees some interesting food. Or his mind wanders and he forgets to hold on and she drops to the floor.

The hairies aren't as patient as the grainy hand hermits; they'll hold the girl for days.

She's game. I wonder if she was impressed by his fancy pants?

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.