Anemones and other wanderers

Residents in my aquarium, some new, some old:

A medium-size grainy hand hermit, Pagurus granosimanus.

These hermits like a shell 'way too big for them. It seems impractical; all that weight and bulk to haul up the blades of eelgrass, but they persist. They don't seem to mind a tumble or three.

Look inside the shell; his small fourth leg, the one he uses to hold the shell in place, is visible.

Orange lined anemone, Haliplanella lineata, on vegetarian snail.

I brought this anemone home on a small stone. Within hours, it had packed up and left. I found it a few days later on the back of the big abalone shell, and a day later, inside the lip. A few days later, after more moves, it met this snail. The snail travels around the walls, down into the sand, up a wall again, eating algae. And the anemone, finally, is content to stay put and let the snail do the chauffering.

Stubby isopod, Gnorimosphaeroma oregonensis*, on a blade of eelgrass

A bunch of these, at least 30, came home on the eelgrass I brought for the hermits. Most of them are very tiny, barely little specks that alternately swim and crawl. When I try to capture one, it rolls up into a tight ball, like a pillbug does. This is one of the larger ones.

*His name is bigger than he is.

Val, growing bigger every day. Last I measured, her tentacles were 4 cm. long.

And she's another wanderer, more of a homebody than the snail rider, but never content to stay in the same corner for too long. Now she's at the far back of the aquarium, making me almost stand on my head to get a good look at her.

Barnacles and snails

Not even the barnacles stay put around here. Sure, they're glued firmly to their base, but in this case, the base is the empty shell of a larger barnacle, and it rolls about as the snails and hermits walk over it or the current takes it. On the beach, they wouldn't survive; they'd be tossed up on shore to dry, or eaten by a passing fish. In the aquarium the only thing they need to fear is Val, and the pump is set so that the current sweeps them away from her.

Workaholic hair

Tonight I watched one of the large hermit crabs steal a partially-digested snail from the anemone's mouth, then dash away before his larger companions could snatch it from him. He ran, at top speed, the full length of the aquarium. Backwards.

I couldn't do that. Not without stumbling, not unless I had eyes in the back of my head.

In the morning, the hermits are quiescent, some apparently sleeping (with their eyes open) in the corners, some stacked on top of each other like sleepy kittens, some meditatively grooming their antennae, some picking at a morsel of seaweed or a barnacle. I drop the day's ration of shrimp pellets into the other end of the tank. The scene changes, even before the pellets have sunk to the tank floor; all the hermits are running, scrambling out from the bottom of a hermit pile, dropping from the seaweed. The crab appears from his hidey-hole behind the abalone shell, but he's already out-done by the hermits; they have collected their breakfast, and are hauling it out of reach. He has to mug a slower one for his meal.

How do they do that? They couldn't see the food; they barely had time to smell it, let alone identify and locate it.

Grainy hand hermit, waving assorted antennae and mouthparts.

Their senses are different than ours. Not better, not worse; just different. Their eyes are compound, on stalks, and arranged so that they look both forwards and backwards. One may be looking at me through the glass wall, but at the same time, he's watching his back, in case of a visit by the crab. Handy trait!

As for smell and taste, the hermit has all the bases covered. He has four antennae; the smaller pair, the antennules, is a sensitive "smeller". Besides that, his legs are covered with sensory hairs; he can smell things just by stepping on them. And this covers a deficiency in his sight. Although he can see backwards, he can't bend those stalks down, so he can't see under his own feet. Not a problem when you can smell the ground under you!

A hermit can identify, by smell, a useful snail shell buried in the sand; he can pick out the species that he likes best, also by smell or taste. The hairs on his legs and pincers are multipurpose sensors that also distinguish temperature, touch, and water current.

Do they hear? Yes; those four antennae do that. How well, I couldn't find out. (Should I play some music to mine, and see if they respond?)

Zooming in, to show facial detail.

And then there are those long, long antennae. In this hermit, they're orangey-red. They are feelers, the equivalent to our fingers. The shorter pair in between the eyes are called antennules. The hermit flicks them continuously, waving and spreading the hairs on the flagella (that blue "flag"), capturing scent and taste from the surrounding water.

In the photo above, two of the three pairs of mouthparts are visible. These are always difficult to see, since they're constantly moving. There is a lower pair, green with orange, hairy tips; these manipulate the food and move it into the mouth. Just above these are a set of long spines, also hairy. I can't see what's behind them.

I don't know if all these mouthparts are sensory organs. I would think so, but haven't found any real info.

The idea of hair in the mouth makes me shudder, but then, I'm not a hermit crab.

Shell game, Part 2

(continuation of Shell game, Part 1)

The shell that the big female hermit had discarded (see Part 1) was too large. Too big for her, too big for her companion, who is slightly smaller than she is. I decided to remove it from the aquarium; it was in the way. I left it for the present in a bowl of water, to allow anything inspecting the inner reaches to leave.

A few hours later, I glanced at it, in passing, and saw the worm:

Red and white banded sea nymph, Cheilonereis cyclurus

I hadn't seen one like this before, but the pattern is quite distinctive; it took only a minute to find it in my Encyclopedia.

"This stunning red-and-white-banded worm has a special commensal relationship ... with large hermit crab species. Together they inhabit the shells of some large snail species, ... Seldom does this sea nymph emerge more than the length of its head, making detection of its presence difficult." 

Side view. The high "collar" around the head distinguishes it from other sea nymphs.

Googling for more information, I found only one good photo, a taxonomic record in the Encyclopedia of Life (with photo of long-dead worm) and WoRMS, and the name on various lists. One scientific article documents its relationship with hermit crabs in Alaska. It is found from Alaska to California, and on the far shore of the Pacific, in China and Japan.

But what does it eat? How does a big worm fit in a shell with a fat hermit? How does it get in there? How common is it? I found very few answers.

Tail end.

What do I know? It's a polychaete, a worm with a pair of paddle "feet" and several bristles on each body segment. It has four eyes (right-click the top photo). The "feet" on this worm are divided into two white paddles on either side.

Like other polychaetes, he sways back and forth along his length, keeping his space open, keeping the water moving.

Paddles (parapodia) and bristles (setae)

He belongs to the Nereid family. These have strong jaws and teeth. Some are carnivorous predators, while others eat algae or other vegetable matter. I tried to lure this one out of the shell with a piece of shrimp; he wasn't interested, even when the shrimp was in contact with his face. I gather that he's vegetarian.

About that relationship: it's called commensalism. The word comes from Latin, "cum mensa", meaning "with table", or sharing a table.

In ecology, commensalism is a class of relationship between two organisms where one organism benefits without affecting the other. (Wikipedia)

This brings up even more questions: Which one benefits, the hermit, or the worm? How do we know they don't both benefit? (This would be mutualism.)

Can the worm live in other places, like burrowing in the sand? Or must it live inside a shell? Does it do better if there's a hermit in the shell?

Does the shell provide shelter, or does the hermit provide food? Or, vice versa, does the worm help to remove the hermit's waste products? Or help with irrigation?

The hermit that moved out was one of the fattest I've ever seen. Was this because of some advantage the worm gave it?

Facebook has it right: it's complicated.

The worm has had the shell to himself now for two days. He is still there, still poking his head out at intervals. Other hermits have looked over the shell, and they keep rolling it about, but have not attempted to move in.

Hairy hairies

Most of the hermit crabs I picked up the other day on the beach were the usual finds; little greenmarks, and slightly bigger hairy hermits. But a few were unlike any I'd seen before.

Yesterday's speedy hermit.

The hairy hermits are more or less hairy. These ones are super hairy. Fuzzy on the body, fuzzy all down the legs, all along the pincers.

This one's furry enough to hide his blue and white knees.

Compare them to the ones I'm used to:

This is a hairy hermit, Pagurus hirsutiusculus. Yes, he's hairy, but not all over.

Another hairy.

One of the hairiest of the hairy hermits.

And the hairiest of the new hermits:

This may be a clue. Even his shell is furry!

In size and coloration (spotted antennae, blue and white knees, basic brownish green body, although these tend a bit towards the orange end of the browns), shape (long antennae, one pincer larger than the other), home site (upper intertidal) and habits (they like a small shell, and they move quickly), they are like the hairy hermits.

My encyclopedia has photos of very hairy hermits, but the colour pattern and body proportions are different.  So these do look like hairies, but why the extra load of fuzz?

The one with a furry shell makes me wonder if they haven't been colonized by hydroids, or some fuzzy algae. The hermits in a clean shell, like the one at the top, may have changed the shell recently.

I found a few images on the web with very hairy hairies, along with photos of normally hairy ones, at WallaWalla U. I notice that the really furry ones have a lot of crud in the hair; so do mine. It would be interesting to examine it under a microscope.

What else I found, I'll show you tomorrow.

Garfield the hermit

Seeing eye to eye with a crab:

"Freckles"

"Peachy"

Did you notice the eyes?

Crabs' eyes are on stalks; the shore crabs' eyes are a graceful paisley shape.

Freckles on a raft of Turkish towel.

Hermit crabs' eyes are stalked, too. But they come in many shapes; round, vertical ellipses, even U-shaped. My hairy hermits have oval eyes with long, horizontal irises, with the pupil at the top; a heavy-lidded, world-weary, Garfield* the cat sort of eye.

"Moi seul sens ce tourment." (See Henri, Paw de Deux)

*Or Henri; watch for 1:30.

Tap-talking to Patience

I know how to speak "hermit crab"! I just managed to suggest a good idea and actually get it across!

I am supposed to be posting one photo and going off to bed; tomorrow's another very busy day. But I can't wait to tell this story.

It started sometime after Christmas. When all the kids were coming for dinner, I had counted all the animals in my tank, and made a list for them; could they find every one? There were 11 hermit crabs, in three species; Grainy Hand hermits, with the blue spots, Hairy hermits, black and white, and the tiny Greenmark hermits, with the orange highlights.

Sometime in February, I counted again. I couldn't find all the Grainy Hands. And a couple of them seemed rather lethargic. I monitored them for a while, until a few died. Then a few Hairy hermits, too. I changed the water, and removed empty shells, and watched. More died. And the rest of the Grainy Hands, my favourites for their personality, their curiosity and mutual helpfulness, looked sick. They lay around, barely moving, not eating.

I removed them to a bowl with clean water, a "hospital" bowl. I babied them, changing the water twice daily, tempting them with bits of food which they ignored. All but one of them died, anyhow.

The one, whom I'm calling "Patience" for now, although I'm not sure of her sex, rested in the bowl for a week, lying upside-down in the shell, barely even moving her mouth parts. But she didn't die, and gradually seemed more alert. After some time, she started to be interested in food again, but couldn't walk. When I positioned her shell in walking position, she struggled a bit, slid around, then the shell rolled out of control again, and she ended up with her feet up. There she stayed, day in and day out. I fed her in this position.

Finally, none of the remaining hermits in the tank, all small Hairies and Greenmarks, seemed sick; maybe the epidemic had run itself out. I returned her to the tank. She liked that; she lay on her back, catching at pieces of seaweed that floated past and nibbling on it. She was active enough: she stretched and twisted, reaching for seaweed, pulling it towards her, but always still lying upside-down.

Several times a day, I rolled her over into walking position. She would start working on the shells and sand, picking up things she found, but when she tried to walk to the next spot, she scrabbled uselessly on the sand until she ended up on her back again.

I thought that maybe she is weaker now, she needs to gain weight and strength again. That big shell might be just too heavy for her. I found her a few smaller shells of the type she likes, and laid them close at hand for her, but she didn't seem to get the idea.

I've been remembering how one hermit convinced another to trade shells; he held the other's shell face to face, then jerked it and clicked it against his shell. Could I do that?

Tonight, I took Patience out of the tank and held her loosely in my hand, but underwater. She seemed contented enough, picking at the skin of my thumb, tasting it. I picked out the best of the smaller shells, and tapped her face opening with it, gently, gently. She retreated into her shell, and I repeated the tapping. Nothing happened. I put her back in the tank beside the proposed home; she reached for it, then slipped and rolled onto her back again.

I tried again. I held her with my hand just under the surface of the tank water and tapped again, once. Suddenly, she slipped out of her big shell, rolled up and off my hand into the tank. I put the small shell down beside her and kept the big one. And she didn't even bother to examine the new shell; she just popped into it, rolled it over to walking position, and hurried off to get a bite to eat.

Yay! She can't be happier than I am! And she is happy; she's been wandering here and there, nibbling at everything she finds. Here she is, a few minutes after the switch:

Patience, waving celebratory red flags.

You see why I've named her Patience. If at some time, she turns out to be male, I'll rename her Job. Whichever it is, she/he's a survivor.

Little Bo Peep ... is fast asleep

(Mating behaviour of intertidal hermit crabs, Part II, following "A friend for Boy Blue".)

The trouble with Googling hermit crabs is that they are popular pets. When I Googled "hermit crab" suppliers, the list included 110,000 sites. And most pet hermits are land species. They don't breed well in captivity, because the young have to hatch and grow in water; they move to the land as they mature. Few pet owners can manage the complicated schedule and arrangements necessary. When I finally realized this, and specified "marine hermit crab mating", I found what I was looking for.

The questions I was asking were: How do I know the sex of my hermits? Do they need to molt before they mate? Are my hermits displaying normal mating behaviour? And, suggested by Laurie; Will they be successful in spite of being in a tank? (Which I am careful to keep with a species, water, and temperature mix that matches their home environment, but still ... a big human peering through the wall all the time? Electric lights? Is that too stressful?)

Grainy hand hermit, Centennial Beach. Already worried.

Sexing a hermit crab is easy. Sort of. On the last set of legs, the female has two small holes in the joints; the gonophores, where the male will insert his sperm. The male has none. The only problem is to catch the female out of the shell far enough and long enough and in the right position to be able to see this. A rare event.

Never mind; I know an easier way. I'll get to that.

I found an article in the Revista Brasileira de Zoologia, by Alexander Turra*. (2005) He studied the mating strategies of 4 species of intertidal hermit crabs on the Atlantic coast of Brazil. One of those species was of the same family as my two, Paguridae, and the same genus, Pagurus. All four of them acted in ways similar to mine, although he noted that the displays were family-related characteristics.

He started out with a collection of around 800 hermits from an intertidal beach and mud flats, and housed them in plastic pools with sand and mud from their home base, in running seawater. More or less the same procedure as I'm using, although I sure don't want 800! He fed them fresh fish and mussel meat; mine get dried fish, seaweeds, and occasionally a bit of mussel or nudibranch.

Then he watched them around the clock. When a couple formed, everything they did was recorded. Let's compare his Pagurids to mine:

1. - Pagurus criniticornis (the Brazilian hermit, from now on called "Crini"): the male grabbed a smaller female and turned her to face him.
- Rex (Pagurus hirsutiusculus) grabbed his little gf and held her facing outward:

- Boy Blue (P. granosimanus) held his smaller girl like Crini did, face to face.

2. - Crini picked at the female's pincers and legs with his pincers.
- I didn't see Rex or Boy Blue do this.

3. - Crini held his female's shell with his pincers or legs.
- Rex used only his smaller pincer for holding her, and the legs for adjusting her position.
- Boy Blue used both pincers or a pair of legs; sometimes, because he was busy eating, he just kept one leg deep inside her shell.

4. - Crini sometimes dragged his girl over the bottom.
So did Rex, but not Boy Blue.

This I thought was very interesting: in some invertebrates, the female resists mating, and with reason; it puts her in a precarious position, and uses much of her strength. The female hermit seems not to mind; watch:

5. - When Crini's mate was ready, she

"... signaled to males they were ready for copulation by touching male eyestalks with their antennules."

- I didn't see this in my hermits; I wasn't watching closely enough.

The pair eased out of their shells and put their gonophores in contact. Copulation lasted from 10 to 36 seconds, and was repeated up to 4 times. No wonder I missed this; that was quick!

Then the female slid back into her shell. Crini continued guarding her, holding her shell or her pincers.

6. - Afterwards, Crini's gf stayed quiet, sometimes buried in the sand, for several hours.
- Rex's mates wandered away. Or maybe he abandoned them; hard to tell, because he dragged them around a lot.
- Boy Blue's girl (she needs a name, since I can recognize her; how about Bo Peep**? "Bo", for short.) sleeps. At least, she stays in the shell and doesn't move for hours. I caught her and Boy together this morning; now she's sleeping again.)

7. - Some of Crini's mates molted; some didn't.

So things line up; I think I can be confident that this is mating behaviour, that the smaller hermits are females, and that, no, she didn't need to molt first.

If everything worked out, the females will be holding eggs alongside their abdomen in the shell. Later, she will release them, they will hatch, and the tank will suddenly have almost microscopic babies swimming about. I may miss these, and if there's an increase in the number of Hairy hermits (Rex's babies, that would be), I wouldn't be sure, since there are quite a few little ones already. I will notice any replicas of Boy and Bo.

If. Laurie's question still needs to be answered.***

I'll let you know.

Young Grainy hand. Not one of mine; she's still on Centennial Beach.

*Turra Alexander. Reproductive behavior of intertidal hermit crabs (Decapoda, Anomura) in southeastern Brazil. Rev. Bras. Zool. [serial on the Internet]. 2005 June [cited 2010 Mar 09] ; 22(2): 313-319. Available from: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0101-81752005000200003&lng=en. doi: 10.1590/S0101-81752005000200003.

** To go with Boy Blue.

*** Alexander Turra's hermits were successful parents: two Pagurus species' eggs hatched at 19 days. (Turra, 2007) I'll be on the lookout in a couple of weeks, then.