Peril and loss and a new, blue arm

Even in a closely monitored aquarium tank, even where the caretaker (me) tries to interrupt any unauthorized bullying, danger lurks. Take this hermit, for example:

He's wearing a shell with a neat, round hole, drilled by a carnivorous snail, a trophon or a whelk, who killed and ate the inoffensive snail inside. Many of the hermits are the beneficiaries of this activity. Not so the small snails, the barnacles, mussels and clams that end up on the trophons' menu.

But it's not only the carnivorous snails that prey on their tankmates. A couple of weeks ago, the large coonstripe shrimp was sporting a fresh, new suit. He'd left the old one, robbed of its colours, hung up in the seaweeds.

Shrimp molt

A newly-molted crustacean is vulnerable; his protective carapace is still soft. This was the last time I saw the shrimp.

And one of the tiniest crabs is missing a front claw.

This is not supposed to happen here! What went wrong?

This guy:

Mr.  C. The Alpha male.

Mr. C. has grown too big for the tank. He has reached his full maturity, as shown by the super-sized pincers, and has been increasingly distressed by the walls around him. He spent much of his time, some days, going around and around, up and down, around again, scrabbling desperately against the glass. He needed space. Space, and a bevy of beautiful crab females.

He was taking out his frustrations on the lesser inhabitants of the tank. I think the shrimp must have gotten too close; a quick pass with one of those big pincers, and a soft-bodied shrimp would be fresh meat.

The larger hermits dared to challenge him; I saw them many times. He would walk over them, and they would lash out with their own pincers. Not a good idea.

Unfortunate hermit, missing one pincer.

Counting legs in the hermit population, I discovered that two large hermits were down to one pincer each. A couple more had no pincers at all; they are managing to eat by using the two front legs as grabbers.  One other has a broken claw on the large pincer.

The small hermits are all fine; they never stood up to Mr. C.

Hairy hermit, missing both pincers.

Without the bulky pincers, the two maimed hermits were finding it difficult to manoeuvre their big shells around. The weaker legs just didn't have the strength. This one, once the largest hermit of them all, wearing the biggest, heaviest shell, lay quietly in his shell, not even trying to walk. If food came near, good; if not, he just waited. (I made sure to drop a morsel right under his nose.)

The next day, he had moved out, and was actively wandering about, shell-less, looking for food. I picked out a few new shells, a bit smaller, more suited to his new size, and dropped them nearby. The next day, he was wearing one, and scrambling about as usual.

Of course, this would not have been feasible if I hadn't done something else a couple of days earlier; the last time we went to the beach, I fished out Mr. C., Mama Crab, and the # 2 male, and took them back to their home territory.

Goodbye, Mr. C. I'll miss you! And Mama, too! Goodbye, and good luck; I hope you find a happy home, mates who will appreciate your robust muscles, Mr. C., and a good swimming place for all your next lot of babies, Mama Crab!

And my poor, de-pincered hermits will recover. They can do something we can't; they can grow new appendages. Here's one, already started:

Grainy-hand hermit, with small hand.

The small, blue pincer is brand-new. It will be the large pincer, when it is full grown; right now, it is smaller than the left-hand one. And the colour will gradually deepen. A few weeks from now, he'll be back to normal.

And the other hermits, and the little white shore crab will do the same. But I'll miss my big shrimp.