Thursday, January 27, 2011

My hermits are hairy, blue, and now orange.

Following up on yesterday's hermit mystery (where we find logs with hermit snails in mudsnail shells, but no mudsnails in the vicinity to provide shells.)

Olivia and Tim, in the comments on that post, came up with a few more scenarios. The logs could have been washed up from some other source; the hermits could have massacred the snails after all (they have been known to do that in a pinch); or it could be a seasonal thing.

I'll have to start paying closer attention to numbers, dates, proportions, demographic ratios.

And I have more data to add; here goes.

As usual, I examined my hermits in a bowl of water before I added them to the tank. Three were quite tiny, and one was in a different shell, not from a mudsnail. I took its photo, before I settled it down in its new home.

Orange hermit in a matching shell, possibly an  olive snail's shell.
It wasn't until I examined the photos that I realized that this was not one of the two common species on these beaches (and the only two in my tank). I had thought it was a small hairy hermit, Pagurus hirsutiusculus, because of the white stripes on the legs, but all the colours were wrong. The antennae are orange, the tips of the legs and pincers are orange, the rest is lighter than the hairy's legs.

Hairy hermits crabs have green and white banded antennae, dark, hairy legs with variable white and/or blue markings.

Small hairy hermit in pretty moonsnail shell.

Two of the orange hermits. The larger one is in a mudsnail shell.

Zooming in.
I think this is a greenmark hermit, Pagurus caurinus. The encyclopedia says they have "White leg banding, orange pincer tips, and unbanded orange antennae." They are smaller than the hairies, too; they grow to half the size, 1 cm. versus 1.9 cm. Walla Walla U. adds, among other details, orange-tipped spines on the upper part of the pincers. I can almost be sure I see these in some of my photos.

By the time I'd discovered this, the 5 new hermits had mingled with the old-timers. I looked for them in the tank, and discovered one of the tinies in an awkward position:

Caught on the back leg of a big shore crab.
"Oops! Sorry, youngster!" After a few steps, the crab noticed and shook off the struggling hermit.

None the worse for wear.

And sure enough, this one has the orange-tipped pincers and antennae, too.

The other common species, the grainyhand hermit, has orange antennae, but otherwise is quite different:

Bluish-green to brown legs and pincers, all covered with blue warts. These are larger hermits, up to 2 cm. They prefer big shells, like this whelk.

This adds to the questions I have. Were all those hermits on the logs greenmarks? Why have I not seen any before? Do they, tiny as they are, kill snails?

We must go back and examine those logs properly.


  1. I love following your crab tails.

  2. I am always amazed at the detail in your photos, and these ones are no exception. Hermit crabs are really neat creatures, and you have fuelled my curiosity. Next time I see one (which is already a treat) I will pay more attention to its colours and features.

  3. I found a few links on mud snails...

    Both seem to indicate either a hibernation or a die-off during winter. Mind you, the common name "mud snail" may refer to two different species between the two beaches you visited, hence different population patterns.


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