Friday, February 26, 2010

A tale of two hermits

Total amazement!

Every time I pass my little salt-water tank, I stop for a few seconds to see what the critters are up to.  Not much, usually; eating, sleeping, digging. The hermits prowl around idly, picking up invisible scraps with the smaller claw, and popping them into their mouths. Limpets on the glass just sit there. So do most of the snails.

Yesterday was different. In the morning, a tiny hermit crab was up at the front, rolling an unattached barnacle over and over. While I watched, he found the mouth, and started digging out the good meat inside. Poor little barnacle!

Half-inch hermit in a Batillaria shell.

A minute later, a Japanese Nassa showed up. These are tiny snails, smaller than the shell the hermit was in. Usually they steer clear of the hermits, which can be aggressive when food is an issue, and are well armed. This time, the snail ignored the danger, slid right over the hermit, and glommed onto the barnacle, rolling it over so that the mouth faced the snail.

Nassaria, with siphon for smelling good food.

The hermit struggled to hold the shell, but lost his grip, couldn't get at the meat anymore, and wandered away. The snail returned to the sand, carrying its catch.

I was amazed; the hermit has big pincers, sharp claws on all its feet. And it's not afraid to use them; these little guys will even take on a crab twice their size, and chase the crab off. And the snail is all soft flesh, and that vulnerable siphon; I expected it to be injured, at least, after that confrontation. But the operation was smooth, practiced, economical, the snail sliding over the back of the hermit and onto the barnacle without facing the pincers. An accomplished thief, this one is.

These snails normally hide under the sand, with only the tip of the siphon exposed to catch the scents of fresh food. When they smell something good, they surface. They eat detritus; whatever falls to the bottom, any dead or dying meat, the remains of other critters' dinners. They are often introduced to marine aquaria to help with the cleaning, and to aerate the sand, plowing through it.

That was the morning's excitement. In the afternoon, I noticed Hermit Rex sitting on a rock, acting oddly. He was holding all his legs and pincers close together in front of his face, and scrubbing at them, as if he were itchy.  As I watched, wondering, I saw the reason; below the face of the rock, there was a ghost, a pale, shadowy copy of Rex.

Hermit Rex's old skin.

Rex had just finished molting, and was getting his limbs limbered up. I watched him until he turned and left, then I retrieved the husk he'd left behind.

Here's the old Rex.

The old carapace was intact, except for a small, round hole at the back of the thorax. Rex had pulled himself, eyestalks, antennae, pincers and legs, through that hole. It is about half the diameter of his big pincer. The abdomen is missing; hermits don't wear a crust there, substituting it with a borrowed shell. So there was no need to shed the skin of the abdomen. It stretches just fine. It's the crusty part that gets too tight when the hermit grows.

More amazement; the eyes are still there, still glassy. All the various appendages are in their proper places. Even the various joints and angles of the mouth parts and legs are intact. And he had pulled long antennae out of the centre of the old antennae without breaking either; how was it possible?

Front view. Eyestalks with glass windows, perfect antennae, hairy legs. The little, short legs at the back are two of the four used to hold onto the chosen shell.

Rex, a few minutes after the transfer. Even the hair had developed underneath the old carapace. Maybe he really was itchy.

I only wish I had stopped to look a few minutes earlier. I would have loved to watch the process. Maybe next time.


  1. Fascinating. They must be relaxing to watch at least when they aren't hurting each other. - Margy

  2. Absolutely fascinating. I was riveted to each word and photo! My sister read over my shoulder and was equally captivated! Thank you so much for sharing this transformation! Wow.


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