Red giant

"What is this?" A girl I'd been talking to on the beach came running, holding a large, red animal, already rolling itself up into a ball.

Giant Pacific chiton, aka gumboot chiton, Cryptochiton stelleri.

It rolls end to end; rolled up like this, it measured a bit over 6 inches. That's side to side, I think.

From the brief glimpse I got of it before it curled up, it's like the much smaller dead chitons I found on the beach last month. Those were almost white, with tiny pinkish protuberances; their fleshy coating had eroded away.

The gumboot chiton can grow up to 14 inches long. This one, I think was a little less than that. A fully mature one may weigh up to 2 kilos.

The fleshy outer coat is hard and rough to the touch, with a slight give on pressure, like strong leather. The flesh, in the brief glimpse I got before the chiton rolled itself up, was a brownish orange.

To touch a gumboot is to feel the fuzzy texture of about 20 species of red algae that live on the mantle and give the gumboot its brick-red color. (From Monterey Bay Aquarium)

At home, I examined my photos closely. The red mantle is covered with tiny flower- or anemone-shaped stalks; whether they are algae or the mantle itself, I couldn't tell.

Algae? The grey stuff is fine sand from the beach.

After I found those dead chitons, I returned a few days later, and found the smaller one where I had seen it before. I brought it home in a double plastic bag (it was stinky!), soaked it repeatedly in hydrogen peroxide for several days, cleaned the rotting flesh away, soaked the rest in alcohol, and then dried it.

The eight internal shells are now visible. Because of their shape, they're often called "butterfly shells".

7 shells (also called plates or valves) are clearly visible. The eighth is almost hidden under the edge on the left.

Top of this chiton. The white mantle is hard and smooth, but those red knobs are rough. They drop off quite easily; they are probably algae.

Total length of the dried chiton: 4 inches, curved in as it is.

Most chitons cling tightly to their rocks; these gumboots are easier to dislodge, and sometimes they can be washed up by the waves. This live one was on the sand, near rocks.

Sometimes in the spring, great numbers of chitons gather on rocky beaches, probably venturing in from deeper waters to spawn. (Monterey Bay Aquarium)

We replaced the chiton on the sand at the water's edge and left him to find his way home. He was still rolled up tightly when I headed back up the trail.

Whoppers

On a third visit to the sandstone and erratics beach, I discovered two of the largest chitons I have seen so far, unfortunately dead, left behind by the retreating tide.

Giant Pacific chiton, aka gumboot chiton, Cryptochiton stelleri. This specimen was a bit over 6 inches long. Adults may grow to 14 inches.

Quoting from my Encyclopedia:

"The largest chiton in the world! The giant Pacific chiton's eight shells are completely and cryptically overgrown by girdle."

No other chiton in this area has all 8 plates covered by the mantle, nor grows this large. (From wallawalla.edu)

The mantle was eroded, firm and slightly porous. The shells were only visible as ridges underneath the flesh of the mantle. And from the underside, where the meat had been torn away.

Upside-down chiton. Three shell shapes are exposed.

This chiton has gills along the sides of the foot. The white lines in the grooves here may be bits of the gills. The mantle covers the whole top and laps over the edges, leaving only the foot exposed. Here, it has retracted somewhat as it dried.

These chitons (at least other, less unlucky, members of their families) may live up to 20 years, never straying more than a few metres from home base, at the bottom of the intertidal zone and a bit further out to sea.

Google image of the beach. Access is from a driveway-length road, Shell Road.

Shell Road Beach location