Wednesday, March 07, 2018

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

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