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Chitons, also known as sea cradles, are sluggish mollusks that creep along the under-sides of rocks on broad feet. Most have eight exposed, overlapping plates on their backs; two species have plates that are partially or completely covered by a thick, fleshy layer called a mantle or girdle. The flexibility of these plates allow chitons to fit snugly into a depression on rocks where it can better hold on. When dislodged it rolls into a ball like a pill bug to protect its soft undersides from predators (and hence its "sea cradle" label). Tufts of gills are tucked in a groove between the body tissues and the plates.

Some chitons have light-sensitive receptors that penetrate the plates. Like other mollusks, chitons use their radulae (scraping tongues) to graze on thin films of algae and diatoms that coat intertidal rocks. And like limpets, chitons frequently have homing spots where they rest when not feeding. Enemies include crabs, fish and anemones. When beachcombing keep an eye out for their remnant plates, known as butterfly shells. -adapted from Pacific Intertidal Life

ChitonLined Chiton
Tonicella lineata
Size: up to 2" long, usually much smaller
Color: a beautiful range of colors, from pink to orange-red. This chiton is named for the alternating light and dark zigzag lines on the plates. Notes: Not as easy to find as the leather chiton because its color often closely matches the pink coralline algae where it is most commonly found feeding (its planktonic larvae settle only on coralline algae). The lined chiton's main enemy is the ochre sea star. (Photo courtesy of Gary Hayes).

Black Katy ChitonBlack Katy Chiton/Leather Chiton
Katharina tunicata
Size: up to 4 3/4" long
Color: a black girdle covers most of this chiton; white diamond shapes are left uncovered on top, looking like a segmented spine. Notes: Like most intertidal inhabitants, the leather chiton is tough, able to withstand both intense wave action at high tide and exposure to the sun at low tide. It is large enough to have been used as food by coastal aboriginal people years ago. This chiton dines primarily on algae found on wave-washed rocks. (Photo courtesy Corsi, California Academy of Sciences)

Gumboot Chiton/Giant Pacific Chiton
Size:
Easily the largest chiton in the world; up to 13" long, 5" wide
Color: brick-red to rusty to brown Notes: If the stars are aligned just right, the tide is very low and the gods are smiling, you might be lucky enough to see a gumboot chiton. A life span of more than 20 years, this huge creature (for a tidepool, anyway) is often found completely detached from intertidal rocks; it can roll into a ball, armadillo-style, for protection. One of it's favorite meals is sea lettuce, a common seaweed. The gumboot is very slow--why don't critters settle on its surface like a barnacle on a crab? Good question. This huge chiton keeps itself uncluttered on top by secreting a mucus that swells on contact with water, preventing organisms from settling on its spines. Underneath the mantle is a different story. The gumboot hosts the red-banded commensal scaleworm that lives in the underside grooves and wards off would-be-predators. Another amazing symbiotic relationship brought to you by Mother Nature.

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