Tonicella lineata

ORDER

Neoloricata

FAMILY

Ischnochitonidae

TAXONOMY

Tonicella lineata Wood, 1815, Sitka, Alaska, United States.

OTHER COMMON NAMES

None known.

PHYSICAL CHARACTERISTICS

Body low, elongate-oval, usually less than 1.2 in (3 cm) long. Possesses shiny shell valves distinctly demarcated with zigzag lines of alternating dark and light red, light (or dark) blue and red, or whitish and red colors. Mantle girdle naked and leathery, usually yellow to green in color, sometimes banded.

DISTRIBUTION

From Alaska (in the Aleutian Islands) south to San Miguel Island in the Channel Islands National Park in California, in the Sea of Okhotsk (Russia) to northern Japan.

HABITAT

Found on temperate rocky shores, on rocks covered with erect or crustose coralline algae, in the mid to low intertidal zone down into the subtidal to depths of 180 ft (54.8 m). On the Monterey Peninsula in California, subtidal individuals show consistent color and size differences, being smaller (0.39–0.78 in [1–2 cm] long) with purple lines on the girdle. On the Oregon coast, it is frequently found living under purple sea urchins (Strongylocentrotus purpuratus) in the burrows that the urchins dig out of rock. The color pattern frequently matches, to some degree, the coralline algal substrate, lending chiton some degree of protective camouflage.

BEHAVIOR

Activity patterns vary with habitat: individuals near Monterey, California, remain stationary in the intertidal zone when exposed at low tide, while subtidal individuals follow a diurnal

rhythm characterized by more twice as much movement at night than during the day.

FEEDING ECOLOGY AND DIET

Feeds on crustose coralline algae (Lithothamnium), which it scrapes with its strong radula, consuming the more superficial layers and removing the film of diatoms and other small organisms coating the surface of this alga. Species that feed on the lined chiton include the sea stars (Pisaster ochraceus and Leptasterias hexactis). However, in Monterey Bay, California, sea stars have rarely been observed to feed on chitons except for those that are removed from the rocks.

REPRODUCTIVE BIOLOGY

Females release eggs into the water column in April along the coasts of California and central Oregon, whereas populations on San Juan Island (off the Washington coast) release eggs in May and June. Cleavage divisions and gastrulation lead to the formation of a trochophore larvae 16–24 hours post-fertilization (depending on temperature), and they hatch roughly 43–44 hours after fertilization. Development of the trochophore larva stops sometime within 150–160 hours post-fertilization, and further development depends on contact with crustose coralline algae (or an extract thereof). Larvae undergo metamorphosis to the adult within 12 hours of settlement, becoming juvenile chitons that begin to feed around 30 days after settlement.

CONSERVATION STATUS

Not listed by the IUCN.

SIGNIFICANCE TO HUMANS

None known.