Mopaliidae Dall 1889

This individual was on the rocky head on the south side of Bowman Bay. Photo by Dave Cowles, July 2008

Another view of Mopalia lignosa. Note the hairs between the plates. Photo by Dave Cowles, San Simeon, CA 1997

This 10 cm individual was between several boulders on Sares Head, April 2011. Photo by Dave Cowles

Mopalia lignosa, San Simeon, CA (Photo by: Dave Cowles, 1997)

This venerable old chiton, just over 8 cm long, was also found at Sares Head. The head is to the right. The plates are so worn that the pattern can hardly be seen. The mantle color is unusual for this species but the mantle hairs are stiff and strap-like and both the Kozloff key and Aaron Baldwin's key identify it as Mopalia muscosa. The mantle and plates of this individual are also a whole city of symbionts, from several species of polychaete worms, small copepods, a tiny limpet (visible above at the top of plate 2), unidentified stalked invertebrates, and even a chironomid (midge fly) larva! I know that insects are rarely found in the ocean but the midge larva was clearly at home--crawling among other invertebrates and across the plates, nestling down in the edge of the mantle at the margin of the plates, etc., even though the chiton was fully immersed in seawater.

Katharina tunicata Black Chiton Katharina tunicata; taken at low tide at Swirl Rocks Photo by: Ryan Lunsford 2002

This closeup of the mantle of the individual above shows the strange yellowish background color of the mantle combined with the familiar thick, strap-like hairs characteristic of this species. The limpet is visible on the edge of the algae-encrusted plate at the bottom right, and a mucus tube of a polychaete worm is visible at the margin between the plate and the mantle. A few strands of red algae intertwine among the mantle hairs.

Here is a view of the underside of the above individual. The mouth is clearly visible on the left. The large central region is the foot, which has several strands of mucus on it. The ring around the foot is the mantle cavity, which contains the gills. The outer ring of tissue is the underside of the mantle (girdle), which is held down fairly tightly against the substrate.

Mopalia muscosa under a rock at San Simeon, CA. Length is about 3 cm. Head and plate 1 are to the left. (Photo by: Dave Cowles, 1995)

Dendrochiton flectens, underwater photo (Photo and identification by: Aaron Baldwin)

These chitons are omnivorous. This individual could well have been feeding on the adjacent bryozoan.

This larger view shows how the chiton is grazing the sponge off the scallop.

lined chiton

This closeup shows the detail on the plates, plus a view of some of the girdle.

The anterior two plates of this individual have a lot of white.

This closeup of some of the sparse girdle hairs, along the lateral margin of the girdle, shows how the larger hairs branch from the base. The orange/pink background is the sponge and scallop that the chiton is crawling on. Other than on these lateral areas and in some areas along the edges of the plates the girdle hairs are quite sparse.

This closeup is of some girdle hairs which are not right at the margin of the girdle.

The underside of the girdle of this species is not orange.

Mopalia hindsii feeding on the sponge Myxilla incrustans which is growing on the shell of the scallop Chlamys hastata. (Photo by: Dave Cowles, July 2007)