Mopalia ciliata (Sowerby, 1840)

Common name(s): Hairy chiton

Synonyms: Mopalia ciliata
Order Neoloricata 
Suborder Ischnochitonina 
Family Mopaliidae 
Mopalia ciliata, about 3 cm long, under a rock overhang at Cape Flattery
(Photo by: Dave Cowles, July 2010 )
Description:  The dorsal surface of the girdle of this chiton is not granular but has numerous soft, flexible, usually brown, strap-shaped hairs which are arranged randomly.  The hairs are scattered randomly and up to 3 mm long, not as long as the girdle is wide.  Magnification of the girdle hairs shows that they have whitish, glassy spicules along one side and side hairs which are usually restricted to the basal 1/3 of the shaft.  The girdle encroaches between the plates.  The plates have low tubercles.  The head plate (to the right in the photo above) has 10 radiating ridges.  The lateral areas of plates 2-7 are often separated from the central region by a ridge of enlarged tubercles.  Plate 8 is not unusually long.  There is a cleft at the posterior end of the chiton.  Plate color variable and often bright or with blotches and streaks; often greenish with red, orange, blue, or white markings.  The interior of the plates are usually whitish with a pink and blue tinge.  Length to 7.5 cm and may be proportionally broader than many chitons.

How to Distinguish from Similar Species:  The mossy chiton Mopalia muscosa has thicker, stiff hairs and is not so brightly colored.

Geographical Range:  Aleutian Islands to Baja California.  Common in Puget Sound and the open coast, and is the most common Mopalia near Juneau, Alaska.

Depth Range:  Mid to low intertidal

Habitat:  Rocky intertidal and floats.  Most common in crevices or on the bottom or downward-facing slopes of rocks.  Sometimes among mussels.

Biology/Natural History:   This species grazes on algae and also on hydroids, bryozoans, sponges, and other small animals.  It feeds mainly at night and on foggy or cloudy days.  Eggs are about 0.2 mm diameter and gray-green.  Larvae swim freely after hatching, developing all 8 valves.  In CA they settle about day 8 and metamorphose to miniature adults by day 16.  Adults grow about 11-40 mm per year.  Predators include the ochre seastar Pisaster ochraceus.



Dichotomous Keys:
  Carlton, 2007
  Kozloff, 1987, 1996

General References:
  Harbo, 1999
  Johnson and Snook, 1955
  Kozloff, 1993
  McConnaughey and McConnaughey, 1985
  Morris et al., 1980
  Niesen, 1997
  O'Clair and O'Clair, 1998
  Ricketts et al, 1985

Scientific Articles:

Web sites:

General Notes and Observations:  Locations, abundances, unusual behaviors:

Authors and Editors of Page:
Dave Cowles (2010):  Created original page
CSS coding for page developed by Jonathan Cowles (2007)

Rosario Invertebrates web site provided courtesy of Walla Walla University