Evergreen Natural History Database

Common name(s): Buckshot barnacle, or brown buckshot barnacle

Size:
Up to about 8 mm in diameter.

Range:
Alaska to San Diego within the high intertidal or splash zone.

Habitat:
Chthamalus dalli is found higher within the intertidal zone than larger barnacles because its smaller size is less susceptible to drying out than larger barnacles, and there are fewer predators farther up the intertidal zone. Chthamalus spp. live closely packed together, with up to 8,000 recorded per square foot.

Misidentification:
Chthamalus dalli is very difficult to tell from Chthamalus fissus, C. dalli has ridges on the inside of its shell, and a ridge on the inside of the scutum. Chthamalus fissus also has a more obviously fluted base than C. dalli.

Life history:
Chthamalus spp. only live to about three years old. They are hermaphroditic, producing sperm and eggs simultaneously, but do not self fertilize if they are within a colony. Instead these barnacles have an inflatable penis that can extend approximately 4.5 cm from its shell to fertilize a neighbor (up to 20 times its body length). Each C. dali reproduces several times from spring to fall, producing thousands of planktonic larvaethat they will inadvertently eat if scooped up while they are filter feeding.

Predators:
Sea stars and snails are their primary predators. If predators are prevalent, Chthamalus spp. will sometimes grow a slight curve to their shell to further protect themselves. This curved shell does have some adverse effects on feeding success, though, and is supposedly rare.

Links:

Chthamalus to illustrate zonation
Identification
Photos

Kozloff, E., (1996). Marine invertebrates of the Pacific Northwest, University of Washington Press

Last updated Friday, August 25, 2006, by Lisa Ferrier